27268161 staadpro 2007 international codes 2007 complete
TRANSCRIPT
STAAD.Pro 2007
INTERNATIONAL DESIGN CODES
DAA037810-1/0001
A Bentley Solutions Center
www.reiworld.com
www.bentley.com/staad
STAAD.Pro 2007 is a suite of proprietary computer programs of Research Engineers,
a Bentley Solutions Center . Although every effort has been made to ensure the
correctness of these programs, REI will not accept responsibility for any mistake,
error or misrepresentation in or as a result of the usage of these programs.
Copyright attribution: ©2008, Bentley Systems, Incorporated. All rights reserved.
Trademark attribution: STAAD.Pro, STAAD.foundation, Section Wizard,
STAAD.Offshore and QSE are either registered or unregistered trademarks or
service marks of Bentley Systems, Incorporated or one of its direct or indirect
wholly-owned subsidiaries. Other brands and product names are trademarks of
their respective owners.
RELEASE 2007
Published February, 2008
About STAAD.Pro
STAAD.Pro is a general purpose structural analysis and design program with
applications primarily in the building industry - commercial buildings, bridges and
highway structures, industrial structures, chemical plant structures, dams, retaining
walls, turbine foundations, culverts and other embedded structures, etc. The program
hence consists of the following facilities to enable this task.
1. Graphical model generation utilities as well as text editor based commands for
creating the mathematical model. Beam and column members are represented
using lines. Walls, slabs and panel type entities are represented using triangular
and quadrilateral finite elements. Solid blocks are represented using brick
elements. These utilities allow the user to create the geometry, assign properties,
orient cross sections as desired, assign materials like steel, concrete, timber,
aluminum, specify supports, apply loads explicitly as well as have the program
generate loads, design parameters etc.
2. Analysis engines for performing linear elastic and pdelta analysis, finite element
analysis, frequency extraction, and dynamic response (spectrum, time history,
steady state, etc.).
3. Design engines for code checking and optimization of steel, aluminum a nd timber
members. Reinforcement calculations for concrete beams, columns, slabs and
shear walls. Design of shear and moment connections for steel members.
4. Result viewing, result verification and report generation tools for examining
displacement diagrams, bending moment and shear force diagrams, beam, plate
and solid stress contours, etc.
5. Peripheral tools for activities like import and export of data from and to other
widely accepted formats, links with other popular softwares for ni che areas like
reinforced and prestressed concrete slab design, footing design, steel connection
design, etc.
6. A library of exposed functions called OpenSTAAD which allows users to access
STAAD.Pro’s internal functions and routines as well as its graphical commands to
tap into STAAD’s database and link input and output data to third -party software
written using languages like C, C++, VB, VBA, FORTRAN, Java, Delphi, etc.
Thus, OpenSTAAD allows users to link in-house or third-party applications with
STAAD.Pro.
About the STAAD.Pro Documentation
The documentation for STAAD.Pro consists of a set of manuals as described below.
These manuals are normally provided only in the electronic format, with perhaps some
exceptions such as the Getting Started Manual which may be supplied as a printed
book to first time and new-version buyers.
All the manuals can be accessed from the Help facilities of STAAD.Pro. Users who
wish to obtain a printed copy of the books may contact Research Engineers. REI also
supplies the manuals in the PDF format at no cost for those who wish to print them on
their own. See the back cover of this book for addresses and phone numbers.
Getting Started and Tutorials : This manual contains information on the contents of
the STAAD.Pro package, computer system requirements, installation process, copy
protection issues and a description on how to run the programs in the package.
Tutorials that provide detailed and step-by-step explanation on using the programs are
also provided.
Examples Manual
This book offers examples of various problems that can be solved using the STAAD
engine. The examples represent various structural analyses and design problems
commonly encountered by structural engineers.
Graphical Environment
This document contains a detailed description of the Graphical User Interface (GUI) of
STAAD.Pro. The topics covered include model generation, structural analysis and
design, result verification, and report generation.
Technical Reference Manual
This manual deals with the theory behind the engineering calculations made by the
STAAD engine. It also includes an explanation of the commands available in the
STAAD command file.
International Design Codes
This document contains information on the various Concrete, Steel, and Alu minum
design codes, of several countries, that are implemented in STAAD.
The documentation for the STAAD.Pro Extension component(s) is available
separately.
Table of Contents
International Codes
Introduction i
Section 1 Australian Codes 1-
1A Concrete Design Per AS3600-2001 1-1
1A.1 Design Operations 1-1 1A.2 Section Types for Concrete Design 1-1 1A.3 Member Dimensions 1-1 1A.4 Design Parameters 1-2 1A.5 Slenderness Effects and Analysis Consideration 1-2 1A.6 Beam Design 1-3 1A.7 Column Design 1-5 1A.8 Slab/Wall Design 1-6
1B Steel Design Per AS 4100-1998 1-9
1B.1 General 1-9
1B.2 Analysis Methodology 1-10 1B.3 Member Property Specifications 1-10 1B.4 Built-in Steel Section Library 1-10 1B.5 Section Classification 1-15 1B.6 Member Resistances 1-15 1B.7 Design Parameters 1-17 1B.8 Code Checking 1-20 1B.9 Member Selection 1-20
1B.10 Tabulated Results of Steel Design 1-21
Section 2 British Codes 2-
2A Concrete Design Per BS8100 2-1
2A.1 Design Operations 2-1 2A.2 Design Parameters 2-1 2A.3 Slenderness Effects and Analysis Considerations 2-4 2A.4 Member Dimensions 2-4 2A.5 Beam Design 2-5
2A.6 Column Design 2-7 2A.7 Slab Design 2-8 2A.8 Shear Wall Design 2-10
2B Steel Design Per BS5950:2000 2-23
2B.1 General 2-23 2B.2 Analysis Methodology 2-25 2B.3 Member Property Specifications 2-25 2B.4 Built-in Steel Section Library 2-25 2B.5 Member Capacities 2-30
2B.6 Design Parameters 2-34 2B.7 Design Operations 2-46 2B.8 Code Checking 2-47 2B.9 Member Selection 2-48 2B.10 Tabulated Results of Steel Design 2-49 2B.11 Plate Girders 2-50 2B.12 Composite Sections 2-51 2B.13 Design of Tapered Beams 2-51
2B1 Steel Design Per BS5950:1990 2-55
2B1.1 General 2-55 2B1.2 Analysis Methodology 2-56 2B1.3 Member Property Specifications 2-56 2B1.4 Built-in Steel Section Library 2-56 2B1.5 Member Capacities 2-60 2B1.6 Design Parameters 2-65 2B1.7 Design Operations 2-73 2B1.8 Code Checking 2-74
2B1.9 Member Selection 2-74 2B1.10 Tabulated Results of Steel Design 2-75 2B1.11 Plate Girders 2-76 2B1.12 Composite Sections 2-77
2C Design Per BS5400 2-79
2C.1 General Comments 2-79 2C.2 Shape Limitations 2-79 2C.3 Section Class 2-80 2C.4 Moment Capacity 2-80
2C.5 Shear Capacity 2-80 2C.6 Design Parameters 2-81 2C.7 Composite Sections 2-82
2D Design Per BS8007 2-85
2D.1 General Comments 2-85 2D.2 Design Process 2-85 2D.3 Design Parameters 2-87 2D.4 Structural Model 2-87
2D.5 Wood & Armer Moments 2-88
2E Design Per British Cold Formed Steel Code 2-91
2E.1 General 2-91 2E.2 Cross-sectional Properties 2-91 2E.3 Design Procedure 2-92 2E.4 Design Equations 2-93
2E.5 Verification Problem 2-101
Section 3 Canadian Codes 3-
3A Concrete Design Per CSA Standard A 23.3-94 3-1
3A.1 Design Operations 3-1 3A.2 Section Types for Concrete Design 3-1 3A.3 Member Dimensions 3-1 3A.4 Slenderness Effects and Analysis Consideration 3-2
3A.5 Design Parameters 3-3 3A.6 Beam Design 3-4 3A.7 Column Design 3-7 3A.8 Slab/Wall Design 3-7
3B Steel Design Per CSA Standard CAN/CSA – S16-01 3-9
3B.1 General Comments 3-9 3B.2 Analysis Methodology 3-10 3B.3 Member Property Specifications 3-10 3B.4 Built-in Steel Section Library 3-10 3B.5 Section Classification 3-17
3B.6 Member Resistances 3-17 3B.7 Design Parameters 3-21 3B.8 Code Checking 3-23 3B.9 Member Selection 3-24 3B.10 Tabulated Results of Steel Design 3-25 3B.11 Verification Problems 3-26
3C Design Per Canadian Cold Formed Steel Code 3-41
3C.1 General 3-41 3C.2 Cross-Sectional Properties 3-41
3C.3 Design Procedure 3-42
3D Wood Design Per CSA Standard CAN/CSA-086-01 3-49
3D.1 General Comments 3-49 3D.2 Analysis Methodology 3-50 3D.3 Member Property Specifications 3-50 3D.4 Built-in Section Library 3-50 3D.5 Member Resistance 3-54
3D.6 Design Parameters 3-57 3D.7 Code Checking 3-59 3D.8 Member Selection 3-60 3D.9 Tabulated Results of Timber Design 3-60 3D.10 Verification Problems 3-61
Section 4 Chinese Codes 4-
4A Concrete Design Per GB50010-2002 4-1
4A.1 Design Operations 4-1 4A.2 Section Types for Concrete Design 4-1 4A.3 Member Dimensions 4-1 4A.4 Design Parameters 4-2 4A.5 Beam Design 4-2 4A.6 Column Design 4-6
4B Steel Design Per GBJ 50017-2003 4-11
4B.1 General 4-11 4B.2 Analysis Methodology 4-12
4B.3 Member Property Specifications 4-12 4B.4 Built-in Chinese Steel Section Library 4-12 4B.5 Member Capacities 4-17 4B.6 Combined Loading 4-18 4B.7 Design Parameters 4-18 4B.8 Code Checking 4-21 4B.9 Member Selection 4-22
Section 5 European Codes 5-
5A Concrete Design Per Eurocode EC2 5-1
5A.1 Design Operations 5-1 5A.2 Eurocode 2 (EC2) 5-1 5A.3 National Application Documents 5-2 5A.4 Material Properties and Load Factors 5-2 5A.5 Columns 5-3
5A.6 Beams 5-3 5A.7 Slabs 5-5 5A.8 Design Parameters 5-5
5B Steel Design Per Eurocode EC3 5-9
5B.1 General Description 5-9 5B.2 Design Parameters 5-14
5B.3 Tabulated Results of Steel Design 5-19 5B.3 Worked Examples 5-20 5B.4 User’s Examples 5-37
5C Timber Design Per EC5 Part 1-1 5-45
5C.1 General Comments 5-45 5C.2 Analysis Methodology 5-49 5C.3 Design Parameters 5-58 5C.4 Verification Problems 5-61
Section 6 Egyptian Codes 6-
6A Concrete Design Per ECCS205 6-1
6A.1 Design Operations 6-1 6A.2 Member Dimensions 6-1 6A.3 Design Parameters 6-2 6A.4 Slenderness Effects and Analysis Considerations 6-3 6A.5 Beam Design 6-3 6A.6 Column Design 6-6
6B Steel Design Per Egyptian Code # 205 6-9
6B.1 General Comments 6-9
6B.2 Allowable Stresses 6-9
6B.2.1 Axial Stress 6-10 6B.2.2 Bending Stress 6-11 6B.2.3 Shear Stress 6-13 6B.2.4 Combined Stress 6-13
6B.3 Stability Requirements 6-14 6B.4 Code Checking 6-14 6B.5 Member Selection 6-15
6B.6 Tabulated Results of Steel Design 6-15
Section 7 French Codes 7-
7A Concrete Design Per B A E L 7-1
7A.1 Design Operations 7-1 7A.2 Design Parameters 7-1
7A.3 Slenderness Effects and Analysis Consideration 7-1 7A.4 Member Dimensions 7-2 7A.5 Beam Design 7-3 7A.6 Column Design 7-5 7A.7 Slab/Wall Design 7-5
7B Steel Design Per the French Code 7-7
7B.1 General Comments 7-7 7B.2 Basis Of Methodology 7-8 7B.3 Member Capacities 7-8
7B.4 Combined Axial Force and Bending 7-9 7B.5 Design Parameters 7-9 7B.6 Code Checking and Member Selection 7-9 7B.7 Tabulated Results of Steel Design 7-9 7B.8 Built-in French Steel Section Library 7-12
Section 8 German Codes 8-
8A Concrete Design Per DIN 1045 8-1
8A.1 Design Operations 8-1 8A.2 Section Types for Concrete Design 8-1 8A.3 Member Dimensions 8-1 8A.4 Slenderness Effects and Analysis Considerations 8-2 8A.5 Beam Design 8-3 8A.6 Column Design 8-5 8A.7 Slab Design 8-6 8A.8 Design Parameters 8-7
8B Steel Design Per the DIN Code 8-11
8B.1 General 8-11
8B.2 Analysis Methodology 8-12 8B.3 Member Property Specifications 8-12 8B.4 Built-in German Steel Section Library 8-12 8B.5 Member Capacities 8-17 8B.6 Combined Loading 8-18 8B.7 Design Parameters 8-19 8B.8 Code Cecking 8-21
8B.9 Member Selection 8-22
Section 9 Indian Codes 9-
9A Concrete Design Per IS456 9-1
9A.1 Design Operations 9-1
9A.2 Section Types for Concrete Design 9-1 9A.3 Member Dimensions 9-1 9A.4 Design Parameters 9-2 9A.5 Slenderness Effects and Analysis Consideration 9-2 9A.6 Beam Design 9-3 9A.7 Column Design 9-7 9A.8 Bar Combination 9-14 9A.9 Wall Design in accordance with IS 456-2000 9-15
9A1 Concrete Design Per IS13920 9-27
9A1.1 Design Operations 9-27 9A1.2 Section Types for Concrete Design 9-27 9A1.3 Design Parameters 9-28 9A1.4 Beam Design 9-28 9A1.5 Column Design 9-32 9A1.6 Bar Combination 9-43
9B Steel Design Per IS900 9-49
9B.1 Design Operations 9-49 9B.2 General Comments 9-50 9B.3 Allowable Stresses 9-50
9B.3.1 Axial Stress 9-51 9B.3.2 Bending Stress 9-52 9B.3.3 Shear Stress 9-53 9B.3.4 Combined Stress 9-54
9B.4 Design Parameters 9-54 9B.5 Stability Requirements 9-54 9B.6 Truss Members 9-55 9B.7 Deflection Check 9-55
9B.8 Code Checking 9-55 9B.9 Member Selection 9-56 9B.10 Member Selection by Optimization 9-56 9B.11 Tabulated Results of Steel Design 9-57 9B.12 Indian Steel Table 9-59 9B.13 Column with Lacings and Battens 9-67
9C Steel Design Per IS802 9-71
9C.1 General Comments 9-71 9C.2 Allowable Stresses 9-71
9C.2.1 Axial Stress 9-72
9C.3 Stability Requirements 9-74 9C.4 Minimum Thickness Requirement 9-76
9C.5 Code Checking 9-76
9C.5.1 Design Steps 9-77
9C.6 Member Selection 9-78 9C.7 Member Selection by Optimization 9-78 9C.8 Tabulated Results of Steel Design 9-79 9C.9 Parameter Table for IS802 9-81 9C.10 Calculation of Net Section Factor 9-83 9C.11 Example Problem No. 28 9-85
9D Design Per Indian Cold Formed Steel Code 9-93
9D.1 General 9-93 9D.2 Cross-Sectional Properties 9-93 9D.3 Design Procedure 9-94
Section 10 Japanese Codes 10-
10A Concrete Design Per AIJ 10-1
10A.1 Design Operations 10-1
10A.2 Section Types for Concrete Design 10-1 10A.3 Member Dimensions 10-1 10A.4 Slenderness Effects and Analysis Consideration 10-2 10A.5 Beam Design 10-3 10A.6 Column Design 10-5 10A.7 Slab/Wall Design 10-7 10A.8 Design Parameters 10-8
10B Steel Design Per AIJ 10-11
10B.1 General 10-11 10B.2 Analysis Methodology 10-12
10B.3 Member Property Specifications 10-12 10B.4 Built-in Japanese Steel Section Library 10-12 10B.5 Member Capacities 10-18 10B.6 Combined Loading 10-22 10B.7 Design Parameters 10-23 10B.8 Code Checking 10-25
10B.9 Member Selection 10-26
Section 11 Mexican Codes 11-
11A Concrete Design Per MEX NTC 1987 11-1
11A.1 Design Operations 11-1 11A.2 Section Types for Concrete Design 11-1 11A.3 Member Dimensions 11-2 11A.4 Design Parameters 11-3 11A.5 Beam Design 11-6 11A.6 Column Design 11-10 11A.7 Column Interaction 11-11 11A.8 Column Design Output 11-12
11A.9 Slab Design 11-13
11B Steel Design Per Mexican Code 11-15
11B.1 General 11-15 11B.2 Limit States Design Fundamentals 11-16 11B.3 Member End Forces and Moments 11-17 11B.4 Section Classification 11-18 11B.5 Member in Axial Tension 11-18 11B.6 Axial Compression 11-19 11B.7 Flexural Design Strength 11-20
11B.8 Design for Shear 11-22 11B.9 Combined Compression Axial Force and Bending 11-22 11B.10 Combined Tension Axial Force and Bending 11-22 11B.11 Design Parameters 11-23 11B.12 Code Checking and Member Selection 11-27 11B.13 Tabulated Results of Steel Design 11-28
Section 12 Russian Codes 12-
12A Concrete Design Per Russian Code 12-1
12A.1 General 12-1 12A.2 Input Data 12-3 12A.3 Beams 12-10 12A.4 Columns 12-16 12A.5 2D (two dimensional) element (slabs, walls, shells) 12-21
12B Steel Design Per Russian Code 12-25
12B.1 General 12-25 12B.2 Axial tension members 12-26
12B.3 Axial compression members 12-26
12B.4 Flexural members 12-27 12B.5 Eccentrical compression/tension members 12-28 12B.6 Input Data 12-29 12B.7 Section selection and check results 12-45
Section 13 South African Codes 13-
13A Concrete Design Per SABS 0100-1 13-1
13A.1 Design Operations 13-1 13A.2 Design Parameters 13-1 13A.3 Member Dimensions 13-3 13A.4 Beam Design 13-4 13A.5 Column Design 13-6
13B Steel Design Per SAB Standard SAB0162–1: 1993 13-9
13B.1 General 13-9 13B.2 Analysis Methodology 13-10 13B.3 Member Property Specifications 13-10 13B.4 Built-in Steel Section Library 13-10 13B.5 Section Classification 13-16 13B.6 Member Resistances 13-16 13B.7 Design Parameters 13-20 13B.8 Code Checking 13-22
13B.9 Member Selection 13-24 13B.10 Tabulated Results of Steel Design 13-24 13B.11 Verification Problems 13-26
Section 14 American Aluminum Code 14-
14 Design Per American Aluminum Code 14-1
14.1 General 14-1 14.2 Member Properties 14-1 14.3 Design Procedure 14-3
14.4 Design Parameters 14-4 14.5 Code Checking 14-8 14.6 Member Selection 14-8
Section 15 American Transmission Tower Code 15-
15A Steel Design Per ASCE 10-97 15-1
15A.1 General Comments 15-1 15A.2 Allowable Stresses Per ASCE 10-97 15-2
15A.3 Critical conditions used as criteria to determine Pass/Fail status 15-3 15A.4 Design Parameters 15-3 15A.5 Code Checking and Member Selection 15-3
15B Steel Design Per ASCE Manuals And Reports 15-7
15B.1 General Comments 15-7 15B.2 Allowable Stresses Per ASCE (Pub.52) 15-8 15B.3 Design Parameters 15-9 15B.4 Code Checking and Member Selection 15-9 15B.5 Parameter Definition Table 15-10
Section 16 American A.P.I. Code 16-
16 Steel Design Per API 16-1
16.1 Design Operations 16-1 16.2 Allowables Per API Code 16-2
16.2.1 Tension Stress 16-2 16.2.2 Beam Stress 16-2
16.3 Stress due to Compression 16-3 16.4 Bending Stress 16-3
16.5 Combined Compression and Bending 16-4 16.6 Design Parameters 16-4 16.7 Code Checking 16-7 16.8 Member Selection 16-7 16.9 Truss Members 16-8 16.10 Punching Shear 16-8 16.11 Generation of the Geometry File 16-9 16.12 Chord Selection and Qf Parameter 16-10
16.13 External Geometry File 16-11 16.14 Limitations 16-12 16.15 Tabulated Results of Steel Design 16-13 16.16 The Two-Step Process 16-14
Introduction
This publication has been prepared to provide information
pertaining to the various international codes supported by STAAD.
These codes are provided as additional codes by Research
Engineers. In other words, they do not come with the standard
package. Hence, information on only some of the codes presented
in this document may be actually pertinent to the individual user's
package. Users may locate the information for the appropriate code
by referring to the Table of Contents shown on the previous few
pages.
This document is to be used in conjunction with the STAAD
Technical Reference Manual and the STAAD Examples Manual.
Effort has been made to provide some basic information about the
analysis considerations and the logic used in the design approach.
A brief outline of the factors affecting the design along with
references to the corresponding clauses in the codes is also
provided. Examples are provided at the appropriate places to
facilitate ease of understanding of the usage of the commands and
design parameters. Users are urged to refer to the Examples
Manual for solved problems that use the commands and features of
STAAD. Since the STAAD output contains references to the
clauses in the code that govern the design, users are urged to
consult the documentation of the code of that country for
additional details on the design criteria.
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Section 1
Australian Codes
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1-1
Concrete Design Per AS3600 - 2001
1A.1 Design Operations
STAAD has the capabilities for performing concrete design based
on the Australian code AS3600-2001 Australian Standard-Concrete
Structures.
1A.2 Section Types for Concrete Design
The following types of cross sections for concrete members can be
designed.
For Beams Prismatic (Rectangular & Square)
For Columns Prismatic (Rectangular, Square and Circular)
1A.3 Member Dimensions
Concrete members which will be designed by the program must
have certain section properties input under the MEMBER
PROPERTY command. The following example shows the required
input:
Section 1A
Concrete Design Per AS 3600
Section 1A
1-2
UNIT MM
MEMBER PROPERTY
1 3 TO 7 9 PRISM YD 450. ZD 250.
11 13 PR YD 350.
In the above input, the first set of members are rectangular (450
mm depth and 250mm width) and the second set of members, with
only depth and no width provided, will be assumed to be circular
with 350 mm diameter. It is absolutely imperative that the user not
provide the cross section area (AX) as an input.
1A.4 Design Parameters
The program contains a number of parameters which are needed to
perform the design. Default parameter values have been selected
such that they are frequently used numbers for conventional design
requirements. These values may be changed to suit the particular
design being performed. Table 1A.1 of this manual contains a
complete list of the available parameters and their default values.
It is necessary to declare length and force units as Millimeter and
Newton before performing the concrete design.
1A.5 Slenderness Effects and Analysis Consideration
Slenderness effects are extremely important in designing
compression members. There are two options by which the
slenderness effect can be accommodated. One option is to perform
an exact analysis which will take into account the influence of
axial loads and variable moment of inertia on member stiffness and
fixed end moments, the effect of deflections on moment and forces
and the effect of the duration of loads. Another option is to
approximately magnify design moments.
Section 1A
1-3
STAAD has been written to allow the use of the first option. To
perform this type of analysis, use the command PDELTA
ANALYSIS instead of PERFORM ANALYSIS. The PDELTA
ANALYSIS will accommodate the requirements of the second-
order analysis described by AS 3600, except for the effects of the
duration of the loads. It is felt that this effect may be safely
ignored because experts believe that the effects of the duration of
loads are negligible in a normal structural configuration.
Although ignoring load duration effects is somewhat of an
approximation, it must be realized that the evaluation of
slenderness effects is also by an approximate method. In this
method, additional moments are calculated based on empirical
formula and assumptions on sidesway.
Considering all of the above information, a PDELTA ANALYSIS,
as performed by STAAD may be used for the design of concrete
members. However the user must note that to take advantage of
this analysis, all the combinations of loading must be provided as
primary load cases and not as load combinations. This is due to the
fact that load combinations are just algebraic combinations of
forces and moments, whereas a primary load case is revised during
the P-delta analysis based on the deflections. Also, note that the
proper factored loads (like 1.5 for dead load etc.) should be
provided by the user. STAAD does not factor the loads
automatically.
1A.6 Beam Design
Beams are designed for flexure, shear and torsion. For all these
forces, all active beam loadings are prescanned to identify the
critical load cases at different sections of the beams. The total
number of sections considered is 13( e.g. 0.,.1,.2,.25,.3,.4,.5,.6,.7,.
75,.8,.9 and 1). All of these sections are scanned to determine the
design force envelopes.
Concrete Design Per AS 3600
Section 1A
1-4
Design for Flexure
Maximum sagging (creating tensile stress at the bottom face of the
beam) and hogging (creating tensile stress at the top face)
moments are calculated for all active load cases at each of the
above mentioned sections. Each of these sections is designed to
resist both of these critical sagging and hogging moments.
Currently, design of singly reinforced sections only is permitted. If
the section dimensions are inadequate as a singly reinforced
section, such a message will be permitted in the output. Flexural
design of beams is performed in two passes. In the first pass,
effective depths of the sections are determined with the
assumption of single layer of assumed reinforcement and
reinforcement requirements are calculated. After the preliminary
design, reinforcing bars are chosen from the internal database in
single or multiple layers. The entire flexure design is performed
again in a second pass taking into account the changed effective
depths of sections calculated on the basis of reinforcement
provided after the preliminary design. Final provisions of flexural
reinforcements are made then. Efforts have been made to meet the
guideline for the curtailment of reinforcements as per AS 3600.
Although exact curtailment lengths are not mentioned explicitly in
the design output (finally which will be more or less guided by the
detailer taking into account of other practical consideration), user
has the choice of printing reinforcements provided by STAAD at
13 equally spaced sections from which the final detailed drawing
can be prepared.
Design for Shear
Shear reinforcement is calculated to resist both shear forces and
torsional moments. Shear design is performed at 13 equally spaced
sections (0.to 1.) for the maximum shear forces amongst the active
load cases and the associated torsional moments. Shear capacity
calculation at different sections without the shear reinforcement is
based on the actual tensile reinforcement provided by STAAD
program. Two-legged stirrups are provided to take care of the
balance shear forces acting on these sections.
Section 1A
1-5
Example of Input Data for Beam Design
UNIT NEWTON MMS
START CONCRETE DESIGN
CODE AUSTRALIAN
FYMAIN 415 ALL
FYSEC 415 ALL
FC 35 ALL
CLEAR 25 MEM 2 TO 6
MAXMAIN 40 MEMB 2 TO 6
TRACK 1.0 MEMB 2 TO 9
DESIGN BEAM 2 TO 9
END CONCRETE DESIGN
1A.7 Column Design
Columns are designed for axial forces and biaxial moments at the
ends. All active load cases are tested to calculate reinforcement.
The loading which yields maximum reinforcement is called the
critical load. Column design is done for square, rectangular and
circular sections. By default, square and rectangular columns are
designed with reinforcement distributed on each side equally. That
means the total number of bars will always be a multiple of four
(4). This may cause slightly conservative results in some cases.
All major criteria for selecting longitudinal and transverse
reinforcement as stipulated by AS 3600 have been taken care of in
the column design of STAAD.
Example of Input Data for Column Design
UNIT NEWTON MMS
START CONCRETE DESIGN
CODE AUSTRALIAN
FYMAIN 415 ALL
FC 35 ALL
Concrete Design Per AS 3600
Section 1A
1-6
CLEAR 25 MEMB 2 TO 6
MAXMAIN 40 MEMB 2 TO 6
DESIGN COLUMN 2 TO 6
END CONCRETE DESIGN
1A.8 Slab/Wall Design
To design a slab or wall, it must be modeled using finite elements.
The command specifications are in accordance with Chapter 2, and
Chapter 6 of the Technical Reference Manual.
Elements are designed for the moments Mx and My. These
moments are obtained from the element force output (see Section
3.8 of the Technical Reference Manual). The r einforcement
required to resist Mx moment is denoted as longitudinal
reinforcement and the reinforcement required to resist My moment
is denoted as transverse reinforcement. The parameters FYMAIN,
FC, MAXMAIN, MINMAIN and CLEAR listed in Table 1A.1 are
relevant to slab design. Other parameters mentioned in Table 1A.1
are not applicable to slab design.
LONG.
TRANS.
X
Y
Z
M
MM
Mx
y
x
y
Section 1A
1-7
Example of Input Data for Slab/Wall Design
UNIT NEWTON MMS
START CONCRETE DESIGN
CODE AUSTRALIAN
FYMAIN 415 ALL
FC 25 ALL
CLEAR 40 ALL
DESIGN ELEMENT 15 TO 20
END CONCRETE DESIGN
Table 1A.1 Australian Concrete Design-AS 3600- Parameters
Parameter
Name
Default Value Description
FYMAIN* 450/mm2 Yield Stress for main reinforcing steel.
FYSEC* 450/mm2 Yield Stress for secondary reinforcing steel.
FC** 40 N/mm2 Concrete Yield Stress.
CLEAR 25 mm
40 mm
For beam members.
For column members
MINMAIN 10 mm Minimum main reinforcement bar size.
MAXMAIN 60 mm Maximum main reinforcement bar size.
MINSEC 8 mm Minimum secondary reinforcement bar size.
MAXSEC 12 mm Maximum secondary reinforcement bar size.
RATIO 4.0 Maximum percentage of longitudinal reinforcement in columns.
WIDTH ZD Width to be used for design. This value defaults to ZD as provided under MEMBER PROPERTIES.
DEPTH YD Total depth to be used for design. This value defaults to YD as provided under MEMBER PROPERTIES.
Concrete Design Per AS 3600
Section 1A
1-8
Table 1A.1 Australian Concrete Design-AS 3600- Parameters
Parameter
Name
Default Value Description
TRACK 0.0 BEAM DESIGN:
For TRACK = 0.0, output consists of reinforcement details at START, MIDDLE and END.
For TRACK = 1.0, critical moments are printed in addition to TRACK 0.0 output.
For TRACK = 2.0, required steel for intermediate sections defined by NSECTION are printed in addition to TRACK 1.0 output.
COLUMN DESIGN:
With TRACK = 0.0, reinforcement details are printed.
REINF 0.0 Tied column. A value of 1.0 will mean spiral reinforcement.
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way STAAD
works for all codes.
* - applicable values are 250, 400, 450 and 500 as per Table 6.2.1 of
the AS 3600-2001 code.
** - applicable values are 20, 25, 32, 40, 50, and 65 as per Clause
6.1.1.1 of the AS 3600-2001 code.
1-9
Steel Design Per AS 4100 - 1998
1B.1 General
This section presents some general statements regarding the
implementation of the specifications recommended by Standards
Australia for structural steel design (AS 4100) in STAAD. The
design philosophy and procedural logistics are based on the
principles of elastic analysis and limit state method of design.
Facilities are available for member selection as well as code
checking.
The design philosophy embodied in this specification is based on
the concept of limit state design. Structures are designed and
proportioned taking into consideration the limit states at which
they would become unfit for their intended use. Two major
categories of limit-state are recognized - ultimate and
serviceability. The primary considerations in ultimate limit state
design are strength and stability, while that in serviceability is
deflection. Appropriate load and resistance factors are used so that
a uniform reliability is achieved for all steel structures under
various loading conditions and at the same time the chances of
limits being surpassed are acceptably remote.
In the STAAD implementation, members are proportioned to resist
the design loads without exceeding the limit states of strength,
stability and serviceability. Accordingly, the most economic
section is selected on the basis of the least weight criteria as
augmented by the designer in specification of allowable member
depths, desired section type, or other such parameters. The code
checking portion of the program checks whether code requirements
for each selected section are met and identifies the governing
criteria.
Section 1B
Steel Design Per AS 4100-1998
Section 1B
1-10
The following sections describe the salient features of the STAAD
implementation of AS 4100. A detailed description of the design
process along with its underlying concepts and assumptions is
available in the specification document.
1B.2 Analysis Methodology
Elastic analysis method is used to obtain the forces and moments
for design. Analysis is done for the primary and combination
loading conditions provided by the user. The user is allowed
complete flexibility in providing loading specifications and using
appropriate load factors to create necessary loading situations.
Depending upon the analysis requirements, regular stiffness
analysis or P-Delta analysis may be specified. Dynamic analysis
may also be performed and the results combined with static
analysis results.
1B.3 Member Property Specifications
For specification of member properties, the steel section library
available in STAAD may be used. The next section describes the
syntax of commands used to assign properties from the built-in
steel table. Member properties may also be specified using the
User Table facility. For more information on these facilities, refer
to the STAAD Technical Reference Manual.
1B.4 Built-in Steel Section Library
The following information is provided for use when the built -in
steel tables are to be referenced for member property specification.
These properties are stored in a database file. If called for, the
properties are also used for member design. Since the shear areas
are built into these tables, shear deformation is always considered
during the analysis of these members. An example of the member
property specification in an input file is provided at the end of this
section.
Section 1B
1-11
A complete listing of the sections available in the built-in steel
section library may be obtained by using the tools of the graphical
user interface.
Following are the descriptions of different types of sections.
UB Shapes
These shapes are designated in the following way.
20 TO 30 TA ST UB150X14.0
36 TO 46 TA ST UB180X16.1
UC Shapes
The designation for the UC shapes is similar to that for the UB
shapes.
25 TO 35 TA ST UC100X14.8
23 56 TA ST UC310X96.8
Welded Beams
Welded Beams are designated in the following way.
25 TO 35 TA ST WB700X115
23 56 TA ST WB1200X455
Welded Columns
Welded Columns are designated in the following way.
25 TO 35 TA ST WC400X114
23 56 TA ST WC400X303
Steel Design Per AS 4100-1998
Section 1B
1-12
Parallel Flange Channels
Shown below is the syntax for assigning names of channel
sections.
1 TO 5 TA ST PFC75
6 TO 10 TA ST PFC380
Double Channels
Back to back double channels, with or without a spacing between
them, are available. The letter D in front of the section name will
specify a double channel.
11 TA D PFC230
17 TA D C230X75X25 SP 0.5
In the above set of commands, member 11 is a back to back double
channel PFC230 with no spacing in between. Member 17 is a
double channel PFC300 with a spacing of 0.5 length units between
the channels.
Angles
Two types of specification may be used to describe an angle. The
standard angle section is specified as follows:
16 20 TA ST A30X30X6
The above section signifies an angle with legs of length 30mm and
a leg thickness of 6 mm. This specification may be used when the
local Z axis corresponds to the z-z axis specified in Chapter 2. If
the local Y axis corresponds to the z-z axis, type specification
"RA" (reverse angle) may be used.
17 21 TA RA A150X150X16
Section 1B
1-13
Double Angles
Short leg back to back or long leg back to back double angles can
be specified by means of input of the words SD or LD,
respectively, in front of the angle size. In case of an equal angle,
either SD or LD will serve the purpose.
33 35 TA SD A65X50X5 SP 0.6
37 39 TA LD A75X50X6
43 TO 47 TA LD A100X75X10 SP 0.75
Tubes (Rectangular or Square Hollow Sections)
Tubes can be assigned in 2 ways. In the first method, the
designation for the tube is as shown below. This method is meant
for tubes whose property name is available in the steel table. In
these examples, members 1 to 5 consist of a 2X2X0.5 inch size
tube section, and members 6 to 10 consist of 10X5X0.1875 inch
size tube section. The name is obtained as 10 times the depth, 10
times the width, and 16 times the thickness.
1 TO 5 TA ST TUB20202.5
6 TO 10 TA ST TUB100503.0
In the second method, tubes are specified by their dimensions. For
example,
6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5
is a tube that has a height of 8 length units, width of 6 length
units, and a wall thickness of 0.5 length units. Only code checking,
no member selection, will be performed for TUBE sections
specified in this latter manner.
Steel Design Per AS 4100-1998
Section 1B
1-14
Pipes (Circular Hollow Sections)
Pipes can be assigned in 2 ways. In the first method, the
designation for the pipe is as shown below. This method is meant
for pipes whose property name is available in the steel table.
1 TO 5 TA ST PIP180X5
6 TO 10 TA ST PIP273X6.5
In the second method, pipe sections may be provided by specifying
the word PIPE followed by the outside and inside diameters of the
section. For example,
1 TO 9 TA ST PIPE OD 25.0 ID 20.0
specifies a pipe with outside diameter of 25 length units and inside
diameter of 20 length units. Only code checking, no member
selection, will be performed on pipes specified in this latter
manner.
Sample File Containing Australian Shapes
STAAD SPACE
UNIT METER KN
JOINT COORD
1 0 0 0 11 100 0 0
MEMB INCI
1 1 2 10
UNIT CM
MEMBER PROPERTIES AUSTRALIAN
* UB SHAPES
1 TA ST UB200X25.4
* UC SHAPES
2 TA ST UC250X89.5
* CHANNELS
3 TA ST PFC125
Section 1B
1-15
* DOUBLE CHANNELS
4 TA D PFC200
* ANGLES
5 TA ST A30X30X6
* REVERSE ANGLES
6 TA RA A150X150X16
* DOUBLE ANGLES - SHORT LEGS BACK TO BACK
7 TA SD A65X50X5 SP 0.6
* DOUBLE ANGLES - LONG LEGS BACK TO BACK
8 TA LD A100X75X10 SP 0.75
* TUBES (RECTANGULAR OR SQUARE HOLLOW SECTIONS)
9 TA ST TUBE DT 8.0 WT 6.0 TH 0.5
* PIPES (CIRCULAR HOLLOW SECTIONS)
10 TA ST PIPE OD 25.0 ID 20.0
PRINT MEMB PROP
FINI
1B.5 Section Classification
The AS 4100 specification allows inelastic deformation of section
elements. Thus, local buckling becomes an important criterion.
Steel sections are classified as compact, non-compact or slender
depending upon their local buckling characteristics. This
classification is a function of the geometric properties of the
section. The design procedures are different depending on the
section class. STAAD determines the section classification for the
standard shapes and user specified shapes. Design is performed for
all three categories of section as mentioned above.
1B.6 Member Resistances
The member resistance is calculated in STAAD according to the
procedures outlined in AS 4100. This depends on several factors
such as members' unsupported lengths, cross-sectional properties,
support conditions and so on. The procedure adopted in STAAD
for calculating the member resistance is explained here.
Steel Design Per AS 4100-1998
Section 1B
1-16
Axial Tension
The criteria governing the capacity of tension members are based
on two limit states. Limit State of yielding of the gross section is
intended to prevent excessive elongation of the member. The
second limit state involves fracture at the section with the
minimum effective net area. The user through the use of the
parameter NSF (see Table 1B.1) may specify the net section area.
STAAD calculates the tension capacity of a member based on
these two limit states per Cl.7.1 and Cl.7.2 respectively of AS
4100. Parameters FYLD, FU, Kt and NSF are applicable for these
calculations.
Axial Compression
The compressive strength of members is determined based on
Clause 6.1 of the code. It is taken as the lesser of nominal section
capacity and nominal member capacity. Nominal section capacity
is a function of form factor (Cl.6.2.2), net area of the cross section
and yield stress of the material. The user through the use of the
parameter NSC (see Table 1B.1) may specify the net section area.
Note here, that this parameter is different from that corresponding
to tension. The program automatically calculates form factor.
Nominal member capacity is a function of nominal section
capacity and member slenderness reduction factor (Cl.6.3.3). Here
user is required to supply the value of b (Cl.6.3.3). Table 1B.1
gives the default value of this parameter (named ALB). The
effective length for the calculation of compressive strength may be
provided through the use of the parameters KY, KZ, LY and LZ
(see Table 1B.1).
Bending
The allowable bending moment of members is determined as the
lesser of nominal section capacity and nominal member capacity
(ref. Cl.5.1). The nominal section moment capacity is the capacity
to resist cross-section yielding or local buckling and is expressed
as the product of yield stress of material and effective section
modulus (ref. Cl.5.2). The effective section modulus is a function
of section type i.e. compact, non-compact or slender. The nominal
Section 1B
1-17
member capacity depends on overall flexural-torsional buckling of
the member (ref.Cl.5.3).
Interaction of axial force and bending
The member strength for sections subjected to axial compression
and uniaxial or biaxial bending is obtained through the use of
interaction equations. Here also the adequacy of a member is
examined against both section (ref. Cl.8.3.4) and member capacity
(ref.Cl.8.4.5). If the summation of the left hand side of the
equations, addressed by the above clauses, exceed 1.0 or the
allowable value provided using the RATIO parameter (see Table
1B.1), the member is considered to have FAILed under the loading
condition.
Shear
Shear capacity of cross section is taken as the shear yield capacity.
User may refer to Cl.5.11 in this context. Once the capacity is
obtained, the ratio of the shear force acting on the cross section to
the shear capacity of the section is calculated. If any of the ratios
(for both local Y & Z-axes) exceed 1.0 or the allowable value
provided using the RATIO parameter (see Table 1B.1), the section
is considered to have failed under shear.
1B.7 Design Parameters
The design parameters outlined in Table 1B.1 may be used to
control the design procedure. These parameters communicate
design decisions from the engineer to the program and thus allow
the engineer to control the design process to suit an application's
specific needs.
The default parameter values have been selected such that they are
frequently used numbers for conventional design. Depending on
the particular design requirements, some or all of these parameter
values may be changed to exactly model the physical structure.
Steel Design Per AS 4100-1998
Section 1B
1-18
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
Table 1B.1- Australian Steel Design Parameters
Parameter
Name
Default Value Description
KY 1.0 K value for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.
KZ 1.0 K value for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.
LY Member Length Length for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.
LZ Member Length Length for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.
FYLD 250.0 MPa Yield strength of steel.
FU 500.0 MPa Ultimate strength of steel.
NSF 1.0 Net section factor for tension members.
MAIN 0.0 0.0 = Check slenderness ratio against the limits.
1.0 = Suppress the slenderness ratio check.
2.0 = Check slenderness ratio only for column buckling, not for web (See Section 3B.6, Shear)
TRACK 0.0 0.0 = Report only minimum design results.
1.0 = Report design strengths also.
2.0 = Provide full details of design.
DMAX 45.0 in. Maximum allowable depth (Applicable for member selection)
DMIN 0.0 in. Minimum required depth (Applicable for member selection)
RATIO 1.0 Permissible ratio of actual load effect to the
Section 1B
1-19
Table 1B.1- Australian Steel Design Parameters
Parameter
Name
Default Value Description
design strength.
IST 1 Steel type - 1 - SR, 2 - HR, 3 - CF, 4 - LW, 5 - HW
PHI 0.9 Capacity reduction factor
NSC 1.0 Net section factor for compression members = An / Ag
(refer cl. 6.2.1)
ALM 1.0 Moment modification factor (refer cl. 5.6.1.1)
ALB 0.0 Member section constant (refer cl. 6.3.3)
KT 1.0 Correction factor for distribution of forces (refer cl. 7.2)
BEAM 0.0 0.0 = design only for end moments and those at locations specified by SECTION command.
1.0 = Perform design for moments at twelfth points along the beam.
UNT Member Length Unsupported length in bending compression of the top flange for calculating moment resistance.
UNB Member Length Unsupported length in bending compression of the bottom flange for calculating moment resistance.
DFF None (Mandatory for deflection
check)
“Deflection Length”/ Maxm. Allowable local deflection.
DJ1 Start Joint of member
Joint No. denoting start point for calculation of “deflection length”
DJ2 End Joint of member
Joint No. denoting end point for calculation of “deflection length”
Steel Design Per AS 4100-1998
Section 1B
1-20
1B.8 Code Checking
The purpose of code checking is to check whether the provided
section properties of the members are adequate. The adequacy is
checked as per AS 4100 requirements.
Code checking is done using forces and moments at every twelfth
point along the beam. The code checking output labels the
members as PASSed or FAILed. In addition, the critical condition,
governing load case, location (distance from the start joint) and
magnitudes of the governing forces and moments are also printed.
The extent of detail of the output can be controlled by using the
TRACK parameter.
Example of commands for CODE CHECKING:
UNIT NEWTON METER
PARAMETER
FYLD 330E6 MEMB 3 4
NSF 0.85 ALL
KY 1.2 MEMB 3 4
RATIO 0.9 ALL
CHECK CODE MEMB 3 4
Code checking cannot be performed on composite and prismatic
sections.
1B.9 Member Selection
The member selection process basically involves determination of
the least weight member that PASSes the code checking procedure
based on the forces and moments of the most recent analysis. The
section selected will be of the same type as that specified initially.
For example, a member specified initially as a channel will have a
Section 1B
1-21
channel selected for it. Selection of members whose properties are
originally provided from a user table will be limited to sections in
the user table.
Composite and prismatic sections cannot be selected.
Example of commands for MEMBER SELECTION:
UNIT NEWTON METER
PARAMETER
FYLD 330E6 MEMB 3 4
NSF 0.85 ALL
KY 1.2 MEMB 3 4
RATIO 0.9 ALL
SELECT MEMB 3 4
1B.10 Tabulated Results of Steel Design
Results of code checking and member selection are presented in a
tabular format. The term CRITICAL COND refers to the section of
the AS 4100 specification which governs the design.
Steel Design Per AS 4100-1998
Section 1B
1-22
Section 2
British Codes
Kjahds;akh
2-1
Concrete Design Per BS8110
2A.1 Design Operations
It is strongly recommended that the user should perform new
concrete design using the RC Designer Module. The following is
provided to allow old STAAD files to be run.
STAAD has the capability of performing design of concrete
beams, columns and slabs according to BS8110. The 1997
revision of the code is currently implemented. Given the width
and depth (or diameter for circular columns) of a section, STAAD
will calculate the required reinforcement to resist the forces and
moments.
2A.2 Design Parameters
The program contains a number of parameters which are needed to
perform and control the design to BS8110. These parameters not
only act as a method to input required data for code calculations
but give the Engineer control over the actual design process.
Default values of commonly used parameters for conventional
design practice have been chosen as the basis. Table 2A.1 contains
a complete list of available parameters with their default values.
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
Section 2A
Concrete Design Per BS8110
Section 2A
2-2
Table 2A.1 – British Concrete Design-BS8110-Parameters
Parameter
Name
Default
Value
Description
FYMAIN *460 N/mm2 Yield Stress for main reinforcement (For slabs, it is for reinforcement in both directions)
FYSEC *460N/mm2 Yield Stress for secondary reinforcement a. Applicable to shear bars in beams
FC * 30N/mm2 Concrete Yield Stress / cube strength
MINMAIN 8mm Minimum main reinforcement bar size Acceptable bar sizes: 6 8 10 12 16 20 25 32 40 50
MINSEC 8mm Minimum secondary bar size a. Applicable to shear reinforcement in beams
CLEAR * 20mm Clearance of reinforcement measured from concrete surface to closest bar perimeter.
MAXMAIN 50mm Maximum required reinforcement bar size Acceptable bars are per MINMAIN above.
SFACE *0.0 Face of support location at start of beam. (Only applicable for shear - use MEMBER OFFSET for bending )
EFACE *0.0 Face of support location at end of beam. (NOTE : Both SFACE & EFACE must be positive numbers.)
TRACK 0.0 0.0 = Critical Moment will not be printed with beam design report. Column design gives no detailed results.
1.0 = For beam gives min/max steel % and spacing. For columns gives a detailed table of output with additional moments calculated.
2.0 = Output of TRACK 1.0 List of design sag/hog moments and corresponding required steel area at each section of member
MMAG 1.0 Factor by which column design moments are magnified
NSECTION 10 Number of equally-spaced sections to be considered in finding critical moment for beam design. The upper limit is 20.
WIDTH *ZD Width of concrete member. This value default is as provided as ZD in MEMBER PROPERTIES.
DEPTH *YD Depth of concrete member. This value default is as provided as YD in MEMBER PROPERTIES.
Section 2A
2-3
Table 2A.1 – British Concrete Design-BS8110-Parameters
Parameter
Name
Default
Value
Description
BRACE 0.0 0.0 = Column braced in both directions. 1.0 = Column unbraced about local Z direction only 2.0 = Column unbraced about local Y direction only 3.0 = Column unbraced in both Y and Z directions
ELY 1.0 Member length factor about local Y direction for column design.
ELZ 1.0 Member length factor about local Z direction for column design.
SRA 0.0 0.0 = Orthogonal reinforcement layout without considering torsional moment Mxy -slabs only
-500 = Orthogonal reinforcement layout with Mxy used to calculate WOOD & ARMER moments for design.
A = Skew angle considered in WOOD & ARMER equations where A is the angle in degrees.
SERV 0.0 0.0 = No serviceability check performed. 1.0 = Perform serviceability check for beams as if they
were continuous. 2.0 = Perform serviceability check for beams as if they
were simply supported. 3.0 = Perform serviceability check for beams as if they
were cantilever beams. * Provided in current unit system
Concrete Design Per BS8110
Section 2A
2-4
2A.3 Slenderness Effects and Analysis Considerations
STAAD provides the user with two methods of accounting for the
slenderness effects in the analysis and design of concrete
members. The first method is equivalent to the procedure
presented in BS8110 Part 1 1985 Section 3.8.2.2 In this section,
the code recognizes that additional moments induced by deflection
are present and states that these 'secondary' moments are
accounted for by the design formula in Section 3.8.3. This is the
method used in the design for concrete in STAAD.
Alternatively STAAD houses a PDELTA ANALYSIS facility,
which allows the effects of these second order moments to be
considered in the analysis rather than the design. In a PDELTA
analysis, after solving the joint displacements of the structure, the
additional moments induced in the structure are calculated. These
can be compared to those calculated using the formulation of
BS8110.
2A.4 Member Dimensions
Concrete members that are to be designed by STAAD must have
certain section properties input under the MEMBER PROPERTIES
command. The following example demonstrates the required input:
UNIT MM
MEMBER PROPERTIES
*RECTANGULAR COLUMN 300mm WIDE X 450mm DEEP
1 3 TO 7 9 PRISM YD 450. ZD 300.
*CIRCULAR COLUMN 300mm diameter
11 13 PR YD 300.
* T-SECTION - FLANGE 1000.X 200.(YD-YB)
* - STEM 250(THICK) X 350.(DEEP)
Section 2A
2-5
14 PRISM YD 550. ZD 1000. YB 350. ZB 250.
In the above input, the first set of members are rectangular
(450mm depth x 300mm width) and the second set of members,
with only depth and no width provided, will be assumed to be
circular with 300mm diameter. Note that area (AX) is not provided
for these members. If shear area areas ( AY & AZ ) are to be
considered in analysis, the user may provide them along with YD
and ZD. Also note that if moments of inertias are not provided, the
program will calculate them from YD and ZD. Finally a T section
can be considered by using the third definition above.
2A.5 Beam Design
Beam design includes both flexure and shear. For both typ es of
beam action, all active beam loadings are scanned to create
moment and shear envelopes and locate the critical sections. The
total number of sections considered is ten, unless that number is
redefined with the NSECTION parameter. From the critical
moment values, the required positive and negative bar pattern is
developed with cut-off lengths calculated to include required
development length.
Shear design as per BS8110 clause 3.4.5 has been followed and the
procedure includes critical shear values plus torsional moments.
From these values, stirrup sizes are calculated with proper spacing.
The program will scan from each end of the member and provide a
total of two shear regions at each, depending on the change of
shear distribution along the beam. If torsion is present, the
program will also consider the provisions of BS8110 - Part 2 -
section 2.4. A table of shear and/or combined torsion is then
provided with critical shear.
Stirrups not bent up bars are assumed in the design. Table 2A.2
shows a sample output of an actual reinforcement pattern
developed by STAAD. The following annotations apply to Table
2A.2
Concrete Design Per BS8110
Section 2A
2-6
1) LEVEL - Serial number of the bar centre which may
contain one or more bar groups.
2) HEIGHT - Height of bar level from the soffit of the beam
in relation to its local y axis.
3) BAR INFO - Reinforcement bar information specifying
number of bars and their size.
4) FROM - Distance from the start of the beam to the start
of the reinforcing bar.
5) TO - Distance from the start of the beam to the end
of the reinforcing bar.
6) ANCHOR - States whether anchorage, either a hook or
(STA,END) continuation, is needed at start (STA) or at the
end (END).
TABLE 2A.2- ACTUAL DESIGN OUTPUT
B E A M N O. 2 D E S I G N R E S U L T S - FLEXURE
LEN - 3854. mm FY - 460. FC - 30. SIZE - 300. X 600. mm
LEVEL HEIGHT BAR INFO FROM TO ANCHOR
mm mm mm STA END
1 29. 6- 8 MM 0. 3854. YES YES
CRITICAL POS MOMENT = 55.31 KN-M AT 1927. mm, LOAD 3
REQD STEEL = 261.mm2, ROW = 0.0014, ROWMX= 0.0400, ROWMN = 0.0013
MAX/MIN/ACTUAL BAR SPACING = 189./ 33./ 40. mm
2 565. 6- 8 MM 0. 3854. YES YES
CRITICAL NEG MOMENT = 55.31 KN-M AT 1927. mm, LOAD 4
REQD STEEL = 261.mm2, ROW = 0.0014, ROWMX= 0.0400, ROWMN = 0.0013
MAX/MIN/ACTUAL BAR SPACING = 189./ 33./ 40. mm
B E A M N O. 2 D E S I G N R E S U L T S - SHEAR
PROVIDE SHEAR AND TORSIONAL LINKS AS FOLLOWS
FROM - TO SHEAR TORSN LOAD LINK NO. SPACING mm C/C
mm kN kNm S T SIZE S T S+T S T S+T
END 1 1156 84.4 12 4 2 8 mm 3 5 9 335 199 116
2697 END 2 86.6 12 3 2 8 mm 3 5 9 335 199 116
EXTRA PERIPHERAL LONGITUDINAL TORSION STEEL: 402 mm2 EVENLY
DISTRIBUTED
* TORSIONAL RIGIDITY SHOULD CONFORM TO CL.2.4.3 - BS8110 *
Section 2A
2-7
2A.6 Column Design
Columns are designed for axial force and biaxial bending at the
ends. All active loadings are tested to calculate reinforcement. The
loading which produces maximum reinforcement is called the
critical load and is displayed. The requirements of BS8110 Part 1 -
section 3.8 are followed, with the user having control on the
effective length in each direction by using the ELZ and ELY
parameters as described in table 2A.1. Bracing conditions are
controlled by using the BRACE parameter. The program will then
decide whether or not the column is short or slender and whether it
requires additional moment calculations. For biaxial bending, the
recommendations of 3.8.4.5 of the code are considered.
Column design is done for square, rectangular and circular sections.
For rectangular and square sections, the reinforcement is always
assumed to be arranged symmetrically. This causes slightly
conservative results in certain cases. Table 2A.3 shows typical
column design results.
Using parameter TRACK 1.0, the detailed output below is obtained.
TRACK 0.0 would merely give the bar configuration, required steel
area and percentage, column size and critical load case.
Concrete Design Per BS8110
Section 2A
2-8
TABLE 2A.3 -COLUMN DESIGN OUTPUT
C O L U M N No. 1 D E S I G N R E S U L T S
FY - 460. FC -30. N/MM2 RECT SIZE - 300. X 600. MM,
AREA OF STEEL REQUIRED = 875. SQ. MM.
BAR CONFIGURATION REINF PCT. LOAD LOCATION
8 12 MM 0.486 3 EACH END
(ARRANGE COLUMN REINFORCEMENTS SYMMETRICALLY)
BRACED /SHORT in z E.L.z = 4500 mm ( 3.8.1.3 & 5 )
BRACED /SLENDER in y E.L.y = 4500 mm ( 3.8.1.3 & 5 )
END MOMS. MZ1 = 1 MZ2 = 25 MY1 = 53 MY2 = 40
SLENDERNESS MOMTS. KNM: MOMZ = 0 MOMY = 2
DESIGN LOADS KN METER: MOM. = 64 AXIAL LOAD = 84
DESIGNED CAP. KN METER: MOM. = 64 AXIAL CAP.= 187
2A.7 Slab Design
Slabs are designed to BS8110 specifications. To design a slab, it
must first be modelled using finite elements. The command
specifications are in accordance with section 5.51.3 of the
Technical Reference Manual.
A typical example of element design output is shown in Table
2A.4. The reinforcement required to resist the Mx moment is
denoted as longitudinal reinforcement and the reinforcement
required to resist the My moment is denoted as transverse
reinforcement ( Fig. 4.1 ). The following parameters are those
applicable to slab design:
1. FYMAIN - Yield stress for all reinforcing steel
2. FC - Concrete grade
3. CLEAR - Distance from the outer surface to the edge of
the bar. This is considered the same on both
surfaces.
Section 2A
2-9
4. SRA - Parameter which denotes the angle of the
required transverse reinforcement relative to
the longitudinal reinforcement for the
calculation of WOOD & ARMER design
moments.
Other parameters, as shown in Table 2A.1 are not applicable.
WOOD & ARMER equations.
Ref: R H WOOD CONCRETE 1968 (FEBRUARY)
If the default value of zero is used for the parameter SRA, the
design will be based on the Mx and My moments which are the
direct results of STAAD analysis. The SRA parameter (Set
Reinforcement Angle) can be manipulated to introduce WOOD &
ARMER moments into the design replacing the pure Mx, My
moments. These new design moments allow the Mxy moment to be
considered when designing the section. Orthogonal or skew
reinforcement may be considered. SRA set to -500 will assume an
orthogonal layout. If however a skew is to be considered, an angle
is given in degrees measured anticlockwise (positive) from the
element local x-axis to the reinforcement bar. The resulting Mx*
and My* moments are calculated and shown in the design format.
The design of the slab considers a fixed bar size of 16mm in both
directions with the longitudinal bar being the layer closest to the
slab exterior face. Typical output is as follows:
Concrete Design Per BS8110
Section 2A
2-10
TABLE 2A.4 -ELEMENT DESIGN OUTPUT
ELEMENT DESIGN SUMMARY-BASED ON 16mm BARS
MINIMUM AREAS ARE ACTUAL CODE MIN % REQUIREMENTS.
PRACTICAL LAYOUTS ARE AS FOLLOWS:
FY=460, 6No.16mm BARS AT 150mm C/C = 1206mm2/metre
FY=250, 4No.16mm BARS AT 250mm C/C = 804mm2/metre
ELEMENT LONG. REINF MOM-X /LOAD TRANS. REINF MOM-Y /LOAD
(mm2/m) (kN-m/m) (mm2/m) (kN-m/m)
WOOD & ARMER RESOLVED MOMENTS FOR ELEMENT: 13 UNITS: METER KN
LOAD MX MY MXY MX* MY*/Ma* ANGLE
1 0.619 0.249 0.000 2.226 1.855 30.000 TOP
1 0.619 0.249 0.000 0.000 0.000 30.000 BOTT
3 0.437 0.184 -0.007 1.586 1.358 30.000 TOP
3 0.437 0.184 -0.007 0.000 0.000 30.000 BOTT
13 TOP : 195. 2.23 / 1 195. 1.86 / 1
BOTT : 195. 0.00 / 3 195. 0.00 / 3
2A.8 Shear Wall Design
Purpose
Design of shear walls in accordance with BS 8110 has been added
to the features of the program.
Description
The program implements the provisions of BS 8110 for the design
of shear walls. It performs in-plane shear, compression, as well as
in-plane and out-of-plane bending design of reinforcing. The shear
wall is modeled by a single or a combination of Surface elements.
The use of the Surface element enables the design er to treat the
entire wall as one entity. It greatly simplifies the modeling of the
wall and adds clarity to the analysis and design output. The results
are presented in the context of the entire wall rather than
individual finite elements thereby allowing users to quickly locate
required information.
Section 2A
2-11
The program reports shear wall design results for each load
case/combination for user specified number of sections given by
SURFACE DIVISION (default value is 10) command. The shear
wall is designed at these horizontal sections. The output includes
the required horizontal and vertical distributed reinforcing, the
concentrated (in-plane bending) reinforcing and the link required
due to out-of-plane shear.
General format:
START SHEARWALL DESIGN CODE BRITISH FYMAIN f1 FC f2 HMIN f3 HMAX f4 VMIN f5 VMAX f6 EMIN f7 EMAX f8 LMIN f9 LMAX f10 CLEAR f11 TWOLAYERED f12 KSLENDER f13 DESIGN SHEARWALL LIST shearwall-list END
The next table explains parameters used in the shear wall design
command block above. Note: Once a parameter is specified, its
value stays at that specified number till it is specified again.
This is the way STAAD works for all codes.
Concrete Design Per BS8110
Section 2A
2-12
SHEAR WALL DESIGN PARAMETERS
Parameter
Name
Default Value Description
FYMAIN 460 Mpa Yield strength of steel, in current units.
FC 30 Mpa Compressive strength of concrete, in current units.
HMIN 6 Minimum size of horizontal reinforcing bars (range 6 mm – 36 mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
HMAX 36 Maximum size of horizontal reinforcing bars (range 6 mm – 36 mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
VMIN 6 Minimum size of vertical reinforcing bars (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
VMAX 36 Maximum size of vertical reinforcing bars (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
EMIN 6 Minimum size of vertical reinforcing bars located in edge zones (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
EMAX 36 Maximum size of vertical reinforcing bars located in edge zones (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
LMIN 6 Minimum size of links (range 6mm – 16mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
LMAX 16 Maximum size of links (range 6mm – 16mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
CLEAR 25 mm Clear concrete cover, in current units. TWOLAYERED 0 Reinforcement placement mode:
Section 2A
2-13
SHEAR WALL DESIGN PARAMETERS
Parameter
Name
Default Value Description
0 - single layer, each direction 1 - two layers, each direction
KSLENDER 1.5 Slenderness factor for finding effective height.
The following example starts from the definition of shear wall and
ends at the shear wall design.
Example
.
.
SET DIVISION 12
SURFACE INCIDENCES
2 5 37 34 SUR 1
19 16 65 68 SUR 2
11 15 186 165 SUR 3
10 6 138 159 SUR 4
.
.
.
SURFACE PROPERTY
1 TO 4 THI 18
SUPPORTS
1 7 14 20 PINNED
2 TO 5 GEN PIN
6 TO 10 GEN PIN
11 TO 15 GEN PIN
19 TO 16 GEN PIN
.
.
Concrete Design Per BS8110
Section 2A
2-14
.
SURFACE CONSTANTS
E 3150
POISSON 0.17
DENSITY 8.68e-005
ALPHA 5.5e-006
.
.
START SHEARWALL DES
CODE BRITISH
UNIT NEW MMS
FC 25
FYMAIN 460
TWO 1
VMIN 12
HMIN 12
EMIN 12
DESIGN SHEA LIST 1 TO 4
END
Notes
1. Command SET DIVISION 12 indicates that the surface
boundary node-to-node segments will be subdivided into 12
fragments prior to finite element mesh generation.
2. Four surfaces are defined by the SURFACE INCIDENCES
command.
3. The SUPPORTS command includes the new support
generation routine. For instance, the line 2 TO 5 GEN PIN
assigns pinned supports to all nodes between nodes 2 and 5.
As the node-to-node distances were previously subdivided
by the SET DIVISION 12 command, there will be an
additional 11 nodes between nodes 2 and 5. As a result, all
13 nodes will be assigned pinned supports. Please note that
the additional 11 nodes are not individually accessible to the
user. They are created by the program to enable the finite
Section 2A
2-15
element mesh generation and to allow application of
boundary constraints.
4. Surface thickness and material constants are specified by the
SURFACE PROPERTY and SURFACE CONSTANTS,
respectively.
5. The shear wall design commands are listed between lines
START SHEARWALL DES and END. The CODE
command selects the design code that will be the basis for
the design. For British code the parameter is BRTISH. The
DESIGN SHEARWALL LIST command is followed by a
list of previously defined Surface elements intended as shear
walls and/or shear wall components.
Technical Overview
The program implements provisions of section 3.9 of BS 8110:Part
1:1997 and relevant provisions as referenced therein, for all active
load cases. The wall is designed as unbraced reinforced wall. The
following steps are performed for each of the horizontal sections
of the wall set using the SURFACE DIVISION command (see
Description above).
Checking of slenderness limit
The slenderness checking is done for out-of-plane direction. For
out-of-plane direction, the wall is assumed to be simply supported.
Hence, the provisions of clause 3.9.3.2.2 and 3.9.4.2 are
applicable. The default effective height is 1.5 times the clear
height. User can change the effective height. The limit for
slenderness is as per table 3.23 for unbraced wall, which is taken
as 30.
Design for in-plane bending (denoted by Mz in the shear wall
force output)
Walls are assumed to be cantilever beams fixed at their base and
carrying loads to the foundation.
Concrete Design Per BS8110
Section 2A
2-16
Extreme compression fibre to centroid of tension (concentrated)
reinforcement distance, d, is taken as 0.8 horizontal length of the
wall. Flexural design of the wall is carried out in accordance with
the provisions of clause no. 3.4.4. The flexural (concentrated
vertical ) reinforcing is located at both ends (edges) of the len gth
of the wall. The edge reinforcement is assumed to be distributed
over a length of 0.2 times horizontal length on each side. This
length is inclusive of the thickness of the wall. Minimum
reinforcements are according to table 3.25.
Design for in-plane shear (denoted by Fxy in the shear wall
force output)
Limit on the nominal shear strength, v is calculated as per clause
no. 3.4.5.2.
Nominal shear strength of concrete is computed as per table 3.8.
The design shear stress is computed as per clause no. 3.4.5.12
taking into consideration the effect of axial load. The area of
reinforcement is calculated and checked against the minimum area
as per clause no. 3.12.7.4.
Design for compression and out-of-plane vertical bending
(denoted by Fy and My respectively in the shear wall force
output)
The wall panel is designed as simply supported (at top and
bottom), axially loaded with out-of-plane uniform lateral load,
with maximum moments and deflections occurring at mid-height.
Design is done as per clause no. 3.8.4 for axially loaded column
with uni-axial bending. The minimum reinforcement percentage is
as per table 3.25. The maximum reinforcement percentage of
vertical reinforcement is as per clause no. 3.12.6.3. Links if
necessary are calculated as per the provisions of clause 3.12.7.5.
Section 2A
2-17
Design for out-of-plane shear (denoted by Qy in the shear wall
force output)
The out-of-plane shear arises from out-of-plane loading. The
design shear stress is calculated as per 3.4.5.2 and shear strength
of concrete section is calculated as per table 3.8 considering
vertical reinforcement as tension reinforcement.
Shear reinforcements in the form of links are computed as per
table 3.7 and the provisions of clause 3.12.7.5.
Design for out-of-plane horizontal bending (denoted by Mx in
the shear wall force output)
The horizontal reinforcement already calculated from in -plane
shear is checked against the whole section subjected to out -of-
plane bending and axial load. The axial load in this case is the in-
plane shear. The section is again designed as axially loaded
column under uni-axial bending as per the provisions of clause
3.8.4. Extra reinforcement in the form of horizontal bars, if
necessary, is reported.
Shear Wall Design With Opening
The Surface element has been enhanced to allow design of shear
walls with rectangular openings. The automatic meshing algorithm
has been improved to allow variable divisions along wall and
opening(s) edges. Design and output are available for user selected
locations.
Description
Shear walls modeled in STAAD.Pro may include an unlimited
number of openings. Due to the presence of openings, the wall
may comprise up with different wall panels.
1. Shear wall set-up
Definition of a shear wall starts with a specification of the surface
element perimeter nodes, meshing divisions along node-to-node
Concrete Design Per BS8110
Section 2A
2-18
segments, opening(s) corner coordinates, and meshing divisions of
four edges of the opening(s).
SURFACE INCIDENCE n1, ..., ni SURFACE s DIVISION sd1,
..., sdj -
RECOPENING x1 y1 z1 x2 y2 z2 x3 y3 z3 x4 y4 z4 DIVISION
od1, ..., odk
where:
n1, ..., ni - node numbers on the perimeter of the shear wall,
s - surface ordinal number,
sd1, ..., sdj - number of divisions for each of the node-to-node
distance on the surface perimeter,
x1 y1 z1 (...) - coordinates of the corners of the opening,
od1, ..., odk - divisions along edges of the opening.
Note:
If the sd1, ..., sdj or the od1, ..., odk list does not include all node-
to-node segments, or if any of the numbers listed equals zero, then
the corresponding division number is set to the default value (=10,
or as previously input by the SET DIVISION command).
Default locations for stress/force output, design, and design output
are set as follows:
SURFACE DIVISION X xd
SURFACE DIVISION Y yd
where:
xd - number of divisions along X axis,
yd - number of divisions along Y axis.
Section 2A
2-19
Note:
xd and yd represent default numbers of divisions for each edge of
the surface where output is requested. The output is provided for
sections located between division segments. For example, if the
number of divisions = 2, then the output will be produced for only
one section (at the center of the edge).
2. Stress/force output printing
Values of internal forces may be printed out for any user -defined
section of the wall. The general format of the command is as
follows:
PRINT SURFACE FORCE (ALONG ) (AT a) (BETWEEN d1, d2)
LIST s1, ...,si
where:
- local axis of the surface element (X or Y),
a - distance along the axis from start of the member to
the full cross-section of the wall, d1, d2 - coordinates in the direction orthogonal to ,
delineating a fragment of the full cross-section for
which the output is desired.**
s1, ...,si - list of surfaces for output generation
** The range currently is taken in terms of local axis. If the local
axis is directed away from the surface, the negative range is to be
entered.
Note:
If command ALONG is omitted, direction Y (default) is assumed.
If command AT is omitted, output is provided for all sections
along the specified (or default) edge. Number of sections will be
determined from the SURFACE DIVISION X or SURFACE
Concrete Design Per BS8110
Section 2A
2-20
DIVISION Y input values. If the BETWEEN command is
omitted, the output is generated based on full cross-section width.
3. Definition of wall panels
Input syntax for panel definition is as follows:
START PANEL DEFINITION
SURFACE i PANEL j ptype x1 y1 z1 x2 y2 z2 x3 y3 z3 x4 y4 z4
END PANEL DEFINITION
where:
i - ordinal surface number,
j - ordinal panel number,
ptype - WALL
x1 y1 z1 (...) - coordinates of the corners of the panel
Note: Design of COLUMN and BEAM panels is currently not
available.
4. Shear wall design
The program implements different provisions of design of walls as
per code BS 8110. General syntax of the design command is as
follows:
START SHEARWALL DESIGN
(...)
DESIGN SHEARWALL (AT c) LIST s
TRACK tr
END SHEARWALL DESIGN
Parameter TRACK specifies how detailed the design output should
be:
Section 2A
2-21
0 - indicates a basic set of results data (default),
1 - full design output will be generated.
Note:
If the command AT is omitted, the design proceeds for all cross
sections of the wall or panels, as applicable, defined by the
SURFACE DIVISION X or SURFACE DIVISION Y input
values.
a. No panel definition.
Design is performed for the specified horizontal full cross-
section, located at a distance c from the origin of the local
coordinates system. If opening is found then reinforcement is
provided along sides of openings. The area of horizontal and
vertical bars provided along edges of openings is equal to
that of the respective interrupted bars.
b. Panels have been defined.
Design is performed for all panels, for the cross-section
located at a distance c from the start of the panel.
Concrete Design Per BS8110
Section 2A
2-22
2-23
Steel Design Per BS5950:2000
2B.1 General
The design philosophy embodied in BS5950:2000 is built around
the concept of limit state design, used today in most modern steel
design codes. Structures are designed and proportioned taking into
consideration the limit states at which they become unfit for their
intended use. Two major categories of limit state are recognized -
serviceability and ultimate. The primary considerations in ultimate
limit state design are strength and stability while that in
serviceability limit state is deflection. Appropriate safety factors
are used so that the chances of limits being surpassed are
acceptably remote.
In the STAAD implementation of BS5950:2000, members are
proportioned to resist the design loads without exceeding the limit
states of strength and stability. Accordingly, the most economic
section is selected on the basis of the least weight criteria. This
procedure is controlled by the designer in specification of
allowable member depths, desired section type or other such
parameters. The code checking portion of the program checks that
code requirements for each selected section are met and identifies
the governing criteria.
The complete B.S.C. steel tables for both hot rolled and hollow
sections are built into the program for use in specifying member
properties as well as for the actual design process. See section
2B.4 for information regarding the referencing of these sections.
In addition to universal beams, columns, joists, piles, channels,
tees, composite sections, beams with cover plates, pipes, tubes and
angles, there is a provision for user provided tables.
Section 2B
Steel Design Per BS5950:2000
Section 2B
2-24
STAAD.Pro 2006, has introduced the additional option to design
tapered I shaped (wide flange) beams according to Annex G of
BS5950. See section 2B.13 for a complete description.
Single Angle Sections
Angle sections are un-symmetrical and when using BS 5950:2000
table 25 we must consider four axes; two principal, u-u and v-v
and two geometric, a-a and b-b. In a TRACK 2.0 design output,
the „Buckling Calculations‟ displays results for the „v-v‟, „a-a‟ and
„b-b‟ axes. The effective length for the v-v axis, Lvv, is taken as
the LVV parameter or LY * KY, if not specified. The a -a and b-b
axes are determined by which leg of the angle is fixed by the
connection and should be specified using the LEG parameter, see
section 2B6.6 for more information on the LEG parameter. The
effective length in the a-a axis is taken as LY * KY and the
effective length in the b-b axis as LZ * KZ.
The following diagram shows the axes for angles which have been
defined with either an ST or RA specification and is connected by
its longer leg, i.e. a-a axis is parallel to the longer leg.
Local Z (u-u)
Local Y (v-v)
a
a
b
b
Local Z (v-v)
Local Y (u-u)
a
a
b
b
ST angle RA angle
and USER table angles
Section 2B
2-25
2B.2 Analysis Methodology
Elastic analysis method is used to obtain the forces and moments
for design. Analysis is done for the primary and combination
loading conditions provided by the user. The user is allowed
complete flexibility in providing loading specifications and using
appropriate load factors to create necessary loading situations.
Depending upon the analysis requirements, regular stiffness
analysis or P-Delta analysis may be specified. Dynamic analysis
may also be performed and the results combined with static
analysis results.
2B.3 Member Property Specifications
For specification of member properties, the steel section library
available in STAAD may be used. The next section describes the
syntax of commands used to assign properties from the built -in
steel table. Member properties may also be specified using the
User Table facility. For more information on these facilities, refer
to the STAAD Technical Reference Manual.
2B.4 Built-In Steel Section Library
The following information is provided for use when the built -in
steel tables are to be referenced for member property specificati on.
These properties are stored in a database file. If called for, the
properties are also used for member design. Since the shear areas
are built into these tables, shear deformation is always considered
during the analysis of these members.
Almost all BSI steel sections are available for input. A complete
listing of the sections available in the built -in steel section library
may be obtained by using the tools of the graphical user interface.
Steel Design Per BS5950:2000
Section 2B
2-26
Following are the descriptions of different types of section s
available:
Universal Beams, Columns And Piles
All rolled universal beams, columns and pile sections are
available. The following examples illustrate the designation
scheme.
20 TO 30 TA ST UB305X165X54
33 36 TA ST UC356X406X287
100 102 106 TA ST UP305X305X186
Rolled Steel Joists
Joist sections may be specified as they are listed in BSI-80 with
the weight omitted. In those cases where two joists have the same
specifications but different weights, the lighter section should be
specified with an "A" at the end.
10 TO 20 TA ST JO152X127
1 2 TA ST JO127X114A
Channel Sections
All rolled steel channel sections from the BSI table have been
incorporated in STAAD. The designation is similar to that of the
joists. The same designation scheme as in BSI tables may be used
with the weight omitted.
10 TO 15 TA ST CH305X102
55 57 59 61 TA ST CH178X76
Section 2B
2-27
Double Channels
Back to back double channels, with or without spacing between them,
are available. The letter "D" in front of the section name will specify
a double channel, e.g. D CH102X51, D CH203X89 etc.
51 52 53 TA D CH152X89
70 TO 80 TA D CH305X102 SP 5.
(specifies a double channel with a spacing of 5 length units)
Tee Sections
Tee sections are not input by their actual designations, but instead
by referring to the universal beam shapes from which they are cut.
For example,
54 55 56 TA T UB254X102X22
(tee cut from UB254X102X22)
Angles
All equal and unequal angles are available for analysis. Two types
of specifications may be used to describe an angle section, either a
standard, ST specification or reversed angle, RA specification.
Note, however, that only angles specified with an RA specification
can be designed.
The standard angle section is specified as follows:
15 20 25 TA ST UA200X150X18
Steel Design Per BS5950:2000
Section 2B
2-28
This specification may be used when the local STAAD z-axis
corresponds to the V-V axis specified in the steel tables. If the
local STAAD y-axis corresponds to the V-V axis in the tables,
type specification "RA" (reverse angle) may be used.
35 TO 45 TA RA UA200X150X18
Double Angles
Short leg back to back or long leg back to back double angles can
be specified by inputting the word SD or LD, respectively, in front
of the angle size. In case of an equal angle, either LD or SD will
serve the purpose. For example,
14 TO 20 TA LD UA200X200X16 SP 1.5
23 27 TA SD UA80X60X6
"SP" denotes spacing between the individual angle
sections.
Note that if the section is defined from a Double Angle User
Table, then the section properties must be defined with an 11 th
value which defines the radius of gyration about an individual
sections‟ principal v-v axis (See Technical Reference Manual, 5.19
User Steel Table Specification)
Pipes (Circular Hollow Sections)
To designate circular hollow sections from BSI tables, use PIP
followed by the numerical value of diameter and thickness of the
section in mm omitting the decimal section of the value provided for
diameter. The following example will illustrate the designation.
10 15 TA ST PIP213.2
(specifies a 21.3 mm dia. pipe with 3.2 mm wall thickness)
Section 2B
2-29
Circular hollow sections may also be provided by specifying the
outside and inside diameters of the section. For example,
1 TO 9 TA ST PIPE OD 25.0 ID 20.0
(specifies a pipe with outside dia. of 25 and inside dia. of
20 in current length units)
Only code checking and no member selection will be performed if
this type of specification is used.
Tubes (Rectangular or Square Hollow Sections)
Designation of tubes from the BSI steel table is illustrated below:
TUB 400 200 12.5
Example: 15 TO 25 TA ST TUB160808.0
Tubes, like pipes, can also be input by their dimensions (Height,
Width and Thickness) and not by any table designations.
6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5
(a tube that has a height of 8, a width of 6, and a wall
thickness of 0.5 length units)
Note that only code checking and no member selection is
performed for TUBE sections specified this way.
Square/Rectangular shape
Height (mm)
Thickness (mm)
Width (mm)
Steel Design Per BS5950:2000
Section 2B
2-30
2B.5 Member Capacities
The basic measure of capacity of a beam is taken as the plastic
moment of the section. This is a significant departure from the
standard practice followed in BS449, in which the limiting
condition was attainment of yield stress at the extreme fibres of a
given section. With the introduction of the plastic moment as the
basic measure of capacity, careful consideration must be given to
the influence of local buckling on moment capacity. To assist this,
sections are classified as either Class 1, plastic, Class 2, compact,
Class 3, semi-compact or Class 4, slender, which governs the
decision whether to use the plastic or the elastic moment capacity.
The section classification is a function of the geometric properties
of the section. STAAD is capable of determining the section
classification for both hot rolled and built up sections. In addition,
for slender sections, BS5950 recommends the use of a 'stress
reduction factor' to reduce the design strength. This factor is again
a function of the geometry of the section and is automatically
determined by STAAD for use in the design process.
Axial Tension
In members with axial tension, the tensile load must not exceed the
tension capacity of the member. The tension capacity of the
member is calculated on the basis of the effective area as outlined
in Section 4.6 of the code. STAAD calculates the tension capacity
of a given member per this procedure, based on a user supplied net
section factor (NSF-a default value of 1.0 is present but may be
altered by changing the input value - see Table 2B.1), proceeding
with member selection or code check accordingly. BS5950 does
not have any slenderness limitations for tension members.
Compression
Compression members must be designed so that the compression
resistance of the member is greater than the axial compressive
load. Compression resistance is determined accordin g to the
compressive strength, which is a function of the slenderness of the
Section 2B
2-31
gross section, the appropriate design strength and the relevant
strut characteristics. Strut characteristics take into account the
considerable influence residual rolling and welding stresses have
on column behaviour. Based on data collected from extensive
research, it has been determined that sections such as tubes with
low residual stresses and Universal Beams and Columns are of
intermediate performance. It has been found that I -shaped sections
are less sensitive to imperfections when constrained to fail about
an axis parallel to the flanges. These research observations are
incorporated in BS5950 through the use of four strut curves
together with a selection of tables to indicate which curve to use
for a particular case. Compression strength for a particular section
is calculated in STAAD according to the procedure outlined in
Annex C of BS5950 where compression strength is seen to be a
function of the appropriate Robertson constan t ( representing Strut
Curve) corresponding Perry factor, limiting slenderness of the
member and appropriate design strength.
A departure from BS5950:1990, generally compression members
are no longer required to be checked for slenderness limitations,
however, this option can be included by specifying a MAIN
parameter. Note, a slenderness limit of 50 is still applied on
double angles checked as battened struts as per clause 4.7.9.
Axially Loaded Members With Moments
In the case of axially loaded members with moments, the moment
capacity of the member must be calculated about both principal
axes and all axial forces must be taken into account. If the section
is plastic or compact, plastic moment capacities will constitute the
basic moment capacities subject to an elastic limitation. The
purpose of this elastic limitation is to prevent plasticity at working
load. For semi-compact or slender sections, the elastic moment is
used. For plastic or compact sections with high shear loads, the
plastic modulus has to be reduced to accommodate the shear loads.
The STAAD implementation of BS5950 incorporates the procedure
outlined in section 4.2.5 and 4.2.6 to calculate the appropriate
moment capacities of the section.
Steel Design Per BS5950:2000
Section 2B
2-32
For members with axial tension and moment, the interaction
formula as outlined in section 4.8.2 is applied based on effective
tension capacity.
For members with axial compression and moment, two principal
interaction formulae must be satisfied – Cross Section Capacity
check (4.8.3.2) and the Member Buckling Resistance check
(4.8.3.3 ). Three types of approach for the member buckling
resistance check have been outlined in BS5950:2000 - the
simplified approach (4.8.3.3.1), the more exact approach
(4.8.3.3.2) and Annex I1 for stocky members. As noted in the
code, in cases where neither the major axis nor the minor axis
moment approaches zero, the more exact approach may be more
conservative than the simplified approach. It has been found,
however, that this is not always the case and STAAD therefore
performs both checks, comparing the results in order that the more
appropriate criteria can be used.
Additionally the equivalent moment factors, m x my and myx, can be
specified by the user or calculated by the program.
Members subject to biaxial moments in the absence of both tensile
and compressive axial forces are checked using the appropriate
method described above with all axial forces set to zero. STAAD
also carries out cross checks for compression only, which for
compact/plastic sections may be more crit ical. If this is the case,
COMPRESSION will be the critical condition reported despite the
presence of moments.
Shear Load
A member subjected to shear is considered adequate if the shear
capacity of the section is greater than the shear load on the
member. Shear capacity is calculated in STAAD using the
procedure outlined in section 4.2.3, also 4.4.5 and Annex H3 if
appropriate, considering the appropriate shear area for the section
specified.
Section 2B
2-33
Lateral Torsional Buckling
Since plastic moment capacity is the basic moment capacity used
in BS5950, members are likely to experience relatively large
deflections. This effect, coupled with lateral torsional buckling,
may result in severe serviceability limit state. Hence, lateral
torsional buckling must be considered carefully.
The procedure to check for lateral torsional buckling as outlined in
section 4.3 has been incorporated in the STAAD implementation
of BS5950. According to this procedure, for a member subjected to
moments about the major axis, the 'equivalent uniform moment' on
the section must be less than the lateral torsional buckling
resistance moment. For calculation of the buckling resistance
moment, the procedure outlined in Annex B.2 has been
implemented for all sections with the exception of angles. In
Annex B.2., the resistance moment is given as a function of the
elastic critical moment, Perry coefficient, and limiting equivalent
slenderness, which are calculated within the program; and the
equivalent moment factor, mLT, which is determined as a function
of the loading configuration and the nature of the load
(stabilizing, destabilizing, etc).
R. H. S Sections - Additional Provisions
Rectangular Hollow sections are treated in accordance with S.C.I.
recommendations in cases when the plastic axis is in the flange. In
such cases, the following expressions are used to calculate the
reduced plastic moduli:
Srx = (A*A/4(B-t))(1-n) [ 2D(B-t)/A + n-1 ]
for n>= 2t(D-2t)/A
Sry = (A*A/4(D-t))(1-n) [ 2B(D-t)/A + n-1 ]
for n>= 2t(B-2t)/A
Steel Design Per BS5950:2000
Section 2B
2-34
2B.6 Design Parameters
Available design parameters to be used in conjunction with
BS5950 are listed in table 2B.1 along with their default values.
The following items should be noted with respect to their use.
1. (PY – Steel Design Strength )
The design parameter PY should only be used when a uniform
design strength for an entire structure or a portion thereof is
required. Otherwise the value of PY will be set according to
the stipulations of BS5950 table 9 in which the design strength
is seen as a function of cross sectional thickness for a
particular steel grade (SGR parameter) and particular element
considered. Generally speaking this option is not required and
the program should be allowed to ascertain the appropriate
value.
2. (UNL, LY and LZ - Relevant Effective Length)
The values supplied for UNL, LY and LZ should be real
numbers greater than zero in current units of length. They are
supplied along with or instead of UNF, KY and KZ (which are
factors, not lengths) to define lateral torsional buckling and
compression effective lengths respectively. Please note that
both UNL or UNF and LY or KY values are required even
though they are often the same values. The former relates to
compression flange restraint for lateral torsional buckling
while the latter is the unrestrained buckling length for
compression checks.
3. (TRACK - Control of Output Formats )
When the TRACK parameter is set to 0.0, 1.0 or 2.0, member
capacities will be printed in design related output (code check
or member selection) in kilonewtons per square metre.
TRACK 4.0 causes the design to carry out a deflection check,
usually with a different load list to the main code check. The
members that are to be checked must have the parameters,
DFF, DJ1 and DJ2 set.
Section 2B
2-35
An example of each TRACK setting follows:-
TRACK 0.0 OUTPUT STAAD CODE CHECKING - (BSI )
--------------------------- ******************************
ALL UNITS ARE - KNS METR (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=================================================================
1 ST UB686X254X170 PASS BS-4.8.3.2 0.036 3
86.72 C 0.00 -22.02 4.50
---------------------------------
TRACK 1.0 OUTPUT STAAD CODE CHECKING - (BSI )
--------------------------- ******************************
ALL UNITS ARE - KNS METR (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=================================================================
1 ST UB686X254X170 PASS BS-4.8.3.2 0.036 3
86.72 C 0.00 -22.02 4.50
CALCULATED CAPACITIES FOR MEMB 1 UNIT - kN,m SECTION CLASS 4
MCZ= 1141.9 MCY= 120.4 PC= 3451.5 PT= 5739.9 MB= 1084.1 PV= 1597.5
BUCKLING CO-EFFICIENTS m AND n : m = 1.000 n = 1.000
PZ= 5739.90 FX/PZ = 0.02 MRZ= 1141.9 MRY= 120.4
Steel Design Per BS5950:2000
Section 2B
2-36
TRACK 2.0 OUTPUT STAAD.Pro CODE CHECKING - (BSI )
--------------------------- ***************************
ALL UNITS ARE - KN METE (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
===================================================================
1 ST UB533X210X92 PASS BS-4.3.6 0.902 100
0.00 0.00 585.41 0.00
===================================================================
MATERIAL DATA
Grade of steel = S 275
Modulus of elasticity = 205 kN/mm2
Design Strength (py) = 275 N/mm2
SECTION PROPERTIES (units - cm)
Member Length = 325.00
Gross Area = 117.00 Net Area = 117.00
Major axis Minor axis
Moment of inertia : 55229.996 2389.000
Plastic modulus : 2360.000 356.000
Elastic modulus : 2072.031 228.285
Shear Area : 58.771 53.843
DESIGN DATA (units - kN,m) BS5950-1/2000
Section Class : PLASTIC
Major axis Minor axis
Moment Capacity : 649.0 94.2
Reduced Moment Capacity : 649.0 97.9
Shear Capacity : 969.7 888.4
BUCKLING CALCULATIONS (units - kN,m)
(axis nomenclature as per design code)
LTB Moment Capacity (kNm) and LTB Length (m): 649.00, 0.001
LTB Coefficients & Associated Moments (kNm):
Section 2B
2-37
mLT = 1.00 : mx = 1.00 : my = 1.00 : myx = 1.00
Mlt = 585.41 : Mx = 585.41 : My = 0.00 : My = 0.00
CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m):
CLAUSE RATIO LOAD FX VY VZ MZ MY
BS-4.2.3-(Y) 0.329 100 - 292.3 - - -
BS-4.3.6 0.902 100 - 292.3 - 585.4 -
BS-4.8.3.2 0.814 100 0.0 68.0 0.0 585.4 0.0
BS-4.8.3.3.1 1.027 100 0.0 - - 585.4 0.0
BS-4.8.3.3.2 0.902 100 0.0 - - 585.4 0.0
Annex I.1 0.902 100 0.0 - - 585.4 0.0
Torsion and deflections have not been considered in the design.
_________________________
4. (MX, MY, MYX and MLT – Equivalent Moment Factors)
The values for the equivalent moment factors can either be
specified directly by the user as a positive value between 0.4
and 1.0 for MX, MY and MYX and 0.44 and 1.0 for MLT.
The program can be used to calculate the values for the
equivalent moment factors by defining the design member with
a GROUP command (see the Technical Reference Manual
section 5.16 Listing of Members/Elements/Joints by
Specification of GROUPS). The nodes along the beam can
then be defined as the location of restraint points with J
settings.
Additionally for the MLT parameter, the joint can be defined
as having the upper flange restrained (positive local Y) with
the a U setting or the lower flange restrained (negative local
Y) with a L setting.
Steel Design Per BS5950:2000
Section 2B
2-38
For example, consider a series of 5 beam elements as a single
continuous member as shown below:
To enable the steel design, the beam needs to be defined as a
group, called MainBeam:
START GROUP DEFINITION
MEMBER
_MainBeam 11 2 38 12 3
END GROUP DEFINITION
Note that this can be done in the GUI by selecting the beams and
clicking on the menu option:
„Tools | Create New Group…‟
Therefore, this 5 beam member has 6 joints such that: -
Joint 1 = Node 3
Joint 2 = Node 1
Joint 3 = Node 33
Section 2B
2-39
Joint 4 = Node 14
Joint 5 = Node 7
Joint 6 = Node 2
a. Consider MX, MY and MYX
Say that this member has been restrained in its‟ major axis
(local Y) only at the ends. In the minor axis (local Z) it has
been restrained at the ends and also at node number 33 (joint
3). For local flexural buckling, it has only been restrained at
its ends. Hence:-
For the major axis, local Y axis:-
MX _MainBeam J1 J6
For the minor axis, local Z axis:-
MY _ MainBeam J1 J3 J6
For the lateral flexural buckling, local X axis: -
MYX _ MainBeam J1 J6
b. Consider MLT
Say that this member has been restrained at its‟ ends against
lateral torsional buckling and the top flange has been
restrained at node number 33 (joint 3) and only the lower
flange at node number 7, (joint 5). Hence:-
MLT _MainBeam J1 T3 L5 J6
To split the beam into two buckling lengths for Ly at joint
14:-
MY _groupname J1 J4 J6
Steel Design Per BS5950:2000
Section 2B
2-40
5. (LEG - Table 25 BS5950 for Fastener Control)
The slenderness of single and double angle, channel and tee
sections are specified in BS 5950 table 25 depending on the
connection provided at the end of the member. To define the
appropriate connection, a LEG parameter should be assigned
to the member.
The following table indicates the value of the LEG parameter
required to match the BS5950 connection definition: -
Clause LEG
4.7.10.2
Single Angle
(a) - 2 bolts short leg 1.0
long leg 3.0
(b) - 1 bolt short leg 0.0
long leg 2.0
4.7.10.3
Double Angle
(a) - 2 bolts short leg 3.0
long leg 7.0
(b) - 1 bolt short leg 2.0
long leg 6.0
(c) - 2 bolts long leg 1.0
short leg 5.0
(d) - 1 bolt long leg 0.0
short leg 4.0
4.7.10.4
Channels
(a) - 2 or more rows of bolts 1.0
(b) - 1 row of bolts 0.0
4.7.10.5
Tee Sections
(a) - 2 or more rows of bolts 1.0
(b) - 1 row of bolts 0.0
For single angles, the slenderness is calculated for the
geometric axes, a-a and b-b as well as the weak v-v axis. The
effective lengths of the geometric axes are defined as:-
La = KY * KY
Lb = KZ * LZ
Section 2B
2-41
The slenderness calculated for the v-v axis is then used to
calculate the compression strength p c for the weaker principal
axis (z-z for ST angles or y-y for RA specified angles). The
maximum slenderness of the a-a and b-b axes is used to
calculate the compression strength p c for the stronger principal
axis.
Alternatively for single angles where the connection is not
known or Table 25 is not appropriate, by setting the LEG
parameter to 10, slenderness is calculated for the two principal
axes y-y and z-z only. The LVV parameter is not used.
For double angles, the LVV parameter is available to comply
with note 5 in table 25. In addition, if using double angles from
user tables, (Technical Reference Manual section 5.19) an
eleventh value, rvv, should be supplied at the end of the ten
existing values corresponding to the radius of gyration of the
single angle making up the pair.
6. (SWAY – Sway Loadcase)
This parameter is used to specify a load case that is to be
treated as a sway load case in the context of clause 4.8.3.3.4.
This load case would be set up to represent the “kampMs”
mentioned in this clause and the steel design module would add
the forces from this load case to the forces of the other load
case it is designed for.
Note that the load case specified with this parameter will not be
designed as a separate load case. The following is the correct
syntax for the parameter:-
SWAY
(load case number)
ALL
MEMBER (member list)
_(group name)
e.g.
SWAY 5 MEM 1 to 10
SWAY 6 _MainBeams
Steel Design Per BS5950:2000
Section 2B
2-42
Table 2B.1 - British Steel Design – BS5950:2000 - Parameters
Parameter
Name
Default
Value
Description
CODE BS5950 Design Code to follow. See section 5.47.1 of the Technical Reference Manual.
SGR 0.0 Steel Grade per BS4360 0.0 = Grade S 275 1.0 = Grade S 355 2.0 = Grade S 460 3.0 = As per GB 1591 – 16 Mn
AD Depth at end/2
Distance between the reference axis and the axis of restraint. See G.2.3
PY * Set according to steel grade
(SGR)
Design strength of steel
KY 1.0 K factor value in local y - axis. Usually, this is the minor axis.
KZ 1.0 K factor value in local z - axis. Usually, this is the major axis.
LY * Member Length
Length in local y - axis (current units) to calculate (KY)(LY)/Ryy slenderness ratio.
LZ * Member Length
Length in local z - axis (current units) to calculate (KZ)(LZ)/Rzz slenderness ratio.
UNF 1.0 Factor applied to unsupported length for Lateral Torsional Buckling effective length per section 4.3.6.7 of BS5950.
UNL * Member Length
Unsupported Length for calculating Lateral Torsional Buckling resistance moment section 4.3.6.7 of BS5950.
NSF 1.0 Net section factor for tension members.
SBLT 0.0 Identify Section type for section classification 0.0 = Rolled Section 1.0 = Built up Section 2.0 = Cold formed section
MAIN 0.0 Slenderness limit for members with compression forces, effective length/ radius of gyration, for a given axis:- 0.0 = Slenderness not performed. 1.0 = Main structural member (180) 2.0 = Secondary member. (250) 3.0 = Bracing etc (350)
Section 2B
2-43
Table 2B.1 - British Steel Design – BS5950:2000 - Parameters
Parameter
Name
Default
Value
Description
TRACK 0.0 0.0 = Suppress all member capacity info. 1.0 = Print all member capacities. 2.0 = Print detailed design sheet. 4.0 = Deflection Check (separate check to main select /
check code)
BEAM 3.0 0.0 = Design only for end moments or those locations specified by the SECTION command.
1.0 = Calculate forces and moments at 12th points along the member. Establish the location where Mz is the maximum. Use the forces and moments at that location. Clause checks at one location.
2.0 = Same as BEAM = 1.0 but additional checks are carried out for each end.
3.0 = Calculate moments at 12th points along the member. Clause checks at each location including the ends of the member.
LEG 0.0 Valid range from 0 – 7 and 10. See section 2B.6.5 for details. The values correspond to table 25 of BS5950 for fastener conditions.
LVV * Maximum of Lyy and Lzz
(Lyy is a term used
by BS5950)
Used in conjunction with LEG for Lvv as per BS5950 table 25 for double angles, note 5.
CB 1.0 1.0 = BS5950 per clause B.2.5 (continuous) to calculate Mb.
2.0 = To calculate Mbs (simple) as per Clause 4.7.7 as opposed to Mb.
DFF None (Mandatory
for deflection check,
TRACK 4.0)
"Deflection Length" / Maxm. allowable local deflection
DJ1 Start Joint of member
Joint No. denoting starting point for calculation of "Deflection Length" (See Note 1)
DJ2 End Joint of member
Joint No. denoting end point for calculation of "Deflection Length" (See Note 1)
Steel Design Per BS5950:2000
Section 2B
2-44
Table 2B.1 - British Steel Design – BS5950:2000 - Parameters
Parameter
Name
Default
Value
Description
CAN 0 0 = deflection check based on the principle that maximum deflection occurs within the span between DJ1 and DJ2.
1 = deflection check based on the principle that maximum deflection is of the cantilever type (see note below)
ESTIFF 0.0 Clauses 4.8.3.3.1 and 4.8.3.3.2 0.0 = Fail ratio uses MIN of 4.8.3.3.1, 4.8.3.3.2. and
Annex I1 checks. 1.0 = Fail ratio uses MAX of 4.8.3.3.1, 4.8.3.3.2. and
Annex I1 checks. WELD 1.0 closed
2.0 open
Weld Type, see AISC steel design 1.0 = Closed sections. Welding on one side only (except
for webs of wide flange and tee sections) 2.0 = Open sections. Welding on both sides (except
pipes and tubes) TB 0.0 0.0 = Elastic stress analysis
1.0 = Plastic stress analysis PNL * 0.0 Transverse stiffener spacing („a‟ in Annex H1)
0.0 = Infinity Any other value used in the calculations.
SAME** 0.0 Controls the sections to try during a SELECT process.
0.0 = Try every section of the same type as original 1.0 = Try only those sections with a similar name as
original, e.g. if the original is an HEA 100, then only HEA sections will be selected, even if there are HEM‟s in the same table.
MX 1.0 Equivalent moment factor for major axis flexural buckling as defined in clause 4.8.3.3.4
MY 1.0 Equivalent moment factor for minor axis flexural buckling as defined in clause 4.8.3.3.4
MYX 1.0 Equivalent moment factor for minor axis lateral flexural buckling as defined in clause 4.8.3.3.4
MLT 1.0 Equivalent moment factor for lateral torsional buckling as defined in clause 4.8.3.3.4
SWAY none Specifies a load case number to provide the sway loading forces in clause 4.8.3.3.4 (See additional notes)
DMAX * 100.0cm Maximum allowable depth
Section 2B
2-45
Table 2B.1 British Steel Design – BS5950:2000 Parameters
Parameter
Name
Default
Value
Description
DMIN * 0.0cm Minimum allowable depth
RATIO 1.0 Permissible ratio of the actual capacities.
Note: Once a parameter is specified, its value stays at that specified
number till it is specified again. This is the way STAAD works for all
codes.
* current units must be considered. **For angles, if the original section is an equal angle, then the selected section will be an equal angle and vice versa for unequal angles. (note there was an NT parameter in STAAD.Pro 2005 build 1003 which is now automatically calculated during the design as it is load case dependant)
NOTES:
1) When performing the deflection check, the user can choose
between two methods. The first method, defined by a value 0 for
the CAN parameter, is based on the local displacement. Local
displacement is described in section 5.43 of this manual.
If the CAN parameter is set to 1, the check will be based on
cantilever style deflection. Let (DX1, DY1, DZ1) represent the
nodal displacements (in global axes) at the node defined by DJ1
(or in the absence of DJ1, the start node of the member). Similarly,
(DX2, DY2, DZ2) represent the deflection values at DJ2 or the end
node of the member.
Compute Delta = SQRT((DX2-DX1)**2 + (DY2-DY1)**2 +
(DZ2-DZ1)**2)
Compute Length = distance between DJ1 & DJ2 or, between start
node and end node, as the case may be.
Then, if CAN is specified a value 1, dff = L/Delta
Ratio due to deflection = DFF/dff
Steel Design Per BS5950:2000
Section 2B
2-46
2) If CAN = 0, deflection length is defined as the length that is used
for calculation of local deflections within a member. It may be
noted that for most cases the “Deflection Length” will be equal to
the length of the member. However, in some situations, the
“Deflection Length” may be different. For example, refer to the
figure below where a beam has been modeled using four joints and
three members. The “Deflection Length” for a ll three members
will be equal to the total length of the beam in this case. The
parameters DJ1 and DJ2 should be used to model this situation.
Also the straight line joining DJ1 and DJ2 is used as the reference
line from which local deflections are measured. Thus, for all three
members here, DJ1 should be "1" and DJ2 should be "4".
3) If DJ1 and DJ2 are not used, "Deflection Length" will default to
the member length and local deflections will be measured from
original member line.
4) It is important to note that unless a DFF value is specified,
STAAD will not perform a deflection check. This is in accordance
with the fact that there is no default value for DFF (see Table 2.1).
5) The above parameters may be used in conjunction with other
available parameters for steel design.
2B.7 Design Operations
STAAD contains a broad set of facilities for the design of
structural members as individual components of an analysed
structure. The member design facilities provide the user with the
ability to carry out a number of different design operations. These
facilities may be used selectively in accordance with the
requirements of the design problem.
Section 2B
2-47
The operations to perform a design are:
Specify the load cases to be considered in the design; the
default is all load cases.
Specify design parameter values, if different from the default
values.
Specify whether to perform code checking or member selection
along with the list of members.
These operations may be repeated by the user any number of times
depending upon the design requirements.
2B.8 Code Checking
The purpose of code checking is to ascertain whether the provided
section properties of the members are adequate. The adequacy is
checked as per BS5950. Code checking is done using the forces
and moments at specific sections of the members. If no sections
are specified, the program uses the start and end forces for code
checking.
When code checking is selected, the program calculates and prints
whether the members have passed or failed the checks; the critical
condition of BS5950 code (like any of the BS5950 specifications
for compression, tension, shear, etc.); the value of the ratio of the
critical condition (overstressed for value more than 1.0 or any
other specified RATIO value); the governing load case, and the
location (distance from the start of the member of forces in the
member where the critical condition occurs).
Code checking can be done with any type of steel section listed in
Section 2B.4 of the STAAD Technical Reference Manual or any of
the user defined sections in section 5.19 with two exceptions;
GENERAL and ISECTION. In BS5950, these will not be considered
for design along with PRISMATIC sections, which are also not
acceptable.
Steel Design Per BS5950:2000
Section 2B
2-48
2B.9 Member Selection
STAAD is capable of performing design operations on specified
members. Once an analysis has been performed, the program can
select the most economical section, i.e. the lightest section, which
fulfills the code requirements for the specified member. The
section selected will be of the same type section as originally
designated for the member being designed. Member selection can
also be constrained by the parameters DMAX and DMIN, which
limits the maximum and minimum depth of the members.
Member selection can be performed with all the types of steel
sections with the same limitations as defined in section 2B.8 -
CODE CHECKING.
Selection of members, whose properties are originally input from a
user created table, will be limited to sections in the user table.
Member selection cannot be performed on members whose section
properties are input as prismatic or as above limitations for code
checking.
Section 2B
2-49
2B.10 Tabulated Results of Steel Design
For code checking or member selection, the program produces the
results in a tabulated fashion. The items in the output table are
explained as follows:
a) MEMBER refers to the member number for which the
design is performed.
b) TABLE refers to steel section name, which has been
checked against the steel code or has been
selected.
c) RESULTS prints whether the member has PASSED or
FAILED. If the RESULT is FAIL, there will
be an asterisk (*) mark on front of the
member.
d) CRITICAL COND refers to the section of the BS5950 code
which governs the design.
e) RATIO prints the ratio of the actual stresses to
allowable stresses for the critical condition.
Normally a value of 1.0 or less will mean
the member has passed.
f) LOADING provides the load case number, which
governed the design.
g) FX, MY, and MZ provide the axial force, moment in local Y-
axis and the moment in local z-axis
respectively. Although STAAD does
consider all the member forces and moments
(except torsion) to perform design, only FX,
MY and MZ are printed since they are the
ones which are of interest, in most cases.
Steel Design Per BS5950:2000
Section 2B
2-50
h) LOCATION specifies the actual distance from the start
of the member to the section where design
forces govern.
i) TRACK If the parameter TRACK is set to 1.0, the
program will block out part of the table and
will print the allowable bending capacities
in compression (MCY & MCZ) and reduced
moment capacities (MRY & MRZ),
allowable axial capacity in compression
(PC) and tension (PT) and shear capacity
(PV). TRACK 2.0 will produce the design
results as shown in section 2B.9.
2B.11 Plate Girders
Sections will be considered for the Plate Girder checks (BS 5950
Section 4.4) if d/t > 70 for „rolled sections‟ or d/t >62 for
„welded sections‟. The parameter SBLT should be used to identify
sections as rolled or welded; see the parameter list for more
information.
If the plate girder has intermediate stiffeners, the spacing is set
with the PNL parameter. These are then used to check against the
code clauses „4.4.3.2 - Minimum web thickness for serviceability‟
and „4.4.3.3 - Minimum web thickness to avoid compression
flange buckling‟. The following printout is then included if a
TRACK 2.0 output is selected:-
Shear Buckling check is required: Vb = 1070 kN : qw = 118 N/mm2
d = 900 mm : t = 10 mm : a = 200 mm : pyf = 275 N/mm2
BS-4.4.3.2 status = PASS : BS-4.4.3.3 status = PASS
The section is then checked for shear buckling resistance using
clause „4.4.5.2 - Simplified method‟ and the result is included in
the ratio checks.
Section 2B
2-51
2B.12 Composite Sections
Sections that have been defined as acting compositely with a
concrete flange either from a standard database section using the
CM option, or from a modified user WIDE FLANGE database with
the additional composite parameters, cannot be designed with
BS5950:2000.
2B.13 Design of Tapered Beams
Design Procedure
Sections will be checked as tapered members provided that are
defined either as a Tapered I section, e.g.
UNIT CM
MEMBER PROPERTY
1 TO 5 TAPERED 100 2.5 75 25 4 25 4
or from a USER table, e.g.
START USER TABLE
TABLE 1
UNIT CM
ISECTION
1000mm_TAPER
100 2.5 75 25 4 25 4 0 0 0
750mm_TAPER
75 2.5 50 25 4 25 4 0 0 0
END
Steel Design Per BS5950:2000
Section 2B
2-52
The user must specify the effective length of unrestrained
compression flange using the parameter UNL.
The program compares the resistance of members with the applied
load effects, in accordance with BS 5950-1:2000. Code checking is
carried out for locations specified by the user via the SECTION
command or the BEAM parameter. The results are presented in a
form of a PASS/FAIL identifier and a RATIO of load effect to
resistance for each member checked. The user may choose the
degree of detail in the output data by setting the TRACK
parameter.
The beam is designed is designed as other wide flange beams apart
from the Lateral Torsional Buckling check which is replaced by
the Annex G.2.2. check.
Design Equations
A beam defined with tapered properties as defined above will be
checked as a regular wide flange (e.g. UB or UC), except that the
following is used in place of clause 4.3.6, the lateral torsional
buckling check.
Check Moment for Taper Members as per clause G.2.2
The following criterion is checked at each defined check position
in the length of the member defined by the BEAM parameter.
)/1( ccbixi PFMM
Where
Fc is the longitudinal compression at the check location ;
Mbi is the buckling resistance moment Mb from 4.3.6 for an
equivalent slenderness TB, see G.2.4.2, based on the
appropriate modulus S, Seff, Z or Zeff of the cross-section
at the point i considered;
Mxi is the moment about the major axis acting at the point i
considered;
Section 2B
2-53
Pc is the compression resistance from 4.7.4 for a slenderness
TC, see G.2.3, based on the properties of the minimum
depth of cross-section within the segment length Ly.
G.2.3 Slenderness TC
TC = y
In which:
5.0
22
2
)/(05.0)/2(1
)/2(1
xha
hay
s
s
= Ly/ry
Where
a is the distance between the reference axis and the axis of
restraint,
hs is the distance between the shear centers of the flanges;
Ly is the length of the segment;
ry is the radius of gyration for buckling about the minor axis;
x torsional index
G.2.4.2 Equivalent slenderness TB for Taper members
TB = cntt
In which for a two-flange haunch:
5.0
22 )/(05.0)/2(1
/4
xha
ha
s
s
t
Where
C is the taper factor, see G.2.5;
Steel Design Per BS5950:2000
Section 2B
2-54
G.2.5 Taper factor
For an I-section with D ≥ 1.2B and x ≥ 20 the taper factor c
should be obtained as follows:
c = 1 +
3/2
min
max 19
3
D
D
x
Dmax is the maximum depth of cross-section within the
length Ly, see Figure G.3;
Dmin is the minimum depth of cross-section within the
length Ly, see Figure G.3;
x is the torsional index of the minimum depth cross -
section, see 4.3.6.8
Otherwise c is taken as 1.0
2-55
Steel Design Per BS5950:1990
2B1.1 General
This code has been withdrawn by the British Standards, but has
been retained in STAAD.Pro for comparative purposes only.
The design philosophy embodied in BS5950 is built around the
concept of limit state design, used today in most modern steel
design codes. Structures are designed and proportioned taking into
consideration the limit states at which they become unfit for their
intended use. Two major categories of limit state are recognized -
serviceability and ultimate. The primary considerations in ultimate
limit state design are strength and stability while that in
serviceability limit state is deflection. Appropriate safety factors
are used so that the chances of limits being surpassed are
acceptably remote.
In the STAAD implementation of BS5950, members are
proportioned to resist the design loads without exceeding the limit
states of strength and stability. Accordingly, the most economic
section is selected on the basis of the least weight criteria. This
procedure is controlled by the designer in specification of
allowable member depths, desired sect ion type or other such
parameters. The code checking portion of the program checks that
code requirements for each selected section are met and identifies
the governing criteria.
The complete B.S.C. steel tables for both hot rolled and hollow
sections are built into the program for use in specifying member
properties as well as for the actual design process. See section
2B.4 for information regarding the referencing of these sections.
In addition to universal beams, columns, joists, piles, channels,
Section 2B1
Steel Design Per BS5950:1990
Section 2B1
2-56
tees, composite sections, beams with cover plates, pipes, tubes and
angles, there is a provision for user provided tables.
2B1.2 Analysis Methodology
Elastic analysis method is used to obtain the forces and moments
for design. Analysis is done for the primary and combination
loading conditions provided by the user. The user is allowed
complete flexibility in providing loading specifications and using
appropriate load factors to create necessary loading situations.
Depending upon the analysis requirements, regular stiffness
analysis or P-Delta analysis may be specified. Dynamic analysis
may also be performed and the results combined with static
analysis results.
2B1.3 Member Property Specifications
For specification of member properties, the steel section li brary
available in STAAD may be used. The next section describes the
syntax of commands used to assign properties from the built -in
steel table. Members properties may also be specified using the
User Table facility. For more information on these facilities, refer
to the STAAD Technical Reference Manual.
2B1.4 Built-In Steel Section Library
The following information is provided for use when the built -in
steel tables are to be referenced for member property specification.
These properties are stored in a database file. If called for, the
properties are also used for member design. Since the shear areas
are built into these tables, shear deformation is always considered
during the analysis of these members.
Almost all BSI steel sections are available for input. A complete
listing of the sections available in the built -in steel section library
may be obtained by using the tools of the graphical user interface.
Section 2B1
2-57
Following are the descriptions of different types of sections
available:
Universal Beams, Columns And Piles
All rolled universal beams, columns and pile sections are
available. The following examples illustrate the designation
scheme.
20 TO 30 TA ST UB305X165X54
33 36 TA ST UC356X406X287
100 102 106 TA ST UP305X305X186
Rolled Steel Joists
Joist sections may be specified as they are listed in BSI-80 with
the weight omitted. In those cases where two joists have the same
specifications but different weights, the lighter section should be
specified with an "A" at the end.
10 TO 20 TA ST JO152X127
1 2 TA ST JO127X114A
Channel Sections
All rolled steel channel sections from the BSI table have been
incorporated in STAAD. The designation is similar to that of the
joists. The same designation scheme as in BSI tables may be used
with the weight omitted.
10 TO 15 TA ST CH305X102
55 57 59 61 TA ST CH178X76
Double Channels
Back to back double channels, with or without spacing between them,
are available. The letter "D" in front of the section name will specify
a double channel, e.g. D CH102X51, D CH203X89 etc.
Steel Design Per BS5950:1990
Section 2B1
2-58
51 52 53 TA D CH152X89
70 TO 80 TA D CH305X102 SP 5.
(specifies a double channel with a spacing of 5 length units)
Tee Sections
Tee sections are not input by their actual designations, but instead
by referring to the universal beam shapes from which they are cut.
For example,
54 55 56 TA T UB254X102X22 (tee cut from
UB254X102X22)
Angles
All equal and unequal angles are available for input. Two types of
specifications may be used to describe an angle. The standard
angle section is specified as follows:
15 20 25 TA ST UA200X150X18
This specification may be used when the local STAAD z-axis
corresponds to the V-V axis specified in the steel tables. If the
local STAAD y-axis corresponds to the V-V axis in the tables,
type specification "RA" (reverse angle) may be used.
35 TO 45 TA RA UA200X150X18
Double Angles
Short leg back to back or long leg back to back double angles can
be specified by inputting the word SD or LD, respectively, in front
of the angle size. In case of an equal angle, either LD or SD will
serve the purpose. For example,
Section 2B1
2-59
14 TO 20 TA LD UA200X200X16 SP 1.5
23 27 TA SD UA80X60X6
"SP" denotes spacing between the individual angle
sections.
Pipes (Circular Hollow Sections)
To designate circular hollow sections from BSI tables, use PIP
followed by the numerical value of diameter and thickness of the
section in mm omitting the decimal section of the value provided for
diameter. The following example will illustrate the designation.
10 15 TA ST PIP213.2 (specifies a 21.3 mm dia. pipe with 3.2
mm wall thickness)
Circular hollow sections may also be provided by specifying the
outside and inside diameters of the section. For example,
1 TO 9 TA ST PIPE OD 25.0 ID 20.0 (specifies a pipe with
outside dia. of 25 and inside dia. of 20 in current length
units)
Only code checking and no member selection will be performed if
this type of specification is used.
Tubes (Rectangular or Square Hollow Sections)
Designation of tubes from the BSI steel table is illustrated below:
TUB 400 200 12.5
Tube symbol
Height (mm)
Thickness (mm)
Width (mm)
Steel Design Per BS5950:1990
Section 2B1
2-60
Example: 15 TO 25 TA ST TUB160808.0
Tubes, like pipes, can also be input by their dimensions (Height,
Width and Thickness) and not by any table designations.
6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 is a tube that has a height
of 8, a width of 6, and a wall thickness of 0.5 length units.
Note that only code checking and no member selection is
performed for TUBE sections specified this way.
2B1.5 Member Capacities
The basic measure of capacity of a beam is taken as the plastic
moment of the section. This is a significant departure from the
standard practice followed in BS449, in which the limiting
condition was attainment of yield stress at the extreme fibres of a
given section. With the introduction of the plastic moment as the
basic measure of capacity, careful consideration must be given to
the influence of local buckling on moment capacity. To assist this,
sections are classified as either plastic, compact, semi-compact or
slender, which governs the decision whether to use the plastic or
the elastic moment capacity. The section classification is a
function of the geometric properties of the section. STAAD is
capable of determining the section classification for both hot
rolled and built up sections. In addition, for slender sections,
BS5950 recommends the use of a 'stress reduction factor' to reduce
the design strength. This factor is again a function of the geometry
of the section and is automatically determined by STAAD for use
in the design process.
Axial Tension
In members with axial tension, the tensile load must not exceed the
tension capacity of the member. The tension capacity of the
member is calculated on the basis of the effective area as outlined
Section 2B1
2-61
in Section 4.6 of the code. STAAD calculates the tension capacity
of a given member per this procedure, based on a user supplied net
section factor (NSF-a default value of 1.0 is present but may be
altered by changing the input value - see Table 2B.1 ), proceeding
with member selection or code check accordingly. BS5950 does
not have any slenderness limitations for tension members.
Compression
Compression members must be designed so that the compression
resistance of the member is greater than the axial compressive
load. Compression resistance is determined according to the
compressive strength which is a function of the slenderness of the
gross section, the appropriate design strength and the relevant strut
characteristics. Strut characteristics take into account the
considerable influence residual rolling and welding stresses have
on column behaviour. Based on data collected from extensive
research, it has been determined that sections such as tubes with
low residual stresses and Universal Beams and Columns are of
intermediate performance. It has been found that I -shaped sections
are less sensitive to imperfections when constrained to fail about
an axis parallel to the flanges. These research observations are
incorporated in BS5950 through the use of four strut curves
together with a selection of tables to indicate which curve to use
for a particular case. Compression strength for a particular section
is calculated in STAAD according to the procedure outlined in
Appendix C of BS5950 where compression strength is seen to be a
function of the appropriate Robertson constant (representing Strut
Curve) corresponding Perry factor, limiting slenderness of the
member and appropriate design strength.
In addition to the compression resistance criteria, compression
members are required to satisfy slenderness limitations which are a
function of the nature of the use of the member (main load
resisting component, bracing member etc). In both the member
selection and the code checking process, STAAD immediately
does a slenderness check on appropriate members before
continuing with the other procedures for determining the adequacy
of a given member.
Steel Design Per BS5950:1990
Section 2B1
2-62
Axially Loaded Members With Moments
In the case of axially loaded members with moments, the moment
capacity of the member must be calculated about both axes and all
axial forces must be taken into account . If the section is plastic or
compact, plastic moment capacities will constitute the basic
moment capacities subject to an elastic limitation. The purpose of
this elastic limitation is to prevent plasticity at working load. For
semi-compact or slender sections, the elastic moment is used. For
plastic or compact sections with high shear loads, the plastic
modulus has to be reduced to accommodate the shear loads. The
STAAD implementation of BS5950 incorporates the procedure
outlined in section 4.2.5 and 4.2.6 to calculate the appropriate
moment capacities of the section.
For members with axial tension and moment, the interaction
formula as outlined in section 4.8.2 is applied based on effective
tension capacity.
For members with axial compression and moment , two principal
interaction formulae must be satisfied - local capacity check
(4.8.3.2) and overall buckling check (section 4.8.3.3). Two types
of approach for the overall buckling check have been outlined in
BS5950 - the simplified approach and the more exact approach. As
noted in the code, in cases where neither the major axis nor the
minor axis moment approaches zero, the more exact approach may
be more conservative than the simplified approach. It has been
found, however, that this is not always the case and STAAD
therefore performs both checks, comparing the results in order that
the more appropriate criteria be used. Members subject to biaxial
moments in the absence of both tensile and compressive axial
forces are checked using the appropriate method described above
with all axial forces set to zero. STAAD also carries out cross
checks for compression only, which for compact/plastic sections
may be more critical. If this is the case, COMPRESSION will be
the critical condition reported despite the presen ce of moments.
Section 2B1
2-63
Shear Load
A member subjected to shear is considered adequate if the shear
capacity of the section is greater than the shear load on the
member. Shear capacity is calculated in STAAD using the
procedure outlined in section 4.2.3 and considering the appropriate
shear area for the section specified.
Lateral Torsional Buckling
Since plastic moment capacity is the basic moment capacity used
in BS5950, members are likely to experience relatively large
deflections. This effect, coupled with la teral torsional buckling,
may result in severe serviceability limit state. Hence, lateral
torsional buckling must be considered carefully.
The procedure to check for lateral torsional buckling as outlined in
section 4.3 has been incorporated in the STAAD implementation
of BS5950. According to this procedure, for a member subjected to
moments about the major axis, the 'equivalent uniform moment' on
the section must be less than the lateral torsional buckling
resistance moment. For calculation of the bucklin g resistance
moment, the procedure outlined in Appendix B.2 has been
implemented for all sections with the exception of angles. In
Appendix B.2., the resistance moment is given as a function of the
elastic critical moment, Perry coefficient, and limiting equivalent
slenderness, which are calculated within the program; and the
equivalent moment factor, m, and slenderness correction factor, n,
which are determined as a function of the loading configuration
and the nature of the load ( stabilizing, destabilizing, etc ).
The user is allowed to control these values through the parameters
CMM & CMN. If CMM is set to -1, the program automatically
calculates the coefficient 'm'. Similarly parameter CMN may be
used for the calculation of coefficient 'n'. BS5950 recommends the
use of tables 15 & 16 for the calculation of coefficient 'n'. The
parameter CMN may be set to -1 or -2 to instruct the program to
obtain coefficient 'n' from table 15 or 16 respectively. If a positive
value is provided for either CMN or CMM, the program will use
this value directly in calculations. The default value for each of
Steel Design Per BS5950:1990
Section 2B1
2-64
these parameters is 1.0 as shown in table 2B.1 of this document. It
may be noted that BS5950 recommends the use of either 'm' or 'n'
in lateral torsional buckling calculat ions. If both 'm' and 'n' are set
to values less than 1 in error, the program will always reset CMN
to 1 and over-ride the provided value. The following table
illustrates the use of parameters 'm' and 'n'.
PARAMETER VALUE STAAD ACTION
CMM ANY POSITIVE Direct use of this value in VALUE calculations. -1 Program calculates 'm' per BS5950 -2 Calculate „m‟ for both axes CMN ANY POSITIVE Direct use of this value in VALUE calculations. -1 Program calculates 'n' per BS5950 - Table 15 -2 Program calculates 'n' per BS5950 - Table 16
IMPORTANT NOTE:
Note that if negative value options are chosen, lateral restraints
should be modelled by nodes and the section command
incorporated to find Mo. Failure to use the SECTION 0.5
command will cause the program to reset CMN to 1.0 and over -
ride any value that may have been provided. In requesting 'n' to be
calculated by the program by using a negative CMN value, the
member properties must be British ( or British combined with user
table sections). If other profiles such as European are being used
then 'n' values are reset conservatively to 1.0 by the program. In
the case of angles, section 4.3.8 of the code is followed.
R. H. S Sections - Additional Provisions
Rectangular Hollow sections are treated in accordance with S.C.I.
recommendations in cases when the plastic axis is in the flange. In
such cases, the following expressions are used to calculate the
reduced plastic moduli:
Section 2B1
2-65
Srx = (A*A/4(B-t))(1-n) [ 2D(B-t)/A + n-1 ]
for n>= 2t(D-2t)/A
Sry = (A*A/4(D-t))(1-n) [ 2B(D-t)/A + n-1 ]
for n>= 2t(B-2t)/A
2B1.6 Design Parameters
Available design parameters to be used in conjunction with
BS5950 are listed in table 2B.1 along with their default values.
The following items should be noted with respect to their use.
1. (PY - STEEL DESIGN STRENGTH )
The design parameter PY should only be used when a uniform
design strength for an entire structure or a portion thereof is
required. Otherwise the value of PY will be set according to
the stipulations of BS5950 table 7 in which the design strength
is seen as a function of cross sectional thickness for a
particular steel grade and particular element considered.
Generally speaking this option is not required and the program
should be allowed to ascertain the appropriate value.
2. (UNL, LY and LZ - relevant EFFECTIVE LENGTHS)
The values supplied for UNL, LY and LZ should be real
numbers greater than zero in current units of length. They are
supplied along with or instead of UNF, KY KZ ( which are
factors, not lengths) to define lateral torsional buckling and
compression effective lengths respectively. Please note that
both UNL or UNF and LY or KY values are required even
though they are often the same values. The former relates to
compression flange restraint for lateral torsional buckling
while the latter is the unrestrained buckling length for
compression checks.
3. (CMN and CMM - Lateral torsional buckling coefficients)
As per section 2B.7 of this manual CMM and CMN should not
both be used in a given design. In such a case the program will
reset CMN to 1.0
Steel Design Per BS5950:1990
Section 2B1
2-66
4. (TRACK - control of output formats )
When the TRACK parameter is set to 1.0 or 2.0, member
capacities will be printed in design related output ( code check
or member selection ) in kilonewtons per square metre. An
example of each follows.
TRACK 0.0 OUTPUT STAAD CODE CHECKING - (BSI )
--------------------------- ******************************
ALL UNITS ARE - KNS METR (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=================================================================
1 ST UB686X254X170 PASS BS-4.8.3.2 0.036 3
86.72 C 0.00 -22.02 4.50
---------------------------------
Section 2B1
2-67
TRACK 1.0 OUTPUT STAAD CODE CHECKING - (BSI )
--------------------------- ******************************
ALL UNITS ARE - KNS METR (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=================================================================
1 ST UB686X254X170 PASS BS-4.8.3.2 0.036 3
86.72 C 0.00 -22.02 4.50
CALCULATED CAPACITIES FOR MEMB 1 UNIT - kN,m SECTION CLASS 4
MCZ= 1141.9 MCY= 120.4 PC= 3451.5 PT= 5739.9 MB= 1084.1 PV= 1597.5
BUCKLING CO-EFFICIENTS m AND n : m = 1.000 n = 1.000
PZ= 5739.90 FX/PZ = 0.02 MRZ= 1141.9 MRY= 120.4
TRACK 2.0 OUTPUT STAAD CODE CHECKING - (BSI ) --------------------------- ****************************** ALL UNITS ARE - KNS METR (UNLESS OTHERWISE NOTED) MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ================================================================= 1 ST UB686X254X170 PASS BS-4.8.3.2 0.036 3 86.72 C 0.00 -22.02 4.50 ================================================================= MATERIAL DATA
Grade of steel = 43 Modulus of elasticity = 205 kN/mm2 Design Strength (py) = 265 N/mm2 Reduced = 232N/mm2
SECTION PROPERTIES (units - cm)
Member Length = 450.00 Gross Area = 216.60 Net Area = 216.60
z-axis y-axis
Moment of inertia : 170147.000 6621.000 Plastic modulus : 5624.000 810.000 Elastic modulus : 4911.156 517.670 Shear Area : 109.122 100.470 Radius of gyration : 28.027 5.529 Effective Length : 450.000 450.000
Steel Design Per BS5950:1990
Section 2B1
2-68
DESIGN DATA (units - kN,m) BS5950/1990
Section Class : SLENDER Squash Load : 5739.90 Axial force/Squash load : 0.015
z-axis y-axis
Slenderness ratio (KL/r) : 16.1 81.4 Compression Capacity : 5036.2 3451.5 Tension Capacity : 5739.9 5739.9 Moment Capacity : 1141.9 120.4 Reduced Moment Capacity : 1141.9 120.4 Shear Capacity : 1561.5 1597.5
BUCKLING CALCULATIONS (units - kN,m) Lateral Torsional Buckling Moment (MB = 1084.1) co-efficients m & n : m =1.00 n =1.00, Effective Length =4.500 CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m): CLAUSE RATIO LOAD FX VY VZ MZ MY BS-4.7 (C) 0.025 3 86.7 3.2 0.0 -22.0 0.0 BS-4.8.3.2 0.036 3 86.7 3.2 0.0 -22.0 0.0 BS-4.8.3.3.1 0.047 1 83.3 7.4 0.0 -27.6 0.0 BS-4.8.3.3.2 0.026 1 83.3 7.4 0.0 -27.6 0.0 BS-4.2.3-(Y) 0.005 1 83.3 7.4 0.0 -27.6 0.0 BS-4.3 (LTB) 0.020 4 -86.7 3.2 0.0 22.0 0.0
Torsion and deflections have not been considered in the design
5. ( LEG - table 24/28 BS5950 for fastner control )
The LEG parameter follows the requirements of BS5950 table
28. This table concerns the fastner restraint conditions for
angles, double angles, tee sections and channels for
slenderness. The following values are available:
Clause 4.7.10.2 (a) Single Angle, short leg 1.0
(b) Single Angle, short leg 0.0
(a) Single Angle, long leg 3.0
(b) Single Angle, long leg 2.0
Section 2B1
2-69
Clause 4.7.10.3 (a) Double angle, short leg 3.0
(b) Double angle, short leg 2.0
(c) Double angle, long leg 1.0
(d) Double angle, long leg 0.0
(a) Double angle, long leg 7.0
(b) Double angle, long leg 6.0
(c) Double angle, short leg 5.0
(d) Double angle, short leg 4.0
Clause 4.7.10.4 (a) Channels, 2 or more rows 1.0
(b) Channels, 1 row 0.0
Clause 4.7.10.5 (a) Tee sections, 2 or more rows 1.0
(b) Tee sections, 1 row 0.0
When defining member properties for single angles, the spec
(manual ref: 5.20.1) should be provided as RA and not ST. See fig
1.6 of the Technical Reference Manual.
Table 28 may be by-passed in favour of table 24 by using:
10 = Table 24 for equal angles or long legs of unequal
angles
11 = Table 24 for short legs of unequal angles
For single angles, LY and KY parameters should be provided
relative to the raa axis while LZ and KZ are related to rbb. Lvv
will be considered as the minimum of the KY*LY and KZ*LZ
values.
For double angles, the LVV parameter is available to comply with
note 5 table 28. In addition, if using double angles from user
tables, (Technical Reference Manual section 5.19) an eleventh
value, rvv, should be supplied at the end of the ten existing values
corresponding to the radius of gyration of the single angle making
up the pair.
Steel Design Per BS5950:1990
Section 2B1
2-70
Table 2B1.1 - British Steel Design – BS5950:1990 - Parameters
Parameter
Name
Default Value Description
KY 1.0 K factor value in local y - axis. Usually, this is the minor axis.
KZ 1.0 K factor value in local z - axis. Usually, this is the major axis.
LY * Member Length
Length in local y - axis (current units) to calculate (KY)(LY)/Ryy slenderness ratio.
LZ * Member Length
Length in local z - axis (current units) to calculate (KZ)(LZ)/Rzz slenderness ratio.
UNF 1.0 Factor applied to unsupported length for Lateral Torsional Buckling effective length per section 4.3.7.5 of BS5950.
UNL * Member Length
Unsupported Length for calculating Lateral Torsional Buckling resistance moment section 4.3.7.5 of BS5950.
PY * Set according to steel grade
(SGR)
Design Strength of steel
NSF 1.0 Net section factor for tension members.
SGR 0.0 Steel Grade per BS4360 0.0 = Grade 43 1.0 = Grade 50 2.0 = Grade 55 3.0 = As per GB 1591 – 16 Mn
SBLT 0.0 0.0 = Rolled Section 1.0 = Built up Section
MAIN 1.0 As per BS5950 4.7.3 1.0 = Main structural member (180) 2.0 = Secondary member. (250) 3.0 = Bracing etc (350)
CMM ! 1.0 Coefficient m for lateral torsional buckling. (see section 2B.5)
CMN ! 1.0 Coefficient n for lateral torsional buckling. (see section 2B.5)
TRACK 0.0 0.0 = Suppress all member capacity info. 1.0 = Print all member capacities. 2.0 = Print detailed design sheet. 4.0 = Deflection Check (separate check to main select / check code)
Section 2B1
2-71
Table 2B1.1 - British Steel Design – BS5950:1990 - Parameters
Parameter
Name
Default Value Description
DMAX * 100.0cm Maximum allowable depth
DMIN * 0.0cm Minimum allowable depth
RATIO 1.0 Permissible ratio of the actual capacities.
BEAM 0.0 0.0 = Design only for end moments or those locations specified by the SECTION command.
1.0 = Calculate moments at 12th points along the member and use the maximum Mz value for design. Clause checks at one location
2.0 = Same as BEAM = 1.0 but additional checks are carried out for each end.
3.0 = Calculate moments at 12th points along the member. Clause checks at each location including the ends of the member.
CODE BS5950 Design Code to follow. See section 5.47.1 of the Technical Reference Manual.
LEG 0.0 Values range from 0 - 12. See section 2B.6.5 for details. The values correspond to table 24/28 of BS5950 for fastner conditions.
LVV * Maximum of Lyy and Lzz
(Lyy is a term used
by BS5950)
Used in conjunction with LEG for Lvv as per BS5950 table 28 for double angles, note 5.
CB 1.0 1.0 = BS5950 per clause B.2.5 (continuous) to calculate Mb.
2.0 = To calculate Mbs (simple) as per Clause 4.7.7 as opposed to Mb.
DFF None (Mandatory for
deflection check)
"Deflection Length" / Maxm. allowable local deflection
DJ1 Start Joint of member
Joint No. denoting starting point for calculation of "Deflection Length" (See Note 1)
DJ2 End Joint of member
Joint No. denoting end point for calculation of "Deflection Length" (See Note 1)
ESTIFF 0.0 Clauses 4.8.3.3.1 and 4.8.3.3.2 1.0 = Pass if member passes EITHER clause. 1.0 = Pass if member passes BOTH clauses.
Steel Design Per BS5950:1990
Section 2B1
2-72
Table 2B1.1 - British Steel Design – BS5950:1990 - Parameters
Parameter
Name
Default Value Description
WELD 1.0 closed
2.0 open
Weld Type, see AISC steel design 1.0 = Welding on one side only (except for webs of wide
flange and tee sections) 2.0 = Welding on both sides (except pipes and tubes)
TB 0.0 2.0 = Elastic stress analysis 3.0 = Plastic stress analysis
PNL * 0.0 Transverse stiffener spacing („a‟ in Appendix H1) 0.0 = Infinity Any other value used in the calculations.
SAME ** 0.0 Controls the sections to try during a SELECT process.
0.0 = Try every section of the same type as original 1.0 = Try only those sections with a similar name as
original, e.g. if the original is an HEA 100, then only HEA sections will be selected, even if there are HEM‟s in the same table.
Note: Once a parameter is specified, its value stays at that specified
number till it is specified again. This is the way STAAD works for all
codes.
! CMN & CMM cannot both be provided. * current units must be considered.
**For angles, if the original section is an equal angle, then the selected section will be an equal angle and vice versa for unequal angles.
NOTES:
1) "Deflection Length" is defined as the length that is used for
calculation of local deflections within a member. It may be
noted that for most cases the "Deflection Length" will be equal
to the length of the member. However, in some situations, the
"Deflection Length" may be differen t. For example, refer to
the figure below where a beam has been modeled using four
joints and three members. Note that the "Deflection Length"
for all three members will be equal to the total length of the
beam in this case. The parameters DJ1 and DJ2 should be used
to model this situation. Also the straight line joining DJ1 and
DJ2 is used as the reference line from which local deflections
Section 2B1
2-73
are measured. Thus, for all three members here, DJ1 should be
"1" and DJ2 should be "4".
D = Maximum local deflection for members1, 2 and 3.
D
1
2 3
4
1
2 3
EXAMPLE : PARAMETERS
DFF 300. ALL
DJ1 1 ALL
DJ2 4 ALL
2) If DJ1 and DJ2 are not used, "Deflection Length" will default
to the member length and local deflections will be measured
from original member line.
3) The above parameters may be used in conjunction with other
available parameters for steel design.
2B1.7 Design Operations
STAAD contains a broad set of facilities for the design of
structural members as individual components of an analysed
structure. The member design facilities provide the user with the
ability to carry out a number of different design operations. These
facilities may be used selectively in accordance with the
requirements of the design problem.
The operations to perform a design are:
Specify the load cases to be considered in the design.
Specify design parameter values, if different from the default
values.
Specify whether to perform code checking or member selection
along with the list of members.
These operations may be repeated by the user any number of times
depending upon the design requirements.
Steel Design Per BS5950:1990
Section 2B1
2-74
2B1.8 Code Checking
The purpose of code checking is to ascertain whether the provided
section properties of the members are adequate. The adequacy is
checked as per BS5950. Code checking is done using the forces
and moments at specific sections of the members. If no sections
are specified, the program uses the start and end forces for code
checking.
When code checking is selected, the program calculates and prints
whether the members have passed or failed the checks; the critical
condition of BS5950 code (like any of the BS5950 specifications
for compression, tension , shear, etc.); the value of the ratio of the
critical condition (overstressed for value more than 1.0 or any
other specified RATIO value); the governing load case, and the
location (distance from the start of the member of forces in the
member where the critical condition occurs).
Code checking can be done with any type of steel section listed in
Section 2B.4 of the STAAD Technical Reference Manual or any of
the user defined sections in section 5.19 with two exceptions ;
GENERAL and ISECTION. In BS5950, these will not be considered
for design along with PRISMATIC sections which are also not
acceptable.
2B1.9 Member Selection
STAAD is capable of performing design operations on specified
members. Once an analysis has been performed, the program can
select the most economical section, i.e. the lightest section, which
fulfills the code requirements for the specified member. The
section selected will be of the same type section as originally
designated for the member being designed. Member selection can
also be constrained by the parameters DMAX and DMIN which
limits the maximum and minimum depth of the members.
Section 2B1
2-75
Member selection can be performed with all the types of steel
sections with the same limitations as defined in section 2B.8 -
CODE CHECKING.
Selection of members, whose properties are originally input from a
user created table, will be limited to sections in the user table.
Member selection can not be performed on members whose section
properties are input as prismatic or as above limitations for code
checking.
2B1.10 Tabulated Results of Steel Design
For code checking or member selection, the program produces the
results in a tabulated fashion. The items in the output table are
explained as follows:
a) MEMBER refers to the member number for which the
design is performed.
b) TABLE refers to steel section name which has been
checked against the steel code or has been
selected.
c) RESULTS prints whether the member has PASSED or
FAILED. If the RESULT is FAIL, there will
be an asterisk (*) mark on front of the
member.
d) CRITICAL COND refers to the section of the BS5950 code
which governs the design.
e) RATIO prints the ratio of the actual stresses to
allowable stresses for the critical condition.
Normally a value of 1.0 or less will mean
the member has passed.
f) LOADING provides the load case number which
governed the design.
Steel Design Per BS5950:1990
Section 2B1
2-76
g) FX, MY, and MZ provide the axial force, moment in local Y-
axis and the moment in local z-axis
respectively. Although STAAD does
consider all the member forces and moments
(except torsion) to perform design, only FX,
MY and MZ are printed since they are the
ones which are of interest, in most cases.
h) LOCATION specifies the actual distance from the start
of the member to the section where design
forces govern.
i) TRACK If the parameter TRACK is set to 1.0, the
program will block out part of the table and
will print the allowable bending capacities
in compression (MCY & MCZ) and reduced
moment capacities (MRY & MRZ),
allowable axial capacity in compression
(PC) and tension (PT) and shear capacity
(PV). TRACK 2.0 will produce the design
results as shown in section 2B.9.
2B1.11 Plate Girders
Plate girders may be considered for design in BS5950. The "py"
used in the calculation of compressive strength is reduced by
20N/mm2 as per the code if parameter SBLT is set to 1.0. The code
requires that for d/t >63E, the interaction checks be modified in
order to check for shear buckling of the web. This is considered in
STAAD (versions 15.0 and over) following clause 4.4.4.2a and
4.4.4.3 of the code. The shear capacity is found from table 21 of
the code and used in clause 4.4.5.3. For plate girders, clauses
4.4.2.2a and 4.4.2.3a are also considered. In order to account for
these checks, the output has been modified to show these
variations from the more common critical checks. An example is
as follows, using TRACK 2.0, showing the bottom part of the
output having been modified as follows:
Section 2B1
2-77
BS5950 Table 7<note 2>: d/t > 63E Web Is Checked For Shear Buckling
d/t =101.7 qcr=191.9 N/mm2 d*t=14639 mm2 (4.4.5.3)Vcr= 2809.4 kN
Flange =COMPACT Pyf=344 N/mm2 4.4.2.2 a=PASS 4.4.2.3 a=PASS
Flange Ratio 4.4.4.2 (a) =0.20 L= 1 Web Ratio =0.05 L= 1
CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m):
CLAUSE RATIO LOAD FX VY VZ MZ MY
BS-4.8.3.3.2 0.177 1 0.0 -150.0 0.0 -1125.0 0.0
BS-4.2.3-(Y) 0.049 1 0.0 150.0 0.0 -1125.0 0.0
BS-4.3 (LTB) 0.151 1 0.0 -150.0 0.0 -1125.0 0.0
BS-4.4.5.3 0.053 1 0.0 150.0 0.0 -1125.0 0.0
BS-4.4.4.2 a 0.203 1 0.0 -150.0 0.0 -1125.0 0.0
2B1.12 Composite Sections
The definition of composite sections has been provided for in the
standard sections definition - section 5.20.1 of the Technical
Reference Manual. This is purely for analysis and for obtaining the
right section properties. It uses the American requirement of 18
times depth (CT) as the effective depth. For more control with
British sections two new options are available in user provided
tables.
1. WIDE FLANGE COMPOSITE:
Using the standard definition of I sections in WIDE FLANGE,
4 additional values can now be provided. The first is the width
of concrete to the left of centre of the steel web (b1). The
second is the concrete width to the right (b2). The third is the
concrete depth (d1) to be considered. The last is the modular
ratio. The above values are accepted in the program by adding
a '-' at the first position on the first line of data. The program
now awaits four extra values on line 2 as described above. If (-
) is provided on the second line the program requires another 2
breadths + 1 thickness for the bottom plate.
Steel Design Per BS5950:1990
Section 2B1
2-78
2. ISECTION:
The same is true for ISECTION definition in user table.
3. EXAMPLE INPUT:
UNIT CM
WIDE FLANGE
C45752
-66.5 44.98 .76 15.24 1.09 21345 645 21.3 34.185 33.223
150 150 30 10
ISECTION
PG9144
-92.05 2.15 92.05 42.05 3.66 42.05 3.66 197.9 153.9 1730
40 40 12 1
The larger British sections have been coded as USER TABLES
under wide flange and are available on request to any existing
user. Please note however that composite design IS NOT available
in this portion of STAAD.
2-79
Design Per BS5400
2C.1 General Comments
BS5400 is an additional code available from Research Engineers.
It does not come as standard with British versions.
The British Standard, BS5400 adopts the limit state design
philosophy and is applicable to steel, concrete and composite
construction. The code is in 10 parts covering various aspects of
bridge design. The implementation of part 3, Code of practice for
design of steel bridges, in STAAD is restricted in its scope to
simply supported spans. It is assumed that the depth remains
constant and both construction and composite stages of steel I -
Sections can be checked. The following sections describe in more
detail features of the design process currently available in STAAD.
2C.2 Shape Limitations
The capacity of sections could be limited by local buckling if the
ratio of flange outstand to thickness is large. In order to preven t
this, the code sets limits to the ratio as per clause 9.3.2. In the
event of exceeding these limits, the design process will terminate
with reference to the clause.
Section 2C
Design Per BS5400
Section 2C
2-80
2C.3 Section Class
Sections are further defined as compact or non -compact. In the
case of compact sections, the full plastic moment capacity can be
attained. In the case of non compact sections, local buckling of
elements may occur prior to reaching the full moment capacity and
for this reason the extreme fibre stresses are limited to first yield.
In STAAD, section types are determined as per clause 9.3.7 and
the checks that follow will relate to the type of section considered.
2C.4 Moment Capacity
Lateral torsional buckling may occur if a member has unrestrained
elements in compression. The code deals with this effect by
limiting the compressive stress to a value depending on the
slenderness parameter which is a modified form of the ratio Le/Ry.
Le is the effective length governed by the provision of lateral
restraints satisfying the requirements of clause 9.12.1. Once the
allowable compressive stress is determined then the moment
capacity appropriate to the section type can be calculated. STAAD
takes the effective length as that provided by the user, defaulting
to the length of the member during construction stage and as zero,
assuming full restraint throughout, for the composite stage. The
program then proceeds to calculate the allowable compressive
stress based on appendix G7 from which the moment capacity is
then determined.
2C.5 Shear Capacity
The shear capacity, as outlined in clause is a function of the
limiting shear strength, l, which is dependant on the slenderness
ratio. STAAD follows the iterative procedure of appendix G8 to
determine the limiting shear strength of the web pan el. The shear
capacity is then calculated based on the formula given under
clause 9.9.2.2.
Section 2C
2-81
2C.6 Design Parameters
Available design parameters to be used in conjunction with BS5400
are listed in table 2C.1. Depending on the value assigned to the 'WET'
parameter, the users can determine the stage under consideration. For a
composite design check, taking into consideration the construction
stage, two separate analyses are required. In the first, member
properties are non-composite and the WET parameter is set to 1.0 . In
the second, member properties should be changed to composite and the
WET parameter set to 2.0. Member properties for composite or non -
composite sections should be specified from user provided tables
(refer to section 5.19 of the manual for specification of user tables).
Rolled sections, composite or non-composite, come under WIDE
FLANGE section-type and built-up sections under ISECTION. When
specifying composite properties the first parameter is assigned a
negative value and four additional parameters provided giving details
of the concrete section. See user table examples provided. Note: Once
a parameter is specified, its value stays at that specified number
till it is specified again. This is the way STAAD works for all codes.
Table 2C.1 - BS5400 Design Parameters
Parameter
Name
Default Value Description
UNL* Member Length
Unsupported Length for calculating allowable compressive bending stress.
PY* Set according to Design Strength of steel SGR
NSF 1.0 Net section factor for tension members.
SGR* 0.0 Steel Grade per BS4360
0.0 = Grade 43
1.0 = Grade 50
2.0 = Grade 55
SBLT 0.0 0.0 = Rolled Section
1.0 = Built up Section
MAIN 1.0 1.0 = Grade of concrete 30 N/mm2
Design Per BS5400
Section 2C
2-82
Table 2C.1 - BS5400 Design Parameters
Parameter
Name
Default Value Description
2.0 = Grade of concrete 40 N/mm2
3.0 = Grade of concrete 50 N/mm2
WET 0.0 0.0 = Wet stage with no data saved for composite stage.
1.0 = Wet stage with data saved for composite stage.
2.0 = Composite and wet stage combined.
3.0 = Composite stage only.
TRACK 1.0 1.0 = Print all member capacities.
0.0 = suppress all member capacities.
BEAM 0.0 MUST BE CHANGED TO 1.0 FOR ALL RUNS
LY* Member Length
Length to calculate slenderness ratio for bending about Y-axis.
LZ* Member Length
Length to calculate slenderness ratio for bending about Z-axis.
KY 1.0 K value for bending about Y-axis. Usually this is minor axis.
KZ 1.0 K value for bending about Z-axis. Usually this is major axis.
STIFF 1.0 Factor of length for panel length in the shear calculation.
* Provided in current unit systems.
2C.7 Composite Sections
The definition of composite sections has been provided for in the
standard sections definition - section 5.20.1 of the Technical
Reference Manual. This is purely for analysis and for obtaining the
right section properties. It uses the American requirement of 18
times depth (CT) as the effective depth. For more control with
British sections two new options are available in user provided
tables.
Section 2C
2-83
1. WIDE FLANGE COMPOSITE:
Using the standard definition of I sections in WIDE FLANGE,
4 additional values can now be provided. The first is the width
of concrete to the left of centre of the steel web (b1). The
second is the concrete width to the right (b2). The third is the
concrete depth (d1) to be considered. The last is the modular
ratio. The above values are accepted in the program by adding
a '-' at the first position on the first line of data. The program
now awaits four extra values on line 2 as described above. If ( -
) is provided on the second line the program requires another 2
breadths + 1 thickness for the bottom plate.
2. ISECTION:
The same is true for ISECTION definition in user table.
3. EXAMPLE INPUT:
UNIT CM
WIDE FLANGE
C45752
-66.5 44.98 .76 15.24 1.09 21345 645 21.3 34.185 33.223
150 150 30 10
ISECTION
PG9144
-92.05 2.15 92.05 42.05 3.66 42.05 3.66 197.9 153.9 1730
40 40 12 1
The larger British sections have been coded as USER TABLES
under wide flange and are available on request to any existing
user. Please note however that composite design IS NOT available
in this portion of STAAD.
Design Per BS5400
Section 2C
2-84
2-85
Design Per BS8007
2D.1 General Comments
BS8007 is an additional code available from Research Engineers.
It does not come as standard with British versions.
STAAD has the capability of performing concrete slab design
according to BS8007. BS8007 provides recommendations for the
design of reinforced concrete structures containing aqueous
liquids. It is recommended that the design of the structure is
carried out according to BS8110, unless modified by the
recommendations given in BS8007.
Please use the following in conjunction with Section 2A of this
Manual - BS8110.
2D.2 Design Process
The design process is carried out in three stages.
1. Ultimate Limit States
The program is structured so that ultimate design is first carried
out in accordance with recommendations given in BS8110. All
active design load cases are considered in turn and a tabulated
output is printed showing possible reinforcement arrangements.
12, 16 and 20 mm bars are considered with possible spacings from
100,125,150,175 and 200 mm. Within these spacings, the layout
providing the closest area of steel is printed under each bar size.
Longitudinal and transverse moments together with critical load
Section 2D
Design Per BS8007
Section 2D
2-86
cases for both hogging and sagging moments are also printed.
Minimum reinforcement is in any case checked and provided in
each direction. WOOD & ARMER moments may also be included
in the design.
2. Serviceability Limit States
In the second stage, flexural crack widths under serviceability load
cases are calculated. The FIRST and EVERY OTHER OCCURING
design load case is considered as a serviceability load case and
crack widths are calculated based on bar sizes and spacings
proposed at the ultimate limit state check.
Crack widths due to longitudinal and transverse moments are
calculated directly under bars, midway between and at corners. A
tabulated output indicating critical serviceability load cases and
moments for top and bottom of the slab is then produced.
3. Thermal crack widths
Finally thermal, crack width calculations are carried out. Through
available parameters, the user is able to provide information on the
type of slab, temperature range and crack width limits.
Surface zone depths are determined based on the type of slab and
critical areas of reinforcements are calculated and printed in a
tabulated form.
Four bar sizes are considered and for each, max crack spacing,
Smax and crack widths are calculated for the critical
reinforcements and printed under each bar size.
Maximum bar spacing to limit crack widths to the user's limit is
also printed under each bar size.
Section 2D
2-87
2D.3 Design Parameters
The program contains a number of parameters which are needed to
perform and control the design to BS8007.
These parameters not only act as a method to input required data
for code calculations but give the Engineer control over the actual
design process. Default values of commonly used values for
conventional design practice have been chosen as the basis. Table
2D.1 contains a complete list of available parameters with their
default values.
2D.4 Structural Model
Structural slabs that are to be designed to BS8007 must be
modelled using finite elements. The manual provides information
on the sign convention used in the program for defining elements,
(See main manual section 2-6).
It is recommended to connect elements in such a way that the
positive local z axis points outwards away, from the centre of the
container. In this manner the "Top" of elements will consistently
fall on the outer surface and internal pressure loads will act in the
positive direction of the local z axis.
An example of a rectangular tank is provided to demonstrate the
above procedure.
Element properties are based on the thickness given under
ELEMENT PROPERTIES command. The following example
demonstrates the required input for a 300 mm slab modelled with
10 elements.
Design Per BS8007
Section 2D
2-88
UNIT MM
ELEMENT PROPERTIES
1 TO 10 THI 300.0
2D.5 Wood & Armer Moments
This is controlled by the SRA parameter. If the default value of
zero is used, the design will be based on the Mx and My moments
which are the direct results of STAAD analysis. The SRA
parameter (Set Reinforcement Angle) can be manipulated to
introduce WOOD & ARMER moments into the design replacing
the pure Mx, My moments. These new design moments allow the
Mxy moment to be considered when designing the section.
Orthogonal or skew reinforcement may be considered. SRA set to -
500 will assume an orthogonal layout. If however a skew is to be
considered, an angle is given in degrees, measured between the
local element x axis anti-clockwise (positive). The resulting Mx*
and My* moments are calculated and shown in the design format.
Section 2D
2-89
Table 2D.1 - BS8007 Design Parameters
Parameter
Name
Default Value Description
FYMAIN * * 460 N/mm2 Yield for all reinforcing steel
FC * 30 N/mm2 Concrete grade.
CLEAR * 20 mm Distance from the outer surface to the edge of the bar. This is considered the same on both surfaces.
SRA 0.0 Orthogonal reinforcement layout without considering torsional moment Mxy - slabs on -500. orthogonal reinforcement layout with Mxy used to calculate WOOD &ARMER moments for design. A* Skew angle considered in WOOD & ARMER EQUATIONS. A* is any angle in degrees.
SCON 1 Parameter which indicates the type of slab ee. ground or suspended as defined in BS8007 1 = Suspended Slab 2 = Ground Slab
TEMP 30°C Temperature range to be considered in thermal crack width calculations
CRACK * 0.2 mm Limiting thermal crack width
Note: Once a parameter is specified, its value stays at that specified
number till it is specified again. This is the way STAAD works for
all codes.
* Provided in current unit systems
Design Per BS8007
Section 2D
2-90
2-91
Design Per British Cold Formed
Steel Code
2E.1 General
Provisions of BS 5950-5:1998, have been implemented. The
program allows design of single (non-composite) members in
tension, compression, bending, shear, as well as their
combinations. Cold work of forming strengthening effects have
been included as an option.
2E.2 Cross-Sectional Properties
The user specifies the geometry of the cross-section by selecting
one of the section shape designations from the Gross Section
Property Tables published in the “The Steel Construction
Institute”, (Design of Structures using Cold Formed Steel
Sections).
The Tables are currently available for the following shapes:
Channel with Lips
Channel without Lips
Z with Lips
Pipe
Tube
Shape assignment may be done using the member property pages
of the graphical user interface (GUI) or by specifying the section
designation symbol in the input file.
Section 2E
Design Per British Cold Formed Steel Code
Section 2E
2-92
The properties listed in the tables are gross section properties.
STAAD.Pro uses unreduced section properties in the structure
analysis stage. Both unreduced and effective section properties are
used in the design stage, as applicable.
2E.3 Design Procedure
The following two design modes are available:
1. Code Checking
The program compares the resistance of members with the applied
load effects, in accordance with BS 5950-5:1998. Code checking is
carried out for locations specified by the user via the SECTION
command or the BEAM parameter. The results are presented in a
form of a PASS/FAIL identifier and a RATIO of load effect to
resistance for each member checked. The user may choose the
degree of detail in the output data by setting the TRACK
parameter.
2. Member Selection
The user may request that the program search the cold formed steel
shapes database (BS standard sections) for alternative members
that pass the code check and meet the least weight criterion. In
addition, a minimum and/or maximum acceptable depth of the
member may be specified. The program will then evaluate all
database sections of the type initially specified (i.e., channel,
angle, etc.) and, if a suitable replacement is found, presents design
results for that section. If no section satisfying the depth
restrictions or lighter than the initial one can be found, the
program leaves the member unchanged, regardless of whether it
passes the code check or not.
Section 2E
2-93
The program calculates effective section properties in accordance
with Section 4 of the subject code. Cross-sectional properties and
overall slenderness of members are checked for compliance with
Clause 6.2.2, Maximum Effective Slenderness Ratio for
members in Compression
Clause 4.2, Maximum Flat Width Ratios for Elements in Compression
2E.4 Design Equations
Tensile Strength
The allowable tensile strength, as calculated in STAAD as per
BS5950-5, section 7 is described below.
The tensile strength, Pt of the member should be determined from
clause 7.2.1
yet pAP
Where
Ae is the net area An determined in accordance with cl.3.5.4
py is the design strength
Combined bending and tension
As per clause 7.3 of BS 5950-5:1998 members subjected to both
axial tension and bending should be proportioned such that the
following relationships are satisfied at the ultimate limit state
1cy
y
cz
z
t
t
M
M
M
M
P
F
And
cz
z
M
M 1
Design Per British Cold Formed Steel Code
Section 2E
2-94
and
cy
y
M
M 1
Where
Ft is the applies tensile strength
Pt is the tensile capacity determined in accordance with
clause 7.2.1 of the subject code
Mz,My,Mcz,Mcy are as defined in clause 6.4.2 of the subject code
Compressive Strength
The allowable Compressive strength, as calculated in STAAD as
per BS5950-5, section 6 is described below
For sections symmetrical about both principal axes or closed
cross-sections which are not subjected to torsional flexural
buckling, the buckling resistance under axial load, Pc, may be
obtained from the following equation as per clause 6.2.3 of the
subject code
csE
csE
PP
PPPc
2
For Sections symmetrical about a single axis and which are not
subject to torsional flexural buckling, the buckling resistance
under axial load, Pc, may be obtained from the following equation
as per clause 6.2.4 of the subject code
)(
'scc
cc
cePM
PMP
Where the meanings of the symbols used are indicated in the
subject clauses.
Section 2E
2-95
Torsional flexural buckling
Design of the members which have at least one axis of symmetry,
and which are subject to torsional flexural buckling should be
done according to the stipulations of the clause 6.3.2 using
factored slenderness ratio LE/r in place of actual slenderness ratio
while reading Table 10 for the value of Compressive strength(p c).
Where
2/1
TF
E
P
P when PE > PTF
= 1 , otherwise
Where the meanings of the symbols used are indicated in the
subject clause.
Combined bending and compression
Members subjected to both axial compression and bending should
be checked for local capacity and overall buckling
Local capacity check as per clause 6.4.2 of the subject code
1cy
y
cz
z
cs
c
M
M
M
M
P
F
Overall buckling check as per clause 6.4.3 of the subject code
For Beams not subjected to lateral buckling, the following
relationship should be satisfied
1
11
Ey
ccyby
y
Ez
c
czbx
z
c
c
P
FMC
M
P
FMC
M
P
F
For Beams subjected to lateral buckling, the following relationship
should be satisfied
Design Per British Cold Formed Steel Code
Section 2E
2-96
1
1
Ey
ccyby
y
b
z
c
c
P
FMC
M
M
M
P
F
Fc is the applied axial load
Pcs is the short strut capacity as per clause 6.2.3 Mz is the applied bending moment about z axis
My is the applied bending moment about y axis
Mcz is the moment capacity in bending about the local Z axis in
the absence of Fc and My, as per clause 5.2.2 and 5.6
Mcy is the moment capacity in bending about the local Y axis,
in the absence of Fc and Mz,as per clause 5.2.2 and 5.6
Mb is the lateral buckling resistance moment as per clause
5.6.2
PEz is the flexural buckling load in compression for bending
about the local Z axis
PEy is the flexural buckling load in compression for bending about the local Y axis
Cbz,Cby are taken as unity unless their values are specified by the
user
The Mcz, Mcy and Mb are calculated from clause numbers 5.2.2 and
5.6 in the manner described herein below.
Calculation of moment capacities
For restrained beams, the applied moment based on factored loads
should not be greater then the bending moment resistance of the
section, Mc
Mcz = Szz po
Mcy = Syy po
y
sw
o pY
t
Dp
2/1
2800019.013.1
Where
Mcz is the Moment resistance of the section in z axis
Mcz is the Moment resistance of the section in z axis
po is the limiting stress for bending elements under stress
gradient and should not greater then design strength py
Section 2E
2-97
For unrestrained beams the applied moment based on factored
loads should not be greater than the smaller of the bending
moment resistance of the section , Mc , and the buckling resistance
moment of the beam, Mb
Then buckling resistance moment, Mb, may be calculated as
follows
c
YEBB
YEb M
MM
MMM
2
Where
2
)1( EYB
MM
MY is the yield moment of the section , product of design
strength py and elastic modules of the gross section with
respect to the compression flange Zc
ME is the elastic lateral buckling resistance as per clause
5.6.2.2
is the Perry coefficient
Please refer clause numbers 5.2.2 and 5.6 of the subject code for a
detailed discussion regarding the parameters used in the
abovementioned equations.
Shear Strength
The maximum shear stress should not be greater then 0.7 py as
per clause 5.4.2
The average shear stress should not exceed the lesser of the shear
yield strength, pv or the shear buckling strength, qcr as stipulated in
clause 5.4.3 of the subject code.
Design Per British Cold Formed Steel Code
Section 2E
2-98
The parameters are calculated as follows : -
pv = 0.6 py
2
2
/1000
mmND
tqcr
Pv = A*Min(pv,qcr)
Where
Pv is the shear capacity in N/mm^2
py is the design strength in N/mm^2
t is the web thickness in mm
D is the web depth in mm
Combined bending and Shear
For beam webs subjected to both bending and shear stresses the
member should be designed to satisfy the following relationship as
per the stipulations of clause 5.5.2 of the subject code
1
22
cv
v
M
M
P
F
Where
Fv is the shear force
M is the bending moment acting at the same section as Fv
Mc is the moment capacity determined in accordance with
5.2.2
The next table contains the input parameters for specifying values
of design variables and selection of design options.
Section 2E
2-99
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
BRITISH COLD FORMED STEEL DESIGN PARAMETERS
Parameter
Name
Default
Value Description
BEAM 1.0 When this parameter is set to 1.0 (default), the adequacy of the member is determined by checking a total of 13 equally spaced locations along the length of the member. If the BEAM value is 0.0, the 13 location check is not conducted, and instead, checking is done only at the locations specified by the SECTION command (See STAAD manual for details. For TRUSS members only start and end locations are designed.
CMZ 1.0 Coefficient of equivalent uniform bending Cb. See BS:5950-5:1998,5.6. Used for Combined axial load and bending design.
CMY 1.0 Coefficient of equivalent uniform bending Cb. See BS:5950-5:1998,5.6. Used for Combined axial load and bending design.
CWY 1.0 Specifies whether the cold work of forming strengthening effect should be included in resistance computation. See BS:5950-5:1998,3.4
Values: 0 – effect should not be included
1 – effect should be included
FLX 1 Specifies whether torsional-flexural buckling restraint is provided or is not necessary for the member. See BS:5950-5:1998, 5.6
Values:
0 – Section not subject to torsional flexural buckling 1 – Section subject to torsional flexural buckling
FU 430 MPa
Ultimate tensile strength of steel in current units.
Design Per British Cold Formed Steel Code
Section 2E
2-100
BRITISH COLD FORMED STEEL DESIGN PARAMETERS
Parameter
Name
Default
Value Description
FYLD 250 MPa
Yield strength of steel in current units.
KX 1.0 Effective length factor for torsional buckling. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.
KY 1.0 Effective length factor for overall buckling about the local Y-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.
KZ 1.0 Effective length factor for overall buckling in the local Z-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.
LX Member length
Unbraced length for twisting. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.
LY Member length
Effective length for overall buckling in the local Y-axis. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.
Section 2E
2-101
BRITISH COLD FORMED STEEL DESIGN PARAMETERS
Parameter
Name
Default
Value Description
LZ Member length
Effective length for overall buckling in the local Z-axis. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.
MAIN 0 0 – Check slenderness ratio
0 – Do not check slenderness ratio
NSF 1.0 Net section factor for tension members DMAX
2540.0 cm. Maximum allowable depth. It is input in the current units of
length.
RATIO 1.0 Permissible ratio of actual to allowable stresses
TRACK 0 This parameter is used to control the level of detail in which the design output is reported in the output file. The allowable values are: 0 - Prints only the member number, section name, ratio,
and PASS/FAIL status. 1 - Prints the design summary in addition to that printed by
TRACK 1 2 - Prints member and material properties in addition to that
printed by TRACK 2.
2E.5 Verification Problem
In the next few pages are included a verification example for reference purposes.
Design Per British Cold Formed Steel Code
Section 2E
2-102
Verification Problem-1
In this problem, we have assigned Channel sections with lips to
different members. Member numbers 28 to 31 have been assigned
section 230CLHS66X16,member numbers 3 TO 6 and 15 TO 19
have been assigned the section 230CLMIL70X30 and member
numbers 1, 2, 7 TO 14 have been assigned the section
170CLHS56X18. These members have been designed as per BS
5950 Part 5. Other sections have been assigned from the AISI
shapes database (American cold-formed steel) and designed in
accordance with that code.
The excerpts from the design output for member number 1 are
given herein below.
Section 2E
2-103
1) Bending Check
As per Clause 5.2.2.2 of BS 5950 –Part 5 the limiting compressive
stress(po ) for stiffened webs is given by the minimum of
y
sw
o pY
t
Dp
2/1
2800019.013.1
And
po = Py where Py = Min ( FYLD, 0.84XFU) = 361.2 N/mm2
So that
2.361280
212.279
8.1
1700019.013.1
2/1
op
= 332.727 N/mm2
The limiting compressive moments in local Y and Z axes will be given
by
Mcz = Szz po = 27632.4 X 332.727 = 9.19 X 106 N-mm
Mcy = Syy po = 27632.4 X 5427.50 = 3.46 X 106 N-mm
Maximum bending moment about local Z = 2159 N-m at node 7
Maximum bending moment about local Y = 19.755 N-m at node 7
Bending Ratio Z = 2.15 X106 / 9.19 X106 = 0.235 ……hence verified
Bending Ratio Y = 19755.3 / 3.46 X106 = 0.0057 ……hence verified
Buckling resistance moment Mb
As per section 5.6.2,
The buckling resistance moment
c
YEBB
YEb M
MM
MMM
2
Design Per British Cold Formed Steel Code
Section 2E
2-104
Where,
The Yield moment(MY) of section is given by MY = Szz po = 9.19 X 10
6 N-mm
The elastic buckling resistance moment(ME ) as per clause 5.6.2.2
is calculated to be
4.649 X106 N-mm
And, 2
)1( EYB
MM
, so that
2
10649.4)0.01(1019.9 66 B
= 2.325 X 1010
Which gives
6621010
66
1019.910649.4)10325.2(10325.2
1019.910649.4
bM
= 9.98 X 106 N-mm
2) Compression Check
The Axial force induced in member# 1 is 3436.75 N
The elastic flexural buckling load PE = 1.185 X 106 N
The short strut capacity (Pcs ) is given by Aeff X py = 457.698 *
344 = 157448 N
Perry Coefficient () = 0.02074
[Pcs + (1+ ) EP
] 0.5 = 683512.45 N
Buckling resistance csE
csE
PP
PPPc
2 = 153782 N
Section 2E
2-105
For Channel section(being singly symmetric) as per clause 6.2.4
Buckling resistance )(
'scc
cc
cePM
PMP
Where
The limiting compressive moment(Mc) in the relevant direction =
9.19 X 106 N-mm,as calculated above
And the distance(es) of the geometric neutral axis of the gross
cross section and that of the effective cross section = 38.24 m
So that,
cP = 24.381537821019.9
1537821019.96
6
= 93788.7 N
Compression ratio =
0366.07.93788
75.3436
……hence verified
3) Axial Compression and Bending
Local capacity check as per clause 6.4.2
1cy
y
cz
z
cs
c
M
M
M
M
P
F
66
6
1081.1
3.19755
1019.9
1015.2
212.379698.457
75.3436
= 0.26
Over all buckling check : 6.4.3
1
11
Ey
ccyby
y
Ez
c
czbx
z
c
c
P
FMC
M
P
FMC
M
P
F
= 0.2773 ……hence verified
Design Per British Cold Formed Steel Code
Section 2E
2-106
4) Shear Check as per clause 5.4.2 and 5.4.3
pv = 0.6 py = 0.6 379.212 = 227.52 N/mm2
2
2
/1000
mmND
tqcr
2
170
8.11000
crq
= 112.11 N/mm2 Pv = A*Min(pv,qcr) = 112.11 N/mm2
Shear resistance Y = 33579.4 N
Shear resistance Z = 21148.6 N
Shear Ratio Y =
1675.04.33579
72.5627
……hence verified
Shear Ratio Z =
0031.06.21148
114.67
……hence verified
5) Shear Check with Bending as per clause 5.5.2
Shear with bending on Z =
1
22
cz
z
v
v
M
M
P
F
=
2
6
62
1019.9
1015.2
4.33579
72.5627
=
0.08327 …… hence verified
Shear with bending on Y =
1
22
cy
y
v
v
M
M
P
F
=
2
6
2
1046.3
3.19755
6.21148
114.67
= 0.000….426 ……hence verified
Section 2E
2-107
Input File:
STAAD SPACE
SET ECHO OFF
INPUT WIDTH 79
UNIT FEET KIP
JOINT COORDINATES
1 0 5 0; 2 0 5 10; 3 10 5 0; 4 10 5 10; 5 5 5 0; 6 5 5 10; 7 0 5 2; 8 0 5 4;
9 0 5 6; 10 0 5 8; 11 10 5 2; 12 10 5 4; 13 10 5 6; 14 10 5 8; 15 5 5 2;
16 5 5 4; 17 5 5 6; 18 5 5 8; 19 10 0 0; 20 10 0 10; 21 0 0 10; 22 0 0 0;
MEMBER INCIDENCES
1 1 7; 2 3 11; 3 1 5; 4 2 6; 5 5 3; 6 6 4; 7 7 8; 8 8 9; 9 9 10; 10 10 2;
11 11 12; 12 12 13; 13 13 14; 14 14 4; 15 5 15; 16 15 16; 17 16 17; 18 17 18;
19 18 6; 20 7 15; 21 15 11; 22 8 16; 23 16 12; 24 9 17; 25 17 13; 26 10 18;
27 18 14; 28 1 22; 29 2 21; 30 3 19; 31 4 20; 32 1 21; 33 21 4; 34 4 19;
35 19 1; 36 2 20; 37 20 3; 38 3 22; 39 22 2;
MEMBER PROPERTY COLDFORMED AMERICAN
32 TO 39 TABLE ST 3LU3X060
20 TO 27 TABLE ST 3HU3X075
MEMBER PROPERTY COLDFORMED BRITISH
28 TO 31 TABLE ST 230CLHS66X16
3 TO 6 15 TO 19 TABLE ST 230CLMIL70X30
1 2 7 TO 14 TABLE ST 170CLHS56X18
UNIT MMS
PRINT MEMBER PROPERTIES LIST 32 20 28 3 1
SUPPORTS
19 TO 22 PINNED
UNIT FEET
DEFINE MATERIAL START
ISOTROPIC STEEL
E 4.176e+006
POISSON 0.3
DENSITY 0.489024
ALPHA 6.5e-006
DAMP 0.03
END DEFINE MATERIAL
Design Per British Cold Formed Steel Code
Section 2E
2-108
CONSTANTS
BETA 90 MEMB 20 TO 27
MATERIAL STEEL MEMB 1 TO 39
MEMBER TENSION
32 TO 39
UNIT FEET KIP
LOAD 1 VERTICAL AND HORIZONTAL
MEMBER LOAD
3 TO 6 20 TO 27 UNI GY -0.3 0 5
JOINT LOAD
1 2 FX 0.6
2 4 FZ -0.6
PERFORM ANALYSIS PRINT STATICS CHECK
UNIT KGS CM
PRINT JOINT DISP LIST 1 4 16
PRINT SUPPORT REACTIONS
PRINT MEMBER FORCES LIST 3 24 28
UNIT KIP INCH
PARAMETER 1
CODE AISI
FYLD 55 ALL
CWY 1 ALL
BEAM 1 ALL
TRACK 2 ALL
CHECK CODE MEMB 20 21
PARAMETER 2
CODE BS5950 COLD
TRACK 2 MEMB 1 TO 19 28 TO 31
CHECK CODE MEMB 1 2
FINISH
Section 2E
2-109
Output File:
****************************************************
* *
* STAAD.Pro *
* Version Bld *
* Proprietary Program of *
* *
* Date= *
* Time= *
* *
* USER ID: *
****************************************************
1. STAAD SPACE
2. SET ECHO OFF
MEMBER PROPERTIES. UNIT - CM
-----------------
MEMB PROFILE AX/ IZ/ IY/ IX/
AY AZ SZ SY
32 ST 3LU3X060 2.26 21.81 5.17 0.02
1.51 1.51 4.05 1.93
20 ST 3HU3X075 4.91 63.15 40.66 0.06
1.24 2.40 10.63 9.59
28 ST 230CLHS66X16 8.78 663.30 42.82 0.18
5.40 2.94 60.93 9.29
3 ST 230CLMIL70X30
11.40 868.90 66.93 0.36
6.72 3.84 80.13 14.15
1 ST 170CLHS56X18 5.23 224.50 20.49 0.06
3.00 1.89 27.96 5.43
************ END OF DATA FROM INTERNAL STORAGE ************
**START ITERATION NO. 2
**NOTE-Tension/Compression converged after 2 iterations, Case= 1
STATIC LOAD/REACTION/EQUILIBRIUM SUMMARY FOR CASE NO. 1
VERTICAL AND HORIZONTAL
***TOTAL APPLIED LOAD ( KIP FEET ) SUMMARY (LOADING 1 )
SUMMATION FORCE-X = 1.20
SUMMATION FORCE-Y = -18.00
SUMMATION FORCE-Z = -1.20
SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 84.00 MY= 12.00 MZ= -96.00
***TOTAL REACTION LOAD( KIP FEET ) SUMMARY (LOADING 1 )
SUMMATION FORCE-X = -1.20
SUMMATION FORCE-Y = 18.00
SUMMATION FORCE-Z = 1.20
SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= -84.00 MY= -12.00 MZ= 96.00
MAXIMUM DISPLACEMENTS ( INCH /RADIANS) (LOADING 1)
MAXIMUMS AT NODE
X = 1.56266E-02 1
Y = -4.80071E-01 16
Z = -1.74873E-02 4
RX= -8.28375E-03 6
RY= -2.10910E-05 14
RZ= -8.31623E-03 7
************ END OF DATA FROM INTERNAL STORAGE ************
Design Per British Cold Formed Steel Code
Section 2E
2-110
JOINT DISPLACEMENT (CM RADIANS) STRUCTURE TYPE = SPACE
------------------
JOINT LOAD X-TRANS Y-TRANS Z-TRANS X-ROTAN Y-ROTAN Z-ROTAN
1 1 0.0397 -0.0184 -0.0339 0.0074 0.0000 -0.0027
4 1 0.0305 -0.0185 -0.0444 -0.0074 0.0000 0.0025
16 1 0.0352 -1.2194 -0.0392 0.0025 0.0000 0.0000
************** END OF LATEST ANALYSIS RESULT **************
SUPPORT REACTIONS -UNIT KGS CM STRUCTURE TYPE = SPACE
-----------------
JOINT LOAD FORCE-X FORCE-Y FORCE-Z MOM-X MOM-Y MOM Z
19 1 -447.32 2312.64 85.08 0.00 0.00 0.00
20 1 -447.10 2041.85 186.39 0.00 0.00 0.00
21 1 174.26 1768.33 187.79 0.00 0.00 0.00
22 1 175.85 2041.85 85.05 0.00 0.00 0.00
************** END OF LATEST ANALYSIS RESULT **************
MEMBER END FORCES STRUCTURE TYPE = SPACE
-----------------
ALL UNITS ARE -- KGS CM (LOCAL )
MEMBER LOAD JT AXIAL SHEAR-Y SHEAR-Z TORSION MOM-Y MOM-Z
3 1 1 669.42 1448.06 2.70 -1.68 -215.75 61582.12
5 -669.42 -767.67 -2.70 1.68 -196.10 107256.50
24 1 9 -0.63 -0.06 -285.30 -0.04 -0.08 1.04
17 0.63 0.06 -395.09 0.04 -8366.18 -9.62
28 1 1 2155.98 -404.11 -85.05 0.00 12961.01 -61586.40
22 -2155.98 404.11 85.05 0.00 0.00 0.00
************** END OF LATEST ANALYSIS RESULT **************
STAAD.Pro CODE CHECKING - (AISI)
***********************
UNITS ARE: IN, KIP, KIP-IN, KSI
|-----------------------------------------------------------------------------|
| MEMBER# 20 SECTION: 3HU3X075 LEN: 60.00 GOV.LOC: 60.00 |
| STATUS: PASS RATIO = 0.285 GOV.MODE: Bend + Compress GOV.LOAD: 1 |
| |
| RESISTANCES: AX.TENS: 0.00 ECC.TENS: 0.00 COMPRESS: 7.51 |
| BEND. Z: 28.21 BEND. Y: 30.98 SHEAR Z: 11.76 SHEAR Y: 5.88 |
| |
| FYLD: 55.00 COLD WORK FYLD: 55.71 FU: 58.00 A: 0.76 AE: 0.76 |
| IZ: 1.5173E+00 IZE: 1.5173E+00 IY: 9.7684E-01 IYE: 9.7684E-01 |
| SZE_T: 6.4841E-01 SZE_C: 6.4841E-01 SYE_T: 5.8539E-01 SYE_C: 7.3374E-01 |
|-----------------------------------------------------------------------------|
|-----------------------------------------------------------------------------|
| MEMBER# 21 SECTION: 3HU3X075 LEN: 60.00 GOV.LOC: 0.00 |
| STATUS: PASS RATIO = 0.285 GOV.MODE: Bend + Compress GOV.LOAD: 1 |
| |
| RESISTANCES: AX.TENS: 0.00 ECC.TENS: 0.00 COMPRESS: 7.51 |
| BEND. Z: 28.21 BEND. Y: 30.98 SHEAR Z: 11.76 SHEAR Y: 5.88 |
| |
| FYLD: 55.00 COLD WORK FYLD: 55.71 FU: 58.00 A: 0.76 AE: 0.76 |
| IZ: 1.5173E+00 IZE: 1.5173E+00 IY: 9.7684E-01 IYE: 9.7684E-01 |
| SZE_T: 1.0115E+00 SZE_C: 1.0115E+00 SYE_T: 7.3374E-01 SYE_C: 5.8539E-01 |
|-----------------------------------------------------------------------------|
Section 2E
2-111
STAAD/Pro CODE CHECKING - (BS5950-5-v1.0)
***********************
UNITS : MM, KN, KNM, MPA
-------------------------------------------------------------------------------
| MEMBER# 1 SECTION: 170CLHS56X18 LEN: 609.60 LOCATION: 609.60 |
| STATUS: PASS RATIO = 0.277 GOV.MODE: Bend + Compress GOV.LOAD: 1 |
|------------------------------------------------ --------------------------|
MATERIAL DATA:
Yield strength of steel: 379.21 N/mm2
Ultimate tensile strength: 430.00 N/mm2
SECTION PROPERTIES:(units - cm)
Section Name: 170CLHS56X18
Member Length: 60.96
Gross Area(Ag): 5.46 Net Area (Ae): 4.58
z-z axis y-y axis
Moment of inertia (I) : 237.68 21.99
Moment of inertia (Ie): 236.04 19.44
Elastic modulus (Zet): 27.91 5.21
Elastic modulus (Zec): 27.63 10.41
DESIGN DATA:
z-z axis y-y axis
Tension Capacity (Pt): 0.00
Compression Capacity (Pc): 93.79
Moment Capacity (Mc): 9.19 3.46
Shear Capacity (Pc): 21.15 33.58
EACH CLAUSE CHECK UNDER CRITICAL LOAD :
CLAUSE COMBINATION RATIO
BS-6.3 Compression ratio - Axial 0.037
BS-6.4 Bend-Compression ratio 0.277
BS-5.1 Bending Ratio - Z 0.235
BS-5.1 Bending Ratio - Y 0.006
BS-5.1 Biaxial Bending Ratio 0.241
BS-5.4 Shear Ratio - Z 0.168
BS-5.4 Shear Ratio - Y 0.003
BS-5.5.2 Bending -Z & Shear - Y Ratio 0.083
BS-5.5.2 Bending -Y & Shear - Z Ratio 0.000
Design Per British Cold Formed Steel Code
Section 2E
2-112
-------------------------------------------------------------------------------
| MEMBER# 2 SECTION: 170CLHS56X18 LEN: 609.60 LOCATION: 609.60 |
| STATUS: PASS RATIO = 0.282 GOV.MODE: Bend + Compress GOV.LOAD: 1 |
|------------------------------------------------ --------------------------|
MATERIAL DATA:
Yield strength of steel: 379.21 N/mm2
Ultimate tensile strength: 430.00 N/mm2
SECTION PROPERTIES:(units - cm)
Section Name: 170CLHS56X18
Member Length: 60.96
Gross Area(Ag): 5.46 Net Area (Ae): 4.58
z-z axis y-y axis
Moment of inertia (I) : 237.68 21.99
Moment of inertia (Ie): 236.04 21.99
Elastic modulus (Zet): 27.91 14.20
Elastic modulus (Zec): 27.63 5.43
DESIGN DATA:
z-z axis y-y axis
Tension Capacity (Pt): 0.00
Compression Capacity (Pc): 93.79
Moment Capacity (Mc): 9.19 1.81
Shear Capacity (Pc): 21.15 33.58
EACH CLAUSE CHECK UNDER CRITICAL LOAD :
CLAUSE COMBINATION RATIO
BS-6.3 Compression ratio - Axial 0.037
BS-6.4 Bend-Compression ratio 0.282
BS-5.1 Bending Ratio - Z 0.235
BS-5.1 Bending Ratio - Y 0.010
BS-5.1 Biaxial Bending Ratio 0.245
BS-5.4 Shear Ratio - Z 0.168
BS-5.4 Shear Ratio - Y 0.003
BS-5.5.2 Bending -Z & Shear - Y Ratio 0.083
BS-5.5.2 Bending -Y & Shear - Z Ratio 0.000
*********** END OF THE STAAD.Pro RUN ***********
Section 3
Canadian Codes
Aksf;ldkjasd
3-1
Concrete Design
Per CSA Standard A23.3-94
3A.1 Design Operations
STAAD can perform design of concrete beams, columns and slabs
according to CSA STANDARD A23.3-94. Given the dimensions of
a section, STAAD will calculate the required reinforcement
necessary to resist the various input loads.
3A.2 Section Types for Concrete Design
The following types of cross sections for concrete members can be
designed.
For Beams Prismatic (Rectangular, Square & Tee)
For Columns Prismatic (Rectangular, Square and Circular)
For Slabs 4-noded Plate Elements
3A.3 Member Dimensions
Concrete members that are to be designed by STAAD must have
certain section properties input under the MEMBER PROPERTIES
command. The following example demonstrates the required input:
Section 3A
Concrete Design Per CSA Standard A23.3-94
Section 3A
3-2
UNIT MM
MEMBER PROPERTIES
1 3 TO 7 9 PRISM YD 450. ZD 300.
11 14 PR YD 300.
In the above input, the first set of members are rectangular
(450mm depth and 300mm width) and the second set of members,
with only depth and no width provided, will be assumed to be
circular with a 300mm diameter.
3A.4 Slenderness Effects and Analysis Considerations
STAAD provides the user with two methods of accounting for the
slenderness effect in the analysis and design of concrete members.
The first method is equivalent to the procedure presented in CSA
STANDARD A23.3-94 Clause 10.13. STAAD accounts for the
secondary moments, due to axial loads and deflections, when the
PDELTA ANALYSIS command is used. After solving for the joint
displacements of the structure, the program calculates the
additional moments induced in the structure due to the P-Delta
effect. Therefore, by performing a PDELTA ANALYSIS, member
forces are calculated which will require no user modification
before beginning member design.
The second method by which STAAD allows the user to account
for the slenderness effect is through user suppl ied moment
magnification factors (see the parameter MMAG in Table 3A.1).
Here the user approximates the additional moment by supplying a
factor by which moments will be multiplied before beginning
member design. This second procedure allows slenderness to be
considered in accordance with Clause 10.14 of the code.
It should be noted that STAAD does not factor loads automatically
for concrete design. All the proper factored loads must be provided
by the user before the ANALYSIS specification.
Section 3A
3-3
While performing a PDELTA ANALYSIS, all load cases must be
defined as primary load cases. If the effects of separate load cases
are to be combined, it should be done either by using the REPEAT
LOAD command or by specifying the load information of these
individual loading cases under one single load case. Usage of the
LOAD COMBINATION command will yield incorrect results for
PDELTA ANALYSIS.
3A.5 Design Parameters
The program contains a number of parameters which are needed to
perform design per CSA STANDARD A23.3-94. These parameters
not only act as a method to input required data for code
calculations but give the engineer control over the actual design
process. Default values, which are commonly used numbers in
conventional design practice, have been used for simplici ty. Table
3A.1 contains a list of available parameters and their default
values. It is necessary to declare length and force units as
Millimeter and Newton before performing the concrete design.
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
Table 3A.1 - Canadian Concrete Design -CSA-A23.3-94 Parameters
Parameter Default Description
Name Value
FYMAIN 400N/mm2 Yield Stress for main reinforcing steel.
FYSEC 400 N/mm2 Yield Stress for secondary reinforcing steel.
FC 30 N/mm2 Specified compressive strength of concrete.
CLT 40mm Clear cover to reinforcing bar at top of cross section.
CLB 40mm Clear cover to reinforcing bar at bottom of cross section.
CLS 40mm Clear cover to reinforcing bar along the side of the cross section.
MINMAIN Number 10 bar Minimum main reinforcement bar size
Concrete Design Per CSA Standard A23.3-94
Section 3A
3-4
Table 3A.1 - Canadian Concrete Design -CSA-A23.3-94 Parameters
Parameter Default Description
Name Value
MINSEC Number 10 bar Minimum secondary (stirrup) reinforcement bar size.
MAXMAIN Number 55 bar Maximum main reinforcement bar size.
SFACE 0.0 Distance of face of support from start node of beam. Used for shear and torsion calculation.
EFACE 0.0 Face of Support Distance of face of support from end node of beam. Used for shear and torsion calculation. (Note: Both SFACE and EFACE are input as positive numbers).
REINF 0.0 Tied Column. A value of 1.0 will mean spiral.
TRACK 0.0 For TRACK = 0.0, Critical Moment will not be printed out with beam design report. For TRACK=1.0, moments will be printed.
MMAG 1.0 A factor by which the column design moments will be magnified.
NSECTION 12 Number of equally-spaced sections to be considered in finding critical moments for beam design.
WIDTH ZD Width of the concrete member. This value defaults to ZD as provided under MEMBER PROPERTIES.
DEPTH YD Depth of the concrete member. This value defaults to YD as provided under MEMBER PROPERTIES.
3A.6 Beam Design
Beams are designed for flexure, shear and torsion. For all these
forces, all active beam loadings are scanned to create moment and
shear envelopes, and locate critical sections. The total number of
sections considered is thirteen (start, end and 11 intermediate),
unless that number is redefined with the NSECTION parameter.
Design for Flexure
Design for flexure is performed per the rules of Chapter 2 of CSA
Standard A23.3-94. Maximum sagging (creating tensile stress at
the bottom face of the beam) and hogging (creating tensile stress
Section 3A
3-5
at the top face) moments are calculated for all active load cases at
each of the thirteen sections. Each of these sections are designed
to resist the critical sagging and hogging moments. Currently,
design of singly reinforced sections only is permitted. If the
section dimensions are inadequate as a singly reinforced section,
such a message will be printed in the output. Flexural design of
beams is performed in two passes. In the first pass, effective
depths of the sections are determined with the assumption of single
layer of assumed reinforcement and reinforcement requirements
are calculated. After the preliminary design, reinforcing bars are
chosen from the internal database in single or multiple layers. The
entire flexure design is performed again in a second pass taking
into account the changed effective depths of sections calculated on
the basis of reinforcement provided after the preliminary design.
Final provision of flexural reinforcements are made then. Efforts
have been made to meet the guideline for the curtailment of
reinforcements as per CSA Standard A23.3-94. Although exact
curtailment lengths are not mentioned explicitly in the design
output (which finally will be more or less guided by the detailer
taking into account other practical considerations), the user has the
choice of printing reinforcements provided by STAAD at 13
equally spaced sections from which the final detailed drawing can
be prepared.
The following annotations apply to the output for Beam Design.
1) LEVEL - Serial number of bar level which may
contain one or more bar group.
2) HEIGHT - Height of bar level from the bottom of
beam.
3) BAR INFOrmation - Reinforcement bar information
specifying number of bars and size.
4) FROM - Distance from the start of the beam to
the start of the rebar.
5) TO - Distance from the start of the beam to
the end of the rebar.
Concrete Design Per CSA Standard A23.3-94
Section 3A
3-6
6) ANCHOR - States whether anchorage, either a hook
(STA,END) or continuation, is needed at start (STA)
or at the end (END) of the bar.
Design for Shear and Torsion
Design for shear and torsion is performed per the rules of Chapter 4
of CSA Standard A23.3-94. Shear reinforcement is calculated to resist
both shear forces and torsional moments. Shear design is performed at
the start and end sections. The location along the member span for
design is chosen as the effective depth + SFACE at the start, and
effective depth + EFACE at the end. The load case which gives rise to
the highest stirrup area for shear & torsion is chosen as the critical
one. The calculations are performed assuming 2-legged stirrups will
be provided. The additional longitudinal steel area r equired for
torsion is reported.
The stirrups are assumed to be U-shaped for beams with no
torsion, and closed hoops for beams subjected to torsion.
Example of Input Data for Beam Design
UNIT NEWTON MMS
START CONCRETE DESIGN
CODE CANADA
FYMAIN 415 ALL
FYSEC 415 ALL
FC 35 ALL
CLEAR 25 MEMB 2 TO 6
MAXMAIN 40 MEMB 2 TO 6
TRACK 1.0 MEMB 2 TO 9
DESIGN BEAM 2 TO 9
END CONCRETE DESIGN
Section 3A
3-7
3A.7 Column Design
Column design is performed per the rules of Chapters 7 & 8 of the
CSA Standard A23.3-94. Columns are designed for axial force and
biaxial moments at the ends. All active loadings are tested to
calculate reinforcement. The loading which produces maximum
reinforcement is called the critical load. Column design is done for
square, rectangular and circular sections. For rectangular and
square sections, the reinforcement is always assumed to be equally
distributed on each side. That means the total number of bars will
always be a multiple of four (4). This may cause slightly
conservative results in some cases.
Example of Input Data for Column Design
UNIT NEWTON MMS
START CONCRETE DESIGN
CODE CANADIAN
FYMAIN 415 ALL
FC 35 ALL
CLEAR 25 MEMB 2 TO 6
MAXMAIN 40 MEMB 2 TO 6
DESIGN COLUMN 2 TO 6
END CONCRETE DESIGN
3A.8 Slab/Wall Design
To design a slab or wall, it must be modeled using finite elements.
The commands for specifying elements are in accordance with the
relevant sections of the Technical Reference Manual.
Elements are designed for the moments Mx and My using the same
principles as those for beams in flexure. The width of the beam is
assumed to be unity for this purpose. These moments are obtained
from the element force output (see the relevant sections of the
Concrete Design Per CSA Standard A23.3-94
Section 3A
3-8
Technical Reference Manual). The reinforcement required to resist
Mx moment is denoted as longitudinal reinforcement and the
reinforcement required to resist My moment is denoted as
transverse reinforcement. The effective depth is calculated
assuming #10 bars are provided. The parameters FYMAIN, FC,
CLT and CLB listed in Table 3A.1 are relevant to slab design.
Other parameters mentioned in Table 3A.1 are not applicable to
slab design. The output consists only of area of steel required.
Actual bar arrangement is not calculated because an element most
likely represents just a fraction of the total slab area.
LONG.
TRANS.
X
Y
Z
M
MM
Mx
y
x
y
Example of Input Data for Slab/Wall Design
UNIT NEWTON MMS
START CONCRETE DESIGN
CODE CANADA
FYMAIN 415 ALL
FC 35 ALL
CLB 40 ALL
DESIGN ELEMENT 15 TO 20
END CONCRETE DESIGN
3-9
Steel Design Per CSA Standard
CAN/CSA-S16-01
3B.1 General Comments
The design of structural steel members in accordance with the
specification CAN/CSA S16-01 Limit States Design of Steel
Structures is now implemented. This code supercedes the previous
edition of the code CAN/CSA – S16.1-94.
The design philosophy embodied in this specification is based on
the concept of limit state design. Structures are designed and
proportioned taking into consideration the limit states at which
they would become unfit for their intended use. Two major
categories of limit-state are recognized - ultimate and
serviceability. The primary considerations in ultimate limit state
design are strength and stability, while that in serviceability is
deflection. Appropriate load and resistance factors are used so that
a uniform reliability is achieved for all steel structures under
various loading conditions and at the same time the chances of
limits being surpassed are acceptably remote.
In the STAAD implementation, members are proportioned to resist
the design loads without exceeding the limit states of strength,
stability and serviceability. Accordingly, the most economic
section is selected on the basis of the least weight criteria as
augmented by the designer in specification of allowable member
depths, desired section type, or other such parameters. The code
checking portion of the program checks whether code requirements
for each selected section are met and identifies the governing
criteria.
Section 3B
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-10
The following sections describe the salient features of the STAAD
implementation of CAN/CSA-S16-01. A detailed description of the
design process along with its underlying concepts and assumptions
is available in the specification document.
3B.2 Analysis Methodology
Elastic analysis method is used to obtain the forces and moments
for design. Analysis is done for the primary and combination
loading conditions provided by the user. The user is allowed
complete flexibility in providing loading specifications and using
appropriate load factors to create necessary loading situations.
Depending upon the analysis requirements, regular stiffness
analysis or P-Delta analysis may be specified. Dynamic analysis
may also be performed and the results combined with static
analysis results.
3B.3 Member Property Specifications
For specification of member properties, the steel section library
available in STAAD may be used. The next section describes the
syntax of commands used to assign properties from the built -in
steel table. Member properties may also be specified using the
User Table facility. For more information on these facilities, refer
to the STAAD Technical Reference Manual.
3B.4 Built-in Steel Section Library
The following information is provided for use when the built -in
steel tables are to be referenced for member property specification.
These properties are stored in a database file. If called for, the
properties are also used for member design. Since the shear areas
are built into these tables, shear deformation is always considered
during the analysis of these members.
Section 3B
3-11
Almost all Canadian steel sections are available for input. A
complete listing of the sections available in the built -in steel
section library may be obtained by using the tools of the graphical
user interface.
Following is the description of the different types of sections
available:
Welded Wide Flanges (WW shapes)
Welded wide flange shapes listed in the CSA steel tables can be
designated using the same scheme used by CSA. The following
example illustrates the specification of welded wide flange shapes.
100 TO 150 TA ST WW400X444
34 35 TA ST WW900X347
Wide Flanges (W shapes)
Designation of wide flanges in STAAD is the same as that in CSA
tables. For example,
10 TO 75 95 TO 105 TA ST W460X106
100 TO 200 TA ST W610X101
S, M, HP shapes
In addition to welded wide flanges and regular wide flanges, other
I shaped sections like S, M and HP shapes are also available. The
designation scheme is identical to that listed in the CSA tables.
While specifying the sections, it should be remembered that the
portion after the decimal point should be omitted. Thus,
M310X17.6 should be specified as M310X17 and S180X22.8
should be specified as S180X22. Examples illustrating
specifications of these shapes are provided below.
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-12
10 TO 20 BY 2 TA ST S510X98
45 TO 55 TA ST M150X6
88 90 96 TA ST HP310X79
Channel Sections (C & MC shapes)
C and MC shapes are designated as shown in the following
example. As in S, M and HP sections, the portion after the decimal
point must be omitted in section designations. Thus, MC250X42.4
should be designated as MC250X42.
55 TO 90 TA ST C250X30
30 TO 45 TA ST MC200X33
Double Channels
Back to back double channels, with or without spacing between
them, are specified by preceding the section designation by the
letter D. For example, a back to back double channel section
C200X28 without any spacing in between should be specified as:
100 TO 120 TA D C200X28
If a spacing of 2.5 length units is used, the specification should be
as follows:
100 TO 120 TA D C200X28 SP 2.5
Note that the specification SP after the section designation is used
for providing the spacing. The spacing should always be provided
in the current length unit.
Section 3B
3-13
Angles
To specify angles, the angle name is preceded by the letter L.
Thus, a 200X200 angle with a 25mm thickness is designated as
L200X200X25. The following examples illustrate angle
specifications.
75 TO 95 TA ST L100X100X8
33 34 35 TA ST L200X100X20
Note that the above specification is for “standard” angles. In this
specification, the local z-axis (see Fig. 2.6 in the Technical
Reference Manual) corresponds to the Y‟-Y‟ axis shown in the
CSA table. Another common practice of specifying angles assumes
the local y-axis to correspond to the Y‟-Y‟ axis. To specify angles
in accordance with this convention, the reverse angle designation
facility has been provided. A reverse angle may be specified by
substituting the word ST with the word RA. Refer to the following
example for details.
10 TO 15 TA RA L55X35X4
The local axis systems for STANDARD and REVERSE angles is
shown in Fig. 2.6 of the STAAD Technical Reference manual.
Double Angles
To specify double angles, the specification ST should be
substituted with LD (for long leg back to back) or SD (short leg
back to back). For equal angles, either SD or LD will serve the
purpose. Spacing between angles may be provided by using the
word SP followed by the value of spacing (in current length unit)
after section designation.
25 35 45 TA LD L150X100X16
80 TO 90 TA SD L125X75X6 SP 2.5
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-14
The second example above describes a double angle section
consisting of 125X75X6 angles with a spacing of 2.5 length units.
Tees
Tee sections obtained by cutting W sections may be specified by
using the T specification instead of ST before the name of the W
shape. For example:
100 TO 120 TA T W200X42
will describe a T section cut from a W200X42 section.
Rectangular Hollow Sections
These sections may be specified in two possible ways. Those
sections listed in the CSA tables may be specified as follows.
55 TO 75 TA ST TUB80X60X4
Tube Symbol Thickness (in) X16
Width (in.) X10
TUB 80 X 60 X 4
Height (in) X 10
In addition, any tube section may be specified by using the DT(for
depth), WT(for width), and TH(for thickness) specifications.
Section 3B
3-15
For example:
100 TO 200 TA ST TUBE DT 8.0 WT 6.0 TH 0.5
will describe a tube with a depth of 8 in., width of 6 in. and a wall
thickness of 0.5 inches. Note that the values of depth, width and
thickness must be provided in current length unit.
Circular Hollow Sections
Sections listed in the CSA tables may be provided as follows:
15 TO 25 TA ST PIP33X2.5
Pipe Symbol Thickness (mm)
Diameter (mm)
PIP 33 X 2.5
(Upto first decimal place only)
without decimal point
In addition to sections listed in the CSA tables, circular hollow
sections may be specified by using the OD (outside diameter) and
ID (inside diameter) specifications. For example:
70 TO 90 TA ST PIPE OD 10.0 ID 9.0
will describe a pipe with an outside diameter of 10 length units
and inside diameter of 9.0 length units. Note that the values of
outside and inside diameters must be provided in terms of current
length unit.
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-16
Sample input file to demonstrate usage of Canadian shapes
STAAD SPACE
UNIT METER KNS
JOINT COORD
1 0 0 0 17 160 0 0
MEMBER INCIDENCES
1 1 2 16
UNIT CM
MEMBER PROPERTIES CANADIAN
* W SHAPES
1 TA ST W250X18
* WW SHAPES
2 TA ST WW700X185
* S SHAPES
3 TA ST S200X27
* M SHAPES
4 TA ST M130X28
* HP SHAPES
5 TA ST HP310X132
* MC CHANNELS
6 TA ST MC150X17
* C CHANNELS
7 TA ST C180X18
* DOUBLE CHANNELS
8 TA D C250X37 SP 1.0
* ANGLES
9 TA ST L55X35X5
* REVERSE ANGLES
10 TA RA L90X75X5
* DOUBLE ANGLES, LONG LEG BACK TO BACK
11 TA LD L100X90X6 SP 2.0
* DOUBLE ANGLES, SHORT LEG BACK TO BACK
12 TA SD L125X75X6 SP 2.5
* TUBES
13 TA ST TUB120807
Section 3B
3-17
* TUBES
14 TA ST TUBE DT 16.0 WT 8.0 TH 0.8
* PIPES
15 TA ST PIP273X6.3
* PIPES
16 TA ST PIPE OD 16.0 ID 13.0
PRINT MEMBER PROPERTIES
FINISH
3B.5 Section Classification
The CSA specification allows inelastic deformation of section
elements. Thus, local buckling becomes an important criterion.
Steel sections are classified as plastic (Class 1), compact (Class 2),
non compact (Class 3) or slender element (Class 4) sections
depending upon their local buckling characteristics (See Clause
11.2 and Table 1 of CAN/CSA-S16-01). This classification is a
function of the geometric properties of the section. The design
procedures are different depending on the section class. STAAD
determines the section classification for the standard shapes and
user specified shapes. Design is performed for sections that fall
into the category of Class 1,2 or 3 sections only. Class 4 sect ions
are not designed by STAAD.
3B.6 Member Resistances
The member resistances are calculated in STAAD according to the
procedures outlined in section 13 of the specification. These
depend on several factors such as members unsupported lengths,
cross-sectional properties, slenderness factors, unsupported width
to thickness ratios and so on. Note that the program automatically
takes into consideration appropriate resistance factors to calculate
member resistances. Explained here is the procedure adopted in
STAAD for calculating the member resistances.
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-18
Axial Tension
The criteria governing the capacity of tension members is based on
two limit states. The limit state of yielding in the gross section is
intended to prevent excessive elongation of the member. The
second limit state involves fracture at the section with the
minimum effective net area. The net section area may be specified
by the user through the use of the parameter NSF (see Table 3B.1).
STAAD calculates the tension capacity of a member based on
these two limits states per Cl.13.2 of CAN/CSA-S16-01.
Parameters FYLD, FU and NSF are applicable for these
calculations.
Axial Compression
The compressive resistance of columns is determined based on
Clause 13.3 of the code. The equations presented in th is section of
the code assume that the compressive resistance is a function of
the compressive strength of the gross section (Gross section Area
times the Yield Strength) as well as the slenderness factor (KL/r
ratios). The effective length for the calcula tion of compression
resistance may be provided through the use of the parameters KX,
KY, KZ, LX, LY and LZ (see Table 3B.1). Some of the aspects of
the axial compression capacity calculations are :
1) For frame members not subjected to any bending, and for t russ
members, the axial compression capacity in general column
flexural buckling is calculated from Cl.13.3.1 using the
slenderness ratios for the local Y-Y and Z-Z axis. The
parameters KY, LY, KZ and LZ are applicable for this.
2) For single angles, which are frame members not subjected to
any bending or truss members, the axial compression capacity
in general column flexural buckling and local buckling of thin
legs is calculated using the rules of the AISC - LRFD code, 2nd
ed., 1994. The reason for this is that the Canadian code doesn‟t
provide any clear guidelines for calculating this value. The
parameters KY, LY, KZ and LZ are applicable for this.
3) The axial compression capacity is also calculated by taking
flexural-torsional buckling into account. The rules of
Appendix D, page 1-109 of CAN/CSA-S16-01are used for this
Section 3B
3-19
purpose. Parameters KX and LX may be used to provide the
effective length factor and effective length value for flexural -
torsional buckling. Flexural-torsional buckling capacity is
computed for single channels, single angles, Tees and Double
angles.
4) The variable “n” in Cl.13.3.1 is assumed as 2.24 for WWF
shapes and 1.34 for all other shapes.
5) While computing the general column flexural buckling
capacity of sections with axial compression + bendin g, the
special provisions of 13.8.1(a), 13.8.1(b) and 13.8.1(c) are
applied. For example, Lambda = 0 for 13.8.1(a), K=1 for
13.8.1(b), etc.)
Bending
The laterally unsupported length of the compression flange for the
purpose of computing the factored moment resistance is specified
in STAAD with the help of the parameter UNL. If UNL is less
than one tenth the member length (member length is the distance
between the joints of the member), the member is treated as being
continuously laterally supported. In this case, the moment
resistance is computed from Clause 13.5 of the code. If UNL is
greater than or equal to one tenth the member length, its value is
used as the laterally unsupported length. The equations of Clause
13.6 of the code are used to arrive at the moment of resistance of
laterally unsupported members. Some of the aspects of the bending
capacity calculations are :
1) The weak axis bending capacity of all sections except single
angles is calculated as
For Class 1 & 2 sections, Phi*Py*Fy
For Class 3 sections, Phi*Sy*Fy
where Phi = Resistance factor = 0.9
Py = Plastic section modulus about the local Y axis
Sy = Elastic section modulus about the local Y axis
Fy = Yield stress of steel
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-20
2) For single angles, the bending capacities are calculated for the
principal axes. The specifications of Section 5, page 6-283 of
AISC-LRFD 1994, 2nd
ed., are used for this purpose because
the Canadian code doesn‟t provide any clear guidelines for
calculating this value.
3) For calculating the bending capacity about the Z-Z axis of
singly symmetric shapes such as Tees and Double angles,
CAN/CSA-S16-01 stipulates in Clause 13.6(d), page 1-31, that
a rational method, such as that given in SSRC‟s Guide to
Stability Design Criteria of Metal Structures, be used. Instead,
STAAD uses the rules of Section 2c, page 6-55 of AISC-LRFD
1994, 2nd ed.
Axial compression and bending
The member strength for sections subjected to axial compression
and uniaxial or biaxial bending is obtained through the use of
interaction equations. In these equations, the additional bending
caused by the action of the axial load is accounted for by using
amplification factors. Clause 13.8 of the code provides the
equations for this purpose. If the summation of the left hand side
of these equations exceed 1.0 or the allowable value provided
using the RATIO parameter (see Table 3B.1), the member is
considered to have FAILed under the loading condition.
Axial tension and bending
Members subjected to axial tension and bending are also designed
using interaction equations. Clause 13.9 of the code is used to
perform these checks. The actual RATIO is determined as the
value of the left hand side of the critical equation.
Shear
The shear resistance of the cross section is determined using the
equations of Clause 13.4 of the code. Once this is obtained, the
ratio of the shear force acting on the cross section to the shear
resistance of the section is calculated. If any of the ratios (for both
local Y & Z axes) exceed 1.0 or the allowable value provided
using the RATIO parameter (see Table 3B.1), the section is
Section 3B
3-21
considered to have failed under shear. The code also requires that
the slenderness ratio of the web be within a certain limit (See
Cl.13.4.1.3, page 1-29 of CAN/CSA-S16-01). Checks for safety in
shear are performed only if this value is within the allowable limit.
Users may by-pass this limitation by specifying a value of 2.0 for
the MAIN parameter.
3B.7 Design Parameters
The design parameters outlined in Table 3B.1 may be used to
control the design procedure. These parameters communicate
design decisions from the engineer to the program and thus allow
the engineer to control the design process to suit an application's
specific needs.
The default parameter values have been selected such that they are
frequently used numbers for conventional design. Depending on
the particular design requirements, some or all of these parameter
values may be changed to exactly model the physical structure.
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
Canadian Steel Design Parameters
Parameter Default Description
Name Value
KT 1.0 K value for flexural torsional buckling.
KY 1.0 K value for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.
KZ 1.0 K value for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.
LT Member Length Length for flexural torsional buckling.
LY Member Length Length for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-22
Canadian Steel Design Parameters
Parameter Default Description
Name Value
LZ Member Length Length for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.
FYLD 300.0 MPa Yield strength of steel.
FU 345.0 MPa Ultimate strength of steel.
NSF 1.0 Net section factor for tension members.
UNT Member Length Unsupported length in bending compression of the top flange for calculating moment resistance.
UNB Member Length Unsupported length in bending compression of the bottom flange for calculating moment resistance.
MAIN 0.0 0.0 = Check slenderness ratio against the limits. 1.1 = Suppress the slenderness ratio check.
2.0 = Check slenderness ratio only for column buckling, not for web (See Section 3B.6, Shear)
CB 1.0 Greater than 0.0 and less than 2.5 : Value of Omega_2 (Cl.13.6) to be used for calculation.
Equal to 0.0 : Calculate Omega_2
CMY 1.0 1.0 = Do not calculate Omega-1 for local Y axis. 2.0 = Calculate Omega-1 for local Y axis. Used in Cl.13.8.4 of code
CMZ 1.0 1.0 = Do not calculate Omega-1 for local Z axis. 2.0 = Calculate Omega-1 for local Z axis. Used in Cl.13.8.4 of code
TRACK 0.0 0.0 = Report only minimum design results.
1.0 = Report design strengths also.
2.0 = Provide full details of design.
DMAX 45.0 in. Maximum allowable depth (Applicable for member selection)
DMIN 0.0 in. Minimum required depth (Applicable for member selection)
RATIO 1.0 Permissible ratio of actual load effect to the design strength.
Section 3B
3-23
Canadian Steel Design Parameters
Parameter Default Description
Name Value
BEAM 0.0 0.0 = design only for end moments and those at locations specified by SECTION command.
1.0 = Perform design for moments at twelfth points along the beam.
DFF None(Mandatory for deflection
check)
“Deflection Length”/Maxm. Allowable local deflection.
DJ1 Start Joint of member
Joint No. denoting start point for calculation of “deflection length”
DJ2 End Joint of member
Joint No. denoting end point for calculation of “deflection length”
3B.8 Code Checking
The purpose of code checking is to check whether the provided
section properties of the members are adequate. The adequacy is
checked as per the CAN/CSA-S16-01 requirements.
Code checking is done using forces and moments at specified
sections of the members. If the BEAM parameter for a member is
set to 1, moments are calculated at every twelfth point along the
beam. When no sections are specified and the BEAM parameter is
set to zero (default), design will be based on member start and end
forces only. The code checking output labels the members as
PASSed or FAILed. In addition, the critical condition, governing
load case, location (distance from the start joint) and magnitudes
of the governing forces and moments are also printed. The extent
of detail of the output can be controlled by using the TRACK
parameter.
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-24
Example of commands for CODE CHECKING:
UNIT NEWTON METER
PARAMETER
FYLD 330E6 MEMB 3 4
NSF 0.85 ALL
KY 1.2 MEMB 3 4
UNL 15 MEMB 3 4
RATIO 0.9 ALL
CHECK CODE MEMB 3 4
3B.9 Member Selection
The member selection process basically involves determination of
the least weight member that PASSes the code checking procedure
based on the forces and moments of the most recent analysis. The
section selected will be of the same type as that specified initially.
For example, a member specified initially as a chann el will have a
channel selected for it. Selection of members whose properties are
originally provided from a user table will be limited to sections in
the user table. Member selection cannot be performed on TUBES,
PIPES or members listed as PRISMATIC.
Section 3B
3-25
Example of commands for MEMBER SELECTION:
UNIT NEWTON METER
PARAMETER
FYLD 330E6 MEMB 3 4
NSF 0.85 ALL
KY 1.2 MEMB 3 4
UNL 15 MEMB 3 4
RATIO 0.9 ALL
SELECT MEMB 3 4
3B.10 Tabulated Results of Steel Design
Results of code checking and member selection are presented in a
tabular format. The term CRITICAL COND refers to the section of
the CAN/CSA-S16-01 specification which governed the design.
If the TRACK parameter is set to 1.0, factored member resistances
will be printed. Following is a description of some of the items
printed.
CR = Factored compressive resistance
TR = Factored tensile resistance
VR = Factored shear resistance
MRZ = Factored moment resistance (about z-axis)
MRY = Factored moment resistance (about y-axis)
Further details can be obtained by setting TRACK to 2.0.
CR1 = CAPACITY (Cr) PER 13.8.2(a)
CR2 = CAPACITY (Cr) PER 13.8.2(b)
CRZ = SEE 13.8.2(b) for uniaxial bending (called CRX in that
Clause)
CTORFLX = Capacity in accordance with 13.8.2(c)
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-26
3B.11 Verification Problems
In the next few pages are included 3 verification examples for
reference purposes. Since the S16-01 code is similar in many
respects to the previous edition of the code (CAN/CSA S16.1-94),
the solved examples of the 1994 edition of the CISC Handbook
have been used as reference material for these examples.
Section 3B
3-27
Verification Problem No. 1
TITLE Steel beam with uniform load, wide flange section.
TYPE Static analysis, 3D beam element.
REFERENCE: CAN/CSA-S16.1-94, National Standard of Canada,
Limit States Design of Steel Structures. The Canadian
Standards Association, 1994 with CISC (Canadian
Institute of Steel Construction) handbook. CISC
Example 1 page 5_91.
PROBLEM: Find the interaction ratio, beam resistance and beam
deflection.
GIVEN: E = 200000 MPa (STEEL).
Fy = 300 Mpa CSA G40.21-M
Beam has a 8.0 m span; Ky is 1.0, Kz 1.0, unsupported
length 1.0 m
Allowable Live Load deflection, L/300 = 8000/300 = 27 mm Factored Uniform Load IS 7 kN/m DEAD, 15 kN/m LIVE.
Steel section is W410X54.
SOLUTION COMPARISON:
CAN/CSA-S16
Interaction
Ratio
Beam
Resistance
(kN*m)
Beam
Deflection
(mm)
REFERENCE 0.88 284 21
STAAD.Pro 0.883 283.20 20.81
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-28
****************************************************
* *
* STAAD.Pro *
* Version Bld *
* Proprietary Program of *
* Research Engineers, Intl. *
* Date= *
* Time= *
* *
* USER ID: *
****************************************************
1. STAAD SPACE VERIFICATION CISC 1994 HANDBOOK EXAMPLE PAGE 5-91
3. * CISC EXAMPLE 1 PAGE 5-91, LIMIT STATES DESIGN, CSA-S16.1-94
4. * SIMPLY SUPPORTED BEAM WITH UNIFORM LOAD
5. * LIVE LOAD DEFLECTION OF L/300
7. UNIT MMS KN
8. JOINT COORDINATES
9. 1 0 0 0; 2 8000 0 0
10. MEMBER INCIDENCES
11. 1 1 2
13. MEMBER PROPERTY CANADIAN
14. 1 TABLE ST W410X54
16. CONSTANTS
17. E STEEL ALL
18. POISSON 0.3 ALL
20. SUPPORTS
21. 1 PINNED
22. 2 FIXED BUT MY MZ
24. UNIT METER KN
25. LOAD 1 DEAD
26. MEMBER LOAD
27. 1 UNI GY -7
29. LOAD 2 LIVE
30. MEMBER LOAD
31. 1 UNI GY -15
33. LOAD COMB 3 1.25DL + 1.5 LL
34. 1 1.25 2 1.5
36. PERFORM ANALYSIS
P R O B L E M S T A T I S T I C S
-----------------------------------
NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 2/ 1/ 2
ORIGINAL/FINAL BAND-WIDTH= 1/ 1/ 5 DOF
TOTAL PRIMARY LOAD CASES = 2, TOTAL DEGREES OF FREEDOM = 5
SIZE OF STIFFNESS MATRIX = 1 DOUBLE KILO-WORDS
REQRD/AVAIL. DISK SPACE = 12.0/ 19641.6 MB
37. LOAD LIST 2
Section 3B
3-29
38. PRINT SECTION DISPLACEMENTS
MEMBER SECTION DISPLACEMENTS
----------------------------
UNIT =INCHES FOR FPS AND CM FOR METRICS/SI SYSTEM
MEMB LOAD GLOBAL X,Y,Z DISPL FROM START TO END JOINTS AT 1/12TH PTS
1 2 0.0000 0.0000 0.0000 0.0000 -0.5471 0.0000
0.0000 -1.0528 0.0000 0.0000 -1.4824 0.0000
0.0000 -1.8086 0.0000 0.0000 -2.0120 0.0000
0.0000 -2.0812 0.0000 0.0000 -2.0120 0.0000
0.0000 -1.8086 0.0000 0.0000 -1.4824 0.0000
0.0000 -1.0528 0.0000 0.0000 -0.5471 0.0000
0.0000 0.0000 0.0000
MAX LOCAL DISP = 2.08115 AT 400.00 LOAD 2 L/DISP= 384
************ END OF SECT DISPL RESULTS ***********
40. LOAD LIST 3
41. PARAMETER
42. CODE CANADIAN
43. TRACK 2 ALL
44. UNL 1 ALL
45. FYLD 300000 ALL
46. BEAM 1 ALL
47. CHECK CODE ALL
STAAD.PRO CODE CHECKING - (CAN/CSA-S16-01)
******************************************
ALL UNITS ARE - KNS MET (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
1 ST W410X54 (CANADIAN SECTIONS)
PASS CSA-13.8.2+ 0.883 3
0.00 C 0.00 -250.00 4.00
MEMBER PROPERTIES (UNIT = CM)
-----------------------------
CROSS SECTION AREA = 6.84E+01 MEMBER LENGTH = 8.00E+02
IZ = 1.86E+04 SZ = 9.26E+02 PZ = 1.05E+03
IY = 1.02E+03 SY = 1.15E+02 PY = 1.77E+02
MATERIAL PROPERTIES (UNIT = MPA)
--------------------------------
FYLD = 300.0 FU = 345.0
SECTION CAPACITIES (UNIT - KN,M)
---------------------------------
CR1 = 1.846E+03 CR2 = 2.732E+02
CRZ = 1.570E+03 CTORFLX = 2.732E+02
TENSILE CAPACITY = 1.805E+03 COMPRESSIVE CAPACITY = 2.732E+02
FACTORED MOMENT RESISTANCE : MRY = 4.778E+01 MRZ = 2.832E+02
FACTORED SHEAR RESISTANCE : VRY = 5.379E+02 VRZ = 4.604E+02
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-30
MISCELLANEOUS INFORMATION
--------------------------
NET SECTION FACTOR FOR TENSION = 1.000
KL/RY = 207.170 KL/RZ = 48.447 ALLOWABLE KL/R = 300.000
UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 1.000
OMEGA-1 (Y-AXIS) = 1.00 OMEGA-1 (Z-AXIS) = 1.00 OMEGA-2 = 1.00
SHEAR FORCE (KNS) : Y AXIS = 0.000E+00 Z AXIS = 0.000E+00
SLENDERNESS RATIO OF WEB (H/W) = 5.08E+01
48. STEEL TAKE OFF ALL
STEEL TAKE-OFF
--------------
PROFILE LENGTH(METE) WEIGHT(KN )
In Steel Takeoff the density of steel is assumed for members with no density.
ST W410X54 8.00 4.203
PRISMATIC STEEL 0.00 0.000
----------------
TOTAL = 4.203
************ END OF DATA FROM INTERNAL STORAGE ************
49. FINISH
Section 3B
3-31
Verification Problem No. 2
TITLE: Steel beam/column, wide flange section.
TYPE: Static Analysis, 3D beam element.
REFERENCE: CAN/CSA-S16.1-94, National Standard of Canada,
Limit States Design of Steel Structures. The Canadian
Standards Association, 1994 with CISC (Canadian
Institute of Steel Construction) handbook. CISC
Handbook Example, Page 4_106.
PROBLEM: Find the interaction ratio, beam and column resistance.
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-32
GIVEN: E = 200000 MPa (STEEL).
Fy = 300 MPa CSA G40.21-M Beam/Column has a 3.7 m span, Ky is 1.0, Kz 1.0
factored axial load is 2000 kN and end moments of
200 kN*m and 300 kN*m
Steel section is W310X129
SOLUTION COMPARISON:
CAN/CSA-S16
Interaction
Ratio
Beam Resistance
(kN*m)
Column Resistance
(kN)
REFERENCE 0.96 583 3800
STAAD.Pro 0.98 584 3820
Section 3B
3-33
****************************************************
* *
* STAAD.Pro *
* Version Bld *
* Proprietary Program of *
* Research Engineers, Intl. *
* Date= *
* Time= *
* *
* USER ID: *
****************************************************
1. STAAD SPACE VERIFICATION CISC 1994 HANDBOOK EXAMPLE PAGE 4-106
2. *
3. * COMPRESSION + MAJOR AXIS BENDING
4. *
5. UNIT METER KN
6. JOINT COORDINATES
7. 1 0 0 0; 2 0 3.7 0
8. *
9. MEMBER INCIDENCES
10. 1 1 2
11. *
12. MEMBER PROPERTY CANADIAN
13. 1 TABLE ST W310X129
14. *
15. CONSTANTS
16. E STEEL ALL
17. POISSON STEEL ALL
18. *
19. SUPPORTS
20. 1 FIXED BUT MX MZ
21. 2 FIXED BUT FY MY MZ
22. *
23. LOAD 1 FACTORED LOAD
24. JOINT LOAD
25. 2 FY -2000
26. 2 MZ 200
27. 1 MZ 300
28. *
29. PDELTA 3 ANALYSIS
P R O B L E M S T A T I S T I C S
-----------------------------------
NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 2/ 1/ 2
ORIGINAL/FINAL BAND-WIDTH= 1/ 1/ 5 DOF
TOTAL PRIMARY LOAD CASES = 1, TOTAL DEGREES OF FREEDOM = 5
SIZE OF STIFFNESS MATRIX = 1 DOUBLE KILO-WORDS
REQRD/AVAIL. DISK SPACE = 12.0/ 19641.2 MB
++ Adjusting Displacements 8:54:35
++ Adjusting Displacements 8:54:35
++ Adjusting Displacements 8:54:35
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-34
31. PRINT MEMBER FORCES
MEMBER END FORCES STRUCTURE TYPE = SPACE
-----------------
ALL UNITS ARE -- KN METE
MEMBER LOAD JT AXIAL SHEAR-Y SHEAR-Z TORSION MOM-Y MOM-Z
1 1 1 2000.00 135.14 0.00 0.00 0.00 300.00
2 -2000.00 -135.14 0.00 0.00 0.00 200.00
************** END OF LATEST ANALYSIS RESULT **************
33. PARAMETER
34. CODE CANADIAN
35. TRACK 2 ALL
36. FYLD 300000 ALL
37. LY 3.7 ALL
38. LZ 3.7 ALL
39. CHECK CODE ALL
STAAD.PRO CODE CHECKING - (CAN/CSA-S16-01)
******************************************
ALL UNITS ARE - KNS MET (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
1 ST W310X129 (CANADIAN SECTIONS)
PASS CSA-13.8.2C 0.980 1
2000.00 C 0.00 300.00 0.00
MEMBER PROPERTIES (UNIT = CM)
-----------------------------
CROSS SECTION AREA = 1.65E+02 MEMBER LENGTH = 3.70E+02
IZ = 3.08E+04 SZ = 1.94E+03 PZ = 2.16E+03
IY = 1.00E+04 SY = 6.51E+02 PY = 9.90E+02
MATERIAL PROPERTIES (UNIT = MPA)
--------------------------------
FYLD = 300.0 FU = 345.0
SECTION CAPACITIES (UNIT - KN,M)
---------------------------------
CR1 = 4.459E+03 CR2 = 3.820E+03
CRZ = 4.296E+03 CTORFLX = 3.820E+03
TENSILE CAPACITY = 4.359E+03 COMPRESSIVE CAPACITY = 3.820E+03
FACTORED MOMENT RESISTANCE : MRY = 2.672E+02 MRZ = 5.840E+02
FACTORED SHEAR RESISTANCE : VRY = 7.419E+02 VRZ = 1.505E+03
Section 3B
3-35
MISCELLANEOUS INFORMATION
--------------------------
NET SECTION FACTOR FOR TENSION = 1.000
KL/RY = 47.477 KL/RZ = 27.094 ALLOWABLE KL/R = 200.000
UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 3.700
OMEGA-1 (Y-AXIS) = 1.00 OMEGA-1 (Z-AXIS) = 1.00 OMEGA-2 = 1.00
SHEAR FORCE (KNS) : Y AXIS = 1.351E+02 Z AXIS = 0.000E+00
SLENDERNESS RATIO OF WEB (H/W) = 2.12E+01
40. STEEL MEMBER TAKE OFF ALL
STEEL TAKE-OFF
--------------
PROFILE LENGTH(METE) WEIGHT(KN )
In Steel Takeoff the density of steel is assumed for members with no density.
ST W310X129 3.70 4.694
PRISMATIC STEEL 0.00 0.000
----------------
TOTAL = 4.694
MEMBER PROFILE LENGTH WEIGHT
(METE) (KN )
1 ST W310X129 3.70 4.694
************ END OF DATA FROM INTERNAL STORAGE ************
42. FINISH
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-36
Verification Problem No. 3
TITLE: Steel beam/column, wide flange section.
TYPE: Static Analysis, 3D beam element.
REFERENCE: CAN/CSA-S16.1-94, National Standard of Canada,
Limit States Design of Steel Structures. The Canadian
Standards Association, 1994 with CISC (Canadian
Institute of Steel Construction) handbook. CISC
Handbook Example, Page 4_108.
PROBLEM: Find the interaction ratio, beam and column resistance.
Section 3B
3-37
GIVEN: E = 200000 MPa (STEEL).
Fy = 300 MPa CSA G40.21-M
Beam/Column has a 3.7 m span, Ky is 1.0, Kz 1.0, Lu = 3.7 m
factored axial load is 2000 kN and end moments of
200 kN*m and 300 kN*m in the strong axis and 100
kN*m at each end in the weak axis.
Steel section is W310X143.
SOLUTION COMPARISON:
CAN/CSA-S16
Interaction
Ratio
Beam Resistance
(kN*m)
weak strong
Column Resistance
(kN)
REFERENCE 0.998 300 653 4200
STAAD.Pro 1.00 299 650 4222
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-38
****************************************************
* *
* STAAD.Pro *
* Version Bld *
* Proprietary Program of *
* Research Engineers, Intl. *
* Date= *
* Time= *
* *
* USER ID: *
****************************************************
1. STAAD SPACE VERIFICATION CISC 1994 HANDBOOK EXAMPLE PAGE 4-108
2. *
3. * ( COMPRESSION + BIAXIAL BENDING )
4. *
5. UNIT METER KN
6. JOINT COORDINATES
7. 1 0 0 0; 2 0 3.7 0
8. *
9. MEMBER INCIDENCES
10. 1 1 2
11. *
12. MEMBER PROPERTY CANADIAN
13. 1 TABLE ST W310X143
14. *
15. CONSTANTS
16. E STEEL ALL
17. POISSON STEEL ALL
18. *
19. SUPPORTS
20. 1 FIXED BUT MX MZ
21. 2 FIXED BUT FY MX MY MZ
22. *
23. LOAD 1 FACTORED LOAD
24. JOINT LOAD
25. 2 FY -2000
26. 2 MZ 200
27. 2 MX 100
28. 1 MZ 300
29. 1 MX 100
30. *
31. PERFORM ANALYSIS
P R O B L E M S T A T I S T I C S
-----------------------------------
NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 2/ 1/ 2
ORIGINAL/FINAL BAND-WIDTH= 1/ 1/ 6 DOF
TOTAL PRIMARY LOAD CASES = 1, TOTAL DEGREES OF FREEDOM = 6
SIZE OF STIFFNESS MATRIX = 1 DOUBLE KILO-WORDS
REQRD/AVAIL. DISK SPACE = 12.0/ 19641.2 MB
Section 3B
3-39
33. PARAMETER
34. CODE CANADIAN
35. CMY 2 ALL
36. CMZ 2 ALL
37. CB 1 ALL
38. TRACK 2 ALL
39. FYLD 300000 ALL
40. CHECK CODE ALL
STAAD.PRO CODE CHECKING - (CAN/CSA-S16-01)
******************************************
ALL UNITS ARE - KNS MET (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
* 1 ST W310X143 (CANADIAN SECTIONS)
FAIL CSA-13.8.2A 1.000 1
2000.00 C -100.00 300.00 0.00
MEMBER PROPERTIES (UNIT = CM)
-----------------------------
CROSS SECTION AREA = 1.82E+02 MEMBER LENGTH = 3.70E+02
IZ = 3.47E+04 SZ = 2.15E+03 PZ = 2.41E+03
IY = 1.12E+04 SY = 7.28E+02 PY = 1.11E+03
MATERIAL PROPERTIES (UNIT = MPA)
--------------------------------
FYLD = 300.0 FU = 345.0
SECTION CAPACITIES (UNIT - KN,M)
---------------------------------
CR1 = 4.912E+03 CR2 = 4.222E+03
CRZ = 4.737E+03 CTORFLX = 4.222E+03
TENSILE CAPACITY = 4.802E+03 COMPRESSIVE CAPACITY = 4.912E+03
FACTORED MOMENT RESISTANCE : MRY = 2.987E+02 MRZ = 6.504E+02
FACTORED SHEAR RESISTANCE : VRY = 8.037E+02 VRZ = 1.678E+03
MISCELLANEOUS INFORMATION
--------------------------
NET SECTION FACTOR FOR TENSION = 1.000
KL/RY = 47.077 KL/RZ = 26.802 ALLOWABLE KL/R = 200.000
UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 3.700
OMEGA-1 (Y-AXIS) = 0.40 OMEGA-1 (Z-AXIS) = 0.40 OMEGA-2 = 1.00
SHEAR FORCE (KNS) : Y AXIS = 1.351E+02 Z AXIS = 5.405E+01
SLENDERNESS RATIO OF WEB (H/W) = 1.98E+01
Steel Design Per CSA Standard CAN/CSA-S16-01
Section 3B
3-40
41. STEEL MEMBER TAKE OFF ALL
STEEL TAKE-OFF
--------------
PROFILE LENGTH(METE) WEIGHT(KN )
In Steel Takeoff the density of steel is assumed for members with no density.
ST W310X143 3.70 5.171
PRISMATIC STEEL 0.00 0.000
----------------
TOTAL = 5.171
MEMBER PROFILE LENGTH WEIGHT
(METE) (KN )
1 ST W310X143 3.70 5.171
************ END OF DATA FROM INTERNAL STORAGE ************
42. FINISH
3-41
Design Per Canadian Cold Formed
Steel Code
3C.1 General
Provisions of CSA S136-94, including revisions dated May, 1995,
have been implemented. The program allows design of single
(non-composite) members in tension, compression, bending,
shear, as well as their combinations. For laterally supported
members in bending, the Initiation of Yielding method has been
used. Cold work of forming strengthening effects have been
included as an option.
3C.2 Cross-Sectional Properties
The user specifies the geometry of the cross-section by selecting
one of the section shape designations from the Gross Section
Property Tables published in the "Cold-Formed Steel Design
Manual", AISI, 1996 Edition.
The Tables are currently available for the following shapes:
Channel with Lips
Channel without Lips
Angle with Lips
Angle without Lips
Z with Lips
Z without Lips
Hat
Section 3C
Design Per Canadian Cold Fomed Steel Code
Section 3C
3-42
Shape selection may be done using the member property pages of
the graphical user interface (GUI) or by specifying the section
designation symbol in the input file.
The properties listed in the tables are gross section properties.
STAAD.Pro uses unreduced section properties in the structure
analysis stage. Both unreduced and effective section properties are
used in the design stage, as applicable.
3C.3 Design Procedure
The following two design modes are available:
1. Code Checking
The program compares the resistance of members with the applied
load effects, in accordance with CSA 136. Code checking is
carried out for locations specified by the user via the SECTION
command or the BEAM parameter. The results are presented in a
form of a PASS/FAIL identifier and a RATIO of load effect to
resistance for each member checked. The user may choose the
degree of detail in the output data by setting the TRACK
parameter.
2. Member Selection
The user may request that the program search the cold formed steel
shapes database (AISI standard sections) for alternative members
that pass the code check and meet the least weight criterion. In
addition, a minimum and/or maximum acceptable depth of the
member may be specified. The program will then evaluate all
database sections of the type initially specified (i.e., channel,
angle, etc.) and, if a suitable replacement is found, present design
results for that section. If no section satisfying the depth
restrictions or lighter than the initial one can be found, the
program leaves the member unchanged, regardless of whether it
passes the code check or not.
Section 3C
3-43
The program calculates effective section properties in accordance
with Clauses 5.6.2.1 through 3 and 5.6.2.6 through 8. Cross-
sectional properties and overall slenderness of members are
checked for compliance with
Clause 5.3, Maximum Effective Slenderness Ratio for
members in Compression
Clause 5.4, Maximum Flat Width Ratios for Elements in
Compression
Clause 5.5, Maximum Section Depths.
The program will check member strength in accordance with
Clause 6 of the Standard as follows:
a. Resistance factors listed in Clauses 6.2 (a), (b), and (e) are used,
as applicable.
b. Members in tension
Resistance is calculated in accordance with Clauses 6.3.1 and
6.3.2.
c. Members in bending and shear
Resistance calculations are based on Clauses:
a. 6.4.1 General,
b. 6.4.2 and 6.4.2.1 Laterally Supported Members, compressive
limit stress based on Initiation of Yielding,
c. 6.4.3 Laterally Unsupported Members,
d. 6.4.4 Channels and Z-Shaped Members with Unstiffened
Flanges - additional limitations,
e. 6.4.5 Shear in Webs,
f. 6.4.6 Combined Bending and Shear in Webs.
Design Per Canadian Cold Fomed Steel Code
Section 3C
3-44
a. Members in compression
Resistance calculations are based on Clauses:
a. 6.6.1.1, 6.6.1.2 (a) and (d), and 6.6.1.3 General,
b. 6.6.2 Sections Not Subject to Torsional-Flexural Buckling,
c. 6.6.3 Singly Symmetric Sections,
d. 6.6.4 Point-Symmetric Sections,
e. 6.6.5 Cylindrical Tubular Sections.
b. Members in compression and bending
Resistance calculations are based on Clause 6.7.1, Singly and
Doubly Symmetric Sections. Input for the coefficients of uniform
bending must be provided by the user.
The following table contains the input parameters for specifying
values of design variables and selection of design options.
CANADIAN COLD FORMED STEEL DESIGN PARAMETERS
Parameter
Name
Default Value Description
BEAM 1.0 When this parameter is set to 1.0 (default), the adequacy of the member is determined by checking a total of 13 equally spaced locations along the length of the member. If the BEAM value is 0.0, the 13 location check is not conducted, and instead, checking is done only at the locations specified by the SECTION command (See STAAD manual for details). If neither the BEAM parameter nor any SECTION command is specified, STAAD will terminate the run and ask the user to provide one of those 2 commands. This rule is not enforced for TRUSS members.
Section 3C
3-45
CANADIAN COLD FORMED STEEL DESIGN PARAMETERS
Parameter
Name
Default Value Description
CMZ 1.0 Coefficient of equivalent uniform bending z. See CSA 136, 6.7.2. Used for Combined axial load and bending design. Values range from 0.4 to 1.0.
CMY 0.0 Coefficient of equivalent uniform bending y. See CSA 136, 6.7.2. Used for Combined axial load and bending design. Values range from 0.4 to 1.0.
CWY 0 Specifies whether the cold work of forming strengthening effect should be included in resistance computation. See CSA 136, 5.2.
Values: 0 – effect should not be included
1 – effect should be included
DMAX 1000.0 Maximum depth permissible for the section during member selection. This value must be provided in the current units.
DMIN 0.0 Minimum depth required for the section during member selection. This value must be provided in the current units.
FLX 1 Specifies whether torsional-flexural buckling restraint is provided or is not necessary for the member. See CSA 136, 6.6.2
Values:
0 – Section subject to torsional flexural buckling and restraint not provided
1 – restraint provided or unnecessary FU 450 MPa Ultimate tensile strength of steel in current units.
FYLD 350 MPa Yield strength of steel in current units.
Design Per Canadian Cold Fomed Steel Code
Section 3C
3-46
CANADIAN COLD FORMED STEEL DESIGN PARAMETERS
Parameter
Name
Default Value Description
KT 1.0 Effective length factor for torsional buckling. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.
KY 1.0 Effective length factor for overall column buckling about the local Y-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.
KZ 1.0 Effective length factor for overall column buckling in the local Z-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.
LT Member length
Unbraced length for twisting. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.
LY Member length
Effective length for overall column buckling in the local Y-axis. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.
Section 3C
3-47
CANADIAN COLD FORMED STEEL DESIGN PARAMETERS
Parameter
Name
Default Value Description
LZ Member length
Effective length for overall column buckling in the local Z-axis. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.
NSF 1.0 Net section factor for tension members, See CSA 136, 6.3.1.
STIFF Member length
Spacing in the longitudinal direction of shear stiffeners for stiffened flat webs. It is input in the current units of length. See section CSA 136, 6.4.5
TRACK 0 This parameter is used to control the level of detail in which the design output is reported in the output file. The allowable values are: 0 - Prints only the member number, section name, ratio,
and PASS/FAIL status. 1 - Prints the design summary in addition to that printed
by TRACK 1 2 - Prints member and material properties in addition to
that printed by TRACK 2. TSA 1 Specifies whether bearing and intermediate transverse
stiffeners satisfy the requirements of CSA 136, 6.5. If true, the program uses the more liberal set of interaction equations in 6.4.6.
Values:
0 – stiffeners do not comply with 6.5
1 – stiffeners comply with 6.5
Note: Once a parameter is specified, its value stays at that specified
number till it is specified again. This is the way STAAD works for all
codes.
Design Per Canadian Cold Fomed Steel Code
Section 3C
3-48
3-49
Wood Design Per CSA Standard
CAN/CSA-086-01
3D.1 General Comments
The Canadian Wood Design facility in STAAD is based on
CSA086-01. A timber section library consisting of Sawn and
Glulam timber is available for member property specification.
The design philosophy of this specification is based on the
concept of limit state design. Structures are designed and
proportioned taking into consideration the limit states at which
they would become unfit for their intended use. Two major
categories of limit-state are recognized - ultimate and
serviceability. The primary considerations in ultimate limit state
design are strength and stability, while that in serviceability is
deflection. Appropriate load and resistance factors are used so that
a uniform reliability is achieved for the entire structure under
various loading conditions and at the same time the chances of
limits being surpassed are acceptably remote.
In the STAAD implementation, the code checking portion of the
program checks whether code requirements for each selected
section are met and identifies the governing criteria.
The following sections describe the salient features of the STAAD
implementation of CSA086-01. A detailed description of the
design process along with its underlying concepts and assumptions
is available in the specification document.
Analysis Methodology
Member Property Specifications
Built-in Section Library
Member Resistances
Section 3D
Design Per Canadian Timber Code
Section 3D
3-50
Design Parameters
Code Checking
Member Selection
Tabulated Results of Timber Design
Verification Examples
3D.2 Analysis Methodology
Analysis is done for the primary and combination loading
conditions provided by the user. The user is allowed complete
flexibility in providing loading specifications and using
appropriate load factors to create necessary loading situations.
3D.3 Member Property Specifications
For specification of member properties, for Sawn timber the timber
section library available in STAAD may be used. The next section
describes the syntax of commands used to assign properties from
the built-in timber table.
For Glulam timber, member properties can be specified using the
YD(depth) and ZD(width) specifications and selecting
Combination and Species specifications from the built -in table.
The assignment is done with the help of the PRISMATIC option
which is explained in STAAD‟s Technical Reference Manual.
3D.4 Built-in Section Library
The following information is provided for use when the built -in
timber tables are to be referenced for member property
specification. These properties are stored in a database file. If
called for, the properties are also used for member design.
Section 3D
3-51
Following are the description of the different types of species
combination available:
Douglas Fir-Larch
The following example illustrates the specification of Douglas Fir -
Larch species combination.
100 TO 150 TABLE ST DFL_SelStr_2X2_BM
Hem-Fir
Designation of Hem-Fir species combination in STAAD is as
follows.
100 TO 150 TABLE ST Hem-Fir_SelStr_2X10_BM
Northern Species
Designation of Northern species combination in STAAD is as
follows.
100 TO 150 TABLE ST Northern_SelStr_3X12_BM
Spruce-Pine-Fir
Designation of Spruce-Pine-Fir species combination in STAAD is
as follows.
100 TO 150 TABLE ST SPF_SelStr_3X8_BM
DFL_SelStr_2X2_BM
Species
Combination
Grade Nominal size
Size classification
Design Per Canadian Timber Code
Section 3D
3-52
Glu Laminated timber
Designation of Glu-lam timber in STAAD involves defining the
material, specifying the dimensions, and associating the material
with the member through the CONSTANTS command.
UNIT CM KN
DEFINE MATERIAL START
ISOTROPIC GLT_D.Fir-L-24f-EX
E 51611.7
POISSON 0.15
DENSITY 2.5e-005
ALPHA 1.2e-011
END DEFINE MATERIAL
MEMBER PROPERTY TIMBER CANADIAN
1 PRIS YD 12 ZD 6
CONSTANTS
MATERIAL GLT_D.Fir-L-24f-EX MEMB 1
GLT_D.Fir-L-24f-EX
Timber type
Species
Grade
Section 3D
3-53
Sample input file to demonstrate usage of Canadian timber
STAAD PLANE EXAMPLE FOR DIMENSIONAL LUMBER
UNIT FEET POUND
JOINT COORDINATES
1 0 0 0; 2 6 0 0; 3 12 0 0; 4 18 0 0;
5 24 0 0; 6 6 3 0; 7 12 6 0; 8 18 3 0;
MEMBER INCIDENCES
1 1 2; 2 2 3; 3 3 4; 4 4 5; 5 1 6; 6 6 7; 7 7 8; 8 8 5;
9 2 6; 10 3 7; 11 4 8; 12 6 3; 13 3 8;
UNIT FEET POUND
DEFINE MATERIAL START
ISOTROPIC SPF_SelStr_4X10_BM
E 1224
POISSON 0.15
DENSITY 25
ALPHA 5.5e-006
END DEFINE MATERIAL
MEMBER PROPERTY tim can
1 TO 4 9 TO 11 TABLE ST SPF_SelStr_4X10_BM
5 TO 8 12 13 TABLE ST SPF_SelStr_4X10_BM
CONSTANTS
MATERIAL SPF_SelStr_4X10_BM memb 1 TO 4 9 TO 11
MATERIAL SPF_SelStr_4X10_BM memb 5 TO 8 12 13
PRINT MEMBER PROPERTIES
FINISH
Design Per Canadian Timber Code
Section 3D
3-54
3D.5 Member Resistance
The member resistances are calculated in STAAD according to the
procedures outlined in section 5 (for sawn lumber) and 6(for
Glulam) of CSA086-01.
These depend on several adjustment factors as fol lows
1. KD = Load duration factor (Clause 4.3.2.2-CSA086-01, Table
4.3.2.2)
2. KH = System factor (Clause 5.4.4 and 6.4.3 and Table
5.4.4 -CSA086-01)
3. K_T = Treatment factor (Clause 5.4.3 and 6.4.4 -CSA086-
01)
4. KSB = Service condition factor applicable to Bending at
extreme fibre (Table 5.4.2 and 6.4.2 -CSA086-01)
5. KSV = Service condition factor applicable to longitudinal
shear (Table 5.4.2 and 6.4.2 CSA086-01)
6. KSC = Service condition factor applicable to Compression
parallel to the grain (Table 5.4.2 and 6.4.2 CSA086-01)
7. K_SCP = Service condition factor applicable to Compression
perpendicular to the grain (Table 5.4.2 and 6.4.2 CSA086-01)
8. KSE = Service condition factor applicable to modulus of
elasticity (Table 5.4.2 and 6.4.2 CSA086-01)
9. KST = Service condition factor applicable to tension parallel
to the grain (Table 5.4.2 and 6.4.2 CSA086-01)
10. KZB = Size factor applicable to bending (Clause 5.4.5 and
Table 5.4.5 -CSA086-01)
11. KZV = size factor applicable to shear(Clause 5.4.5 and Table
5.4.5 -CSA086-01)
12. KZT = size factor applicable to tension parallel to grain
(Clause 5.4.5 and Table 5.4.5 -CSA086-01)
13. KZCP = size factor applicable to compression perpendicular to
grain (Clause 5.4.5 and Table 5.4.5 -CSA086-01)
14. K_ZC = size factor applicable to compression parallel to grain
(Clause 5.4.5 and Table 5.4.5 -CSA086-01)
15. CHIX = Curvature factor (Clause 6.5.6.5.2-CSA086-01)
Section 3D
3-55
16. CV = shear load coefficient (Table 6.5.7.4A- CSA086-01)
17. KN = Notch factor(Clause 5.5.5.4-CSA086-01)
The user has to give all these factors as input according to the
classification of timber and stress grade.
Explained here is the procedure adopted in STAAD for calculating
the member resistances.
Axial Tension
i. For Sawn timber
The criterion governing the capacity of tension members is
based on one limit state. The limit state involves fracture at
the section with the minimum effective net area. The net
section area may be specified by the user through the use of
the parameter NSF (see Table 3B.1). STAAD calculates the
tension capacity of a member based on this limit state per
Clause 5.5.9 of CSA086-01.
ii. For Glulam timber
The design of glulam tension members differs from sawn
timber since CSA 086-01 assigns different specified strength
for gross and net section. The specified strength at net section
is slightly higher than the strength of the gross section.
Therefore, Glulam tension members are designed based on
two limit states. The first one is the limit state of yielding in
the gross section. The second limit state involves fracture at
the section with the minimum effective net area. The net -
section area may be specified by the user through the use of
the parameter NSF (see Table 3B.1). STAAD calculates the
tension capacity of a member based on these two limits states
per Clause.6.5.11 of CSA086-01.
Axial Compression
The compressive resistance of columns is determined based on
Clause.5.5.6 and Clause.6.5.8.4 of CSA086-01. The equations
presented in this section of the code assume that the compressive
Design Per Canadian Timber Code
Section 3D
3-56
resistance is a function of the compressive strength of the gross
section (Gross section Area times the Yield Strength) as well as
the slenderness factor (Kc). The effective length for the
calculation of compression resistance may be provided through the
use of the parameters KX, KY, KZ, LX, LY and LZ (see Table
3B.1).
Bending
The bending resistance of Sawn members are determined based on
Clause 5.5.4 of CSA086-01 and for glulam members are
determined based on Clause 6.5.6.5 of CSA086-01. The allowable
stress in bending is multiplied by Lateral stability factor, KL to
take in account whether lateral support is provided at points of
bearing to prevent lateral displacement and rotation
Axial compression and bending
The member strength for sections subjected to axial compression
and uni-axial or biaxial bending is obtained through the use of
interaction equations. Clause 5.5.10 and 6.5.12 of the code
provides the equations for this purpose. If the summation of the
left hand side of these equations exceeds 1.0 or the allowable
value provided using the RATIO parameter (see Table 3B.1), the
member is considered to have FAILed under the loading condition.
Axial tension and bending
The member strength for sections subjected to axial tension and
uniaxial or biaxial bending is obtained through the use of
interaction equations. Clause 5.5.10 and 6.5.12 of the code
provides the equations for this purpose. If the summation of the
left hand side of these equations exceeds 1.0 or the allowable
value provided using the RATIO parameter (see Table 3B.1), the
member is considered to have FAILed under the loading condition.
Section 3D
3-57
Shear
The shear resistance of the cross section is determined using the
equations of Clause 5.5.5 and 6.5.7.2 of the code. Once this is
obtained, the ratio of the shear force acting on the cross section to
the shear resistance of the section is calculated. If any of the ratios
(for both local Y & Z axes) exceed 1.0 or the allowable value
provided using the RATIO parameter (see Table 3B.1), the section
is considered to have failed under shear.
3D.6 Design Parameters
The design parameters outlined in Table below may be used to
control the design procedure. These parameters communicate
design decisions from the engineer to the program and thus allows
the engineer to control the design process to suit an application's
specific needs.
The default parameter values have been selected such that they are
frequently used numbers for conventional design. Depending on
the particular design requirements, some or all of these parameter
values may be changed to exactly model the physical structure.
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
Canadian Timber design parameters
Parameter
Name
Default
Value
Description
Nsf 1.0 Net section factor for tension members
KX 1.0 K value for flexural torsional buckling
KY 1.0 K value in local Y-axis, usually minor axis
KZ 1.0 K value in local Z-axis, usually major axis
LX Member
length Length for flexural torsional buckling
Design Per Canadian Timber Code
Section 3D
3-58
Canadian Timber design parameters
Parameter
Name
Default
Value
Description
LY Member
length
Length in local Y axis for slenderness value
KL/r
LZ Member
length
Length in local Z axis for slenderness value
KL/r
KD 1.0 Load Duration Factor [Clause.4.3.2, Table
4.3.2]
KH 1.0 System Factor [Clause 5.4.4/6.4.3, Table
5.4.4]
K_T 1.0 Treatment Factor [Clause 5.4.3/6.4.4]
KSB 1.0
Service Condition Factor for Bending at
Extreme Fibre
Applicable for bending at extreme fibre
[Table 5.4.2 and 6.4.2]
KSV 1.0
Service Condition Factor for Shear,
Applicable for longitudinal shear [Table 5.4.2
and 6.4.2]
KSC 1.0
Service Condition Factor for Compression,
Applicable for compression parallel to grain
[Table 5.4.2 and 6.4.2]
KSE 1.0
Service Condition Factor for Modulus of
Elasticity,
Applicable for modulus of elasticity [Table
5.4.2 and 6.4.2]
KST 1.0
Service Condition Factor for Tension,
Applicable for tension parallel to grain [Table
5.4.2 and 6.4.2]
KZB 1.0
Size Factor for Bending,
Applicable for bending [Clause.5.4.5 and
Table 5.4.5]
KZV 1.0 Size Factor for Shear [Clause 5.4.5 and Table
5.4.5]
Section 3D
3-59
Canadian Timber design parameters
Parameter
Name
Default
Value
Description
KZT 1.0
Size Factor for Tension,
Applicable for tension parallel to grain
[Clause 5.4.5 and Table 5.4.5]
KZCP 1.0
Size Factor for Compression,
Applicable for compression perpendicular to
grain [Clause .5.4.5 and Table 5.4.5]
K_ZC 1.0
Size Factor for Compression,
Applicable for compression parallel to grain
[Clause 5.4.5 and Table 5.4.5]
CV 1.0 Shear Load Coefficient [Table 6.5.7.4A]
KN 1.0 Notch Factor [Clause 5.4.7.2.2]
K_SCP 1.0
Service Condition Factor for Compression,
Applicable for compression perpendicular to
grain [Clause 5.4.2 and Table 6.4.2]
CHIX 1.0 Curvature Factor for Compression [Clause
6.5.6.5.2]
RATIO 1.0 Permissible Ratio of Actual to Allowable
Value
3D.7 Code Checking
The purpose of code checking is to check whether the provided
section properties of the members are adequate. The adequacy is
checked as per the CSA086-01 requirements.
Code checking is done using forces and moments at specified
sections of the members. The code checking output labels th e
members as PASSed or FAILed. In addition, the critical condition,
governing load case, location (distance from the start joint) and
magnitudes of the governing forces and moments are also printed.
Design Per Canadian Timber Code
Section 3D
3-60
PARAMETER
CODE TIMBER CAN
KD 0.99 ALL
KH 0.99 ALL
K_T 0.99 ALL
KSB 0.99 ALL
KSV 0.99 ALL
KSC 0.99 ALL
KSE 0.99 ALL
KST 0.99 ALL
KZB 0.99 ALL
KZV 0.99 ALL
KZT 0.99 ALL
KZCP 0.99 ALL
K_ZC 0.99 ALL
CV 0.99 ALL
KN 0.99 ALL
K_SCP 0.99 ALL
CHIX 0.99 ALL
RATIO 0.99 ALL
CHECK CODE ALL
FINISH
3D.8 Member Selection
Member selection based CSA086-2001 is not available.
3D.9 Tabulated Results of Timber Design
Results of code checking and member selection are presented in a
tabular format. The term CRITICAL COND refers to the section of
the CSA086-01 specification, which governed the design.
Section 3D
3-61
Pu = Actual Load in Compression
Tu = Actual Load in Tension
Muy = Ultimate moment in y direction
Muz = Ultimate moment in z direction
V = Ultimate shear force
SLENDERNESS_Y = Actual Slenderness ratio in y direction
SLENDERNESS_Z = Actual Slenderness ratio in z direction
PY = Factored Compressive capacity in y direction
PZ = Factored Compressive capacity in z direction
T = Factored tensile capacity
MY = Factored moment of resistance in y direction
MZ = Factored moment of resistance in z direction
V = Factored shear resistance
SLENDERNESS = Allowable slenderness ratio
3D.10 Verification Problems
In the next few pages are included 6 verification examples for
reference purposes.
Design Per Canadian Timber Code
Section 3D
3-62
Verification Problem: 1
Objective: - To determine the Canadian Glulam section column in
axial compression. Column is effectively pinned at
both ends and braced at mid-height in all direction..
Design Code: - Canadian wood design code (CSA:086-01)
Reference: - Example 4, page 116, Canadian Wood Design Manual, 2001
Given: - Length = 9000mm
Comparison: -
Solution Design Strength (kN)
Theory 295
STAAD 293.739
Difference -0.427 %
Input: -
STAAD PLANE EXAMPLE FOR GLULAM DESIGN INPUT FILE:
GLULAMCOLUMN.STD
START JOB INFORMATION
ENGINEER DATE 10-JUN-05
END JOB INFORMATION
INPUT WIDTH 79
UNIT METER KN
JOINT COORDINATES
1 0 0 0; 2 0 9 0;
MEMBER INCIDENCES
1 1 2;
UNIT INCHES KIP
DEFINE MATERIAL START
ISOTROPIC GLT_SPRUCE-PINE-12C-E
E 9.7
POISSON 0.15
DENSITY 1.44676e-005
ALPHA 5.5e-006
END DEFINE MATERIAL
UNIT FEET POUND
Section 3D
3-63
MEMBER PROPERTY TIMBER CANADIAN
1 PRIS YD 0.748031 ZD 0.574147
UNIT INCHES KIP
CONSTANTS
MATERIAL GLT_SPRUCE-PINE-12C-E MEMB 1
SUPPORTS
1 PINNED
UNIT METER KN
LOAD 1 LOADTYPE None TITLE LOAD CASE 1
JOINT LOAD
2 FY -214
PERFORM ANALYSIS
PARAMETER
CODE TIMBER CANADIAN
KY 0.5 ALL
KZ 0.5 ALL
CHECK CODE ALL
FINISH
Relevant portion of Output:-
STAAD.Pro CODE CHECKING - (S086)
***********************
ALL UNITS ARE - KN METE (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
1 175.00X228.00 CANADIAN GLULAM GRADE:GLT_SPRUCE-PINE-12C-E
PASS CL.5.5.10/6.5 0.728 1
214.00 C 0.00 0.00 0.0000
|--------------------------------------------------------------------------|
| LEZ = 4500.000 LEY = 4500.000 LUZ = 9000.000 LUY = 9000.000mm |
| |
| KD = 1.000 KH = 1.000 KT = 1.000 KSB = 1.000 KSV = 1.000 |
| KSC = 1.000 K_SCP = 1.000 KSE = 1.000 KST = 1.000 KZB = 1.000 |
| KZV = 1.000 KZT = 1.000 KZCP = 1.000 K_ZC = 1.000 CHIX = 1.000 |
| CV = 1.000 KN = 1.000 |
| |
| ACTUAL LOADS : (KN-m) |
| Pu = 214.000 |
| Tu = 0.000 |
| Muy = 0.000 |
| Muz = 0.000 |
| V = 0.000 |
| SLENDERNESS_Y = 19.737 |
| SLENDERNESS_Z = 25.714 |
| ALLOWABLE CAPACITIES OF THE SECTION: (KN-m) |
| PY = 413.943 |
| PZ = 293.793 |
| T = 0.000 |
| MY = 0.000 |
| MZ = 0.000 |
| V = 0.000 |
| SLENDERNESS = 50.000 |
|--------------------------------------------------------------------------|
37. FINISH
Design Per Canadian Timber Code
Section 3D
3-64
Verification Problem: 2
Objective: - To determine the bending capacity of a Canadian
Glulam section single span floor beam. The
compression edge assumed fully supported.
Design Code: - Canadian wood design code (CSA:086-01)
Reference: - Example 2, page 59, Canadian Wood Design Manual, 2001
Given: - Length =7500mm, Beam Spacing = 5000mm, Standard load
condition, Dry service condition, Untreated
Comparison: -
Input: -
STAAD PLANE EXAMPLE FOR GLULAM DESIGN INPUT FILE: glulamBEAM.STD
START JOB INFORMATION
ENGINEER DATE 10-JUN-05
END JOB INFORMATION
INPUT WIDTH 79
UNIT METER KN
JOINT COORDINATES
1 0 0 0; 2 7.5 0 0
MEMBER INCIDENCES
1 1 2
UNIT INCHES KIP
Solution Design
Strength in
bending (kN-
m)
Design
Strength in
shear (kN)
Theory 208 101
STAAD 208.323 100.776
Difference 0.155 % -0.221 %
Section 3D
3-65
DEFINE MATERIAL START
ISOTROPIC GLT_SPRUCE-PINE-12C-E
E 9.7
POISSON 0.15
DENSITY 1.44676E-005
ALPHA 5.5E-006
ISOTROPIC GLT_D.FIR-L-20F-E
E 12.4
POISSON 0.15
DENSITY 1.44676E-005
ALPHA 5.5E-006
ISOTROPIC CONCRETE
E 3150
POISSON 0.17
DENSITY 8.68E-005
ALPHA 5.5E-006
DAMP 0.05
END DEFINE MATERIAL
UNIT FEET POUND
MEMBER PROPERTY TIMBER CANADIAN
1 PRIS YD 2.11942 ZD 0.426508
UNIT INCHES KIP
CONSTANTS
MATERIAL GLT_D.FIR-L-20F-E MEMB 1
SUPPORTS
1 2 PINNED
UNIT METER KN
LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1
MEMBER LOAD
1 UNI GY -27.1
PERFORM ANALYSIS
PARAMETER
CODE TIMBER CANADIAN
CHECK CODE ALL
FINISH
Design Per Canadian Timber Code
Section 3D
3-66
Relevant portion of Output:-
STAAD.Pro CODE CHECKING - (S086)
***********************
ALL UNITS ARE - KN METE (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
1 130.00X646.00 CANADIAN GLULAM GRADE:GLT_D.FIR-L-20F-E
FAIL CL.5.5.5/6.5. 1.008 1
0.00 T 0.00 0.00 0.0000
|--------------------------------------------------------------------------|
| LEZ = 7500.000 LEY = 7500.000 LUZ = 7500.000 LUY = 7500.000mm |
| |
| KD = 1.000 KH = 1.000 KT = 1.000 KSB = 1.000 KSV = 1.000 |
| KSC = 1.000 K_SCP = 1.000 KSE = 1.000 KST = 1.000 KZB = 1.000 |
| KZV = 1.000 KZT = 1.000 KZCP = 1.000 K_ZC = 1.000 CHIX = 1.000 |
| CV = 1.000 KN = 1.000 |
| |
| ACTUAL LOADS : (KN-m) |
| Pu = 0.000 |
| Tu = 0.000 |
| Muy = 0.000 |
| Muz = 0.000 |
| V = 101.625 |
| SLENDERNESS_Y = 16.932 |
| SLENDERNESS_Z = 1.529 |
| ALLOWABLE CAPACITIES OF THE SECTION: (KN-m) |
| PY = 0.000 |
| PZ = 0.000 |
| T = 0.000 |
| MY = 41.923 |
| MZ = 208.323 |
| V = 100.776 |
| SLENDERNESS = 50.000 |
|--------------------------------------------------------------------------|
46. FINISH
Section 3D
3-67
Verification Problem: 3
Objective: - To determine the capacity of a Canadian Glulam
section in axial tension.
Design Code: - Canadian wood design code (CSA:086-01)
Reference: - Example 3, page 158, Canadian Wood Design
Manual, 2001
Given: - Dry service condition, Untreated
Comparison: -
Solution Design Strength in
Tension (kN)
Theory 257
STAAD 256.636
Difference -0.141 %
Input: -
STAAD PLANE EXAMPLE FOR GLULAM DESIGN INPUT FILE: glulamTENSION.STD
START JOB INFORMATION
ENGINEER DATE 10-JUN-05
END JOB INFORMATION
INPUT WIDTH 79
UNIT METER KN
JOINT COORDINATES
1 0 0 0; 2 0 9 0
MEMBER INCIDENCES
1 1 2
UNIT INCHES KIP
DEFINE MATERIAL START
ISOTROPIC GLT_SPRUCE-PINE-14T-E
E 10.7
POISSON 0.15
DENSITY 1.44676E-005
Design Per Canadian Timber Code
Section 3D
3-68
ALPHA 5.5E-006
ISOTROPIC CONCRETE
E 3150
POISSON 0.17
DENSITY 8.68E-005
ALPHA 5.5E-006
DAMP 0.05
END DEFINE MATERIAL
UNIT FEET POUND
MEMBER PROPERTY TIMBER CANADIAN
1 PRIS YD 0.872702 ZD 0.262467
UNIT INCHES KIP
CONSTANTS
MATERIAL GLT_SPRUCE-PINE-14T-E MEMB 1
SUPPORTS
1 PINNED
UNIT METER KN
LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1
JOINT LOAD
2 FY 250
PERFORM ANALYSIS PRINT STATICS CHECK
PARAMETER
CODE TIMBER CANADIAN
KY 0.5 ALL
KZ 0.5 ALL
CHECK CODE ALL
FINISH
Section 3D
3-69
Relevant portion of Output:-
STAAD.Pro CODE CHECKING - (S086)
***********************
ALL UNITS ARE - KN METE (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
1 80.00X266.00 CANADIAN GLULAM GRADE:GLT_SPRUCE-PINE-14T-E
PASS CL.5.5.10/6.5 0.974 1
250.00 T 0.00 0.00 0.0000
|--------------------------------------------------------------------------|
| LEZ = 4500.000 LEY = 4500.000 LUZ = 9000.000 LUY = 9000.000mm |
| |
| KD = 1.000 KH = 1.000 KT = 1.000 KSB = 1.000 KSV = 1.000 |
| KSC = 1.000 K_SCP = 1.000 KSE = 1.000 KST = 1.000 KZB = 1.000 |
| KZV = 1.000 KZT = 1.000 KZCP = 1.000 K_ZC = 1.000 CHIX = 1.000 |
| CV = 1.000 KN = 1.000 |
| |
| ACTUAL LOADS : (KN-m) |
| Pu = 0.000 |
| Tu = -250.000 |
| Muy = 0.000 |
| Muz = 0.000 |
| V = 0.000 |
| ALLOWABLE CAPACITIES OF THE SECTION: (KN-m) |
| PY = 0.000 |
| PZ = 0.000 |
| T = 256.636 |
| MY = 0.000 |
| MZ = 0.000 |
| V = 0.000 |
|--------------------------------------------------------------------------|
Design Per Canadian Timber Code
Section 3D
3-70
Verification Problem: 4
Objective: - To determine the Canadian Sawn section column in
axial compression. Column is effectively pinned at
both ends.
Design Code: - Canadian wood design code (CSA:086-01)
Reference: - Example 2, page 113, Canadian Wood Design Manual, 2001
Given: - Unbraced Length = 5000mm
Comparison: -
Solution Design Strength (kN)
Theory 130
STAAD 129.223
Difference -0.597 %
Input: -
STAAD PLANE EXAMPLE FOR DIMENSIONAL LUMBER INPUT FILE: sawn_ lumber_ COLUMN.STD
START JOB INFORMATION
ENGINEER DATE 08-JUN-05
END JOB INFORMATION
UNIT FEET POUND
JOINT COORDINATES
1 0 0 0; 2 0 16.4042 0
MEMBER INCIDENCES
1 1 2
DEFINE MATERIAL START
ISOTROPIC DFL_NO2_8X8_POST
E 1.368E+006
POISSON 0.15
DENSITY 25
ALPHA 5.5E-006
END DEFINE MATERIAL
UNIT METER KN
CONSTANTS
Section 3D
3-71
MATERIAL DFL_NO2_8X8_POST MEMB 1
UNIT FEET POUND
MEMBER PROPERTY TIMBER CANADIAN
1 TABLE ST DFL_NO2_8X8_POST
SUPPORTS
1 PINNED
UNIT METER KN
LOAD 1 DEAD+LIVE LOAD
JOINT LOAD
2 FY -114
PERFORM ANALYSIS PRINT STATICS CHECK
PARAMETER
CODE TIMBER CANADIAN
KSC 0.91 ALL
K_ZC 1.05 ALL
CHECK CODE
FINISH
Relevant portion of Output:-
STAAD.Pro CODE CHECKING - (S086)
***********************
ALL UNITS ARE - KN METE (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
1 ST DFL_NO2_8X8_POST
PASS CL.5.5.10/6.5.12 0.882 1
114.00 C 0.00 0.00 0.0000
|--------------------------------------------------------------------------|
| LEZ = 5000.000 LEY = 5000.000 LUZ = 5000.000 LUY = 5000.000mm |
| |
| KD = 1.000 KH = 1.000 KT = 1.000 KSB = 1.000 KSV = 1.000 |
| KSC = 0.910 K_SCP = 1.000 KSE = 1.000 KST = 1.000 KZB = 1.000 |
| KZV = 1.000 KZT = 1.000 KZCP = 1.000 K_ZC = 1.050 CHIX = 1.000 |
| CV = 1.000 KN = 1.000 |
| |
| ACTUAL LOADS : (KN-m) |
| Pu = 114.000 |
| Tu = 0.000 |
| Muy = 0.000 |
| Muz = 0.000 |
| V = 0.000 |
| SLENDERNESS_Y = 26.178 |
| SLENDERNESS_Z = 26.178 |
| ALLOWABLE CAPACITIES OF THE SECTION: (KN-m) |
| PY = 129.223 |
| PZ = 129.223 |
| T = 0.000 |
| MY = 0.000 |
| MZ = 0.000 |
| V = 0.000 |
| SLENDERNESS = 50.000 |
|--------------------------------------------------------------------------|
Design Per Canadian Timber Code
Section 3D
3-72
Verification Problem: 5
Objective: - To determine the bending capacity of a Canadian
sawn section single span floor beam.
Design Code: - Canadian wood design code (CSA:086-01)
Reference: - Example 1, page 58, Canadian Wood Design Manual,
2001
Given: - Length =6000mm, Beam Spacing = 3000mm, Standard
load condition, Dry service condition, Untreated
Comparison: -
Solution Design Strength in
bending (kN-m)
Design Strength
in shear (kN)
Theory 79.8 46.1
STAAD 79.732 46.170
Difference -0.085 % No
Input: -
STAAD PLANE EXAMPLE FOR DIMENSIONAL LUMBER: SAWN_LUMBER_BEAM.STD START JOB INFORMATION ENGINEER DATE 08-JUN-05 END JOB INFORMATION UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 6 0 0; 3 3 0 0; MEMBER INCIDENCES 1 1 3; 2 3 2; UNIT FEET POUND DEFINE MATERIAL START ISOTROPIC DFL_NO1_10X16_BM E 1.728e+006 POISSON 0.15 DENSITY 25 ALPHA 5.5e-006 END DEFINE MATERIAL UNIT METER KN CONSTANTS
Section 3D
3-73
MATERIAL DFL_NO1_10X16_BM MEMB 1 2 UNIT FEET POUND MEMBER PROPERTY TIMBER CANADIAN 1 2 TABLE ST DFL_NO1_10X16_BM SUPPORTS 1 2 FIXED UNIT METER KN LOAD 1 DEAD+LIVE LOAD MEMBER LOAD 1 2 UNI GY -16.4 PERFORM ANALYSIS PARAMETER CODE TIMBER CANADIAN KD 1.0 ALL K_T 1.0 ALL KSB 1.0 ALL KZB 0.90 ALL KZV 0.90 ALL K_ZC 1.05 ALL CHECK CODE ALL FINISH
Relevant portion of Output:-
ALL UNITS ARE - KN METE (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
2 ST DFL_NO1_10X16_BM
FAIL CL.5.5.5/6.5.6 1.066 1
0.00 T 0.00 49.20 3.0000
|--------------------------------------------------------------------------|
| LEZ = 3000.000 LEY = 3000.000 LUZ = 3000.000 LUY = 3000.000mm |
| |
| KD = 1.000 KH = 1.000 KT = 1.000 KSB = 1.000 KSV = 1.000 |
| KSC = 1.000 K_SCP = 1.000 KSE = 1.000 KST = 1.000 KZB = 0.900 |
| KZV = 0.900 KZT = 1.000 KZCP = 1.000 K_ZC = 1.050 CHIX = 1.000 |
| CV = 1.000 KN = 1.000 |
| |
| ACTUAL LOADS : (KN-m) |
| Pu = 0.000 |
| Tu = 0.000 |
| Muy = 0.000 |
| Muz = 49.200 |
| V = -49.200 |
| SLENDERNESS_Y = 4.511 |
| SLENDERNESS_Z = 2.158 |
| ALLOWABLE CAPACITIES OF THE SECTION: (KN-m) |
| PY = 0.000 |
| PZ = 0.000 |
| T = 0.000 |
| MY = 79.800 |
| MZ = 79.732 |
| V = 46.170 |
| SLENDERNESS = 50.000 |
|--------------------------------------------------------------------------|
Design Per Canadian Timber Code
Section 3D
3-74
Verification Problem: 6
Objective: - To determine the capacity of a Canadian Sawn section in axial
tension.
Design Code: - Canadian wood design code (CSA:086-01)
Reference: - Example 2, page 158, Canadian Wood Design Manual, 2001
Given: - Dry service condition, Untreated
Comparison: -
Solution Design Strength in
Tension (kN)
Theory 185
STAAD 184.338
Difference -0.357%
Input: -
STAAD PLANE EXAMPLE FOR DIMENSIONAL LUMBER SAWN_LUMBER_TENSION.STD START JOB INFORMATION ENGINEER DATE 08-JUN-05 END JOB INFORMATION UNIT FEET POUND JOINT COORDINATES 1 0 0 0; 2 0 16.4042 0; MEMBER INCIDENCES 1 1 2; DEFINE MATERIAL START ISOTROPIC DFL_NO1_6X8_BM E 1.728e+006 POISSON 0.15 DENSITY 25 ALPHA 5.5e-006 END DEFINE MATERIAL UNIT METER KN CONSTANTS MATERIAL DFL_NO1_6X8_BM MEMB 1
Section 3D
3-75
UNIT FEET POUND MEMBER PROPERTY TIMBER CANADIAN 1 TABLE ST DFL_NO1_6X8_BM SUPPORTS 1 PINNED UNIT METER KN LOAD 1 DEAD+LIVE LOAD JOINT LOAD 2 FY 144 PERFORM ANALYSIS PRINT STATICS CHECK PARAMETER CODE TIMBER CANADIAN KH 1.1 ALL KSC 0.91 ALL K_ZC 1.05 ALL CHECK CODE ALL FINISH
Relevant portion of Output:-
STAAD.Pro CODE CHECKING - (S086)
***********************
ALL UNITS ARE - KN METE (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
1 ST DFL_NO1_6X8_BM
PASS CL.5.5.10/6.5.12 0.781 1
144.00 T 0.00 0.00 0.0000
|--------------------------------------------------------------------------|
| LEZ = 5000.000 LEY = 5000.000 LUZ = 5000.000 LUY = 5000.000mm |
| |
| KD = 1.000 KH = 1.100 KT = 1.000 KSB = 1.000 KSV = 1.000 |
| KSC = 0.910 K_SCP = 1.000 KSE = 1.000 KST = 1.000 KZB = 1.000 |
| KZV = 1.000 KZT = 1.000 KZCP = 1.000 K_ZC = 1.050 CHIX = 1.000 |
| CV = 1.000 KN = 1.000 |
| |
| ACTUAL LOADS : (KN-m) |
| Pu = 0.000 |
| Tu = -144.000 |
| Muy = 0.000 |
| Muz = 0.000 |
| V = 0.000 |
| ALLOWABLE CAPACITIES OF THE SECTION: (KN-m) |
| PY = 0.000 |
| PZ = 0.000 |
| T = 184.338 |
| MY = 0.000 |
| MZ = 0.000 |
| V = 0.000 |
|--------------------------------------------------------------------------|
Design Per Canadian Timber Code
Section 3D
3-76
Section 4
Chinese Codes
Kjahds;akh
4-1
Concrete Design Per GB50010-2002
4A.1 Design Operations
STAAD has the capabilities for performing concrete design per
GB50010-2002. It can calculate the reinforcement needed for
sections assigned through the PRISMATIC attribute. The concrete
design calculations are based on the limit state method of
GB50010-2002.
4A.2 Section Types for Concrete Design
The following types of cross sections for concrete members can be
designed.
For Beams Prismatic (Rectangular, Square, Tee and
Trapezoidal)
For Columns Prismatic (Rectangular, Square and Circular)
4A.3 Member Dimensions
Concrete members which will be designed by the program must
have certain section properties input under the MEMBER
PROPERTY command. The following example shows the required
input:
Section 4A
Concrete Design Per GB50010-2002
Section 4A
4-2
UNIT MM
MEMBER PROPERTY
1 3 TO 7 9 PRISM YD 450. ZD 250.
11 13 PR YD 350.
14 TO 16 PRIS YD 400. ZD 750. YB 300. ZB 200 .
will be done accordingly. In the above input, the first set of
members are rectangular (450 mm depth and 250mm width) and
the second set of members, with only depth and no width provided,
will be assumed to be circular with 350 mm diameter. The third set
numbers in the above example represents a T-shape with 750 mm
flange width, 200 width, 400 mm overall depth and 100 mm flange
depth (See section 6.20.2). The program will determine whether
the section is rectangular, flanged or circular and the beam or
column design
4A.4 Design Parameters
The program contains a number of parameters which are needed to
perform design as per GB50010-2002. Default parameter values
have been selected such that they are frequently used numbers for
conventional design requirements. These values may be changed to
suit the particular design being performed. Table 9A.1 of this
manual contains a complete list of the available parameters and
their default values. It is necessary to declare length and force
units as Millimeter and Newton before performing the concrete
design. Please note as per GB50010-2002, STAAD supports
Characteristic Values of Concrete Strength and Design Value of
Strength of Steel Bar only as per Table 4.1.4 and Table 4.2.3-1
respectively.
4A.5 Beam Design
Beams are designed for flexure, shear and torsion. If required the
effect the axial force may be taken into consideration. For all
Section 4A
4-3
these forces, all active beam loadings are prescanned to identify
the critical load cases at different sections of the beams. The total
number of sections considered is 13( e.g.
0.,.1,.2,.25,.3,.4,.5,.6,.7,.75,.8,.9 and 1). All of these sections are
scanned to determine the design force envelopes.
Design for Flexure
Maximum sagging (creating tensile stress at the bottom face of the
beam) and hogging (creating tensile stress at the top face)
moments are calculated for all active load cases at each of the
above mentioned sections. Each of these sections are designed to
resist both of these critical sagging and hogging moments. Where
ever the rectangular section is inadequate as singly reinforced
section, doubly reinforced section is tried. However, presently the
flanged section is designed only as singly reinforced section under
sagging moment. It may also be noted all flanged sections are
automatically designed as rectangular section under hogging
moment as the flange of the beam is ineffective under hogging
moment. Flexural design of beams are performed in two passes. In
the first pass, effective depths of the sections are determined with
the assumption of single layer of assumed reinforcement and
reinforcement requirements are calculated. After the preliminary
design, reinforcing bars are chosen from the internal database in
single or multiple layers. The entire flexure design is performed
again in a second pass taking into account of the changed effective
depths of sections calculated on the basis of reinforcement provide
after the preliminary design. Final provision of flexural
reinforcements is made then. Efforts have been made to meet the
guideline for the reinforcement detailing as per GB50010-2002
Although exact curtailment lengths are not mentioned explicitly in
the design output (finally which will be more or less guided by the
detailer taking into account of other practical considera tion), user
has the choice of printing reinforcements provided by STAAD at
11 equally spaced sections from which the final detail drawing can
be prepared.
Concrete Design Per GB50010-2002
Section 4A
4-4
Design for Shear
Shear reinforcement is calculated to resist both shear forces and
torsional moments. Shear design are performed at 11 equally
spaced sections (0.to 1.) for the maximum shear forces amongst
the active load cases and the associated torsional moments. Shear
capacity calculation at different sections without the shear
reinforcement is based on the actual tensile reinforcement
provided by STAAD program. Two-legged stirrups are provided to
take care of the balance shear forces acting on these sections.
Beam Design Output
The default design output of the beam contains flexural and shear
reinforcement provided at 5 equally spaced (0,.25,.5,.75 and 1.)
sections along the length of the beam. User has option to get a
more detail output. All beam design outputs are given in IS units.
An example of rectangular beam design output with the default
output option (TRACK 0.0) is presented below:
Section 4A
4-5
============================================================================ B E A M N O. 12 D E S I G N R E S U L T S C20 HRB400 (Main) HRB400 (Sec.) LENGTH: 4000.0 mm SIZE: 250.0 mm X 350.0 mm COVER: 30.0 mm DESIGN LOAD SUMMARY (KN MET) ---------------------------------------------------------------------------- SECTION |FLEXTURE (Maxm. Sagging/Hogging moments)| SHEAR (in mm) | P MZ MX Load Case | VY MX Load Case ---------------------------------------------------------------------------- 0.0 | 0.00 0.00 0.00 4 | 29.64 1.23 4
| 0.00 -25.68 1.23 4 | 400.0 | 0.00 0.00 0.00 4 | 27.97 1.23 4 | 0.00 -16.05 1.23 4 | 800.0 | 0.00 0.00 0.00 4 | 25.12 1.23 4 | 0.00 -7.17 1.23 4 | 1200.0 | 0.00 0.97 0.49 5 | 21.11 1.23 4
| 0.00 -0.14 1.32 6 | 1600.0 | 0.00 6.77 1.23 4 | 15.93 1.23 4 | 0.00 0.00 0.00 4 |
2000.0 | 0.00 11.06 1.23 4 | 9.59 1.23 4 | 0.00 0.00 0.00 4 | 2400.0 | 0.00 13.04 1.23 4 | 2.08 1.23 4
| 0.00 0.00 0.00 4 | 2800.0 | 0.00 12.45 1.23 4 | -5.43 1.23 4 | 0.00 0.00 0.00 4 | 3200.0 | 0.00 9.55 1.23 4 | -11.77 1.23 4 | 0.00 0.00 0.00 4 | 3600.0 | 0.00 4.73 1.23 4 | -16.95 1.23 4
| 0.00 0.00 0.00 4 | 4000.0 | 0.00 0.00 0.00 4 | -25.48 1.23 4 | 0.00 -17.36 1.23 4 | ----------------------------------------------------------------------------
SUMMARY OF REINF. AREA (Sq.mm) ---------------------------------------------------------------------------- SECTION 0.0 mm 1000.0 mm 2000.0 mm 3000.0 mm 4000.0 mm ----------------------------------------------------------------------------
TOP 259.04 161.29 0.00 0.00 176.31 REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm)
BOTTOM 0.00 160.78 160.78 160.78 0.00 REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) ----------------------------------------------------------------------------
SUMMARY OF PROVIDED REINF. AREA
---------------------------------------------------------------------------- SECTION 0.0 mm 1000.0 mm 2000.0 mm 3000.0 mm 4000.0 mm ---------------------------------------------------------------------------- TOP 4-10Ø 3-10Ø 2-10Ø 2-10Ø 3-10Ø REINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)
BOTTOM 2-12Ø 2-12Ø 2-12Ø 2-12Ø 2-12Ø REINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)
SHEAR 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø REINF. @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c
----------------------------------------------------------------------------
============================================================================
Concrete Design Per GB50010-2002
Section 4A
4-6
4A.6 Column Design
Columns are designed for axial forces and biaxial moments at the
ends. All active load cases are tested to calculate reinforcement.
The loading which yield maximum reinforcement is called the
critical load. Column design is done for square, rectangular and
circular sections. By default, square and rectangular columns and
designed with reinforcement distributed on each side equally for
the sections under biaxial moments and with reinforcement
distributed equally in two faces for sections under uniaxial
moment. User may change the default arrangement of the
reinforcement with the help of the parameter RFACE (see Table
4A.1). Depending upon the member lengths, section dimensions
and effective length coefficients specified by the user STAAD
automatically determine the criterion (short or long) of the column
design. All major criteria for selecting longitudinal and transverse
reinforcement as stipulated by GB50010-2002 have been taken
care of in the column design of STAAD.
Column Design Output
Default column design output (TRACK 0.0) contains the
reinforcement provided by STAAD and the capacity of the section.
With the option TRACK 1.0, the output contains intermediate
results such as the design forces, effective length coefficients,
additional moments etc. A special output TRACK 9.0 is introduced
to obtain the details of section capacity calculations. All design
output is given in SI units. An example of a long column design
output (with option TRACK 1.0) is given below.
Section 4A
4-7
============================================================================ C O L U M N No. 1 D E S I G N R E S U L T S C20 HRB400 (Main) HRB400 (Sec.)
LENGTH: 3000.0 mm CROSS SECTION: 250.0 mm dia. COVER: 40.0 mm ** GUIDING LOAD CASE: 5 BRACED LONG COLUMN
DESIGN FORCES (KNS-MET) ----------------------- DESIGN AXIAL FORCE (Pu) : 62.0
About Z About Y INITIAL MOMENTS : 2.21 32.29
MOMENTS DUE TO MINIMUM ECC. : 1.24 1.24 SLENDERNESS RATIOS : 12.00 12.00 MOMENTS DUE TO SLENDERNESS EFFECT : 1.12 1.12 MOMENT REDUCTION FACTORS : 1.00 1.00 ADDITION MOMENTS (Maz and May) : 1.12 1.12
TOTAL DESIGN MOMENTS : 3.32 33.40 REQD. STEEL AREA : 1822.71 Sq.mm. MAIN REINFORCEMENT : Provide 17 - 12 dia. (3.92%, 1922.65 Sq.mm.) (Equally distributed)
TIE REINFORCEMENT : Provide 8 mm dia. rectangular ties @ 190 mm c/c SECTION CAPACITY (KNS-MET) --------------------------
Puz : 992.70 Muz1 : 36.87 Muy1 : 36.87
INTERACTION RATIO: 1.00
============================================================================
Concrete Design Per GB50010-2002
Section 4A
4-8
Table 4A.1 Chinese Concrete Design GB50010-2002 Parameters
Parameter Default Description Name Value
FYMAIN 210 N/mm2 Yield Stress for main reinforcing
steel.
FYSEC 210 N/mm2 Yield Stress for secondary
reinforcing steel.
FC 15 N/mm2 Concrete Yield Stress.
CLEAR 25 mm 40 mm
For beam members. For column members
MINMAIN 10 mm Minimum main reinforcement bar size.
MAXMAIN 60 mm Maximum main reinforcement bar size.
MINSEC 8 mm Minimum secondary reinforcement bar size.
MAXSEC 12 mm Maximum secondary reinforcement bar size.
BRACING 0.0 BEAM DESIGN
A value of 1.0 means the effect of axial force will be taken into account for beam design.
COLUMN DESIGN
A value of 1.0 means the column is unbraced about major axis.
A value of 2.0 means the column is unbraced about minor axis.
A value of 3.0 means the column is unbraced about both axis.
RATIO 4.0 Maximum percentage of longitudinal reinforcement in columns.
Section 4A
4-9
Table 4A.1 Chinese Concrete Design GB50010-2002 Parameters
Parameter Default Description Name Value
RFACE 4.0 A value of 4.0 means longitudinal reinforcement in column is arranged equally along 4 faces.
A value of 2.0 invokes 2 faced distribution about major axis.
A value of 3.0 invokes 2 faced distribution about minor axis.
WIDTH ZD Width to be used for design. This value defaults to ZD as provided under MEMBER PROPERTIES.
DEPTH YD Total depth to be used for design. This value defaults to YD as provided under MEMBER PROPERTIES.
TRACK 0.0 BEAM DESIGN:
For TRACK = 0.0, output consists of reinforcement details at START, MIDDLE and END. For TRACK = 1.0, critical moments are printed in addition to TRACK 0.0 output. For TRACK = 2.0, required steel for intermediate sections defined by NSECTION are printed in addition to TRACK 1.0 output.
COLUMN DESIGN:
With TRACK = 0.0, reinforcement details are printed. With TRACK = 1.0, column interaction analysis results are printed in addition to TRACK 0.0 output. With TRACK = 2.0, a schematic interaction diagram and intermediate interaction values are printed in addition to TRACK 1.0 output.
REINF 0.0 Tied column. A value of 1.0 will mean spiral reinforcement.
Concrete Design Per GB50010-2002
Section 4A
4-10
Table 4A.1 Chinese Concrete Design GB50010-2002 Parameters
Parameter Default Description Name Value
ELZ 1.0 Ratio of effective length to actual length of column about major axis.
ELY 1.0 Ratio of effective length to actual length of column about minor axis.
Note: Once a parameter is specified, its value stays at that specified
number till it is specified again. This is the way STAAD works for all
codes.
4-11
Steel Design Per GBJ 50017-2003
4B.1 General
This section presents some general statements regarding the
implementation in STAAD of the National Standard of the
People‟s Republic of China specifications for Design of Steel
Structures (GB50017-2003). The design philosophy and procedural
logistics are based on the principles of limit state design method.
Facilities are available for member selection as well as code
checking. The following sections describe the salient features of
the design approach.
Members are proportioned to resist the design loads without
exceedance of the capacities. The most economical section is
selected on the basis of the least weight criteria. The code
checking part of the program also checks the slenderness
requirements and the stability criteria. It is generally assumed that
the user will take care of the detailing requirements like flange
buckling, web crippling etc. Users are recommended to adopt the
following steps in performing the steel design:
1. Specify the geometry and factored loads. Perform the
analysis.
2. Specify the design parameter values if different from the
default values.
3. Specify whether to perform code checking or member
selection.
Section 4B
Steel Design Per GBJ 50017-33
Section 4B
4-12
4B.2 Analysis Methodology
Elastic analysis method is used to obtain the forces and moments
for design. Analysis is done for the primary and combination
loading conditions provided by the user. The user is allowed
complete flexibility in providing loading specifications and using
appropriate load factors to create necessary loading situations.
Depending upon the analysis requirements, regular stiffness
analysis, P-Delta analysis or Non-linear analysis may be specified.
Dynamic analysis may also be performed and the results combined
with static analysis results.
4B.3 Member Property Specifications
For specification of member properties, the steel section library
available in STAAD may be used. The next section describes the
syntax of commands used to assign properties from the built -in
steel table. Member properties may also be specified using the
User Table facility. For more information on these facilities, r efer
to the STAAD Program Technical Reference manual.
4B.4 Built-in Chinese Steel Section Library
The following information is provided for use when the built -in
steel tables are to be referenced for member property specification.
These properties are stored in a database file. If called for, the
properties are also used for member design. Since the shear areas
are built into these tables, shear deformation is always considered
for these members. An example of the member property
specification in an input file is provided at the end of this section.
A complete listing of the sections available in the built -in steel
section library may be obtained by using the tools of the graphical
user interface.
Section 4B
4-13
Following are the descriptions of different types of sections.
I Shapes
I shaped sections are designated in the following way.
1 TO 5 15 16 TABLE ST I22B
H Shapes
H shaped sections are designated in the following way.
6 TO 8 TABLE ST HW250X250
T Shapes
T shaped sections are designated in the following way.
24 25 33 to 36 TABLE ST TM244X300
Channels
Channels are specified in the following way.
29 30 TABLE ST CH25A
Double Channels
Back to back double channels, with or without a spacing between
them, are available. The letter D in front of the section name will
specify a double channel.
11 TABLE D CH22B
17 TABLE D CH40C SP 0.15
Steel Design Per GBJ 50017-33
Section 4B
4-14
In the above set of commands, member 11 is a back to back double
channel CH22B with no spacing in between. Member 17 is a
double channel CH40C with a spacing of 0.15 length units between
the channels.
Angles
Two types of specifications may be used to describe an angle. The
standard angle section is specified as follows:
19 TABLE ST L100X100X7
Two types of specifications may be used to describe an angle. The
standard angle section is specified as follows:
27 TABLE RA L40X25X3
The above section signifies an angle with legs of length 40mm and
25mm and a leg thickness of 3 mm. This specification may be used
when the local Z axis corresponds to the z-z axis specified in
Chapter 2. If the local Y axis corresponds to the z-z axis, type
specification "RA" (reverse angle) may be used.
Double Angles
Short leg back to back or long leg back to back double angles can
be specified by means of input of the words SD or LD,
respectively, in front of the angle size. In case of an equal angle,
either SD or LD will serve the purpose.
22 TABLE LD L56X36X3
32 TABLE SD L45X28X4
20 TABLE LD L56X36X3 SP 0.15
28 TABLE SD L56X36X4 SP 0.15
Section 4B
4-15
Tubes (Rectangular or Square Hollow Sections)
Tubes can be assigned in 2 ways. In the first method, the
designation for the tube is as shown below. This method is meant
for tubes whose property name is available in the steel table. In
these examples, member 12 consist of a 10X6X0.3 cm size tube
section,
12 TABLE ST TUB100603.0
In the second method, tubes are specified by their dimensions. For
example,
13 TABLE ST TUBE TH 0.15 WT 0.8 DT 0.6
is a tube that has a height of 0.6 length units, width of 0.6 length
units, and a wall thickness of 0.15 length un its.
Pipes (Circular Hollow Sections)
Pipes can be assigned in 2 ways. In the first method, the
designation for the pipe is as shown below. This method is meant
for pipes whose property name is available in the steel table.
21 31 TABLE ST PIP203X6.5
In the second method, pipe sections may be provided by specifying
the word PIPE followed by the outside and inside diameters of the
section. For example,
9 10 14 18 23 26 TABLE ST PIPE OD 0.6 ID
0.55
specifies a pipe with outside diameter of 0.6 length units and
inside diameter of .55 length units.
Steel Design Per GBJ 50017-33
Section 4B
4-16
Sample File Containing Chinese Shapes
STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 04-Aug-05
END JOB INFORMATION
UNIT METER KN
JOINT COORDINATES
1 0 0 0; 2 4 0 0; 3 9 0 0; 4 0 0 4; 5 4 0 4; 6 0 0 8; 7 4 0 8; 8 9 0 8;
9 0 3.5 0; 10 4 3.5 0; 11 9 3.5 0; 12 0 3.5 4; 13 4 3.5 4; 14 0 3.5 8;
15 4 3.5 8; 16 9 3.5 8; 17 0 7 0; 18 4 7 0; 19 9 7 0; 20 0 7 4;
21 4 7 4; 22 0 7 8; 23 4 7 8; 24 9 7 8;
MEMBER INCIDENCES
1 1 9; 2 2 10; 3 3 11; 4 4 12; 5 5 13; 6 6 14; 7 7 15; 8 8 16; 9 9 17;
10 10 18; 11 11 19; 12 12 20; 13 13 21; 14 14 22; 15 15 23; 16 16 24;
17 9 10; 18 10 11; 19 12 13; 20 14 15; 21 15 16; 22 17 18; 23 18 19;
24 20 21; 25 22 23; 26 23 24; 27 9 12; 28 12 14; 29 10 13; 30 13 15;
31 11 16; 32 17 20; 33 20 22; 34 18 21; 35 21 23; 36 19 24;
MEMBER PROPERTY CHINESE
*I SHAPES
1 TO 5 15 16 TABLE ST I22B
*H SHAPES
6 TO 8 TABLE ST HW250X250
*T SHAPES
24 25 33 to 36 TABLE ST TM244X300
*CHANNELS
29 30 TABLE ST CH25A
*DOUBLE CHANNELS
11 TABLE D CH22B
17 TABLE D CH40C SP 0.15
*ANGLES
19 TABLE ST L100X100X7
*DOUBLE ANGLES
27 TABLE RA L40X25X3
22 TABLE LD L56X36X3
32 TABLE SD L45X28X4
20 TABLE LD L56X36X3 SP 0.15
Section 4B
4-17
28 TABLE SD L56X36X4 SP 0.15
*TUBES
12 TABLE ST TUB100603.0
13 TABLE ST TUBE TH 0.15 WT 0.8 DT 0.6
*PIPES
21 31 TABLE ST PIP203X6.5
9 10 14 18 23 26 TABLE ST PIPE OD 0.6 ID 0.55
PRINT MEMBER PROPERTIES
FINISH
4B.5 Member Capacities
The basic measure of member capacities are the allowable stresses
on the member under various conditions of applied loading such as
allowable tensile stress, allowable compressive stress etc. These
depend on several factors such as cross sectional properties,
slenderness factors, unsupported width to thickness ratios and so
on. Explained here is the procedure adopted in STAAD for
calculating such capacities.
Allowable stress for Axial Tension
In members with axial tension, the tensile load must not exceed the
tension capacity of the member. The tension capacity of the
member is calculated on the basis of allowable tensile stresses
provided in Table 3.4.1-1 of the code. STAAD calculates the
tension capacity of a given member per this allowable stress value
and a user supplied net section factor (NSF-a default value of 1.0
is present but may be altered by changing the input value, see
Table 1) and proceeds with member selection or code checking.
Allowable stress for Axial Compression
The allowable stress for members in compression is determined
according to Table 3.4.1-1. Compressive resistance is a function of
the slenderness of the cross-section (Kl/r ratio) and the user may
control the slenderness value by modifying parameters such as
Steel Design Per GBJ 50017-33
Section 4B
4-18
KY, LY, KZ and LZ. The provisions of Section 5 are used to check
the adequacy of sections in compression.
Allowable stress for Bending and Shear
Sections subjected to bending moments and shear forces are to be
designed according to the provisions of section 4. The permissible
bending compressive and tensile stresses are dependent on such
factors as outstanding legs and thickness of flanges, unsupported
length of the compression flange (UNL, defaults to member
length) etc. Shear capacities are calculated according to Table
3.4.1-1 and Section 4 and are a function of web depth, web
thickness etc. Users may use a value of 1.0 or 2.0 for the TRACK
parameter to obtain a listing of the bending and shear capacities.
Allowable stress for Combined Loading
For members experiencing combined loading (axial force, bending
and shear), applicable interaction formulas are checked at different
locations of the member for all modeled loading situations. The
procedure of Section 5 is implemented for combined axial load and
bending.
4B.6 Combined Loading
For members experiencing combined loading (axial force, bending
and shear), applicable interaction formulas are checked at different
locations of the member for all modeled loading situations. The
procedure of Section 5 is implemented for combined axial load and
bending.
4B.7 Design Parameters
The user is allowed complete control over the design process
through the use of parameters mentioned in Table 4B.1 of this
chapter. These parameters communicate design decisions from the
engineer to the program.
Section 4B
4-19
The default parameter values have been selected such that they are
frequently used numbers for conventional design. Depending on
the particular design requirements of an analysis, some or all of
these parameter values may have to be changed to exactly model
the physical structure. Note: Once a parameter is specified, its
value stays at that specified number till it is specified again.
This is the way STAAD works for all codes.
Table 4B.1 Chinese Steel Design Parameters
Parameter
Name Definition
Reference
(GB50017-2003)
Default Value
Remarks
Ly
Length in local Y axis for slenderness value KL/r
- 0 Default is selected beam's length
Lz
Length in local Z axis for slenderness value KL/r
- 0 Default is selected beam's length
Dmax Maximum allowable depth
- 100 cm -
Dmin Minimum required depth - 0 cm -
Ky K value in local Y-axis, usually minor axis
- 1 -
Kz K value in local Z-axis, usually major axis
- 1 -
Nsf
Net section factor for tension members
- 1 -
Main
Flag for controlling slenderness check
- -
0 = Check for slenderness. 1 = Do not check for slenderness
Track Track parameter - 0
0 = Suppress critical member stress. 1 = Print all critical member stress. 2 = Print expanded output.
Steel Design Per GBJ 50017-33
Section 4B
4-20
Table 4B.1 Chinese Steel Design Parameters
Parameter
Name Definition
Reference
(GB50017-2003)
Default Value
Remarks
Ratio
Permissible ratio of actual to allowable stress
- 1 -
Beam Beam parameter - 1
0 = Perform design at ends and those locations specified in the section command. 1 = Perform design at ends and 1/12th section locations along member length.
Grade Grade of steel Clause 3.4.1 1
The Following values represent the various grades of steel. Q235 - 1 Q345 - 2 Q390 - 3 Q420 - 4
Compression Allowable KL/r value in compression
- 150 -
Tension Allowable KL/r value in tension
- 300 -
Pfy
Plasticity adaptation factor Y direction
Table - 5.2.1 1.2 -
Pfz
Plasticity adaptation factor Z direction
Table - 5.2.1 1.05 -
Section 4B
4-21
Table 4B.1 Chinese Steel Design Parameters
Parameter
Name Definition
Reference
(GB50017-2003)
Default Value
Remarks
Sfy Stability factor for Y direction Appendix-C 1
Stability factor for axial compression members shall be selected from appendix –C based on its slenderness ratio, yield strength, classification of the section in Table 5.1.2-1 and Table 5.1.2-2
Sfz Stability factor for Z direction Appendix-C 1
Stability factor for axial compression members shall be selected from appendix –C based on its slenderness ratio, yield strength, classification of the section in Table 5.1.2-1 and Table 5.1.2-2
SBY Overall Stability factor for Y direction
Appendix-B 1 -
SBZ Overall Stability factor for Z direction
Appendix-B 0 -
4B.8 Code Checking
The purpose of code checking is to check whether the provided
section properties of the members are adequate. The adequacy is
checked per the GB50017-2003 requirements.
Code checking is done using forces and moments at specified
sections of the members. If the BEAM parameter for a member is
set to 1, moments are calculated at every twelfth point along the
beam, and the maximum moment about the major axis is used.
Steel Design Per GBJ 50017-33
Section 4B
4-22
When no sections are specified and the BEAM parameter is set to
zero (default), design will be based on member start and end
forces. The code checking output labels the members as PASSed or
FAILed. In addition, the critical condition, governing load case,
location (distance from start joint) and magnitudes of the
governing forces and moments are also printed.
4B.9 Member Selection
The member selection process basically involves determination of
the least weight member that PASSes the code checking procedure
based on the forces and moments of the most recent analysis. The
section selected will be of the same type as that specified initially.
For example, a member specified initially as a channel will have a
channel selected for it. Selection of members whose properties are
originally provided from a user table will be limited to sections in
the user table.
Sample Input data for Steel Design
UNIT METER
PARAMETER
CODE CHINESE
NSF 0.85 ALL
GRADE 3.0 MEMBER 7
KY 1.2 MEMBER 3 4
RATIO 0.9 ALL
TRACK 1.0 ALL
CHECK CODE ALL
Section 5
European Codes
5-1
Concrete Design Per Eurocode EC2
5A.1 Design Operations
STAAD provides a comprehensive set of national codes for the
design of concrete structures. In general, all the available codes,
including EC2, follow the same procedure for the design of the
concrete members.
The main steps in performing a design operation are:
1. Selecting the applicable load cases to be considered in the
design process.
2. Providing appropriate parameter values if different from the
default values.
3. Perform the design for the member as appropriate.
These operations can be repeated by the user any number of times
depending on the design requirements. The parameters referred to
above provide the user with the ability to allocate specific design
properties to individual members considered in the design
operation.
5A.2 Eurocode 2 (EC2)
Eurocode 2, Design of concrete structures, Part 1, General rules
and rules for buildings, provides design rules applicable to plain,
reinforced or prestressed concrete used in buildings and civil
engineering works. It is based on the limit state philosophy
common to modern standards.
Section 5A
Concrete Design Per Eurocode EC2
Section 5A
5-2
The objective of this method of design is to ensure that possibility
of failure is reduced to a negligible level. This is achieved through
application of factors to both the applied loads and the material
properties. The code also provides guidelines on the global method
of analysis to be used for calculating internal member forces and
moments. STAAD provides a number of methods for analys is,
allowing Geometric Nonlinearity as well as P-Delta effects to be
considered.
5A.3 National Application Documents
Various authorities of the CEN member countries have prepared
National Application Documents to be used with EC2. These
documents provide alternative factors for loads and may also
provide supplements to the rules in EC2.
The current version of EC2 implemented in STAAD adheres to the
factors and rules provided in EC2 and has not been modified by
any National Application Documents.
5A.4 Material Properties and Load Factors
Design resistances are obtained by dividing the characteristic yield
strengths, as given in table 2.3 of EC2, by the material partial
safety factors c for concrete and s for reinforcements. The
magnitude in STAAD is 1.5 for concrete and 1.15 for
reinforcements.
Material coefficients in STAAD take the following default values
unless replaced by user's numerical values provided in the input
file.
Modulus of Elasticity E = 21.71 KN/mm2
Shear Modulus G = E / 2 (1 + v)
Poisson's Ratio v = 0.25
Unit weight = 23.56 KN/m3
Section 5A
5-3
The magnitude of design loads is dependent on F, the partial
safety factor for the action under consideration. In STAAD the
user is allowed total control in providing applicable values for the
factors and their use in various load combinations.
5A.5 Columns
Columns are designed for axial compressive loads and possible
moments at the ends of the member. If a particular load case
causes tension in the column being designed that load case is
ignored, the design proceeds with a warning message given to that
affect.
All active load cases will be considered in the design and
reinforcements are assumed symmetrically arranged in the cross
section.
The maximum reinforcement calculated after all design load cases
have been considered is then reported as the critical required area
of reinforcement.
Slender columns are also covered in the design process, the
program will make due allowance for the additional moment that
has to be considered in the design.
Please note that sway type structures are not directly covered in
the current implementation of EC2. This effect, however, can be
catered for by the P-DELTA analysis option.
5A.6 Beams
Beams are designed for flexure, shear and torsion. For all these
actions active load cases are scanned to create appropriate
envelopes for the design process. Maximum torsional moment is
also identified and incorporated in the design.
Concrete Design Per Eurocode EC2
Section 5A
5-4
Design for flexure
Reinforcement for both positive and negative moments is
calculated on the basis of the section properties provided by the
user. If the required reinforcement exceeds the maximum
allowable then the section size is inadequate and a massage to that
effect is given in the output. Parabolic-rectangular stress
distribution for the concrete section is adopted and as moment
redistribution is not available in STAAD analysis, the limit for
N.A to depth ratio is set according to clause 2.5.3.4.2 (5) of the
code.
If required, compression reinforcement will be provided in order to
satisfy the above limits. It is important to know that beams are
designed for the flexural moment MZ only. The moment MY is not
considered in the design at all.
Design for Shear
Shear reinforcement design is based on the standard method
mentioned in clause 4.3.2.4.3 where it is assumed the notional
strut inclination is constant. Depending on the shear distribution
within the member it may be possible that nominal shear
reinforcement will be sufficient to cater for the design shear
forces. If this is not the case an attempt is made to identify regions
where nominal reinforcement is insufficient and appropriate
reinforcement is then calculated to cover the excess design shear
force.
The maximum shear force that can be carried without crushing the
concrete is also checked and if exceeded, a message to revise the
section size is given in the output file.
Design for Torsion
Torsional moments arising as a result of equilibrium requirements
need to be designed for at the ultimate limit state. Reinforcement
for torsional moments consists of stirrups combined with
longitudinal bars. The combined magnitude of shear stress arising
from shear forces and torsional moments are checked in order to
establish whether the section size is adequate. If section size is
Section 5A
5-5
inadequate a massage is given in the output file, otherwise, full
design is carried out and both shear links and longitudinal bars
required are calculated and, where necessary, links are combined
with the shear force links and printed in a tabulated manner in the
output file.
5A.7 Slabs
Slabs can only be designed for if finite elements are used to
represent them in the model of the structure. In the main the
design follows the same procedure as for flexure except that shear
forces are assumed to be resisted without the provision of shear
reinforcements. In cases where this may not be the case users must
ensure that necessary checks are carried out. The output for the
slab design refers to longitudinal reinforcements, which coincides
with the local x direction of the element, and, transverse
reinforcement, which coincides with the local y direction of the
element. Also, reference is made to 'TOP' and BOTT'
reinforcement which relates to the element's 'TOP' and 'BOTTOM'
as determined from the connectivity of the element. This may not
coincide with the slab's actual top and bottom and, if desired, users
must ensure this through the numbering scheme of the elements
(see figure 1.13 in the STAAD Technical Reference Manual). The
design of the slab considers a fixed bar size of 16mm in both
directions with the longitudinal bar being the layer closest to the
slab exterior faces.
5A.8 Design Parameters
Design parameters communicate specific design decisions to the
program. They are set to default values to begin with and may be
altered to suite the particular structure. Depending on the model
being designed, the user may have to change some or all of the
parameter default values. Some parameters are unit dependent and
when altered, the new setting must be compatible with the active
"unit" specification. Table 5A.1 lists all the relevant EC2
parameters together with description and default values.
Concrete Design Per Eurocode EC2
Section 5A
5-6
Note: Once a parameter is specified, its value stays at that speci fied
number till it is specified again. This is the way STAAD works for
all codes.
Table 5A.1 – Concrete Design Parameters-EC2
Parameter Default Description
Name Value
FYMAIN *460 N/mm2 Yield Stress for main reinforcement (For slabs, it is for reinforcement in both directions)
FYSEC *460N/mm2 Yield Stress for secondary reinforcement. Applicable to shear bars in beams
FC * 30N/mm2 Concrete Yield Stress / cube strength
MINMAIN 8mm Minimum main reinforcement bar size Acceptable bar sizes: 6 8 10 12 16 20 25 32 40 50
MINSEC 8mm Minimum secondary bar size a. Applicable to shear reinforcement in beams
CLEAR * 20mm Clearance of reinforcement measured from concrete surface to closest bar perimeter.
MAXMAIN 50mm Maximum required reinforcement bar size Acceptable bars are per MINMAIN above.
SFACE *0.0 Face of support location at start of beam. (Only applicable for shear - use MEMBER OFFSET for bending )
EFACE *0.0 Face of support location at end of beam. (NOTE: Both SFACE & EFACE must be positive numbers.)
TRACK 0.0 0.0 = Critical Moment will not be printed with beam design report. Column design gives no detailed results.
1.0 = For beam gives min/max steel % and spacing. For columns gives a detailed table of output with additional moments calculated.
2.0 = Output of TRACK 1.0 List of design sag/hog moments and corresponding required steel area at each section of member
MMAG 1.0 Factor by which column design moments are magnified
Section 5A
5-7
NSECTION 10 Number of equally-spaced sections to be considered in finding critical moment for beam design. The upper limit is 20.
WIDTH *ZD Width of concrete member. This value default is as provided as ZD in MEMBER PROPERTIES.
DEPTH *YD Depth of concrete member. This value default is as provided as YD in MEMBER PROPERTIES.
BRACE 0.0 0.0 = Column braced in both directions. 1.0 = Column unbraced about local Z direction
only 2.0 = Column unbraced about local Y
direction only 3.0 = Column unbraced in both Y and Z
directions
ELY 1.0 Member length factor about local Y direction for column design.
ELZ 1.0 Member length factor about local Z direction for column design.
SRA 0.0 0.0 = Orthogonal reinforcement layout without considering torsional moment Mxy -slabs only
-500 = Orthogonal reinforcement layout with Mxy used to calculate WOOD & ARMER moments for design.
A = Skew angle considered in WOOD & ARMER equations where A is the angle in degrees.
SERV 0.0 0.0 = No serviceability check performed. 1.0 = Perform serviceability check for beams
as if they were continuous. 2.0 = Perform serviceability check for beams
as if they were simply supported. 3.0 = Perform serviceability check for beams
as if they were cantilever beams. * Provided in current unit system
Concrete Design Per Eurocode EC2
Section 5A
5-8
5-9
Steel Design Per Eurocode EC3
5B.1 General Description
Introduction
The design of structural steel members in accordance with the
specification Eurocode 3: Design of steel structures – part 1-1:
General Rules and rules for buildings has been implemented.
Two versions of the code are currently implemented, the EC3_94/1
and BS EN 1993-1-1:2005.
To access the EC3_94/1 edition, specify the commands:
PARAMETERS CODE
EC3
Or
PARAMETERS
CODE
EURO
To access the BS EN 1993-1-1:2005 edition, specify the
commands:
PARAMETERS
CODE
EC3 BS
Section 5B
Steel Design Per Eurocode EC3
Section 5B
5-10
The main steps in performing a design operation are:
1. Selecting the applicable load cases to be
considered in the design process.
2. Providing appropriate parameter values if different
from the default values.
3. Specify whether to perform code-checking and/or
member selection.
These operations can be repeated by the user any number of times
depending on the design requirements.
The parameters, referred to above, provide the user with the
ability to allocate specific design properties to individual members
considered in the design operation.
Eurocode (EC3)
Eurocode 3, Design of steel structures, Part 1.1 General rules and
rules for buildings (EC3) provides design rules applicable to
structural steel used in buildings and civil engineering works. It is
based on the limit states philosophy common to modern standards.
The objective of this method of design is to ensure that possibility
of failure is reduced to a negligible level. This is achieved through
application of factors to both the applied loads and the material
properties.
The code also provides guidelines on the global method of analysis
to be used for calculating internal member forces and moments.
STAAD uses the elastic method of analysis which may be used in
all cases. Also there are three types of framing referred to in EC3.
These are “Simple”, “Continuous”, and “Semi -continuous” which
reflect the ability of the joints in developing moments. In STAAD,
only “Simple” and “Continuous” joint types can be assumed when
carrying out global analysis.
Section 5B
5-11
Axes convention in STAAD and EC3
By default, STAAD defines the major axis of the cross-section as
zz and the minor axis as yy. A special case where zz is the minor
axis and yy is the major axis is available if the “SET Z UP”
command is used and is discussed in the Technical Reference
Manual. The longitudinal axis of the member is defined as x and
joins the start joint of the member to the end with the same
positive direction.
EC3, however, defines the principal cross-section axes in reverse
to that of STAAD, but the longitudinal axis is defined in the same
way. Both of these axes definitions follow the orthogonal right
hand rule. See figure below.
Users must bear this difference in mind when examining the code-
check output from STAAD.
STAAD EC3
Figure 1 Axes Convention in STAAD and EC3.
National Application Documents
Various authorities of the CEN member countries have prepared
National Application Documents to be used wi th EC3. These
documents provide alternative factors for loads and may also
provide supplements to the rules in EC3.
The current version of EC3 implemented in STAAD adheres to the
factors and rules provided in EC3 and have not been modified by
any National Application Documents.
Steel Design Per Eurocode EC3
Section 5B
5-12
Section Classification
The occurrence of local buckling of the compression elements of a
cross-section prevents the development of full section capacity. It
is therefore imperative to establish this possibility prior to
determining the section capacities. Cross sections are classified in
accordance with their geometrical properties and the stress pattern
on the compression elements. For each load case considered in the
design process, STAAD determines the section class and calculates
the capacities accordingly.
Material Properties and Load Factors
Design resistances are obtained by dividing the characteristic yield
strength, as given in table 3.1, by the material partial safety factor
gm. The magnitude of gm in STAAD is 1.1 which is applicable to
all section types.
Material coefficients in STAAD take the following default values
unless replaced by user‟s numerical values provided in the input
file.
Modulus of Elasticity E = 205 N/mm2
Shear Modulus G = E / 2 (1+v)
Poisson‟s Ratio v = 0.3
Unit weight r = 76.8 KN/m3
The magnitude of design loads is dependent on g f, the partial
safety factor for the action under consideration. In STAAD, the
user is allowed total control in providing applicable values for the
factors and their use in various load combinations.
Axially Loaded Members
For members subject to tension loads only, tension capacity is
calculated based on yield strength, material factor g m and cross-
sectional area of the member with possible reduction due to bolt
holes. When bolt holes need to be considered in the capacity
calculations, the value used for gm is 1.2 and the yield strength is
replaced with the ultimate tensile strength of the material. The
Section 5B
5-13
tension capacity is then taken as the smaller of the full section
capacity and the reduced one.
For members subject to compression only, cross-section resistance
as well as buckling resistance must be checked. The latter is often
more critical as it is influenced by a number of factors including
the section type and member unbraced length.
Beams
The main requirement for a beam is to have sufficient cross -
section resistance to the applied bending moment and shear force.
Also the possibility of lateral-torsional buckling must be taken
into consideration when the full length of the member is not
laterally restrained.
The bending capacity is primarily a function of the section type
and the material yield strength. There are four classes of cross -
sections defined in EC3. Class 1 and 2 sections can both attain full
plastic capacity with the exception that the class 2 sections cannot
sustain sufficient rotation required for plastic analysis of the
model.
Class 3 sections, due to local buckling, cannot develop plastic
moment capacity and the yield stress is limited to the extreme
compression fiber of the section. The elastic section modulus is
used to determine the moment capacity.
Class 4 sections do suffer from local buckling and explicit
allowance must be made for the reduction in section properties
before the moment capacity can be determined. Further, because of
interaction between shear force and bending moment, the moment
resistance of the cross-section may be reduced. This, however,
does not occur unless the value of applied shear forces exceeds
50% of the plastic shear capacity of the section. In such cases the
web is assumed to resist the applied shear force as well as
contributing towards the moment resistance of the cross-section.
Steel Design Per Eurocode EC3
Section 5B
5-14
The plastic shear capacity is calculated using the appropriate shear
area for the section and the yield strength in shear, taken as3
fy.
As mentioned earlier, lateral-torsional buckling must also be
considered whenever the full length of the member is not laterally
restrained. The buckling capacity is dependent on the section type
as well as the unrestrained length, restraint conditions and type of
applied loading.
Axially Loaded Members With Moments
The bending resistance of members subject to coexistent axial load
is reduced by the presence of the axial load. The presence of large
shear, as mentioned above, can also reduce the bending resistance
of the section under consideration.
If the shear load is large enough to cause a reduction in bending
resistance, then the reduction due to shear has to be taken into
account before calculating the effect of the axial load on the
bending resistance of the section.
Generally, EC3 requires checking cross-section resistance for local
capacity and also checking the overall buckling capacity of the
member. In the case of members subject to axial tension and
bending, there is provision to take the stabilizing effect of the
tension load into consideration. This is achieved by modifying the
extreme compression fiber stress and calculating an effective
applied moment for the section. This is then checked against the
lateral-torsional buckling resistance of the section.
5B.2 Design Parameters
Introduction
Design parameters communicate specific design decisions to the
program. They are set to default values to begin with and may be
altered to suite the particular structure.
Section 5B
5-15
Depending on the model being designed, the user may have to
change some or all of the parameter default values. Some
parameters are unit dependent and when altered, the new setting
must be compatible with the active “unit” specification.
Table 5B.1 lists all the relevant EC3 parameters together with
description and default values. Note: Once a parameter is
specified, its value stays at that specified number till it is
specified again. This is the way STAAD works for all codes.
Table 5B.1 – Steel Design Parameters EC3
Parameter Default Definition
Name Value
KY 1.0 K factor in local y axis. KZ 1.0 K factor in local z axis. LY Member Length Compression length in local y axis,
Slenderness ratio = (KY)*(LY)/(Ryy) LZ Member Length Compression length in local z axis,
Slenderness ratio = (KZ)*(LZ)/(Rzz) UNL Member Length Unrestraint length of member used in
calculating the lateral-torsional resistance moment of the member.
PY Yield Strength The yield strength default value is set based on the default value of the “SGR” parameter.
NSF 1.0 Net tension factor for tension capacity calculation.
SGR 0.0 Steel grade as per table 3.1 in EC3. 0.0 = Fe 360 1.0 = Fe 430 2.0 = Fe 510
SBLT 0.0 Indicates if the section is rolled or built-up. 0.0 = Rolled 1.0 = Built-up.
CMM 1.0 Indicates type of loading on member. Can take a value from 1 to 6. Refer to Table 5B.2 for more information on its use.
CMN 1.0 Indicates the level of End-Restraint. 1.0 1.0 = No fixity 0.5 = Full fixity
0.7 = One end free and other end fixed
Steel Design Per Eurocode EC3
Section 5B
5-16
Table 5B.1 – Steel Design Parameters EC3
Parameter Default Definition
Name Value
DMAX 100.0 cm Maximum allowable depth for the member. DMIN 0 Minimum required depth for the member. RATIO 1 Permissible ratio of loading to capacity. BEAM 0 Indicates the number of sections to be
checked for during the design. 0 = Check the end sections only or the locations
specified by the SECTION command. 1 = Consider 13 sections along the member and
select the maximum Mz location for the design check.
2 = Same as BEAM = 1.0 but checks the end sections of the member as well.
3 = Consider 13 sections along the member and design check every section.
CODE Undefined User must specify EC3. TRACK 0 Controls the level of descriptivity of output.
0 = Minimum 1 = Intermediate 2 = Maximum 4 = option 4 for performing a deflection check
UNF 1.0 Unsupported buckling length as a factor of the beam length
LEG 0.0 Connection type LVV Maximum of Lyy and
Lzz (Lyy is a term used
by BS5950)
Buckling length for angle about its principle axis
FU Ultimate tensile strength of steel DFF None
(Mandatory for deflection check)
Deflection limit
DJ1 Start Joint of member
Joint No. denoting starting point for calculation of "Deflection Length"
DJ2 End Joint of member Joint No. denoting end point for calculation of "Deflection Length"
Section 5B
5-17
Notes:
1. LEG - Table 25 BS5950 for Fastener Control
The slenderness of single and double angle, channel and tee
sections are specified in BS 5950 table 25 depending on the
connection provided at the end of the member. To define the
appropriate connection, a LEG parameter should be assigned
to the member.
The following table indicates the value of the LEG parameter
required to match the BS5950 connection definition: -
Clause LEG
4.7.10.2
Single Angle
(a) - 2 bolts short leg 1.0
long leg 3.0
(b) - 1 bolt short leg 0.0
long leg 2.0
4.7.10.3
Double Angle
(a) - 2 bolts short leg 3.0
long leg 7.0
(b) - 1 bolt short leg 2.0
long leg 6.0
(c) - 2 bolts long leg 1.0
short leg 5.0
(d) - 1 bolt long leg 0.0
short leg 4.0
4.7.10.4
Channels
(a) - 2 or more rows of bolts 1.0
(b) - 1 row of bolts 0.0
4.7.10.5
Tee Sections
(a) - 2 or more rows of bolts 1.0
(b) - 1 row of bolts 0.0
Steel Design Per Eurocode EC3
Section 5B
5-18
For single angles, the slenderness is calculated for the
geometric axes, a-a and b-b as well as the weak v-v axis. The
effective lengths of the geometric axes are defined as:-
La = KY * KY
Lb = KZ * LZ
The slenderness calculated for the v-v axis is then used to
calculate the compression strength pc for the weaker principal
axis (z-z for ST angles or y-y for RA specified angles). The
maximum slenderness of the a-a and b-b axes is used to
calculate the compression strength p c for the stronger principal
axis.
Alternatively for single angles where the connection is not
known or Table 25 is not appropriate, by setting the LEG
parameter to 10, slenderness is calculated for the two principal
axes y-y and z-z only. The LVV parameter is not used.
For double angles, the LVV parameter is available to comply
with note 5 in table 25. In addition, if using double angles from
user tables, (Technical Reference Manual section 5.19) an
eleventh value, rvv, should be supplied at the end of the ten
existing values corresponding to the radius of gyration of the
single angle making up the pair.
2. BEAM
Ensure that the “BEAM” parameter is set to either 1 or 2 while
performing code checking for members susceptible to Lateral -
Torsional Buckling.
Section 5B
5-19
Table 5B.2
5B.3 Tabulated Results of Steel Design
A design performed to the new Eurocode 3 standard is displayed in
the output file (*.ANL) with the following header: -
STAAD.PRO CODE CHECKING - (BS EN 1993-1-1:2005) **************************
PROGRAM CODE REVISION V1.1 BS_EC3_2005/1
Steel Design Per Eurocode EC3
Section 5B
5-20
The equivalent header for a code check (or member selection) to
the older standard is displayed thus:-
STAAD.PRO CODE CHECKING - (DD ENV) ***********************
PROGRAM CODE REVISION V1.14_EC3_94/1
5B.4 Worked Examples
Example 1: Restrained simply supported beam.
The figure below shows a simply supported beam spanning 7
meters and assumed to be fully restrained laterally. Fe 430 steel is
assumed and the beam will be checked to the clauses of EC3
currently implemented in STAAD.
Unfactored Loading
Permanent Load:
UDL including selfweight assume 20 KN/m
Variable Load:
UDL load assume 25 KN/m
Partial safety factor for permanent load (ULS) 1.35
Partial safety factor for variable load (ULS) 1.5
Factored Load: 1.35 X 15 + 1.5 X 25 = 64.5 KN/m
Section 5B
5-21
64.5 KN/m
Try 457 X 191 X 82UB.
h = 460.2 mm d = 407.9mm tw = 9.9 mm
b = 191.3 mm tf = 16.0 mm A = 104.5cm2
ly = 37103 cm4 Wpl.y = 1833 cm3 Av = 48.13 cm2
Grade Fe 430 Fy = 275 N/mm2
Section Classification
Outstand Flanges in Compression, limit for rolled section
c/t = 10e = 9.2
c/t ratio for the selected section is 95.65/16 = 5.9 < 9.2
Flange is therefore a class 1 element.
Web with N.A. at mid depth, limit for rolled section
d/tw = 72e = 66.6
d/ tw ratio for the selected section is 407.9/9.9 = 41.2 < 66.6
Web is therefore a class 1 element.
Section is class 1
Steel Design Per Eurocode EC3
Section 5B
5-22
Shear Resistance
Maximum design shear force (64.5 X 7) / 2 = 225.7 KN
Plastic shear resistance Vpl.Rd = (Av / gM0) (fy / 3 )
= (4813 / 1.1) (275 / 1.732) / 1000
= 694.7 KN
Maximum design shear force = 225.7 KN < 694.7 KN
Therefore shear resistance is satisfactory.
Moment Resistance
Maximum design moment at mid-span of beam
(wl2 / 8) = 395 Knm
Maximum resistance of section Mc.Rd = ( Wpl.yfy) / gM0
= (1833 X 103 X 275) / (1.1 X 106)
= 458.2KNm
Lateral Torsional Buckling
As it is assumed that the full length of member is restrained
laterally there is no need to check for Lateral Torsional Buckling
of the member.
Maximum design moment = 395 KNm < 458.2 KNm
Therefore moment resistance is satisfactory.
457 X 191 X 82 UB In Fe 430 Steel is satisfactory.
Section 5B
5-23
Example 2: Unrestrained simply supported beam.
Figure 2 shows a simply supported beam spanning 5 meters and
assumed to be laterally unrestrained. Fe 430 steel is assumed and
the beam will be checked to the clauses of EC3 currently
implemented in STAAD.
5m
Unfactored Loading
Permanent Load:
UDL including selfweight assume 15 KN/m
Variable Load:
UDL load assume 20 KN/m
Partial safety factor for permanent load (ULS) 1.35
Partial safety factor for variable load (ULS) 1.5
Factored Load: 1.35 X 15 + 1.5 X 20 = 50.3 KN/m
50.3 KN/m
5m
Steel Design Per Eurocode EC3
Section 5B
5-24
Try 457 X 191 X 82 UB.
h = 460.2 mm d = 407.9 mm tw = 9.9 mm
b = 191.3 mm tf = 16.0 mm A = 104.5 cm2
ly = 37103cm4 Wpl.y = 1833cm3 Av = 48.13cm2
Grade Fe 430fy = 275 N/mm2
Section Classification
Outstand Flanges in compression, limit for rolled section
c/t = 10e = 9.2
c/t ratio for the selected section is 95.65/16 = 5.9 < 9.2
Flange is therefore a class 1 element.
Web with N.A. at mid depth, limit for rolled section
d/tw = 72e = 66.6
d/ tw ratio for the selected section is 407.9/9.9 = 41.2 < 66.6
Web is therefore a class 1 element.
Shear Resistance
Maximum design shear force (50.3 X 5) / 2 = 120.8 KN
Plastic shear resistance Vpl.Rd = (Av / gM0) (fy / 3 )
= (4813 / 1.1) (275 / 1.732) / 1000
= 694.7 KN
Maximum design shear force = 120.8 KN < 694.7 KN
Therefore shear resistance is satisfactory.
Section is class 1
Section 5B
5-25
Moment Resistance
Maximum design moment at mid-span of beam
(wl2 / 8) = 157.2 KNm
Maximum resistance of section Mc.Rd = ( Wpl.yfy) / gM0
= (1833 X 103 X 275) / (1.1 X 106)
= 458.2KNm
Lateral Torsional Buckling
Buckling resistance moment Mb.Rd = XLTbwWPl.yfy / gM1
bw = 1 for Class 1 or Class 2 sections.
XLT = 0.5
LT2
LT2
LT ]l[ff
1
fLT = 0.5 [1 + aLT( lLT – 0.2 ) + l2LT ]
aLT = 0.21 for rolled sections.
lLT = [ lLT / l1 ] [bw]0.5
l1 = 93.9e
lLT is the geometrical slenderness ratio for lateral -torsional
buckling.
lLT = /25.66])(L/a[1)(C
L/i
2LT
0.51
LT
aLT = ( Iw / l t ) 0.5
Maximum design moment = 157.2 KNm < 458.2 KNm
Therefore moment resistance is satisfactory.
Steel Design Per Eurocode EC3
Section 5B
5-26
lw = lzhs2 / 4
hs = h - tf
iLT = [lzIw / Wpl.y2]0.25
C1 is a factor depending on transverse loading type.
For the selected section:
hs = 460.2 – 16.0 = 444.2 mm
lw = 1871 X 44.422 / 4 = 922934.6 cm6
iLT = [1871 X 922934.6 / (18332) ]0.25 = 4.76 cm
aLT = ( 922934.6 / 69.2 ) 0.5 = 115.4 cm
C1 = 1.132 (From EC3 Table F.1.2)
lLT = 0.2520.5 /25.66])(500/115.4[11.132
500/4.76
= 86.06
l1 = 93.9 (235 / 275)0.5 86.8
lLT = 86.06 / 86.8 0.99
fLT = 0.5 [1 + 0.21 (0.99 – 0.2) + 0.992] 1.07
XLT = 1 / { 1.07 + [ 1.072 – 0.992 ] 0.5} 0.67
Mb.Rd = 0.67 X 1 X 1833 X 103 X 275 / 1.1 X 106
Mb.Rd = 307.0 KNm
Maximum design moment = 157.2 KNm < 307.0 KNm
Therefore buckling resistance moment is satisfactory.
Section 5B
5-27
Example 3: Axially Loaded Column.
Figure 3 shows a pinned end column 5m long subject to a factored
load of 3500 kN. Fe 430 steel is assumed and the column will be
checked to the clauses of EC3 currently implemented in STAAD.
3500 KN
5m
3500 KN
Try 305 X 305 X 158 UC
h = 327.2 mm d = 246.6 mm tw = 15.7 mm
b = 310.6 mm tf = 25.0 mm A = 210.2 cm2
iy = 13.9 cm iz = 7.89 cm fy = 275 N/ mm2
Section Classification
Outstand flanges in compression, limit for rolled section
c/t = 10e = 9.2
c/t ratio for the selected section is 155.3/25 = 6.21 < 9.2
Flange is therefore a class 1 element.
Steel Design Per Eurocode EC3
Section 5B
5-28
Web with N.A. at mid depth, limit for rolled section
d/tw = 33e = 30.5
d/ tw ratio for the selected section is 246.6/15.7 = 15.7 < 30.5
Web is therefore a class 1 element.
Compressive resistance
Design compression resistance of the cross-section,
Nc.Rd = ( Afy) / gM0
Nc.Rd = ( 210.2 X 102 X 275 ) / ( 1.1 X 103 )
Nc.Rd = 5255 KN
Buckling resistance
The design buckling resistance of the member Nb.Rd = XbAAfy /
gM0
bA = 1 for class 1, 2 or 3 cross-sections.
X is a reduction factor for the relevant buckling mode.
X =
5.02_
2 ]lf[f
1
f = 0.5 [ 1 + a (_
l – 0.2) +
2_
l ]
a is an imperfection factor.
_
l = [ l / l1 ] [ bA ]0.5
l is the slenderness for the relevant buckling mode.
Section is class 1
Applied design load NSd = 3500 KN < 5255
Therefore compression resistance is satisfactory .
Section 5B
5-29
l1 = 93.9 e
From table 5.5.3 for buckling about y-y-axis, a is 0.34.
From table 5.5.3 for buckling about z-z axis, a is 0.49.
ly = 500 / 13.9
ly = 35.97
lz = 500 / 7.89
lz = 63.37
Consider buckling about the y-y axis.
_
l y = [ ly / l1] [bA]0.5
l1 = 93.9 X 0.924 = 86.8
_
l y = [35.9 / 86.8 ] = 0.41
fy = 0.5 [1 + ay (_
l y – 0.2) + l2y]
fy = 0.5 [1 + 0.34 (0.41 – 0.2) + 0.412]
fy = 0.62
Xy =
0.5y
2_
y2
y ]l[ff
1
= 0.522 ]0.41[0.620.62
1
Xy = 0.92 but cannot be greater than 1, therefore Xy = 0.92.
Nb.Rdy = XyAfy / gM0 = (0.92 X 275 X 201.2 X 102) / (1.1 X 103)
= 4627KN
Steel Design Per Eurocode EC3
Section 5B
5-30
Consider buckling about the z-z axis.
_
l z = [ lz / l1] [bA]0.5
l1 = 93.9 X 0.924 = 86.8
_
l z = [63.37 / 86.8 ] = 0.73
fz = 0.5 [1 + az (_
l z – 0.2) +
2_
l z]
fz = 0.5 [1 + 0.49 (0.73 – 0.2) + 0.732]
fz = 0.89
Xz =
5.0z
2_
z2
z ]lf[f
1
= 0.522 ]0.73[0.890.89
1
Xz = 0.71 but cannot be greater than 1, therefore X z = 0.71.
Nb.Rdz = XzAfz / gM0 = (0.71 X 275 X 201.2 X 102) / (1.1 X 103)
= 3571KN
3400 KN design load is less than 3571 KN, therefore section is
satisfactory.
Section 5B
5-31
Example 4: Column subject to axial load and
bending
The figure below shows a pinned end column 5m long subject to a
factored load of 1500 KN and factored bending moment of 250
KNm about the major axis. Fe 430 steel is assumed and the column
will be checked to the clauses of EC3 currently implemented in
STAAD.
Try 305 X 305 X 137 UC
h = 320.5 mm d = 246.6 mm tw = 13.8 mm
b = 308.7mm tf = 21.7 mm A = 174.6cm2
Wpl.y = 2298cm3 Wel.y= 2049 cm3 Av = 50.6 cm2
iy = 13.7 cm iz = 7.82 cm fy = 275 N/mm2
Steel Design Per Eurocode EC3
Section 5B
5-32
Section classification
Shear Resistance
Maximum design shear force 250 / 5 = 50 KN
Plastic shear resistance Vpl.Rd = ( Av / gM0 ) ( fy / 3 )
= (5060 / 1.1) (275 / 1.732) / 1000
= 730 KN
Moment Resistance
Design bending moment must not exceed the reduced plastic
resistance moment of the section given by the following equations.
MNy.Rd = Mpl.y.Rd ( 1 – n ) / ( 1 – 0.5 a )
a = ( A – 2btf ) / A but „a‟ must not exceed 0.5.
n = Nsd / Npl.Rd
If „n‟ does not exceed „a‟ then MNy.Rd = Mpl.y.Rd
a = ( 17460 – 2 X 308.7 X 21.7 ) / 17460
a = 0.232
Npl.Rd = ( 275 X 17460 ) ( 1.1 X 1000 ) = 4365 KN
n = 1500 / 4365 = 0.343
Section by inspection is class 1.
Design shear force is less than 730 KN. Shear resistance is
satisfactory.
Section 5B
5-33
Mpl.y.Rd = ( 275 X 2298 ) / ( 1.1 X 1000 ) = 574.5 KN
MNy.Rd = 574.5 ( 1 – 0.343 ) / ( 1 – 0.5 X 0.232 )
MNy.Rd = 426.97 KNm
Flexural Buckling and Bending Check
Members subject to axial load and bending must satisfy:
/gM1AfX
N
ymin
sd + /gM1fW
MK
ypl.y
y.sdy 1
Ky = 1 - yy
sdy
AfX
Nm but Ky 1.5
my = _
l y (2bMy – 4) + el.y
el.ypl.y
W
WW but my 0.90
Xmin is the lesser of Xy and Xz, where Xy and Xz are reduction
factors as calculated in the previous example.
bMy is equivalent moment factor for flexural buckling.
From Figure 5.5.3 in EC3,
bMy = 1.8 – 0.7 y but in this example, y = 0.0
bMy = 1.8
The design bending moment is less than the reduced moment
capacity. The section therefore has sufficient moment resistance.
Steel Design Per Eurocode EC3
Section 5B
5-34
Consider buckling about the y-y axis.
_
l y = [ ly / l1] [bA]0.5
bA = 1.0 for class 1 sections.
l1 = 93.9 X 0.924 = 86.8
ly = [500 / 13.7 ] = 36.5
_
l y = [36.5 / 86.8 ] = 0.42
fy = 0.5 [1 + ay (_
l y – 0.2) + l2y]
fy = 0.5 [1 + 0.34 (0.42 – 0.2) + 0.422]
fy = 0.62
Xy = 0.5
y2
y2
y ]l[ff
1
=
0.522 ]0.42[0.620.62
1
Xy = 0.93 but 1, therefore Xy = 0.93.
Consider buckling about the z-z axis.
_
l z = [ lz / l1] [bA]0.5 bA = 1.0 for class 1 sections.
l1 = 93.9 X 0.924 = 86.8
lz = [500 / 7.82 ] = 63.9
_
l z = [63.9 / 86.8] = 0.73
fz = 0.5 [1 + az (_
l z – 0.2) + _
l 2z]
fz = 0.5 [1 + 0.49 (0.73 – 0.2) + 0.732]
fz = 0.89
Section 5B
5-35
Xz =
0.5z
2_
z2
z ]l[ff
1
= 0.522 ]0.73[0.890.89
1
Xz = 0.71 but 1, therefore Xz = 0.71.
Xmin is therefore 0.71.
_
l y = 0.42
my = 0.42 (2 X 1.8 – 4) + 2049
20492298 = - 0.046
Ky = 1 - X2750.93X17.46
0.046X1500 = 1.015 1.5
/gM1AfX
N
ymin
sd + /gM1fW
MK
ypl.y
y.sdy 1
X275/1.10.71X17.46
1500 +
1.12.298X275/
1.015X250 = 0.92 1
Members for which lateral-torsional buckling is a potential
problem must also satisfy:
/gM1AfX
N
yz
sd + /gM1fWX
MK
ypl.yLT
y.sdLT 1
KLT = 1 -
yz
sdLT
AfX
Nm but KLT 1
mLT = 0.15 lzbM.LT – 0.15, but mLT 0.90
Using the equations used in Example 2, we have the following.
Steel Design Per Eurocode EC3
Section 5B
5-36
For the selected selection:
iLT = 8.33 cm
aLT = 97.6 cm
C1 = 1.879 (From EC3 Table F.1.2)
lLT = 0.2520.5 /25.66](500/97.6)[11.879
500/8.33
= 36.71
l1 = 93.9 (235 / 275)0.5 = 86.8
lLT = 36.71 / 86.8 = 0.42
fLT = 0.5 [ 1 + 0.21 (0.42 – 0.2) + 0.422 ] = 0.61
XLT = 1 / { 0.61 + [ 0.612 – 0.422 ]0.5 } = 0.95
bMLT = 1.8
lz = 0.73
mLT = 0.15 X 0.73 X 1.8 – 0.15 = 0.047
KLT = 1 - X2750.71X17.46
0.047X1500 = 0.98
/gM1AfX
N
yz
sd + /gM1fWX
MK
ypl.yLT
y.sdLT 1
X275/1.10.71X17.46
1500 +
X275/1.10.95X2.298
0.98X250 = 0.932
305X305X137UC is therefore satisfactory.
Section 5B
5-37
5B.5 User’s Examples
Example 1.
The following input file is for the single beam in example 1. Only
code check related output is enclosed.
STAAD PLANE INPUT FILE FOR EX.1 IN THE EC3 MANUAL.
INPUT WIDTH 79
UNIT METER KNS
JOINT COORDINATES 1 0.000 0.000 0.000
2 5.000 0.000 0.000
MEMBER INCIDENCES
1 1 2
MEMBER PROPERTY BRITISH
1 TABLE ST UB457X191X82
CONSTANTS
E STEEL ALL
SUPPORTS
1 PINNED
2 FIXED BUT FX MZ
LOAD 1 MEMBER LOAD
1 UNI GY-20.0
LOAD 2
MEMBER LOAD
1 UNI GY -25.0
LOAD COMBINATION 3
1 1.35 2 1.5
PERFORM ANALYSIS
LOAD LIST 3
PARAMETER
CODE EC3 UNL 0.0 ALL
BEAM 2.0 ALL
TRACK 2 .ALL
SGR 1 .ALL
CHECK CODE ALL
FINISH
Steel Design Per Eurocode EC3
Section 5B
5-38
Section 5B
5-39
Example 2.
The following input file is for the beam in example 2. Only code
check related output is enclosed.
STAAD PLANE INPUT FILE FOR EXAMPLE 2
INPUT WIDTH 79
UNIT METER KNS
JOINT COORDINATES
1 0.000 0.000 0.000 2 5.000 0.000 0.000
MEMBER INCIDENCES
1 1 2
MEMBER PROPERTY BRITISH
1 TABLE ST UB457X191X82
CONSTANTS
E STEEL ALL
SUPPORTS
1 PINNED
2 FIXED BUT FX MZ
LOAD 1
MEMBER LOAD 1 UNI GY -15.0
LOAD 2
MEMBER LOAD
1 UNI GY -20.0
LOAD COMBINATION 3
1 1.35 2 1.5
PERFORM ANALYSIS
LOAD LIST 3
PARAMETER
CODE EC3
BEAM 2.0 ALL TRACK 2. ALL
SGR 1. ALL
CHECK CODE ALL
FINISH
Steel Design Per Eurocode EC3
Section 5B
5-40
Section 5B
5-41
Example 3.
The following input file is for the simple column in example 3.
Only code check related output is enclosed.
STAAD PLANE INPUT FILE FOR EXAMPLE 3.
UNIT METER KNS
JOINT COORDINATES
1 0 0 0
2 0 5 0 MEMBER INCIDENCES
1 1 2
MEMBER PROPERTIES BRITISH
1 TA ST UC305X305X158
CONSTANTS
E STEEL ALL
SUPPORT
1 FIXED
LOAD 1
JOINT LOAD
2 FY -3500
PERFORM ANALYSIS PARAMETERS
CODE EC3
TRACK 2.0 ALL
SGR 1. ALL
CHECK CODE ALL
FINISH
Steel Design Per Eurocode EC3
Section 5B
5-42
Section 5B
5-43
Example 4.
The following input file is for the column in example 4. Only code
check related output is enclosed.
STAAD PLANE INPUT FILE FOR EXAMPLE 4.
UNIT METER KNS
JOINT COORDINATES
1 0 0 0
2 0 5 0 MEMBER INCIDENCES
1 1 2
MEMBER PROPERTIES BRITISH
1 TA ST UC305X305X137
CONSTANTS
E STEEL ALL
SUPPORT
1 PINNED
2 FIXED BUT FY MZ
LOAD 1
JOINT LOAD
2 FY -1500 2 MZ 250
PERFORM ANALYSIS
PARAMETERS
CODE EC3
BEAM 2.0 ALL
TRACK 2.0 ALL
CMM 6
SGR 1.0 ALL
CHECK CODE ALL
FINISH
Steel Design Per Eurocode EC3
Section 5B
5-44
5-45
Timber Design Per EC 5: Part 1-1.
(BS EN 1995-1-1:2004)
5C.1 General Comments
The Timber Design facility as per EC5 in STAAD is based on the
European Standard Eurocode 5: Design of Timber Structures - Part
1-1 - General - Common rules and rules for buildings. Principles
of Limit States Design of Timber Structures are adopted as
specified in the code.
The application is limited to the PRISMATIC rectangular shapes
only. There is no Eurocode-specific timber section database /
library consisting of pre-defined shapes for analysis or for design.
The feature of member selection is thus not applicable to this code.
The design philosophy of this specification is based on the concept
of limit state design. Structures are designed and proportioned
taking into consideration the limit states at which they would
become unfit for their intended use. Two major categories of limit-
state are recognized - ultimate and serviceability. The primary
considerations in ultimate limit state design are strength and
stability, while that in serviceability is deflection. Appropriate
load and resistance factors are used so that a uniform reliability is
achieved for all timber structures under various loading conditions
and at the same time the chances of limits being surpassed are
acceptably remote.
In the STAAD implementation, members are proportioned to resist
the design loads without exceeding the limit states of strength,
stability and serviceability. Accordingly, the most economic
section is selected on the basis of the least weight criteria as
augmented by the designer in specification of allowable member
depths, desired section type, or other such parameters. The code
Section 5C
Timber Design Per EC 5: Part 1-1.
Section 5C
5-46
checking portion of the program checks whether code requirements
for each selected section are met and identifies the governing
criteria.
The following sections describe the salient features of the STAAD
implementation of EC 5. A detailed description of the design
process along with its underlying concepts and assumptions is
available in the specification document.
Axes convention in STAAD and EC5
STAAD defines the major axis of the cross-section as zz and the
minor axis as yy. The longitudinal axis of the member is defined
as x and joins the start joint of the member to the end with the
same positive direction.
EC5, however, defines the principal cross-section axes in reverse
to that of STAAD, but the longitudinal axis is defined in the same
way. Both of these axes definitions follow the orthogonal right
hand rule. See figure 1 below:
y z
z z y y
y z
STAAD EC5
Figure 1 Axes convention in STAAD and EC5
Section 5C
5-47
Determination of Factors
(A) Kmod – Modification factor taking into account of Load-
duration (LDC) and Moisture-content (Service Class -
SCL). Reference Table 3.1 of EC-5-2004.
For “Solid Timber”, the values are incorporated in the
program.
(B) m – Partial factor for Material Property values.
Reference Table 2.3 of EC-5-2004.
For “Solid Timber”, the value of m (= 1.3) is
incorporated in the program.
(C) Kh – Size Factor.
For members, subjected to tension, whose maximum c/s
dimension is less than the reference width in tension the
characteristic strength in tension (ft0k) is to be increased
by the factor Kh.
For members, subjected to bending, whose depth is less
than reference depth in bending, the characteristic strength
in bending (fmk) is to be increased by the factor Kh.
As per clause 3.2(3) of EC 5- 2004, for rectangular solid
timber with a characteristic timber density k 700 kg/m3
the reference depth in bending or the reference width
(maximum cross-sectional dimension) is 150 mm.
The value of Kh = Minimum of {(150/h) 0.2 and 1.3) for
such solid timber is incorporated in the software. Please
refer clause numbers 3.3 and 3.4 for the value of Kh for
Glued laminated timber and Laminated veener lumber
respectively.
Timber Design Per EC 5: Part 1-1.
Section 5C
5-48
(D) KC90 – Factor taking into account the load
configuration, possibility of splitting and degree of
compressive deformation.
For members, subjected to compression, perpendicular to
the direction of grain alignment, this factor should be
taken into account. Default value of 1 is used in
STAAD.Pro. User may override the value. Please refer
clause 6.1.5 of EC-5-2004 in this regard.
(E) Km – Factor considering re-distribution of bending
stress in cross section.
For members, subjected to bending, this factor is taken
into account for stress checking. For rectangular section
the value of Km is 0.7, and this value is incorporated in
STAAD.Pro. User may override the value. Please refer
clause 6.1.6 of EC-5-2004 in this regard.
(F) Kshape – Factor depending on shape of cross section.
For members, subjected to torsional force, design torsional
stress should be less than equal design shear strength
multiplied by the factor Kshape. This factor is determined
by STAAD.Pro internally using the guidelines of clause
6.1.8 of EC-5-2004 .
Section 5C
5-49
5C.2 Analysis Methodology
Symbols Description
St0d Design tensile stress parallel (at zero degree) to grain
alignment. St90d Design tensile stress perpendicular (at 90 degrees) to
grain alignment. Sc0d Design compressive stress parallel to grain alignment. Sc90d Design compressive stress perpendicular to grain
alignment. Smzd Design bending stress about zz axis. Smyd Design bending stress about yy axis. Svd Design shear stress. Stor_d Design torsional stress.
Ft0d Design tensile strength - parallel to the grain
alignment. Ft90d Design tensile strength - perpendicular to the grain
alignment. Fc0d Design compressive strength - parallel to the grain
alignment. Fc90d Design compressive strength - perpendicular to the
grain alignment. Fmzd Design bending strength - about zz-axis. Fmyd Design bending strength - about yy-axis. Fvd Design shear strength about yy axis.
RATIO Permissible ratio of stresses as provided by the user.
The default value is 1.
Timber Design Per EC 5: Part 1-1.
Section 5C
5-50
Symbols Description
z ,rel ,z Slenderness ratios corresponding to bending about zz
axis. y,rel ,y Slenderness ratios corresponding to bending about yy
axis.
E0,05 Fifth percentile value of modulus of elasticity parallel
to grain. G0,05 Fifth percentile value of shear modulus parallel to
grain. Iz Second moment of area about the strong z-axis. Iy Second moment of area about the weak y-axis. Itor Torsional moment of inertia.
fmk Characteristic bending strength.
b, h Width and depth of beam.
Equations for Characteristic Values of Timber Species as per
Annex-A of EN 338:2003
The following equations were used to determine the characteristic
values:
Basic Inputs: For a particular Timber Strength Class (TSC), the
following characteristic strength values are
required to compute the other related characteristic
values.
1. Bending Strength – fm,k
2. Mean Modulus of Elasticity in bending – E0, mean
3. Density - k
Section 5C
5-51
Sl.
No. Property Symbol
Wood Type
Softwood
(C) Hardwood (D)
1. Tensile Strength
parallel to grain ft ,0,k 0.6 * fm,k
2. Tensile Strength
perpendicular to grain ft ,90,k Minimum of {0.6 and (0.0015*k)}
3. Compressive Strength
parallel to grain fc,0,k 5 * (fm,k )
0.45
4. Compressive Strength
perpendicular to grain fc,90,k 0.007*k 0.0015*k
5. Shear Strength fv,k Minimum of {3.8 and (0.2*fm,k 0.8)}
6. Modulus of Elasticity
parallel to grain E0,05 0.67* E0,mean 0.84* E0,mean
7.
Mean Modulus of
Elasticity
perpendicular to grain
E90,mean E0,mean /30 E0,mean /15
8. Mean Shear Modulus Gmean E0,mean /16
9. Shear Modulus G0,05 E0,05 /16
The values of the characteristic strengths computed using the
above equations, may differ with the tabulated values in Table-1 of
EN 338:2003. However, in all such cases, the values obtained from
the provided equations are treated as actual and is used by the
program, as the values of Table-1 are based on these equations.
Finding the Design values of Characteristic Strength
As per clause 2.4.1, Design values of a strength property shall be
calculated as:
mkd XmodKX
Timber Design Per EC 5: Part 1-1.
Section 5C
5-52
Where Xd is design value of strength property, Xk characteristic
value of strength property and m is partial factor for material
properties.
The member resistance in timber structure is calculated in STAAD
according to the procedures outlined in EC5. This depends on
several factors such as cross sectional properties, different load
and material factors, timber strength class, load duration class,
service class and so on. The methodology adopted in STAAD for
calculating the member resistance is explained here.
Check for Tension stresses
If the direction of applied axial tension is parallel to the direction
of timber grain alignment, the following formula should be
checked:
RATIO F S t0dt0d …….(cf : Equation 6.1 of EC-5-2004)
If the direction of applied axial tension is perpendicular to the
direction of timber grain alignment, the following formula should
be checked:
RATIO F S t90dt90d
Check for Compression stresses
If the direction of applied axial compression is parallel to the
direction of timber grain alignment, the following formula should
be checked:
RATIO F S c0dc0d …….(cf: Equation 6.2 of EC-5-
2004)
If the direction of applied axial compression is perpendicular to
the direction of timber grain alignment, the following formula
should be checked:
Section 5C
5-53
RATIO Kc90F S c90dc90d (cf: Equation 6.3 of EC-5-
2004)
Check for Bending stresses
If members are under bending stresses, the following conditions
should be satisfied. Please note that in STAAD z-z axis is the
strong axis:
RATIOF
SKm
F
S
myd
myd
mzd
mzd
.(cf: Equation 6.11 of EC-5-2004)
RATIOF
S
F
SKm
myd
myd
mzd
mzd
.(cf: Equation 6.12 of EC-5-2004)
Check for Shear stresses
Horizontal stresses are calculated and checked against allowable
values:
RATIOF
S
vd
vd
…….( cf: Equation 6.13 of EC-5-2004)
Check for Torsional stresses
Members subjected to torsional stress should satisfy the following
equation:
RATIOFKshape
S
tor_d
tor_d
.( cf: Equation 6.14 of EC-5-2004)
Timber Design Per EC 5: Part 1-1.
Section 5C
5-54
Check for combined Bending and Axial tension
Members subjected to combined action of bending and axial
tension stress should satisfy the following conditions. Please note
that in STAAD z-z axis is the strong axis:
RATIO F
SKm
F
S
F
S
myd
myd
mzd
mzd
t0d
t0d
…. (cf: Equation 6.17 of EC-5-2004)
RATIO F
S
F
SKm
F
S
myd
myd
mzd
mzd
t0d
t0d
…. ( cf: Equation 6.18 of EC-5-2004)
Check for combined Bending and axial Compression
If members are subjected to bending and axial compression stress,
following equations should be satisfied. Please note that in
STAAD z-z axis is the strong axis:
RATIO F
SKm
F
S
F
S
myd
myd
mzd
mzd
2
c0d
c0d
…. ( cf: Equation 6.19 of EC-5-2004)
RATIO F
S
F
SKm
F
S
myd
myd
mzd
mzd
2
c0d
c0d
…. ( cf: Equation 6.20 of EC-5-2004)
Section 5C
5-55
Stability check
(A) Column Stability check
The relative slenderness ratios should be calculated as
follows. Please note that in STAAD z-z axis is the strong
axis:
0,05
c0kzz,rel
E
S
…….( Equation 6.21 of EC-5-2004)
0,05
c0ky
y,relE
S
…….( Equation 6.22 of EC-5-2004)
If both rel ,z and rel ,y are less than or equal to 0.3 the
following conditions should be satisfied:
RATIO F
SKm
F
S
F
S
myd
myd
mzd
mzd
2
c0d
c0d
RATIO F
S
F
SKm
F
S
myd
myd
mzd
mzd
2
c0d
c0d
In other cases, the following conditions should be satisfied.
Please note that in STAAD z-z axis is the strong axis:
RATIO F
SKm
F
S
FKcz
S
myd
myd
mzd
mzd
c0d
c0d
… ( cf: Equation 6.23 of EC-5-2004)
Timber Design Per EC 5: Part 1-1.
Section 5C
5-56
RATIO F
S
F
SKm
FKcy
S
myd
myd
mzd
mzd
c0d
c0d
... ( cf: Equation 6.24 of EC-5-2004)
Where the symbols Kcz and Kcy are defined as follows.
Please note that in STAAD z-z axis is the strong axis:
2z,rel
2KzKz
1Kcz
...( Equation 6.25 of EC-5-2004)
2y,rel
2KzKy
1Kcy
…( Equation 6.26 of EC-5-2004)
2
z,relz,relc 3.015.0Kz ( Equation 6.27 of EC-5-2004)
2
y,rely,relc 3.015.0Ky .( Equation 6.28 of EC-5-2004)
The value of c incorporated in the software is the one for
solid timber ,i.e. 0.2.
(B) Beam Stability check
If members are subjected to only a moment about the strong
axis z, the stresses should satisfy the following equation:
RATIOFKcrit
S
mzd
mzd
.( cf: Equation 6.33 of EC-5-2004)
Section 5C
5-57
Where a combination of moment about the strong z -axis and
compressive force exists, the stresses should satisfy the
following equation:
RATIOFKcz
S
FKcrit
S
c0d
c0d
2
mzd
mzd
…… ( cf: Equation 6.35 of EC-5-2004)
Where,
mrel,2
mrel,
mrel,m,rel
mrel,
4.1for1
1.475.0for75.056.1
0.75 for 1
Kcrit
….. ( Equation 6.34 of EC-5-2004)
crit,m
mkm,rel
S
f ……..( Equation 6.30 of EC-5-2004)
For hardwood:
…. (Equation 6.31 of EC-5-2004)
For softwood:
05,0
ef
2
crit,m Elh
b78.0S
….( Equation 6.32 of EC-5-2004)
zef
tor05,0y05,0
crit,mWl
IGIES
Timber Design Per EC 5: Part 1-1.
Section 5C
5-58
5C.3 Design Parameters
Design parameters communicate specific design decisions to the
program. They are set to default values to begin with and may be
altered to suite the particular structure.
Depending on the model being designed, the user may have to
change some or all of the parameter default values. Some
parameters are unit dependent and when altered, the new setting
must be compatible with the active “unit” specification.
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
Parameter
Name
Default
Value
Description
SCL 3 Service Class (Ref. Cl.2.3.1.3)
1 = Class 1, Moisture content <= 12%
2 = Class 2, Moisture content <= 20%
3 = Class 3, Moisture content > 20%
LDC 1 Load Duration Class (Ref. Cl.2.3.1.2),
required to get the K-MOD value from
Table – 3.1.
1 - Permanent action
2 - Long term action
3 - Medium term action
4 - Short term action
5 - Instantaneous action
Section 5C
5-59
Parameter
Name
Default
Value
Description
TSC 6 (C24) Timber Strength Class (Ref. Reference
EN338 – 2003)
Softwood: 1 = C14, 2 = C16, 3 = C18,
4 = C20, 5 = C22, 6 = C24, 7 = C27, 8 =
C30, 9 = C35, 10 = C40, 11 = C45, 12 =
C50.
Hardwood: 13 = D30, 14 = D35, 15 =
D40, 16 = D50, 17 = D60, 18 = D70.
This TSC definition will calculate the
corresponding characteristic strength
values using the equations as given in
BS-EN-338, Annex - A.
ALPHA 0.0 Angle of inclination of load to the grain
alignment. (Ref. Cl.6.1.1, Cl.6.1.2,
Cl.6.1.3, Cl.6.1.4)
0.0 = Load parallel to grain,
90.0 = Load Perpendicular to grain
KC90 1.0 Factor taking into account the load
configuration, possibility of splitting and
degree of compressive deformation. (Ref.
Cl.6.1.5-(2))
Range: 1.0 KC90 4.0
Other than the default value, user may
specify any value within the range,
depending on load-position, load-
dispersion, contact length at support
locations etc.
Timber Design Per EC 5: Part 1-1.
Section 5C
5-60
Parameter
Name
Default
Value
Description
MTYP 0 Member Type: Beam/Column. (Ref.
Cl.6.3.2, Cl.6.3.3)
0 – Not defined by the user – checks
both clauses (Default).
1 – Beam Member
2 – Column Member
This information is required to find which
stability check will be performed as per
the Cl 6.3 according to the Member Type.
KLEF 1.0
(Member
Length)
Effective Length Factor to check Lateral
Torsional Buckling. (Ref. Table 6.1)
Span of the beam depending on the
support conditions and load
configurations. The user will put the
appropriate value from the Table 6.1.
Required only for MTYP has a value of 1
(Beam).
KLY 1.0
(Member
Length)
Effective Length Factor for Local-y-axis.
(Ref. Cl.6.3.2), for the computation of the
relative slenderness ratios.
KLZ 1.0
(Member
Length)
Effective Length Factor for Local-z-axis.
(Ref. Cl.6.3.2), for the computation of the
relative slenderness ratios.
TRACK 0 Degree/Level of Details of design output
results.
Available options: 0 / 1 / 2
RATIO 1.0 Permissible ratio of actual to allowable
value.
Section 5C
5-61
Parameter
Name
Default
Value
Description
SERV No Default
Value
Defines the load case numbers – those are
to be considered for serviceability
(deflection) check.
The list of this parameter must contain
only the valid load-case numbers.
Deflection checks will be performed
only on those load-case results.
If this parameter is not provided ,
then in-spite of the presence of the
parameter DFF – the deflection check
will NOT be performed.
DFF No Default
Value
“Deflection Length” / Max. Allowable
Net Final Local Deflection.
In this case, deflection check will be
performed, if both the parameters SERV
and DFF are present with specific values.
For appropriate range of values, please
refer Cl.7.2 (Table 7.2)
DJ1 Start node number for a physical member
under consideration for Deflection Check.
DJ2 End node number for a physical member
under consideration for Deflection Check.
5C.4 Verification Problems
In the next few pages are included 2 verification examples for
reference purposes.
Timber Design Per EC 5: Part 1-1.
Section 5C
5-62
Verification Problem No. 1
A Timber Column of length 1.0 meter, having c/s dimension of 73
mm X 198 mm, is subjected to an axial compressive force of 50.0
kN.
Design of the member - ULTIMATE LIMIT STATE
Material properties:
Timber class: C24
Service classes: Class 2, moisture content <= 20%
Load duration classes: Medium-term
Cross section properties:
Length of the member is 1 m.
Rectangular cross section, b = 73 mm, h = 198 mm,
Effective cross sectional area A = 14454 mm²,
Radius of gyration of cross section about y-axis ry = 21 mm,
Radius of gyration of cross section about z-axis rz = 57 mm,
Section modulus of cross section about z-axis: Wz = 4.770x105 mm³
Section modulus of cross section about y-axis: Wy = 1.759x105 mm³
Characteristic material properties for timber:
Modification factor Kmod = 0.80 …from table 3.1
Material factors m = 1.30 … from table 2.3
fc0k = 21.00 N/mm²,
Fc0d = (Kmod.fc0k)/m = (0.80x21.00)/1.30 = 12.92 N/mm²[Cl
2.4.1(1)P]
Section 5C
5-63
Cross section loads:
Fx = 50.000 kN
Compression parallel to the grain:
Sc0d = (1000xFx)/A = (1000x50.000)/14454
= 3.46N/mm² < 12.92N/mm² (Fc0d)
The ratio of actual compressive stress to allowable
compressive strength:
= 3.46 / 12.92 = 0.268 < 1.0 [Cl. 6.1.4.(1)P]
Check for Slenderness:
Slenderness ratios: z = (1000/57) = 17.54 and y = (1000/21)
= 47.62
E0,mean = 1.1031 kN/m2
As timber grade is C24, i.e., Soft Wood, E0,05 = 0.67 * E0,mean
… [Annex A,EN 338:2003]
05,0
k0cy
y,relE
f
= 0.809
05,0
k0czz,rel
E
f
= 0.298
Since, rel ,y is greater than 0.3, following conditions should be
satisfied:
RATIO F
SKm
F
S
FK
S
mzd
mzd
myd
myd
c0dyc,
c0d
[Cl.
6.3.2.(3)]
Timber Design Per EC 5: Part 1-1.
Section 5C
5-64
RATIO F
SKm
F
S
FKcz
S
myd
myd
mzd
mzd
c0d
c0d
[Cl.
6.3.2.(3)]
2
yrel,yrel,y 3.1.5K = 0.878
2
zrel,zrel,z 3.1.5K = 0.541
2
y,rel
2
yy
y,c
KK
1K
= 0.82
2
z,rel
2
zz
z,c
KK
1K
= 1.0
For Rectangular cross section Km = 0.70. The member is
subjected to Compression only, so actual bending stress is
zero.
F
SKm
F
S
FK
S
mzd
mzd
myd
myd
c0dyc,
c0d= 0.326 + 0.0 + 0.0
= 0.326
F
SKm
F
S
FKcz
S
myd
myd
mzd
mzd
c0d
c0d= 0.268 + 0.0 + 0.0
= 0.268
Hence the critical ratio is 0.326 < 1.0 and the section is safe.
Section 5C
5-65
The Input File:
STAAD SPACE START JOB INFORMATION ENGINEER DATE END JOB INFORMATION INPUT WIDTH 79 UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 1.0 0 0; MEMBER INCIDENCES 1 1 2; DEFINE MATERIAL START ISOTROPIC WOOD E 1.10316e+007 POISSON 0.15 DENSITY 0.00231749 ALPHA 5.5e-006 END DEFINE MATERIAL CONSTANTS MATERIAL WOOD MEMB 1 MEMBER PROPERTY 1 PRIS YD 0.198 ZD 0.073 SUPPORTS 1 FIXED LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1 JOINT LOAD 2 FX -50 PERFORM ANALYSIS PARAMETER CODE TIMBER EC5 ALPHA 0 ALL LDC 3 ALL SCL 2 ALL TSC 6 ALL TRACK 2 ALL CHECK CODE ALL FINISH
Timber Design Per EC 5: Part 1-1.
Section 5C
5-66
The member checking part of the output file:
Section 5C
5-67
Verification Problem No. 2
A Timber Column of length 1.0 meter, having c/s dimension of 73
mm X 198 mm, is subjected to an axial compressive force of 5.0
kN and moments of 2.0 kN.m and 1.0 kN.m about its major and
minor axes respectively.
Design of the member - ULTIMATE LIMIT STATE
Material properties:
Timber Strength Class: C24
Service classes: Class 2, moisture content <=20%
Load duration: Medium-term
Cross section properties:
Length of the member is 1 m.
Rectangular cross section, b = 73 mm, h = 198 mm,
Effective cross sectional area A = 14454 mm²,
Radius of gyration of cross section about y-axis ry = 21 mm,
Radius of gyration of cross section about z-axis rz = 57 mm,
Section modulus of cross section about z-axis: Wz = 4.770x105 mm³
Section modulus of cross section about y-axis: Wy = 1.759x105 mm³
Characteristic material properties for timber:
Modification factor, Kmod = 0.80
Material factor m = 1.30
fc0k = 21.00 N/mm², E0,05 = 7370 N/mm2,
Fc0d = Kmod.fc0k/m = (0.80x21.00)/1.30 = 12.92N/mm²
fmyk = 24.00 N/mm²,
Fmyd = Kmod.fmyk/m = (0.80x24.00)/1.30 = 14.77N/mm²
fmzk = 24.00 N/mm²,
Fmzd = Kmod.fmzk/m = (0.80x24.00)/1.30 = 14.77N/mm²
Timber Design Per EC 5: Part 1-1.
Section 5C
5-68
Cross section loads:
Fx = 5.000 kN, Mz = 2.000 kN.m, My = 1.000 kN.m
Check for Slenderness:
Slenderness ratios: z = (1000/57) = 17.54 and y = (1000/21)
= 47.62
05,0
k0cy
y,relE
f
= 0.809
05,0
k0czz,rel
E
f
= 0.298
Since, rel ,y is greater than 0.3, following conditions should be
satisfied:
RATIO F
SKm
F
S
FK
S
mzd
mzd
myd
myd
c0dyc,
c0d
[Cl. 6.3.2.(3)]
RATIO F
SKm
F
S
FKcz
S
myd
myd
mzd
mzd
c0d
c0d
[Cl. 6.3.2.(3)]
2
yrel,yrel,y 3.1.5K = 0.878
2
zrel,zrel,z 3.1.5K = 0.541
2
y,rel
2
yy
y,c
KK
1K
= 0.82
2
z,rel
2
zz
z,c
KK
1K
= 1.0
Section 5C
5-69
For Rectangular cross section Km = 0.70
Sc0d = (1000Fx/A) = (1000x5.000)/14454 = 0.35 N/mm²
Smzd = (106xMz)/Wz = (106x2.000)/(4.770x105) = 4.19 N/mm²
Smyd = (106xMy)/Wy = (106x1.000)/(1.759x105) = 5.69 N/mm²
F
SKm
F
S
FK
S
mzd
mzd
myd
myd
c0dyc,
c0d
= 0.033 + 0.385 + 0.198 = 0.616
F
SKm
F
S
FKcz
S
myd
myd
mzd
mzd
c0d
c0d
= 0.027 + 0.283 + 0.269 = 0.579
Hence the critical ratio is 0.616 < 1.0 and the section is safe.
Timber Design Per EC 5: Part 1-1.
Section 5C
5-70
The Input File:
STAAD SPACE START JOB INFORMATION ENGINEER DATE 08-Jun-05 END JOB INFORMATION INPUT WIDTH 79 UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 0 1 0; MEMBER INCIDENCES 1 1 2; DEFINE MATERIAL START ISOTROPIC WOOD E 1.10316e+007 POISSON 0.15 DENSITY 0.00231749 ALPHA 5.5e-006 END DEFINE MATERIAL CONSTANTS MATERIAL WOOD MEMB 1 MEMBER PROPERTY 1 PRIS YD 0.198 ZD 0.073 SUPPORTS 1 FIXED LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1 JOINT LOAD 2 FY -5.0 MX 1.0 MZ 2.0 PERFORM ANALYSIS PARAMETER CODE TIMBER EC5 ALPHA 0 ALL LDC 3 ALL SCL 2 ALL TSC 6 ALL TRACK 2 ALL CHECK CODE ALL FINISH
Section 5C
5-71
The member checking part of the output file:
Timber Design Per EC 5: Part 1-1.
Section 5C
5-72
Section 6
Egyptian Codes
A‟lkjdfl‟akjsfd
6-1
Concrete Design Per EGYPTIAN CODE - ECCS205
6A.1 Design Operations
STAAD has the capability of performing design of concrete
beams, columns and slabs according to ECCS 203. The 2004
revision of the code is currently implemented. Given the width
and depth of a section, STAAD will calculate the required
reinforcement to resist the forces and moments.
6A.2 Member Dimensions
Concrete members which will be designed by the program must
have certain section properties input under the MEMBER
PROPERTY command. The following example shows the required
input:
UNIT MM
MEMBER PROPERTY
1 3 TO 7 9 PRISM YD 450. ZD 250.
11 13 PR YD 350.
Section 6A
Concrete Design Per Egyptian Code ECC S205
Section 6A
6-2
6A.3 Design Parameters
The program contains a number of parameters which are needed to
perform the design. Default parameter values have been selected
such that they are frequently used numbers for conventional design
requirements. These values may be changed to suit the particular
design being performed. The following Beam Design Brief
contains a complete list of the available parameters and their
default values.
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
Section 6A
6-3
6A.4 Slenderness Effects and Analysis Considerations
STAAD provides the user with two methods of accounting for the
slenderness effects in the analysis and design of concrete
members. The first method is equivalent to the procedure
presented in ECCS203-2004 equation 4-11. In this section, the
code recognizes that additional moments induced by deflection are
present and states that these 'secondary' moments are accounted for
by the design formula in equation 6-38, 6-37 etc. This is the
method used in the design for concrete in STAAD.
Alternatively STAAD houses a PDELTA ANALYSIS facility,
which allows the effects of these second order moments to be
considered in the analysis rather than the design. In a PDELTA
analysis, after solving the joint displacements of the structure, the
additional moments induced in the structure are calculated. These
can be compared to those calculated using the formulation of
ECCS203-2004.
6A.5 Beam Design
Beams are designed for flexure, shear and torsion. For all these
forces, all active beam loadings are pre scanned to identify the
critical load cases at different sections of the beams. The total
number of sections considered is 13( e.g. 0.,.1,.2,.25,.3,.4,.5,.6,.7,.
75,.8,.9 and 1). All of these sections are scanned to determine the
design force envelopes.
Concrete Design Per Egyptian Code ECC S205
Section 6A
6-4
Design for Flexure
Maximum sagging (creating tensile stress at the bottom face of the
beam) and hogging (creating tensile stress at the top face)
moments are calculated for all active load cases at each of the
above mentioned sections. Each of these sections is designed to
resist both of these critical sagging and hogging moments.
Currently, design of singly reinforced sections only is permitted. If
the section dimensions are inadequate as a singly reinforced
section, such a message will be permitted in the output. Flexural
design of beams is performed in two passes. In the first pass,
effective depths of the sections are determined with the
assumption of single layer of assumed reinforcement and
reinforcement requirements are calculated. After the preliminary
design, reinforcing bars are chosen from the internal database in
single or multiple layers. The entire flexure design is performed
again in a second pass taking into account the changed effective
depths of sections calculated on the basis of reinforcement
provided after the preliminary design. Final provision s of flexural
reinforcements are made then. Efforts have been made to meet the
guideline for the curtailment of reinforcements as per ECCS203-
2004. Although exact curtailment lengths are not mentioned
explicitly in the design output (finally which will be more or less
guided by the detailer taking into account of other practi cal
consideration), user has the choice of printing reinforcements
provided by STAAD at 13 equally spaced sections from which the
final detailed drawing can be prepared.
Design for Shear
Shear reinforcement is calculated to resist both shear forces and
torsional moments. Shear design is performed at 13 equally spaced
sections (0.to 1.) for the maximum shear forces amongst the active
load cases and the associated torsional moments. Shear capacity
calculation at different sections without the shear reinfor cement is
based on the actual tensile reinforcement provided by STAAD
program. Two-legged stirrups are provided to take care of the
balance shear forces acting on these sections.
Section 6A
6-5
Beam Design Output
Concrete Design Per Egyptian Code ECC S205
Section 6A
6-6
6A.6 Column Design
Columns are designed for axial force and biaxial bending at the
ends. All active loadings are tested to calculate reinforcement. The
loading which produces maximum reinforcement is called the
critical load and is displayed. The requirements of ECCS203-2004
equation 6-37,6-38,6-41 etc are followed, with the user having
control on the effective length parameters. Bracing conditions are
controlled by using the BRACE parameter. The program will then
decide whether or not the column is short or slender and whether it
requires additional moment calculations.
Section 6A
6-7
Column Design output
Concrete Design Per Egyptian Code ECC S205
Section 6A
6-8
Shear Design Output
6-9
Steel Design Per EGYPTIAN CODE #205
6B.1 General Comments
This section presents some general statements regarding the
implementation of Egyptian code of practice for structural steel
construction and bridges Code No. 205(Min Dec #279/2001)
design in STAAD. The design philosophy and procedural logistics
for member selection and code checking are based upon the
principles of allowable stress design. Two major failure modes are
recognized: failure by overstressing, and failure by stability
considerations. The flowing sections describe the salient features
of the allowable stresses being calculated and the stability criteria
being used. Members are proportioned to resist the design loads
without exceeding the allowable stresses and the most economic
section is selected on the basis of least weight criteria. The code
checking part of the program checks stability and strength
requirements and reports the critical loading condition and the
governing code criteria. It is generally assumed that the user will
take care of the detailing requirements like provision of stiffeners
and check the local effects such as flange buckling and web
crippling.
6B.2 Allowable Stresses
The member design and code checking in STAAD are based upon
the allowable stress design method as per Egyptian Code No. 205,
It is a method for proportioning structural members using design
loads and forces, allowable stresses, and design limitations for the
appropriate material under service conditions. It would not be
possible to describe every aspect of Egyptian Code: 205 in this
Section 6B
Steel Design Per Egyptian Code # 205
Section 6B
6-10
manual. This section, however, will discuss the salient features of
the allowable stresses specified by Egyptian Code: 205 and
implemented in STAAD. Appropriate sections of Egyptian Code:
205 will be referenced during the discussion of various types of
allowable stresses.
6B.2.1 Axial Stress
Tensile Stress
The allowable tensile stress, as calculated in STAAD as per
Egyptian Code: 205 is described below.
The estimated stress on the net effective sectional area in various
members, multiplied by the appropriate factor of safety shall not
exceed minimum guaranteed yield stress of the material.
The permissible stress in axial tension, at in MPa on the net
effective area of the sections shall not exceed: Clause: 2.6.2
Ft = 0.58 fy
where,
fy = minimum yield stress of steel in Mpa
Compressive Stress
Allowable compressive stress on the gross section of axially
loaded compression members shall not exceed the permissible
stress calculated based on the following formula: (Clause: 2.6.4)
Fc = 2
410
)75.058.0(58.0
y
y
FF
For all grade of steel:
For = kl/r 100
Fc = 7500/2
where,
Section 6B
6-11
Fc = Permissible stress in axial compression, in Mpa
fy = Yield stress of steel, in Mpa
=l/r = Slenderness ratio of the member, ratio of the effective
length to appropriate radius of gyration
6B.2.2 Bending Stress
The allowable bending stress in a member subjected to bending is
calculated based on the following formula: (Clause: 2.6.5)
The laterally unsupported length (Lu) of the compression flange is
limited by
y
f
uf
bL
20
Fbt or Fbc = 0.64 fy
Clause 2.6.5.5 Tension Fbt
Fbt = 0.58 Fy
Clause 2.6.5.5 Compression Fbc
I. Compression flange is braced laterally at intervals exceeding L u,
the allowable bending stress in compression Fbc will be taken as
follows.
i. for shallow thick flanged sections, where approximately
,4db
Lt
f
ufthe lateral tensional buckling stress is governed
by the torsion strength given by:
yb FC 58.0/AL
800 F
fudltb1
ii. For Deep flanged sections, where approximately
,4.0db
Lt
f
ufthe lateral torsional buckling stress governed
by the buckling strength given by:
Steel Design Per Egyptian Code # 205
Section 6B
6-12
a. When y
bTu
F
CrL 84/ then
Fl tb2 = 0.58 Fy
b. When y
bTu
y
b
F
CrL
F
C188/84 then
Fl tb2 =
yyb
yTuFF
C
FrL58.0
105176.1
2/64.0
c. When y
bTu
F
CrL 188/ then
Fl tb2
yb
Tu
FCrL
58.0/
12002
where,
Lu = Effective laterally unsupported length of compression flange.
k = Effective length factor
rT = radius of gyration about minor axis of a section compressing
the compression web area (in cms)
bf = Compression flange width
d = Total depth
Cb = Coefficient depending on the type of load and support
conditions as given in table 2.2
II. Compression on extreme fibers of channels bent about their major
axis
Fl tb = ybfu
FCAdL
58.0/.
800
where,
Fbt = Bending stress in tension
Fbc = Bending stress in compression
fy = Yield stress of steel, in MPa
Section 6B
6-13
6B.2.3 Shear Stress
Allowable shear stress calculations are based on Section 2.6.3 of
Egyptian code 205. For shear on the web, the gross section taken into
consideration consists of the product of the total depth and the web
thickness.
yall Fq 35.0
where,
allq = Allowable shear stress
6B.2.4 Combined Stress
Members subjected to both axial and bending stresses are
proportioned accordingly to following
Axial Compression and Bending
All the members subjected to bending and axial compression are
required to satisfy the equation of section 2.6.7.1
0.121 AF
fA
F
f
F
f
bcy
bcy
bcx
bcx
c
ca
where,
Ex
ca
mx
f
f
CA
1
1 ,
Ey
ca
my
f
f
CA
1
2
caf = Actual compression stress
Fc = Allowable compressive stress, clause 2.6.4.
bcxf bcyf = Actual Bending stress about x and y-axes respectively.
Fbcx,Fbcy = Allowable compressive bending stress, clause 2.6.5.
FEx,FEy = Euler stress in t/cm2
Cm = Moment modification factor
Steel Design Per Egyptian Code # 205
Section 6B
6-14
Axial Tension and Bending
All the members subject to bending and axial tension are required to satisfy
the equation of section 2.6.7.2
0.1bty
bty
btx
btx
t
ta
F
f
F
f
F
f
6B.3 Stability Requirements
Slenderness ratios are calculated for all members and checked
against the appropriate maximum values. Table 5.1 of Egyptian
code #205: summarizes the maximum slenderness ratios for
different types of members. In STAAD implementation of
Egyptian code #205, appropriate maximum slenderness ratio can
be provided for each member. If no maximum slenderness ratio is
provided, compression members will be checked against a
maximum value of 180 and tension members will be checked
against a maximum value of 300
6B.4 Code Checking
The purpose of code checking is to verify whether the specified
section is capable of satisfying applicable design code
requirements. The code checking is based on the Egyptian code
#205 requirements. Forces and moments at specified sections of
the members are utilized for the code checking calculations.
Sections may be specified using the BEAM parameter or the
SECTION command. If no sections are specified, the code
checking is based on forces and moments at the member ends.
The code checking output labels the members as PASSed or
FAILed. In addition, the critical condition, governing load case,
location (distance from the start) and magnitudes of the governing
forces and moments are also printed out.
Section 6B
6-15
6B.5 Member Selection
STAAD is capable of performing design operations on specified
members. Once an analysis has been performed, the program can
select the most economical section, that is , the lightest section,
which satisfies the applicable code requirements. The section
selected will be of the same type (I-Section, Channel etc.) as
originally specified by the user. Member selection may be
performed with all types of steel sections and user provided tables.
Selection of members, whose properties are originally provided
from user specified table, will be limited to sections in the user
provided table. Member selection can not be performed on
members whose cross sectional properties are specified as
PRISMATIC.
The process of MEMBER SELECTION may be controlled using
the parameters listed in Table 13B.1. It may be noted that the
parameters DMAX and DMIN may be used to specify member
depth constraints for selection. If PROFILE parameter is provided,
the search for the lightest section is restricted to that profile. Up to
three (3) profiles may be provided for any member with a section
being selected from each one.
6B.6 Tabulated Results of Steel Design
For code checking or member selection, the program produces the
result in a tabulated fashion as well as step by step procedure.
Steel Design Per Egyptian Code # 205
Section 6B
6-16
Section 6B
6-17
Table 6B.1 Egyptian Steel Design – Code #205 Parameters
Parameter
Name
Default Value Description
FYLD 250 MPA
(36.25 KSI) Yield strength of steel.
NSF 1.0 Net section factor for tension members.
SSY 0.0 0.0 = Sidesway in local y-axis. 1.0 = No sidesway
SSZ 0.0 Same as above except in local z-axis.
CMY
CMZ
0.85 for sidesway and
calculated for no sidesway
Cm value in local y & z axes
MAIN 180 (Comp. Memb.)
Allowable Kl/r for slenderness calculations for compression members.
TMAIN 300 (Tension Memb)
Allowable Kl/r for slenderness calculations for tension members.
DMAX 100.0 cm. Maximum allowable depth.
DMIN 0.0 cm. Minimum allowable depth.
RATIO 1.0 Permissible ratio of the actual to allowable stresses.
BEAM 3.0
0.0 = design only for end moments and those at locations specified by the SECTION command.
1.0 = calculate section forces at twelfth points along the beam, design at each intermediate location and report the critical location where ratio is maximum.
PROFILE - Search for the lightest section for the profile mentioned.
DFF None
(Mandatory for deflection check)
"Deflection Length" / Maxm. allowable local deflection
Note: Once a parameter is specified, its value stays at that specified
number till it is specified again. This is the way STAAD works for
all codes.
Steel Design Per Egyptian Code # 205
Section 6B
6-18
Section 7
French Codes
A‟lkjdfl‟akjsfd
7-1
Concrete Design Per B.A.E.L.
7A.1 Design Operations
STAAD has the capabilities for performing design of concrete
beams, columns and slabs according to B.A.E.L. - 1983. Given the
width and depth (or diameter for circular columns) of a section,
STAAD will calculate the required reinforcing to resist the various
input loads.
7A.2 Design Parameters
The program contains a number of parameters which are needed to
perform design per B.A.E.L. These parameters not only act as a
method to input required data for code calculations but give the
engineer control over the actual design process. Default values, of
commonly used numbers in conventional design practice, have
been used for simplicity. Table 5A.1 contains a complete list of
available parameters and their default values.
7A.3 Slenderness Effects and Analysis Consideration
STAAD provides the user two methods of accounting for the
slenderness effect in the analysis and design of concrete members.
The first method is a procedure which takes into account second
order effects. Here, STAAD accounts for the secondary moments,
due to axial loads and deflections, when the PDELTA ANALYSI S
command is used. STAAD, after solving for the joint
displacements of the structure, calculates the additional moments
induced in the structure. Therefore, by using PDELTA
Section 7A
Concrete Design Per B.A.E.L.
Section 7A
7-2
ANALYSIS, member forces are calculated which will require no
user modification before beginning member design.
The second method by which STAAD allows the user to account
for the slenderness effect is through user supplied moment
magnification factors. Here the user approximates the additional
moment by supplying a factor by which moments will be
multiplied before beginning member design.
7A.4 Member Dimensions
Concrete members that are to be designed by STAAD must have
certain section properties input under the MEMBER PROPERTIES
command. The following example demonstrates the required input:
UNIT MM
MEMBER PROPERTIES
1 3 to 7 9 PRISM YD 450 ZD 300.
11 13 PR YD 300.
In the above input, the first set of members are rectangular (450
mm depth and 300 mm width) and the second set of members, with
only depth and no width provided, will be assumed to be circular
with a 300 mm diameter. Note that area (AX) is not provided for
these members. If shear areas (AY & AZ) are to be considered in
analysis, the user may provide them along with YD and ZD. Also
note that moments of inertia may be provided, but if not provided,
the program will calculate values from YD and ZD.
Section 7A
7-3
7A.5 Beam Design
Beam design includes both flexure and shear. For both types of
beam action, all active beam loadings are scanned to create
moment and shear envelopes, and locate critical sections. The total
number of sections considered is twelve, unless that number is
redefined with the NSECTION parameter. From the critical
moment values, the required positive and negative bar pattern is
developed, with cut-off lengths calculated to include required
development length.
Shear design includes critical shear values plus torsional moments.
From these values, stirrup sizes are calculated with proper spacing.
The stirrups are assumed to be U-shaped for beams with no
torsion, and closed hoops for beams subject to torsion.
Table 7A.1 French Concrete Design Parameters
Parameter Default Description
Name Value
FYMAIN * 300 N/mm2 Yield Stress for main reinforcing steel.
FYSEC * 300 N/mm2 Yield Stress for secondary reinforcing steel.
FC * 30 N/mm2 Concrete Yield Stress.
CLEAR * 20 mm Clearance of reinforcing bar. Value is automatically set to 20 mm for C35 and higher.
MINMAIN 8 mm Minimum main reinforcement bar size. (8mm - 60mm).
MINSEC 8 mm Minimum secondary reinforcement bar size. (8mm - 60mm).
MAXMAIN 50 mm Maximum main reinforcement bar size. (8mm - 60mm).
SFACE *0.0 Face of support location at start of beam. (Only considers shear - use MEMBER OFFSET for bending).
Concrete Design Per B.A.E.L.
Section 7A
7-4
Table 7A.1 French Concrete Design Parameters
Parameter Default Description
Name Value
EFACE *0.0 Face of Support Location at end of beam. (Note: Both SFACE and EFACE are input as positive numbers.).
TRACK 0.0 Critical Moment will not be printed out with beam design report. A value of 1.0 will mean a print out.
MMAG 1.0 A factor by which the design moments will be magnified.
NSECTION 10 Number of equally-spaced sections to be considered in finding critical moments for beam design.
WIDTH ZD Width of the concrete member. This value defaults to ZD as provided under MEMBER PROPERTIES.
DEPTH YD Depth of concrete member. This value defaults to YD as provided under MEMBER PROPERTIES.
Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. * These values must be provided in the units the user is currently using for input.
Example of Input Data for Beam Design
UNIT NEWTON MMS
START CONCRETE DESIGN
CODE FRENCH
FYMAIN 415 ALL
FYSEC 415 ALL
FC 35 ALL
CLEAR 25 MEM 2 TO 6
MAXMAIN 40 MEMB 2 TO 6
SFACE 100 MEMB 7 TO 9
EFACE 100 MEMB 7 TO 9
TRACK 1.0 MEMB 2 TO 6
Section 7A
7-5
TRACK 2.0 MEMB 7 TO 9
DESIGN BEAM 2 TO 9
END CONCRETE DESIGN
7A.6 Column Design
Columns are designed for axial force and biaxial moments at the
ends. All active loadings are tested to calculate reinforcement. The
loading which produces maximum reinforcement i s called the
critical load. Column design is done for square, rectangular and
circular sections. For rectangular and square sections, the
reinforcement is always assumed to be equally distributed on each
side. That means the total number of bars will always be a multiple
of four (4). This may cause slightly conservative results in some
cases.
Example of Input Data for Column Design
UNIT NEWTON MMS
START CONCRETE DESIGN
CODE FRENCH
FYMAIN 415 ALL
FC 35 ALL
CLEAR 25 MEMB 2 TO 6
MMAG 1.5 MEMB 4 5
MAXMAIN 40 MEMB 2 TO 6
DESIGN COLUMN 2 TO 6
END CONCRETE DESIGN
7A.7 Slab/Wall Design
Slab and walls are designed per BAEL 1983 specifications. To
design a slab or wall, it must be modeled using finite elements.
Concrete Design Per B.A.E.L.
Section 7A
7-6
The command specifications are in accordance with Chapter II,
section 6.40.
Elements are designed for the moments Mx and My. These
moments are obtained from the element force output (see Chapter
2 of the Technical Reference Manual). The reinforcement required
to resist Mx moment is denoted as longitudinal reinforcement and
the reinforcement required to resist My moment is denoted as
transverse reinforcement. The parameters FYMAIN, FC, and
CLEAR listed in Table 5A.1 are relevant to slab design. Other
parameters mentioned in Table 5A.1 are not applicable to s lab
design.
LONG.
TRANS.
X
Y
Z
M
MM
Mx
y
x
y
Example of Input Data for Slab/Wall Design
UNIT NEWTON MMS
START CONCRETE DESIGN
CODE FRENCH
FYMAIN 415 ALL
FC 25 ALL
CLEAR 40 ALL
DESIGN ELEMENT 15 TO 20
END CONCRETE DESIGN
7-7
Steel Design Per the French Code
7B.1 General Comments
STAAD implementation of French Steel Design is based on Centre
Technique Industriel de la Construction Metallique publication
entitled "Design Rules for Structural Steelwork."
The design philosophy embodied in this specification is based on
the concept of limit state design. Structures are designed and
proportioned according to the limit states of which they would
become unfit for their intended use. Two major categories of limit -
states are recognized: ultimate and serviceability. The primary
considerations in ultimate limit state design are strength and
stability; that in serviceability is deflection. Appropriate load and
resistance factors are used so that uniform reliability is achieved
for all steel structures under various loading conditions and at the
same time the chances of limits being surpassed are acceptably
remote.
In the STAAD implementation, members are proportioned to resist
the design loads without exceeding the limit states of strength,
stability and serviceability. Accordingly, the most economic
section is selected on the basis of the least weight criteria, as
augmented by the designer in specification of allowable member
depths, desired section type, or other related parameters. The code
checking portion of the program verifies that code requirements
for each selected section are met and also identifies the governing
criteria.
Section 7B
Steel Design per the French Code
Section 7B
7-8
The following sections describe the salient features of STAAD
implementation of "Design Rules for Structural Steelwork." A
detailed description of the design process, along with its
underlying concepts and assumptions, is available in the
specification document.
7B.2 Basis of Methodology
The "Design Rules for Structural Steelwork (Revision 80)" permits
the usage of elastic analysis. Thus, in STAAD, linear elastic
analysis method is used to obtain the forces and moments in the
members. However, strength and stability considerations are based
on the principles of plastic behaviour. Axial compression buckling
and lateral torsional buckling are taken into consideration for
calculation of axial compression resistance and flexural resistance
of members. Slenderness calculations are made and overall
geometric stability is checked for all members.
7B.3 Member Capacities
The member strengths are calculated in STAAD according to the
procedures outlined in section 4 of this specification. Note that the
program automatically considers co-existence of axial force, shear
and bending in calculating section capacities.
For axial tension capacity, procedures of section 4.2 are followed.
For axial compression capacity, formulas of section 5.3 are used.
Moment capacities about both axes are calculated using the
procedures of sections 4.5 and 4.6. Lateral torsional buckling is
considered in calculating ultimate twisting moment per section
5.22 of the specification. The parameter UNL (see Table 6B.1)
must be used to specify the unsupported length of the compression
flange for a laterally unsupported member. Note that this length i s
also referred to as twisting length.
Section 7B
7-9
7B.4 Combined Axial Force and Bending
The procedures of sections 4.55 and 5.32 are implemented for
interaction of axial forces and bending. Appropriate interaction
equations are used and the governing criterion is determined.
7B.5 Design Parameters
The design parameters outlined in Table 6B.1 may be used to
control the design procedure. These parameters communicate
design decisions from the engineer to the program, thus allowing
the engineer to control the design process to suit an application's
specific needs.
The default parameter values have been selected as frequently used
numbers for conventional design. Depending on the particular
design requirements, some or all of these parameter values may be
changed to exactly model the physical structure.
7B.6 Code Checking and Member Selection
Both code checking and member selection options are available in
STAAD implementation of CM 66 (Revn. 80). For general
information on these options, refer to Chapter II, sections 3.4 and
3.5. For information on specification of these commands, refer to
Chapter II, and section 6.46.
7B.7 Tabulated Results of Steel Design
Results of code checking and member selection are presented in
the output file in a tabular format.
Please note the following: COND CRITIQUE refers to the section
of the CM 66 (Revn. 80) specification which governed the design.
Steel Design per the French Code
Section 7B
7-10
If the TRACK parameter is set to 1.0, calculated member
capacities will be printed. The following is a detailed description
of printed items:
PC = Member Compression Capacity
TR = Member Tension Capacity
MUZ = Member Moment Capacity (about z-axis)
MUY = Member Moment Capacity (about y-axis)
VPZ = Member Shear Capacity (z-axis)
VPY = Member Shear Capacity (y-axis)
Table 7B.1 French Steel Design Parameters
Parameter Default Description
Name Value
KY 1.0 K value for axial compression buckling about local Y-axis. Usually, this is the minor axis.
KZ 1.0 K value for axial compression buckling about local Z-axis. Usually, this is the major axis.
LY Member Length Length to calculate slenderness ratio about Y-axis for axial compression.
LZ Member Length Length to calculate slenderness ratio about Z-axis for axial compression.
FYLD 250.0 MPa Yield strength of steel.
NSF 1.0 Net section factor for tension members.
UNL Member Length Unsupported length of compression flange for calculating moment resistance.
UNF 1.0 Same as above provided as a fraction of member length.
TRACK 0.0 0.0 = Suppress printing of all design strengths. 1.0 = Print all design strengths.
DMAX 100.0 cm. Maximum allowable depth (used in member selection).
DMIN 0.0 cm. Minimum allowable depth (used in member selection).
RATIO 1.0 Permissible ratio of actual load effect and design strength.
Section 7B
7-11
Table 7B.1 French Steel Design Parameters
Parameter Default Description
Name Value
BEAM 0.0 0.0 = design only for end moments and those at locations specified by SECTION command. 1.0 = calculate moments at tenth points along the beam, and use maximum Mz for design.
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
STAAD contains a broad set of facilities for designing structural
members as individual components of an analyzed structure. The
member design facilities provide the user with the ability to carry
out a number of different design operations. These facilities may
be used selectively in accordance with the requirements of the
design problem. The operations to perform a design are:
Specify the members and the load cases to be considered in the
design.
Specify whether to perform code checking or member
selection.
Specify design parameter values, if different from the default
values.
These operations may be repeated by the user any number of times
depending upon the design requirements.
Currently STAAD supports steel design of wide flange, S, M, HP
shapes, angle, double angle, channel, double channel, beams with
cover plate, composite beams and code checking of prismatic
properties.
Steel Design per the French Code
Section 7B
7-12
Sample Input data for Steel Design
UNIT METER
PARAMETER
CODE FRENCH
NSF 0.85 ALL
UNL 10.0 MEMBER 7
KY 1.2 MEMBER 3 4
RATIO 0.9 ALL
TRACK 1.0 ALL
CHECK CODE ALL
7B.8 Built-in French Steel Section Library
The following information is provided for use when the built-in
steel tables are to be referenced for member property specification.
These properties are stored in a database file. If called for, the
properties are also used for member design. Since the shear areas
are built into these tables, shear deformation is always considered
for these members.
An example of the member property specification in an input file is
provided at the end of this section.
A complete listing of the sections available in the built -in steel
section library may be obtained by using the tools of the graphical
user interface.
Following are the descriptions of different types of sections.
Section 7B
7-13
IPE Shapes
These shapes are designated in the following way.
10 15 TA ST IPE140
20 TO 30 TA ST IPEA120
33 36 TO 46 BY 2 TA ST IPER180
HE shapes
HE shapes are specified as follows.
3 5 TA ST HEA120A
7 10 TA ST HEM140
13 14 TA ST HEB100
IPN Shapes
The designation for the IPN shapes is similar to that for the IPE
shapes.
25 TO 35 TA ST IPN200
23 56 TA ST IPN380
T Shapes
Tee sections are not input by their actual designations, but instead
by referring to the I beam shapes from which they are cut. For
example,
1 5 TA T IPE140
2 8 TA T HEM120
Steel Design per the French Code
Section 7B
7-14
U Channels
Shown below is the syntax for assigning 4 different names of channel
sections.
1 TO 5 TA ST UAP100
6 TO 10 TA ST UPN220
11 TO 15 TA ST UPN240A
16 TO 20 TA ST UAP250A
Double U Channels
Back to back double channels, with or without a spacing between
them, are available. The letter D in front of the section name will
specify a double channel.
11 TA D UAP150
17 TA D UAP250A SP 0.5
In the above set of commands, member 11 is a back to back double
channel UAP150 with no spacing in between. Member 17 is a
double channel UAP250A with a spacing of 0.5 length units
between the channels.
Angles
Two types of specification may be used to describe an angle. The
standard angle section is specified as follows:
16 20 TA ST L30X30X2.7
The above section signifies an angle with legs of length 30mm and
a leg thickness of 2.7mm. This specification may be used when the
local Z axis corresponds to the z-z axis specified in Chapter 2. If
the local Y axis corresponds to the z-z axis, type specification
"RA" (reverse angle) should be used instead of ST.
17 21 TA RA L25X25X4
Section 7B
7-15
22 24 TA RA L100X100X6.5
Note that if the leg thickness is a round number such as 4.0, only
the number 4 appears in the section name, the decimal part is not
part of the section name.
Double Angles
Short leg back to back or long leg back to back double angles can
be specified by means of input of the words SD or LD,
respectively, in front of the angle size. In case of an equal angle,
either SD or LD will serve the purpose.
33 35 TA SD L30X20X4 SP 0.6
37 39 TA LD L80X40X6
43 TO 47 TA LD L80X80X6.5 SP 0.75
Tubes (Rectangular or Square Hollow Sections)
Section names of tubes, just like angles, consist of the depth,
width and wall thickness as shown below.
64 78 TA ST TUB50252.7
66 73 TA ST TUB2001008.0
Members 64 and 78 are tubes with a depth of 50mm, width of 25mm
and a wall thickness of 2.7mm. Members 66 and 73 are tubes with a
depth of 200mm, width of 100mm and a wall thickness of 8.0mm.
Unlike angles, the ".0" in the thickness is part of the section name.
Tubes can also be input by their dimensions instead of by their table
designations. For example,
6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5
Steel Design per the French Code
Section 7B
7-16
is a tube that has a depth of 8 length units, width of 6 length units,
and a wall thickness of 0.5 length units. Only code checking, no
member selection, will be performed for TUBE sections specified i n
this way.
Pipes (Circular Hollow Sections)
To designate circular hollow sections, use PIP followed by numerical
value of the diameter and thickness of the section in mm omitting the
decimal portion of the value provided for the diameter. The following
example illustrates the designation.
8 TO 28 TA ST PIP422.6
3 64 78 TA ST PIP21912.5
Members 8 to 28 are pipes 42.4mm in dia, having a wall thickness
of 2.6mm. Members 3, 64 and 78 are pipes 219.1mm in dia, having
a wall thickness of 12.5mm.
Circular hollow sections may also be provided by specifying the
outside and inside diameters of the section. For example,
1 TO 9 TA ST PIPE OD 25.0 ID 20.0
specifies a pipe with outside dia. of 25 length units and inside dia.
of 20 length units. Only code checking, no member selection will
be performed if this type of specification is used.
SAMPLE FILE CONTAINING FRENCH SHAPES
STAAD SPACE
UNIT METER KN
JOINT COORD
1 0 0 0 15 140 0 0
MEMB INCI
1 1 2 14
Section 7B
7-17
UNIT CM
MEMBER PROPERTIES FRENCH
* IPE SHAPES
1 TA ST IPEA120
* IPN SHAPES
2 TA ST IPN380
*HE SHAPES
3 TA ST HEA200
* T SHAPES
4 TA T HEM120
* U CHANNELS
5 TA ST UAP100
* DOUBLE U CHANNELS
6 TA D UAP150 SP 0.5
* ANGLES
7 TA ST L30X30X2.7
* REVERSE ANGLES
8 TA RA L25X25X4
* DOUBLE ANGLES - SHORT LEGS BACK
* TO BACK
9 TA SD L30X20X4 SP 0.25
* DOUBLE ANGLES - LONG LEGS BACK
* TO BACK
10 TA LD L80X40X6 SP 0.75
* TUBES (RECTANGULAR OR SQUARE
* HOLLOW SECTIONS)
11 TA ST TUB50252.7
* TUBES (RECTANGULAR OR SQUARE
* HOLLOW SECTIONS)
12 TA ST TUBE DT 8.0 WT 6.0 TH 0.5
* PIPES (CIRCULAR HOLLOW SECTIONS)
13 TA ST PIP422.6
* PIPES (CIRCULAR HOLLOW SECTIONS)
14 TA ST PIPE OD 25.0 ID 20.0
PRINT MEMB PROP
FINI
Steel Design per the French Code
Section 7B
7-18
Section 8
German Codes
Aslkdfj;alskjdf‟
8-1
Concrete Design Per DIN 1045
8A.1 Design Operations
STAAD has the capabilities of performing concrete design based
on the DIN 1045 - November 1989. Slab design is also avai lable
but this follows the requirements of Baumann, Munich, which is
the basis for Eurocode 2. Design for a member involves
calculation of the amount of reinforcement required for the
member. Calculations are based on the user specified properties
and the member forces obtained from the analysis. In addition, the
details regarding placement of the reinforcement on the cross
section are also reported in the output.
8A.2 Section Types for Concrete Design
The following types of cross sections for concrete members can be
designed.
For Beams - Prismatic (Rectangular & Square)
For Columns - Prismatic (Rectangular, Square and Circular)
8A.3 Member Dimensions
Concrete members which will be designed by the program must
have certain section properties input under the MEMBER
PROPERTY command. The following example shows the required
input:
Section 8A
Concrete Design Per DIN 1045
Section 8A 8-2
UNIT MM
MEMBER PROPERTY
1 3 TO 7 9 PRISM YD 450. ZD 250.
11 13 PR YD 350.
In the above input, the first set of members are rectangular (450
mm depth and 250mm width) and the second set of members, with
only depth and no width provided, will be assumed to be circular
with 350mm diameter. It is absolutely imperative that the user not
provide the cross section area (AX) as an input.
8A.4 Slenderness Effects and Analysis Considerations
Slenderness effects are extremely important in designing
compression members. There are two options by which the
slenderness effect can be accommodated.
The first method is equivalent to the procedure presented in DIN
1045 17.4.3/17.4.4 which is used as the basis for commonly used
design charts considering e/d and sk/d for conditions where the
slenderness moment exceeds 70. This method has been adopted in
the column design in STAAD per the DIN code.
The second option is to compute the secondary moments through
an analysis. Secondary moments are caused by the interaction of
the axial loads and the relative end displacements of a member.
The axial loads and joint displacements are first determined from
an elastic stiffness analysis and the secondary moments are then
evaluated. To perform this type of analysis, use the command
PDELTA ANALYSIS instead of PERFORM ANALYSIS in the
input file. The user must note that to take advantage of this
analysis, all the combinations of loading must be provided as
primary load cases and not as load combinations. This is due to the
fact that load combinations are just algebraic combinations of
forces and moments, whereas a primary load case is revised during
Section 8A
8-3
the P-delta analysis based on the deflections. Also, note that the
proper factored loads (like 1.5 for dead load etc.) should be
provided by the user. STAAD does not factor the loads
automatically. The column is designed for the total moment which
is the sum of the primary and secondary forces. The secondar y
moments can be compared to those calculated using the charts of
DIN 1045.
8A.5 Beam Design
Beams are designed for flexure, shear and torsion. For all these
forces, all active beam loadings are prescanned to identify the
critical load cases at different sections of the beams. The total
number of sections considered is 13 (e.g. 0., .1, .2, .25, .3, .4, .5,
.6, .7, .75, .8, .9 and 1). All of these sections are scanned to
determine the design force envelopes.
Design for Flexure
Maximum sagging (creating tensile stress at the bottom face of the
beam) and hogging (creating tensile stress at the top face) moments
are calculated for all active load cases at each of the above mentioned
sections. Each of these sections is designed to resist these critical
sagging and hogging moments. Currently, design of singly reinforced
sections only is permitted. If the section dimensions are inadequate as
a singly reinforced section, such a message will be printed in the
output. Flexural design of beams is performed in two passes. In the
first pass, effective depths of the sections are determined with the
assumption of single layer of assumed reinforcement and
reinforcement requirements are calculated. After the preliminary
design, reinforcing bars are chosen from the internal database in
single or multiple layers. The entire flexural design is performed
again in a second pass taking into account the changed effective
depths of sections calculated on the basis of reinforcement provided
after the preliminary design. Final provisions of flexural
reinforcements are made then. Efforts have been made to meet the
guideline for the curtailment of reinforcements as per the DIN code.
Although exact curtailment lengths are not mentioned explicitly in the
design output (finally which will be more or less guided by the
Concrete Design Per DIN 1045
Section 8A 8-4
detailer taking into account of other practical considerations), the user
has the choice of printing reinforcements provided by STAAD at 13
equally spaced sections from which the final detailed drawing can be
prepared.
Design for Shear and Torsion
Shear design in STAAD conforms to the specifications of section
17.5 of DIN 1045. Shear reinforcement is calculated to resist both
shear forces and torsional moments. Shear and torsional design is
performed at the start and end sections of the member at a distance
"d" away from the node of the member where "d" is the effective
depth calculated from flexural design. The maximum shear forces
from amongst the active load cases and the associated torsional
moments are used in the design. The capacity of the concrete in
shear and torsion is determined at the location of design and the
balance, if any, is carried by reinforcement. It is assumed that no
bent-up bars are available from the flexural reinforcement to carry
and "balance" shear. Two-legged stirrups are provided to take care
of the balance shear forces acting on these sections. Stirrups are
assumed to be U-shaped for beams with no torsion, and closed
hoops for beams subject to torsion.
Example of Input Data for Beam Design
UNIT NEWTON MMS
START CONCRETE DESIGN
CODE GERMAN
FYMAIN 415 ALL
FYSEC 415 ALL
FC 35 ALL
CLEAR 25 MEM 2 TO 6
MAXMAIN 40 MEMB 2 TO 6
TRACK 1.0 MEMB 2 TO 9
DESIGN BEAM 2 TO 9
END CONCRETE DESIGN
Section 8A
8-5
8A.6 Column Design
Columns are designed for axial forces and biaxial moments at the
ends. All active load cases are tested to calculate reinforcement.
The loading which yields maximum reinforcement is called the
critical load. The requirements of DIN 1045-figure 13, for
calculating the equilibrium equations for rectangular and circular
sections from first principles, is implemented in the design. The
user has control of the effective length (sk) in each direction by
using the ELZ and ELY parameters as described on Table 8A.1.
This means that the slenderness will be evaluated along with e/d to
meet the requirements of DIN 1045 section 17.4.3 and 17.4.4.
Column design is done for square, rectangular and circular
sections. Square and rectangular columns are designed with
reinforcement distributed on all four sides equally. That means the
total number of bars will always be a multiple of four (4). This
may cause slightly conservative results in some cases. The
TRACK parameter may be used to obtain the design details in
various levels of descriptivity.
Example of Input Data for Column Design
UNIT NEWTON MMS
START CONCRETE DESIGN
CODE GERMAN
FYMAIN 415 ALL
FC 35 ALL
CLEAR 25 MEMB 2 TO 6
MAXMAIN 40 MEMB 2 TO 6
DESIGN COLUMN 2 TO 6
END CONCRETE DESIGN
Concrete Design Per DIN 1045
Section 8A 8-6
8A.7 Slab Design
To design a slab, it must first be modeled using finite elements and
analysed. The command specifications are in accordance with
Chapter 2 and Chapter 6 of the Technical Reference Manual. Slabs
are designed to specifications as described by BAUMANN of
MUNICH which is the basis for Eurocode 2.
Elements are designed for the moments Mx and My. These
moments are obtained from the element force output (see Chapter
2 of the Technical Reference Manual). The reinforcement required
to resist the Mx moment is denoted as longitudinal reinforcement
and the reinforcement required to resist the My moment is denoted
as transverse reinforcement. The following parameters are those
applicable to slab design:
1. FYMAIN Yield stress for all reinforcing steel
2. FC Concrete grade
3. CLEAR Distance from the outer surface of the elemen t to
the edge of the bar. This is considered the same on
both top and bottom surfaces of the element.
4. SRA Parameter which denotes the angle of direction of
the required transverse reinforcement relative to
the direction of the longitudinal reinforcement for
the calculation of BAUMANN design forces.
The other parameters shown in Table 7A.1 are not applicable to
slab design.
BAUMANN equations
If the default value of zero is used, the design will be based on Mx
and My forces which are obtained from the STAAD analysis. The
SRA parameter (Set Reinforcement Angle) can be manipulated to
introduce resolved BAUMANN forces into the design replacing
the pure Mx and My moments. These new design moments allow
the Mxy moment to be considered when designing the section,
resolved as an axial force. Orthogonal or skew reinforcement may
Section 8A
8-7
be considered. If SRA is set to -500, an orthogonal layout will be
assumed. If however a skew is to be considered, an angle is given
in degrees measured from the local element X axis anticlockwise
(positive). The resulting Mx* and My* moments are calculated and
shown in the design format.
The design of the slab considers a fixed bar size of 10mm in the
longitudinal direction and 8mm in the transverse. The longitudinal
bar is the layer closest to the slab exterior face.
8A.8 Design Parameters
The program contains a number of parameters which are needed to
perform the design. Default parameter values have been selected
such that they are frequently used numbers for conventional design
requirements. These values may be changed to suit the particular
design being performed. Table 8A.1 of this manual contains a
complete list of the available parameters and their default values.
It is necessary to declare length and force units as Millimeter and
Newton before performing the concrete design. Note: Once a
parameter is specified, its value stays at that specified number
till it is specified again. This is the way STAAD works for all
codes.
Table 8A.1 German Concrete Design Parameters
Parameter
Name
Default Value Description
FYMAIN 420 N/mm2 Yield Stress for main reinforcement (For slabs it is 500 N/mm2 for both directions)
FYSEC 420N/mm2 Yield Stress for secondary reinforcement. Applicable to shear and torsion reinforcement in beams
FC 25N/mm2 Concrete Yield Stress/ cube strength
MINMAIN 16mm Minimum main reinforcement bar size [Acceptable bar sizes: 6 8 10 12 14 16 20 25 32 40 50]
MINSEC 8mm Minimum secondary reinforcement bar
Concrete Design Per DIN 1045
Section 8A 8-8
Table 8A.1 German Concrete Design Parameters
Parameter
Name
Default Value Description
size. Applicable to shear and torsion reinforcement in beams.
CLEAR 25mm Clear cover for reinforcement measured from concrete surface to closest bar perimeter.
MAXMAIN 50 mm Maximum required reinforcement bar size. Acceptable bars are per MINMAIN above.
SFACE 0.0 Face of support location at start of beam, measured from the start joint. (Only applicable for shear - use MEMBER OFFSET for bending)
EFACE 0.0 Face of support location at end of beam, measured from the end joint. (NOTE: Both SFACE & EFACE must be positive numbers.)
TRACK 0.0 0.0 = Critical Moment will not be printed with beam design report.
1.0 = For beam gives min/max steel % and spacing. For columns gives a detailed table of output with additional moments calculated.
2.0 = For beams gives area of steel required at intermediate sections. (see NSECT)
MMAG 1.0 Factor by which design moments are magnified for column design
NSECTION 10 Number of equally-spaced sections to be considered in finding critical moment for beam design. The upper limit is 20
WIDTH ZD Width of concrete member. The default value is as provided as ZD in MEMBER PROPERTIES.
DEPTH YD Depth of concrete member. The default value is as provided as YD in MEMBER PROPERTIES.
ELY 1.0 Member length factor about local Y direction
Section 8A
8-9
Table 8A.1 German Concrete Design Parameters
Parameter
Name
Default Value Description
for column design
ELZ 1.0 Member length factor about local Z direction for column design
SRA 0.0 0.0 = Orthogonal reinforcement layout without considering torsional moment Mxy -slabs only
-500 = Orthogonal reinforcement layout considering Mxy
A = Skew angle considered in BAUMANN equations. A is the angle in degrees.
Concrete Design Per DIN 1045
Section 8A 8-10
8-11
Steel Design Per the DIN Code
8B.1 General
This section presents some general statements regarding the
implementation of the DIN code of practice for structural steel
design (DIN 18800 and DIN 4114) in STAAD. The design
philosophy and procedural logistics are based on the principles of
elastic analysis and allowable stress design. Facilities are available
for member selection as well as code checking. Two major failure
modes are recognized: failure by overstressing and failure by
stability considerations. The following sections describe the
salient features of the design approach.
Members are proportioned to resist the design loads without
exceedance of the allowable stresses or capacities and the most
economical section is selected on the basis of the least weight
criteria. The code checking part of the program also checks the
slenderness requirements and the stability criteria. Users are
recommended to adopt the following steps in performing the steel
design:
1) Specify the geometry and loads and perform the analysis.
2) Specify the design parameter values if different from the
default values.
3) Specify whether to perform code checking or member
selection.
Section 8B
Steel Design per the DIN Code
Section 8B 8-12
8B.2 Analysis Methodology
Elastic analysis method is used to obtain the forces and moments
for design. Analysis is done for the primary and combination
loading conditions provided by the user. The user is allowed
complete flexibility in providing loading specifications and in
using appropriate load factors to create necessary loading
situations. Depending upon the analysis requirements, regular
stiffness analysis or P-Delta analysis may be specified. Dynamic
analysis may also be performed and the results combined with
static analysis results.
8B.3 Member Property Specifications
For specification of member properties of standard German steel
sections, the steel section library available in STAAD may be
used. The next section describes the syntax of commands used to
assign properties from the built-in steel table. Member properties
may also be specified using the User Table facility. For more
information on these facilities, refer to the STAAD Program User's
manual.
8B.4 Built-in German Steel Section Library
The following information is provided for use when the built-in
steel tables are to be referenced for member property specification.
These properties are stored in a database file. If called for, these
properties are also used for member design. Since the shear areas
are built into these tables, shear deformation is always considered
for these members during the analysis. An example of member
property specification in an input file is provided at the end of this
section.
Section 8B
8-13
A complete listing of the sections available in the built -in steel
section library may be obtained using the tools of the graphical
user interface.
Following are the descriptions of different types of sections.
IPE Shapes
These shapes are designated in the following way:
20 TO 30 TA ST IPEA120
33 36 TO 46 BY 2 TA ST IPER140
HE Shapes
The designation for HE shapes is similar to that for IPE shapes.
25 TO 35 TA ST HEB300
23 56 TA ST HEA160
I Shapes
I shapes are identified by the depth of the section. The following
example illustrates the designation.
14 15 TA ST I200 (indicates an I-section with 200mm depth)
T Shapes
Tee sections are not input by their actual designations, but instead
by referring to the I beam shapes from which they are cut. For
example,
1 5 TA T HEA220
2 8 TA T IPE120
Steel Design per the DIN Code
Section 8B 8-14
U Channels
The example below provides the command for identifying two
channel sections. The former (U70X40) has a depth of 70mm and a
flange width of 40mm. The latter (U260) has a depth of 260mm.
11 TA D U70X40
27 TA D U260
Double Channels
Back to back double channels, with or without spacing between
them, are available. The letter “D” in front of the section name
will specify a double channel, e.g. D U180. The spacing between
the double channels is provided following the expression “SP”.
11 TA D U180
27 TA D U280 SP 0.5 (Indicates 2 channels back to back
spaced at 0.5 length units)
Angles
Two types of specifications may be used to describe an angle. The
standard angle section is specified as follows:
16 20 TA ST L20X20X2.5
The above section signifies an angle with legs of length 20mm and
a leg thickness of 2.5mm. The above specification may be used
when the local z-axis corresponds to the Z-Z axis specified in
Chapter 2. If the local y-axis corresponds to the Z-Z axis, type
specification "RA" (reverse angle) may be used.
17 21 TA RA L40X20X5
Section 8B
8-15
Double Angles
Short leg back to back or long leg back to back double angles can
be specified by using the word SD or LD, respectively, in front of
the angle size. In case of an equal angle, either SD or LD will
serve the purpose. Spacing between the angles is provided by
using the word SP and the spacing value following the section
name.
14 TO 20 TA SD L40X20X4 SP 0.5
21 TO 27 TA LD L40X20X4 SP 0.5
Pipes (Circular Hollow Sections)
To designate circular hollow sections, use PIP followed by
numerical value of the diameter and thickness of the section in mm
omitting the decimal section of the value provided for diameter.
The following example will illustrate the designation.
8 TO 28 TA ST PIP602.9 (60.3mm dia, 2.9mm wall
thickness)
3 64 67 TA ST PIP40612.5 (406.4mm dia, 12.5mm wall
thickness)
Circular hollow sections may also be provided by specifying the
outside and inside diameters of the section. For example,
1 TO 9 TA ST PIPE OD 25.0 ID 20.0
specifies a pipe with outside dia. of 25 and inside dia. of 20 in
current length units. Only code checking and no member selection
will be performed if this type of specification is used.
Steel Design per the DIN Code
Section 8B 8-16
Tubes (Rectangular or Square Hollow Sections)
Tube names are input by their dimensions. For example,
15 TO 25 TA ST TUB100603.6
is the specification for a tube having sides of 100mmX60mm and
the wall thickness of 3.6mm.
Tubes, like pipes can also be input by their dimensions (Height,
Width and Thickness) instead of by their table designations.
6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5
is a tube that has a height of 8, a width of 6, and a wall thickness
of 0.5 in current length units. Only code checking and no member
selection will be performed for TUBE sections specified this way.
SAMPLE INPUT FILE CONTAINING GERMAN SHAPES
STAAD SPACE
UNIT METER KN
JOINT COORDINATES
1 0 0 0 15 140 0 0
MEMBER INCIDENCES
1 1 2 14
UNIT CM
MEMBER PROPERTIES GERMAN
* IPE SHAPES
1 TA ST IPEA120
* HE SHAPES
2 TA ST HEB300
* I SHAPES
3 TA ST I200
* T SHAPES
4 TA T HEA220
Section 8B
8-17
* U CHANNELS
5 TA ST U70X40
* DOUBLE U CHANNELS
6 TA D U260
* ANGLES
7 TA ST L20X20X2.5
* REVERSE ANGLES
8 TA RA L40X20X5
* DOUBLE ANGLES - LONG LEGS BACK TO BACK
9 TA LD L40X20X4 SP 0.5
* DOUBLE ANGLES - SHORT LEGS BACK TO BACK
10 TA SD L40X20X4 SP 0.5
* PIPES
11 TA ST PIP602.9
* PIPES
12 TA ST PIPE OD 25.0 ID 20.0
* TUBES
13 TA ST TUB100603.6
* TUBES
14 TA ST TUBE DT 8.0 WT 6.0 WT 0.5
*
PRINT MEMBER PROPERTIES
FINISH
8B.5 Member Capacities
The allowable stresses used in the implementation are based on
DIN 18800 (Part 1) - Section 7. The procedures of DIN 4114 are
used for stability analysis. The basic measure of member
capacities are the allowable stresses on the member under various
conditions of applied loading such as allowable tensile stress,
allowable compressive stress etc. These depend on several factors
such as cross sectional properties, slenderness factors, unsupported
width to thickness ratios and so on. Explained here is the
procedure adopted in STAAD for calculating such capacities.
Steel Design per the DIN Code
Section 8B 8-18
Allowable stress for Axial Tension
In members with axial tension, the tensile load must not exceed the
tension capacity of the member. The tension capacity of the
member is calculated on the basis of the member area. STAAD
calculates the tension capacity of a given member based on a user
supplied net section factor (NSF-a default value of 1.0 is present
but may be altered by changing the input value, see Table 6B.1)
and proceeds with member selection or code checking.
Allowable stress for Axial Compression
The allowable stress for members in compression is determined
according to the procedure of DIN 4114 (Part 1) - Section 7.
Compressive resistance is a function of the slenderness of the
cross-section (Kl/r ratio) and the user may control the slenderness
value by modifying parameters such as KY, LY, KZ and LZ.
Allowable stress for Bending and Shear
The permissible bending compressive and tensile stresses are
dependent on such factors as length of outstanding legs, thickness
of flanges, unsupported length of the compression flange (UNL,
defaults to member length) etc. Shear capacities are a function of
web depth, web thickness etc. Users may use a value of 1.0 or 2.0
for the TRACK parameter to obtain a listing of the bending and
shear capacities.
8B.6 Combined Loading
For members experiencing combined loading (axial force, bending
and shear), applicable interaction formulas are checked at different
locations of the member for all modeled loading situations.
Members subjected to axial force and bending are checked using
the criteria of DIN 18800 (Part 1) - Section 6.1.6. In addition, for
members with compression and bending, the criteria of DIN 4114
(Part 1) - Section 10 is used. Similarly, for members with axial
tension and bending, the criteria of DIN 4114 (Part 1) - Section 15
is used.
Section 8B
8-19
8B.7 Design Parameters
The user is allowed complete control over the design process
through the use of parameters mentioned in Table 8B.1 of this
chapter. These parameters communicate design decisions from the
engineer to the program. The default parameter values have been
selected such that they are frequently used numbers for
conventional design. Depending on the particular design
requirements of the situation, some or all of these parameter
values may have to be changed to exactly model the physical
structure. Note: Once a parameter is specified, its value stays at
that specified number till it is specified again. This is the way
STAAD works for all codes.
Table 8B.1 German Steel Design Parameters
Parameter
Name
Default Value Description
KY 1.0 K value in local y-axis. Usually, this is the minor axis.
KZ 1.0 K value in local z-axis. Usually, this is the major axis.
LY Member Length Length in local y-axis to calculate slenderness ratio.
LZ Member Length Length in local z-axis to calculate slenderness ratio.
PY 240 N/sq.mm Strength of steel.
NSF 1.0 Net section factor for tension members.
UNL Member Length Unrestrained member length in lateral torsional buckling checks.
UNF 1.0 Same as above provided as a factor of actual member length.
BEAM 0.0 Number of sections to be checked per member: 0.0 = Design only for end sections. 1.0 = Check at location of maximum MZ
along member.
Steel Design per the DIN Code
Section 8B 8-20
Table 8B.1 German Steel Design Parameters
Parameter
Name
Default Value Description
2.0 = Check ends plus location of beam 1.0 check.
3.0 = Check at every 1/13th of the member length and report the maximum.
TRACK 0.0 Level of detail in output file: 0.0 = Output summary of results 1.0 = Output summary of results plus
member capacities
2.0 = Output detailed results
RATIO 1.0 Permissible ratio of actual to allowable stresses
SGR 0.0 Grade of steel:
0.0 = St 37-2
1.0 = St 52-3
2.0 = StE 355
SBLT 0 Specify section as either rolled or built-up:
0 = Rolled
1 = Built-up
Cb 0 Beam coefficient n, defined in Table 9: If Cb = 0, program will use n = 2.5 for rolled sections and 2.0 for welded sections.
Cmm 1.0 Moment factor, Zeta, defined in Table 10:
1.0 = fixed ended member with constant moment, Zeta = 1.0
2.0 = pin ended member with UDL, Zeta = 1.12
3.0 = pin ended member with central point load, Zeta = 1.35
4.0 = fixed ended member, Zeta calculated from end moments.
DMAX 1.0 m Maximum allowable depth during member selection
DMIN 0.0 m Minimum required depth during member
Section 8B
8-21
Table 8B.1 German Steel Design Parameters
Parameter
Name
Default Value Description
selection
SAME 0.0 Control of sections to try during a SELECT process:
0.0 = Try every section of the same type as the original.
1.0 = Try only those with a similar name.
8B.8 Code Checking
The purpose of code checking is to check whether the provided
section properties of the members are adequate to carry the forces
transmitted to it by the loads on the structure. The adequacy is
checked per the DIN requirements.
Code checking is done using forces and moments at specified
sections of the members. If the BEAM parameter for a member is
set to 1, moments are calculated at every twelfth point along the
beam, and the maximum moment about the major axis is used.
When no sections are specified and the BEAM parameter is set to
zero (default), design will be based on member start and end
forces. The code checking output labels the members as PASSed or
FAILed. In addition, the critical condition, governing load case,
location (distance from start joint) and magnitudes of the
governing forces and moments are also printed.
Steel Design per the DIN Code
Section 8B 8-22
8B.9 Member Selection
The member selection process basically involves determination of
the least weight member that PASSes the code checking procedure
based on the forces and moments of the most recent analysis. The
section selected will be of the same type as that specified initially.
For example, a member specified initially as a channel will have a
channel selected for it. Selection of members whose properties are
originally provided from a user table will be limited to sections in
the user table. Member selection cannot be performed on TUBES,
PIPES or members listed as PRISMATIC.
Sample Input data for Steel Design
UNIT METER
PARAMETER
CODE GERMAN
NSF 0.85 ALL
UNL 10.0 MEMBER 7
KY 1.2 MEMBER 3 4
RATIO 0.9 ALL
TRACK 1.0 ALL
CHECK CODE ALL
Section 9
Indian Codes
Ad;flaksd;lfka
9-1
Concrete Design Per IS456
9A.1 Design Operations
STAAD has the capabilities of performing concrete design based
on limit state method of IS: 456 (2000).
9A.2 Section Types for Concrete Design
The following types of cross sections for concrete members can be
designed.
For Beams Prismatic (Rectangular & Square), T-Beams and
L-shapes
For Columns Prismatic (Rectangular, Square and Circular)
9A.3 Member Dimensions
Concrete members which will be designed by the program must
have certain section properties input under the MEMBER
PROPERTY command. The following example shows the required
input:
Section 9A
Concrete Design Per IS456
Section 9A
9-2
UNIT MM
MEMBER PROPERTY
1 3 TO 7 9 PRISM YD 450. ZD 250.
11 13 PR YD 350.
14 TO 16 PRIS YD 400. ZD 750. YB 300. ZB 200.
will be done accordingly. In the above input, the first set of
members are rectangular (450 mm depth and 250mm width) and
the second set of members, with only depth and no width provided,
will be assumed to be circular with 350 mm diameter. The third set
numbers in the above example represen ts a T-shape with 750 mm
flange width, 200 width, 400 mm overall depth and 100 mm flange
depth (See section 6.20.2). The program will determine whether
the section is rectangular, flanged or circular and the beam or
column design
9A.4 Design Parameters
The program contains a number of parameters which are needed to
perform design as per IS:456(2000). Default parameter values
have been selected such that they are frequently used numbers for
conventional design requirements. These values may be changed to
suit the particular design being performed. Table 8A.1 of this
manual contains a complete list of the available parameters and
their default values. It is necessary to declare length and force
units as Millimeter and Newton before performing the concrete
design.
9A.5 Slenderness Effects and Analysis Consideration
Slenderness effects are extremely important in designing
compression members. The IS:456 code specifies two options by
which the slenderness effect can be accommodated (Clause 39.7).
Section 9A
9-3
One option is to perform an exact analysis which will take into
account the influence of axial loads and variable moment of inertia
on member stiffness and fixed end moments, the effect of
deflections on moment and forces and the effect of the duration of
loads. Another option is to approximately magnify design
moments.
STAAD has been written to allow the use of the first options. To
perform this type of analysis, use the command PDELTA
ANALYSIS instead of PERFORM ANALYSIS. The PDELTA
ANALYSIS will accommodate all requirements of the second-
order analysis described by IS:456, except for the effects of the
duration of the loads. It is felt that this effect may be safely
ignored because experts believe that the effects of the duration of
loads are negligible in a normal structural configuration.
Although ignoring load duration effects is somewhat of an
approximation, it must be realized that the approximate evaluation
of slenderness effects is also an approximate method. In this
method, additional moments are calculated based on empirical
formula and assumptions on sidesway
(Clause 39.7.1 and 39.7.1.1,IS: 456 - 2000).
Considering all these information, a PDELTA ANALYSIS, as
performed by STAAD may be used for the design of concrete
members. However the user must note, to take advantage of this
analysis, all the combinations of loading must be provided as
primary load cases and not as load combinations. This is due to the
fact that load combinations are just algebraic combinations of
forces and moments, whereas a primary load case is revised during
the P-delta analysis based on the deflections. Also note that the
proper factored loads (like 1.5 for dead load etc.) should be
provided by user. STAAD does not factor the loads automatically.
9A.6 Beam Design
Beams are designed for flexure, shear and torsion. If required the
effect the axial force may be taken into consideration. For all
Concrete Design Per IS456
Section 9A
9-4
these forces, all active beam loadings are prescanned to identify
the critical load cases at different sections of the beams. The total
number of sections considered is 13( e.g. 0.,.1,.2,.25,.3,.4,.5,.6,.7,.
75,.8,.9 and 1). All of these sections are scanned to determine the
design force envelopes.
Design for Flexure
Maximum sagging (creating tensile stress at the bottom face of the
beam) and hogging (creating tensile stress at the top face)
moments are calculated for all active load cases at each of the
above mentioned sections. Each of these sections is designed to
resist both of these critical sagging and hogging moments. Where
ever the rectangular section is inadequate as singly reinforced
section, doubly reinforced section is tried. However, presently the
flanged section is designed only as singly reinforced section under
sagging moment. It may also be noted all flanged sections are
automatically designed as rectangular section under hogging
moment as the flange of the beam is ineffective under hogging
moment. Flexural design of beams is performed in two passes. In
the first pass, effective depths of the sections are determined with
the assumption of single layer of assumed reinforcement and
reinforcement requirements are calculated. After the preliminary
design, reinforcing bars are chosen from the internal database in
single or multiple layers. The entire flexure design is per formed
again in a second pass taking into account of the changed effective
depths of sections calculated on the basis of reinforcement provide
after the preliminary design. Final provisions of flexural
reinforcements are made then. Efforts have been made to meet the
guideline for the curtailment of reinforcements as per IS:456-2000
(Clause 26.2.3). Although exact curtailment lengths are not
mentioned explicitly in the design output (finally which will be
more or less guided by the detailer taking into account of other
practical consideration), user has the choice of printing
reinforcements provided by STAAD at 11 equally spaced sections
from which the final detail drawing can be prepared.
Section 9A
9-5
Design for Shear
Shear reinforcement is calculated to resist both shear forces and
torsional moments. Shear design are performed at 11 equally
spaced sections (0.to 1.) for the maximum shear forces amongst
the active load cases and the associated torsional moments. Shear
capacity calculation at different sections with out the shear
reinforcement is based on the actual tensile reinforcement
provided by STAAD program. Two-legged stirrups are provided to
take care of the balance shear forces acting on these sections.
As per Clause 40.5 of IS:456-2000 shear strength of sections (< 2d
where d is the effective depth) close to support has been enhanced,
subjected to a maximum value of cmax.
Beam Design Output
The default design output of the beam contains flexural and shear
reinforcement provided at 5 equally spaced (0,.25,.5,.75 and 1.)
sections along the length of the beam. User has option to get a
more detail output. All beam design outputs are given in IS units.
An example of rectangular beam design output with the default
output option (TRACK 0.0) is presented below:
Concrete Design Per IS456
Section 9A
9-6
============================================================================ B E A M N O. 12 D E S I G N R E S U L T S M20 Fe415 (Main) Fe415 (Sec.) LENGTH: 4000.0 mm SIZE: 250.0 mm X 350.0 mm COVER: 30.0 mm DESIGN LOAD SUMMARY (KN MET) ---------------------------------------------------------------------------- SECTION |FLEXTURE (Maxm. Sagging/Hogging moments)| SHEAR (in mm) | P MZ MX Load Case | VY MX Load Case ---------------------------------------------------------------------------- 0.0 | 0.00 0.00 0.00 4 | 29.64 1.23 4
| 0.00 -25.68 1.23 4 | 400.0 | 0.00 0.00 0.00 4 | 27.97 1.23 4 | 0.00 -16.05 1.23 4 | 800.0 | 0.00 0.00 0.00 4 | 25.12 1.23 4 | 0.00 -7.17 1.23 4 | 1200.0 | 0.00 0.97 0.49 5 | 21.11 1.23 4
| 0.00 -0.14 1.32 6 | 1600.0 | 0.00 6.77 1.23 4 | 15.93 1.23 4 | 0.00 0.00 0.00 4 |
2000.0 | 0.00 11.06 1.23 4 | 9.59 1.23 4 | 0.00 0.00 0.00 4 | 2400.0 | 0.00 13.04 1.23 4 | 2.08 1.23 4
| 0.00 0.00 0.00 4 | 2800.0 | 0.00 12.45 1.23 4 | -5.43 1.23 4 | 0.00 0.00 0.00 4 | 3200.0 | 0.00 9.55 1.23 4 | -11.77 1.23 4 | 0.00 0.00 0.00 4 | 3600.0 | 0.00 4.73 1.23 4 | -16.95 1.23 4
| 0.00 0.00 0.00 4 | 4000.0 | 0.00 0.00 0.00 4 | -25.48 1.23 4 | 0.00 -17.36 1.23 4 | ----------------------------------------------------------------------------
SUMMARY OF REINF. AREA (Sq.mm) ---------------------------------------------------------------------------- SECTION 0.0 mm 1000.0 mm 2000.0 mm 3000.0 mm 4000.0 mm ----------------------------------------------------------------------------
TOP 259.04 161.29 0.00 0.00 176.31 REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm)
BOTTOM 0.00 160.78 160.78 160.78 0.00 REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) ----------------------------------------------------------------------------
SUMMARY OF PROVIDED REINF. AREA
---------------------------------------------------------------------------- SECTION 0.0 mm 1000.0 mm 2000.0 mm 3000.0 mm 4000.0 mm ---------------------------------------------------------------------------- TOP 4-10Ø 3-10Ø 2-10Ø 2-10Ø 3-10Ø REINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)
BOTTOM 2-12Ø 2-12Ø 2-12Ø 2-12Ø 2-12Ø REINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)
SHEAR 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø REINF. @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c
----------------------------------------------------------------------------
============================================================================
Section 9A
9-7
9A.7 Column Design
Columns are designed for axial forces and biaxial moments at the
ends. All active load cases are tested to calculate reinforcement.
The loading which yield maximum reinforcement is called the
critical load. Column design is done for square, rectangular and
circular sections. By default, square and rectangular columns and
designed with reinforcement distributed on each side equally for
the sections under biaxial moments and with reinforcement
distributed equally in two faces for sections under uniaxial
moment. User may change the default arrangement of the
reinforcement with the help of the parameter RFACE (see Table
8A.1). Depending upon the member lengths, section dimensions
and effective length coefficients specified by the user STAAD
automatically determine the criterion (short or long) of the column
design. All major criteria for selecting longitudinal and transverse
reinforcement as stipulated by IS:456 have been taken care of in
the column design of STAAD. Default clear spacing between main
reinforcing bars is taken to be 25 mm while arrangement of
longitudinal bars.
Column Design Output
Default column design output (TRACK 0.0) contains the
reinforcement provided by STAAD and the capacity of the section.
With the option TRACK 1.0, the output contains intermediate
results such as the design forces, effective length coefficients,
additional moments etc. A special output TRACK 9.0 is introduced
to obtain the details of section capacity calculations. All design
output is given in SI units. An example of a long column design
(Ref.Example9 of SP:16, Design Aids For Reinforced Concrete to
IS:456-1978) output (with option TRACK 1.0) is given below.
Concrete Design Per IS456
Section 9A
9-8
============================================================================ C O L U M N N O. 1 D E S I G N R E S U L T S M20 Fe415 (Main) Fe415 (Sec.)
LENGTH: 3000.0 mm CROSS SECTION: 250.0 mm dia. COVER: 40.0 mm ** GUIDING LOAD CASE: 5 BRACED LONG COLUMN
DESIGN FORCES (KNS-MET) ----------------------- DESIGN AXIAL FORCE (Pu) : 62.0
About Z About Y INITIAL MOMENTS : 2.21 32.29
MOMENTS DUE TO MINIMUM ECC. : 1.24 1.24 SLENDERNESS RATIOS : 12.00 12.00 MOMENTS DUE TO SLENDERNESS EFFECT : 1.12 1.12 MOMENT REDUCTION FACTORS : 1.00 1.00 ADDITION MOMENTS (Maz and May) : 1.12 1.12
TOTAL DESIGN MOMENTS : 3.32 33.40 REQD. STEEL AREA : 1822.71 Sq.mm. MAIN REINFORCEMENT : Provide 17 - 12 dia. (3.92%, 1922.65 Sq.mm.) (Equally distributed)
TIE REINFORCEMENT : Provide 8 mm dia. rectangular ties @ 190 mm c/c SECTION CAPACITY (KNS-MET) --------------------------
Puz : 992.70 Muz1 : 36.87 Muy1 : 36.87
INTERACTION RATIO: 1.00 (as per Cl. 38.6, IS456)
============================================================================
Section 9A
9-9
Table 9A.1 Indian Concrete Design IS456 Parameters
Parameter Default Description Name Value
FYMAIN 415 N/mm2 Yield Stress for main reinforcing steel.
FYSEC 415 N/mm2 Yield Stress for secondary reinforcing steel.
FC 30 N/mm2 Concrete Yield Stress.
CLEAR 25 mm 40 mm
For beam members. For column members
MINMAIN 10 mm Minimum main reinforcement bar size.
MAXMAIN 60 mm Maximum main reinforcement bar size.
MINSEC 8 mm Minimum secondary reinforcement bar size.
MAXSEC 12 mm Maximum secondary reinforcement bar size.
BRACING 0.0 BEAM DESIGN
A value of 1.0 means the effect of axial force will be taken into account for beam design.
COLUMN DESIGN
A value of 1.0 means the column is unbraced about major axis.
A value of 2.0 means the column is unbraced about minor axis.
A value of 3.0 means the column is unbraced about both axis.
RATIO 4.0 Maximum percentage of longitudinal reinforcement in columns.
Concrete Design Per IS456
Section 9A
9-10
Table 9A.1 Indian Concrete Design IS456 Parameters
Parameter Default Description Name Value
RFACE 4.0 A value of 4.0 means longitudinal reinforcement in column is arranged equally along 4 faces.
A value of 2.0 invokes 2 faced distribution about major axis.
A value of 3.0 invokes 2 faced distribution about minor axis.
WIDTH ZD Width to be used for design. This value defaults to ZD as provided under MEMBER PROPERTIES.
DEPTH YD Total depth to be used for design. This value defaults to YD as provided under MEMBER PROPERTIES.
TRACK 0.0 BEAM DESIGN:
For TRACK = 0.0, output consists of reinforcement details at START, MIDDLE and END. For TRACK = 1.0, critical moments are printed in addition to TRACK 0.0 output. For TRACK = 2.0, required steel for intermediate sections defined by NSECTION are printed in addition to TRACK 1.0 output.
COLUMN DESIGN:
With TRACK = 0.0, reinforcement details are printed. With TRACK = 1.0, column interaction analysis results are printed in addition to TRACK 0.0 output. With TRACK = 2.0, a schematic interaction diagram and intermediate interaction values are printed in addition to TRACK 1.0 output.
With TRACK = 9.0, the details of section capacity calculations are printed.
REINF 0.0 Tied column. A value of 1.0 will mean spiral reinforcement.
Section 9A
9-11
Table 9A.1 Indian Concrete Design IS456 Parameters
Parameter Default Description Name Value
ELZ 1.0 Ratio of effective length to actual length of column about major axis.
ELY 1.0 Ratio of effective length to actual length of column about minor axis.
ULY 1.0 Ratio of unsupported length to actual length of column about minor axis.
ULZ 1.0 Ratio of unsupported length to actual length of column about major axis.
TORSION 0.0 A value of 0.0 means torsion to be considered in beam design. A value of 1.0 means torsion to be neglected in beam design.
SPSMAIN 25 mm Minimum clear distance between main reinforcing bars in beam and column. For column centre to centre distance between main bars cannot exceed 300mm.
SFACE 0.0 Face of support location at start of beam. It is used to check against shear at the face of the support in beam design. The parameter can also be used to check against shear at any point from the start of the member.
EFACE 0.0 Face of support location at end of beam. The parameter can also be used to check against shear at any point from the end of the member. (Note: Both SFACE and EFACE are input as positive numbers).
Concrete Design Per IS456
Section 9A
9-12
Table 9A.1 Indian Concrete Design IS456 Parameters
Parameter Default Description Name Value
ENSH 0.0 Perform shear check against enhanced shear strength as per Cl. 40.5 of IS456:2000. ENSH = 1.0 means ordinary shear check to be performed ( no enhancement of shear strength at sections close to support) For ENSH = a positive value(say x ), shear strength will be enhanced up to a distance x from the start of the member. This is used only when a span of a beam is subdivided into two or more parts. (Refer note ) For ENSH = a negative value(say –y), shear strength will be enhanced up to a distance y from the end of the member. This is used only when a span of a beam is subdivided into two or more parts.(Refer note) If default value (0.0) is used the program will calculate Length to Overall Depth ratio. If this ratio is greater than 2.5, shear strength will be enhanced at sections (<2d) close to support otherwise ordinary shear check will be performed.
RENSH 0.0 Distance of the start or end point of the member from its nearest support. This parameter is used only when a span of a beam is subdivided into two or more parts. (Refer note)
Bar combination has been introduced for detailing. Please refer section 8A.8 for details. Notes: Value of ENSH parameter (other than 0.0 and 1.0) is used only
when the span of a beam is subdivided into two or more parts. When this
condition is aroused RENSH parameter is also to be used.
Once a parameter is specified, its value stays at that specified
number till it is specified again. This is the way STAAD works for all
codes.
Section 9A
9-13
The span of the beam is subdivided four parts, each of length L
metre. The shear strength will be enhanced up to X metre from
both supports. The input should be the following:
Steps:
ENSH L MEMB 1 => Shear strength will be enhanced
throughout the length of the member 1,
positive sign indicates length
measured from start of the member
ENSH (X-L) MEMB 2 => Shear strength will be enhanced up to
a length (X-L) of the member 2, length
measured from the start of the member
ENSH –L MEMB 4 => Shear strength will be enhanced
throughout the length of the member 4,
negative sign indicates length
measured from end of the member
ENSH –(X-L) MEMB 3 => Shear strength will be enhanced up to
a length (X-L) of the member 3, length
measured from the end of the member
RENSH L MEMB 2 3 => Nearest support lies at a distance L
from both the members 2 and 3.
DESIGN BEAM 1 TO 4=> This will enhance the shear strength
up to length X from both ends of the
beam consisting of members 1 to 4 and
gives spacing accordingly.
Concrete Design Per IS456
Section 9A
9-14
At section = y1 from start of member 1 av = y1
At section = y2 from the start of member 2 av = y2+L
At section = y3 from the end of member 3 av = y3+L
At section = y4 from end of member 4 av = y4
where c, enhanced = 2dc/av
At section 0.0, av becomes zero. Thus enhanced shear strength will
become infinity. However for any section shear stress cannot
exceed c, max. Hence enhanced shear strength is limited to a
maximum value of c, max.
9A.8 Bar Combination
Initially the program selects only one bar to calculate the number
of bars required and area of steel provided at each section along
the length of the beam. Now, two bar diameters can be specified to
calculate a combination of each bar to be provided at each section.
The syntax for bar combination is given below.
START BAR COMBINATION
MD1 <bar diameter> MEMB <member list>
MD2 <bar diameter> MEMB <member list>
END BAR COMBINATION
Section 9A
9-15
MD2 bar diameter should be greater than MD1 bar diameter. The typical output for bar combination is shown below:
OUTPUT FOR BAR COMBINATION
--------------------------------------------------------------
| M A I N R E I N F O R C E M E N T |
--------------------------------------------------------------
SECTION | 0.0- 2166.7 | 2166.7- 6500.0 | 6500.0- 8666.7 |
| mm | mm | mm |
--------------------------------------------------------------
TOP | 6-20í + 1-25í| 2-20í + 1-25í | 2-20í |
| in 2 layer(s)| in 1 layer(s) | in 1 layer(s) |
Ast Reqd| 2330.22 | 1029.90 | 582.55 |
Prov| 2376.79 | 1119.64 | 628.57 |
Ld (mm) | 940.2 | 940.2 | 940.2 |
--------------------------------------------------------------
BOTTOM | 4-20í | 2-20í | 2-20í |
|in 1 layer(s) | in 1 layer(s) | in 1 layer(s) |
Ast Reqd| 1165.11 | 582.55 | 582.55 |
Prov| 1257.14 | 628.57 | 628.57 |
Ld (mm) | 940.2 | 940.2 | 940.2 |
-------------------------------------------------------------
The beam length is divided into three parts, two at its ends and one at span. Ld gives the development length to be provided at the two ends of each section.
9A.9 Wall Design in accordance with IS 456-2000
Design of walls in accordance with IS 456-2000 is available in
STAAD.Pro.
Design is performed for in-plane shear, in-plane and out-of-plane
bending and out-of-plane shear. The wall has to be modeled using
STAAD‟s Surface elements. The use of the Surface element
enables the designer to treat the entire wall as one entity. It greatly
simplifies the modeling of the wall and adds clarity to the analysis
and design output. The results are presented in the context of the
entire wall rather than individual finite elements thereby allowing
users to quickly locate required information.
Concrete Design Per IS456
Section 9A
9-16
The program reports shear wall design results for each load
case/combination for user specified number of sections given by
SURFACE DIVISION (default value is 10) command. The shear
wall is designed at these horizontal sections. The output includes
the required horizontal and vertical distributed reinforcing, the
concentrated (in-plane bending) edge reinforcing and the link
required for out-of-plane shear.
General format:
START SHEARWALL DESIGN
CODE INDIAN
FYMAIN f1
FC f2
HMIN f3
HMAX f4
VMIN f5
VMAX f6
EMIN f7
EMAX f8
LMIN f9 LMAX f10
CLEAR f11
TWOLAYERED f12
KSLENDER f13
DESIGN SHEARWALL LIST shearwall-list
END
Section 9A
9-17
The following table explains the parameters used in the shear wall
design. Note: Once a parameter is specified, its value stays at
that specified number till it is specified again. This is the way
STAAD works for all codes.
SHEAR WALL DESIGN PARAMETERS
Parameter Name Default
Value
Description
FYMAIN 415 Mpa Yield strength of steel, in current units.
FC 30 Mpa Compressive strength of concrete, in current units.
HMIN 8 Minimum size of horizontal reinforcing bars (range 6 mm – 36 mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
HMAX 36 Maximum size of horizontal reinforcing bars (range 6 mm – 36 mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
VMIN 8 Minimum size of vertical reinforcing bars (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
VMAX 36 Maximum size of vertical reinforcing bars (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
EMIN 8 Minimum size of vertical reinforcing bars located in edge zones (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
EMAX 36 Maximum size of vertical reinforcing bars located in edge zones (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
LMIN 6 Minimum size of links (range 6mm – 16mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
Concrete Design Per IS456
Section 9A
9-18
SHEAR WALL DESIGN PARAMETERS
Parameter Name Default
Value
Description
LMAX 16 Maximum size of links (range 6mm – 16mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.
CLEAR 25 mm Clear concrete cover, in current units. TWOLAYERED 0 Reinforcement placement mode:
0 - single layer, each direction 1 - two layers, each direction
KSLENDER 1.0 Slenderness factor for finding effective height. Table 6
The following example illustrates the input for the definition of
shear wall and design of the wall.
Example
.
.
SET DIVISION 12
SURFACE INCIDENCES
2 5 37 34 SUR 1
19 16 65 68 SUR 2
11 15 186 165 SUR 3
10 6 138 159 SUR 4
.
.
.
SURFACE PROPERTY
1 TO 4 THI 18
SUPPORTS
1 7 14 20 PINNED
2 TO 5 GEN PIN
6 TO 10 GEN PIN
Section 9A
9-19
11 TO 15 GEN PIN
19 TO 16 GEN PIN
.
.
.
SURFACE CONSTANTS
E 2.17185e+007
POISSON 0.17
DENSITY 23.5616
ALPHA 1e-005
.
.
START SHEARWALL DES
CODE INDIAN
UNIT NEW MMS
FC 25
FYMAIN 415
TWO 1
VMIN 12
HMIN 12
EMIN 12
DESIGN SHEA LIST 1 TO 4
END
Notes
1. Command SET DIVISION 12 indicates that the surface
boundary node-to-node segments will be subdivided into 12
fragments prior to finite element mesh generation.
2. Four surfaces are defined by the SURFACE INCIDENCES
command.
3. The SUPPORTS command includes the new support
generation routine. For instance, the line 2 TO 5 GEN PIN
assigns pinned supports to all nodes between nodes 2 and 5.
As the node-to-node distances were previously subdivided
by the SET DIVISION 12 command, there will be an
Concrete Design Per IS456
Section 9A
9-20
additional 11 nodes between nodes 2 and 5. As a result, all
13 nodes will be assigned pinned supports. Please note that
the additional 11 nodes are not individually accessible to the
user. They are created by the program to enable the finite
element mesh generation and to allow application of
boundary constraints.
4. Surface thickness and material constants are specified by the
SURFACE PROPERTY and SURFACE CONSTANTS,
respectively.
5. The shear wall design commands are listed between lines
START SHEARWALL DES and END. The CODE
command selects the design code that will be the basis for
the design. For Indian code the parameter is INDIAN. The
DESIGN SHEARWALL LIST command is followed by a
list of previously defined Surface elements intended as shear
walls and/or shear wall components.
Technical Overview
The program implements provisions of section 32 of IS 456-2000
and relevant provisions as referenced therein, for all active load
cases. The following steps are performed for each of the horizontal
sections of the wall.
Checking of slenderness limit
The slenderness checking is done as per clause no. 32.2.3. The
default effective height is the height of the wall. User can change
the effective height. The limit for slenderness is taken as 30.
Design for in-plane bending and vertical load (denoted by Mz
& Fy in the shear wall force output)
Walls when subjected to combined in-plane horizontal and vertical
forces produce in-plane bending in conjunction with vertical load.
According to clause no. 32.3.1, in-plane bending may be neglected
in case a horizontal cross section of the wall is always under
compression due combined effect of horizontal and vertical loads.
Otherwise, the section is checked for combined vertical load and
Section 9A
9-21
in-plane moment as column with axial load and uni-axial bending.
For this purpose, the depth is taken as 0.8 x horizontal length of
wall and breadth is the thickness of the wall. The reinforcement is
concentrated at both ends (edges) of the wall. The edge
reinforcement is assumed to be distributed over a len gth of 0.2
times horizontal length on each side. Minimum reinforcements are
according to clause no. 32.5.(a). Maximum 4% reinforcement is
allowed.
Design for in-plane shear (denoted by Fxy in the shear wall
force output)
By default, the program does not design only at the critical section
but at all the horizontal sections. By suitable use of the surface
division command, design at critical section as per clause no.
32.4.1 can be performed.
The design for in-plane shear is done as per clause no. 32.4. The
nominal shear stress is calculated as per clause no. 32.4.2 and it is
checked with the maximum allowable shear stress as per clause no.
32.4.2.1. The design shear strength of concrete is calculated as per
clause no. 32.4.3. Design of shear reinforcement is done as per
clause no. 32.4.4. Minimum reinforcements are as per clause no.
32.5.
Design for vertical load and out-of-plane vertical bending
(denoted by Fy and My respectively in the shear wall force
output)
Apart from the in-plane bending and horizontal shear force, the
wall is also subjected to out-of-plane bending in the vertical and
horizontal directions. The part of the wall which is not having
edge reinforcements (i.e. a zone of depth 0.6 x Length of the wall),
is designed again as column under axial load (i.e. vertical load)
and out-of-plane vertical bending. The minimum reinforcements
and maximum allowable spacings of reinforcements are as per
clause no. 32.5
Concrete Design Per IS456
Section 9A
9-22
Design for out-of-plane horizontal bending (denoted by Mx in
the shear wall force output)
The horizontal reinforcement which is already provided for in -
plane shear is checked against out-of-plane horizontal bending.
The wall is assumed as a slab for this purpose.
Design for out-of-plane shears (denoted by Qx and Qy in the
shear wall force output)
The out-of-plane shear arises from out-of-plane loading. The
nominal shear stresses are calculated as per clause no. 40.1.
Maximum allowable shear stresses are as per table 20. For shear
force in the vertical direction, shear strength of concrete section is
calculated as per section 4.1 of SP 16 : 1980 considering vertical
reinforcement as tension reinforcement. Similarly, for shear force
in the horizontal direction, shear strength of concrete section is
calculated considering horizontal reinforcement as tension
reinforcement. Shear reinforcements in the form of links are
computed as per the provisions of clause no. 40.4.
Shear Wall Design With Opening
The Surface element has been enhanced to allow design of shear
walls with rectangular openings. The automatic meshing algorithm
has been improved to allow variable divisions along wall and
opening(s) edges. Design and output are available for user selected
locations.
Description
Shear walls modeled in STAAD.Pro may include an unlimited
number of openings. Due to the presence of openings, the wall
may comprise up with different wall panels.
Section 9A
9-23
1. Shear wall set-up
Definition of a shear wall starts with a specification of the surface
element perimeter nodes, meshing divisions along node-to-node
segments, opening(s) corner coordinates, and meshing divisions of
four edges of the opening(s).
SURFACE INCIDENCE n1, ..., ni SURFACE s DIVISION sd1, ...,
sdj -
RECOPENING x1 y1 z1 x2 y2 z2 x3 y3 z3 x4 y4 z4 DIVISION
od1, ..., odk
where,
n1, ..., ni - node numbers on the perimeter of the shear wall,
s - surface ordinal number,
sd1, ..., sdj - number of divisions for each of the node-to-node distance on the surface perimeter,
x1 y1 z1 (...) - coordinates of the corners of the opening,
od1, ..., odk - divisions along edges of the opening.
Note:
If the sd1, ..., sdj or the od1, ..., odk list does not include all node-
to-node segments, or if any of the numbers listed equals zero, then
the corresponding division number is set to the default value (=10,
or as previously input by the SET DIVISION command).
Default locations for stress/force output, design, and design output
are set as follows:
SURFACE DIVISION X xd
SURFACE DIVISION Y yd
Concrete Design Per IS456
Section 9A
9-24
where,
xd - number of divisions along X axis,
yd - number of divisions along Y axis.
Note:
xd and yd represent default numbers of divisions for each edge of
the surface where output is requested. The output is provided for
sections located between division segments. For example, if the
number of divisions = 2, then the output will be produced for only
one section (at the center of the edge).
2. Stress/force output printing
Values of internal forces may be printed out for any user -defined
section of the wall. The general format of the command is as
follows:
PRINT SURFACE FORCE (ALONG ) (AT a) (BETWEEN d1, d2)
LIST s1, ...,si
where,
- local axis of the surface element (X or Y),
a - distance along the axis from start of the member
to the full cross-section of the wall,
d1, d2 - coordinates in the direction orthogonal to ,
delineating a fragment of the full cross-section for
which the output is desired. **
s1, ...,si - list of surfaces for output generation
** The range currently is taken in terms of local axis. If the local
axis is directed away from the surface, the negative range is to be
entered.
Section 9A
9-25
Note:
If command ALONG is omitted, direction Y (default) is assumed.
If command AT is omitted, output is provided for all sections
along the specified (or default) edge. Number of sections will be
determined from the SURFACE DIVISION X or SURFACE
DIVISION Y input values. If the BETWEEN command is
omitted, the output is generated based on full cross-section width.
3. Definition of wall panels
Input syntax for panel definition is as follows:
START PANEL DEFINITION
SURFACE i PANEL j ptype x1 y1 z1 x2 y2 z2 x3 y3 z3 x4 y4 z4
END PANEL DEFINITION
where,
i - ordinal surface number,
j - ordinal panel number,
ptype - panel type, one of: WALL, COLUMN, BEAM
x1 y1 z1 (...) - coordinates of the corners of the panel,
4. Shear wall design
The program implements different provisions of design of walls as
per code BS 8110. General syntax of the design command is as
follows:
START SHEARWALL DESIGN
(...)
DESIGN SHEARWALL (AT c) LIST s
END SHEARWALL DESIGN
Concrete Design Per IS456
Section 9A
9-26
Note:
If the command AT is omitted, the design proceeds for all cross
sections of the wall or panels, as applicable, defined by the
SURFACE DIVISION X or SURFACE DIVISION Y input
values.
a. No panel definition.
Design is performed for the specified horizontal full cross-section,
located at a distance c from the origin of the local coordinates
system. If opening is found then reinforcement is provided along
sides of openings. The area of horizontal and vertical bars
provided along edges of openings is equal to that of the respective
interrupted bars.
b. Panels have been defined.
Only wall panel design is supported in Indian code.
9-27
Concrete Design Per IS13920
9A1.1 Design Operations
Earthquake motion often induces force large enough to cause
inelastic deformations in the structure. If the structure is brittle,
sudden failure could occur. But if the structure is made to behave
ductile, it will be able to sustain the earthquake effects better with
some deflection larger than the yield deflection by absorption of
energy. Therefore ductility is also required as an essential element
for safety from sudden collapse during severe shocks.
STAAD has the capabilities of performing concrete design as per
IS 13920. While designing it satisfies all provisions of IS 456 –
2000 and IS 13920 for beams and columns.
9A1.2 Section Types for Concrete Design
The following types of cross sections for concrete members can be
designed.
For Beams Prismatic (Rectangular & Square) & T-shape
For Columns Prismatic (Rectangular, Square and Circular)
Section 9A1
Concrete Design Per IS13920
Section 9A1
9-28
9A1.3 Design Parameters
The program contains a number of parameters that are needed to
perform design as per IS 13920. It accepts all parameters that are
needed to perform design as per IS:456. Over and above it has
some other parameters that are required only when designed is
performed as per IS:13920. Default parameter values have been
selected such that they are frequently used numbers for
conventional design requirements. These values may be changed to
suit the particular design being performed. Table 8A1.1 of this
manual contains a complete list of the available parameters and
their default values. It is necessary to declare length and force
units as Millimeter and Newton before performing the concrete
design.
9A1.4 Beam Design
Beams are designed for flexure, shear and torsion. If required the
effect of the axial force may be taken into consideration. For all
these forces, all active beam loadings are prescanned to identify
the critical load cases at different sections of the beams. The total
number of sections considered is 13. All of these sections are
scanned to determine the design force envelopes.
For design to be performed as per IS:13920 the width of the
member shall not be less than 200mm(Clause 6.1.3). Also the
member shall preferably have a width-to depth ratio of more than
0.3 (Clause 6.1.2).
The factored axial stress on the member should not exceed 0.1fck
(Clause 6.1.1) for all active load cases. If it exceeds allowable
axial stress no design will be performed.
Section 9A1
9-29
Design for Flexure
Design procedure is same as that for IS 456. However while
designing following criteria are satisfied as per IS-13920:
1. The minimum grade of concrete shall preferably be M20. (Clause
5.2)
2. Steel reinforcements of grade Fe415 or less only shall be used.
(Clause 5.3)
3. The minimum tension steel ratio on any face, at any section, is
given by
min = 0.24fck/fy (Clause 6.2.1b)
The maximum steel ratio on any face, at any section, is given by max = 0.025 (Clause 6.2.2)
4. The positive steel ratio at a joint face must be at least equal to half
the negative steel at that face. (Clause 6.2.3)
5. The steel provided at each of the top and bottom face, at any
section, shall at least be equal to one-fourth of the maximum
negative moment steel provided at the face of either joint. (Clause
6.2.4)
Design for Shear
The shear force to be resisted by vertical hoops is guided by the
Clause 6.3.3 of IS 13920:1993 revision. Elastic sagging and
hogging moments of resistance of the beam section at ends are
considered while calculating shear force. Plastic sagging and
hogging moments of resistance can also be considered for shear
design if PLASTIC parameter is mentioned in the input file. (Refer
Table 8A1.1)
Shear reinforcement is calculated to resist both shear forces and
torsional moments. Procedure is same as that of IS 456.
Concrete Design Per IS13920
Section 9A1
9-30
The following criteria are satisfied while performing design for
shear as per Cl. 6.3.5 of IS-13920:
The spacing of vertical hoops over a length of 2d at either end of
the beam shall not exceed
a) d/4
b) 8 times the diameter of the longitudinal bars
In no case this spacing is less than 100 mm.
The spacing calculated from above, if less than that calculated
from IS 456 consideration is provided.
Beam Design Output
The default design output of the beam contains flexural and shear
reinforcement provided at 5 equally spaced sections along the
length of the beam. User has option to get a more detail output. All
beam design outputs are given in IS units. An example of
rectangular beam design output with the default output option
(TRACK 1.0) is presented below:
Section 9A1
9-31 ============================================================================
B E A M N O. 11 D E S I G N R E S U L T S
M20 Fe415 (Main) Fe415 (Sec.)
LENGTH: 3500.0 mm SIZE: 250.0 mm X 350.0 mm COVER: 30.0 mm
DESIGN LOAD SUMMARY (KN MET)
----------------------------------------------------------------------------
SECTION |FLEXTURE (Maxm. Sagging/Hogging moments)| SHEAR
(in mm) | P MZ MX Load Case | VY MX Load Case
----------------------------------------------------------------------------
0.0 | 0.00 0.00 0.00 4 | 17.67 0.00 4
| 0.00 -2.74 0.00 5 |
291.7 | 0.00 1.15 0.00 5 | 16.26 0.00 4
| 0.00 0.00 0.00 4 |
583.3 | 0.00 4.61 0.00 5 | 13.97 0.00 4
| 0.00 0.00 0.00 4 |
875.0 | 0.00 7.44 0.00 5 | 10.78 0.00 4
| 0.00 0.00 0.00 4 |
1166.7 | 0.00 9.41 0.00 5 | 6.69 0.00 4
| 0.00 0.00 0.00 4 |
1458.3 | 0.00 10.33 0.00 5 | 1.10 0.00 5
| 0.00 0.00 0.00 4 |
1750.0 | 0.00 9.98 0.00 5 | -3.60 0.00 5
| 0.00 0.00 0.00 4 |
2041.7 | 0.00 8.23 0.00 5 | -10.02 0.00 4
| 0.00 0.00 0.00 4 |
2333.3 | 0.00 5.21 0.00 5 | -15.00 0.00 4
| 0.00 0.00 0.00 4 |
2625.0 | 0.00 1.14 0.00 5 | -19.08 0.00 4
| 0.00 0.00 0.00 4 |
2916.7 | 0.00 0.00 0.00 4 | -22.27 0.00 4
| 0.00 -3.79 0.00 5 |
3208.3 | 0.00 0.00 0.00 4 | -24.57 0.00 4
| 0.00 -9.35 0.00 5 |
3500.0 | 0.00 0.00 0.00 4 | -25.97 0.00 4
| 0.00 -15.34 0.00 5 |
*** DESIGN SHEAR FORCE AT SECTION 0.0 IS 68.60 KN.
- CLAUSE 6.3.3 OF IS-
13920
*** DESIGN SHEAR FORCE AT SECTION 3500.0 IS 75.24 KN.
- CLAUSE 6.3.3 OF IS-
13920
----------------------------------------------------------------------------
SUMMARY OF REINF. AREA (Sq.mm)
----------------------------------------------------------------------------
SECTION 0.0 mm 875.0 mm 1750.0 mm 2625.0 mm 3500.0 mm
----------------------------------------------------------------------------
TOP 226.30 0.00 0.00 0.00 226.30
REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm)
BOTTOM 0.00 203.02 203.02 203.02 0.00
REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm)
----------------------------------------------------------------------------
SUMMARY OF PROVIDED REINF. AREA
----------------------------------------------------------------------------
SECTION 0.0 mm 875.0 mm 1750.0 mm 2625.0 mm 3500.0 mm
----------------------------------------------------------------------------
TOP 3-10í 2-10í 2-10í 2-10í 3-10í
REINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)
BOTTOM 2-12í 2-12í 2-12í 2-12í 2-12í
REINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)
SHEAR 2 legged 8í 2 legged 8í 2 legged 8í 2 legged 8í 2 legged 8í
REINF. @ 100 mm c/c @ 150 mm c/c @ 150 mm c/c @ 150 mm c/c @ 100 mm c/c
----------------------------------------------------------------------------
============================================================================
Concrete Design Per IS13920
Section 9A1
9-32
9A1.5 Column Design
Columns are designed for axial forces and biaxial moments per IS
456:2000. Columns are also designed for shear forces as per
Clause 7.3.4. All major criteria for selecting longitudinal and
transverse reinforcement as stipulated by IS:456 have been taken
care of in the column design of STAAD. However following
clauses have been satisfied to incorporate provisions of IS 13920:
1. The minimum grade of concrete shall preferably be M20.
(Clause 5.2)
2. Steel reinforcements of grade Fe415 or less only shall be used.
(Clause 5.3)
3. The minimum dimension of column member shall not be less
than 200 mm. For columns having unsupported length
exceeding 4m, the shortest dimension of column shall not be
less than 300 mm. (Clause 7.1.2)
4. The ratio of the shortest cross-sectional dimension to the
perpendicular dimension shall preferably be not less than 0.4.
(Clause 7.1.3)
5. The spacing of hoops shall not exceed half the least lateral
dimension of the column, except where special confining
reinforcement is provided. (Clause 7.3.3)
6. Special confining reinforcement shall be provided over a
length lo from each joint face, towards mid span, and on either
side of any section, where flexural yielding may occur. The
length lo shall not be less than a) larger lateral dimension of
the member at the section where yielding occurs, b) 1/6 of
clear span of the member, and c) 450 mm. (Clause 7.4.1)
7. The spacing of hoops used as special confining reinforcement
shall not exceed ¼ of minimum member dimension but need
not be less than 75 mm nor more than 100 mm. (Clause 7.4.6)
Section 9A1
9-33
8. The area of cross-section of hoops provided are checked
against the provisions for minimum area of cross-section of
the bar forming rectangular, circular or spiral hoops, to be
used as special confining reinforcement. (Clause 7.4.7 and
7.4.8)
Column Design Output
Default column design output (TRACK 0.0) contains the
reinforcement provided by STAAD and the capacity of the section.
With the option TRACK 1.0, the output contains intermediate
results such as the design forces, effective length coefficients,
additional moments etc. A special output TRACK 9.0 is introduced
to obtain the details of section capacity calculations. All design
output is given in SI units. An example of a column design output
(with option TRACK 1.0) is given below. ============================================================================
C O L U M N N O. 3 D E S I G N R E S U L T S
M20 Fe415 (Main) Fe415 (Sec.)
LENGTH: 3000.0 mm CROSS SECTION: 350.0 mm X 400.0 mm COVER: 40.0 mm
** GUIDING LOAD CASE: 5 END JOINT: 2 SHORT COLUMN
DESIGN FORCES (KNS-MET)
-----------------------
DESIGN AXIAL FORCE (Pu) : 226.7
About Z About Y
INITIAL MOMENTS : 0.64 146.28
MOMENTS DUE TO MINIMUM ECC. : 4.53 4.53
SLENDERNESS RATIOS : - -
MOMENTS DUE TO SLENDERNESS EFFECT : - -
MOMENT REDUCTION FACTORS : - -
ADDITION MOMENTS (Maz and May) : - -
TOTAL DESIGN MOMENTS : 4.53 146.28
** GUIDING LOAD CASE: 5
Along Z Along Y
DESIGN SHEAR FORCES : 43.31 76.08
REQD. STEEL AREA : 3313.56 Sq.mm.
MAIN REINFORCEMENT : Provide 12 - 20 dia. (2.69%, 3769.91 Sq.mm.)
(Equally distributed)
CONFINING REINFORCEMENT : Provide 10 mm dia. rectangular ties @ 85 mm c/c
over a length 500.0 mm from each joint face towards
midspan as per Cl. 7.4.6 of IS-13920.
TIE REINFORCEMENT : Provide 10 mm dia. rectangular ties @ 175 mm c/c
SECTION CAPACITY (KNS-MET)
--------------------------
Puz : 2261.52 Muz1 : 178.71 Muy1 : 150.75
INTERACTION RATIO: 1.00 (as per Cl. 39.6, IS456:2000)
============================================================================
********************END OF COLUMN DESIGN RESULTS********************
Concrete Design Per IS13920
Section 9A1
9-34
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
Table 9A1.1 Indian Concrete Design IS13920 Parameters
Parameter
Name
Default Value Description
FYMAIN 415 N/mm2 Yield Stress for main reinforcing steel.
FYSEC 415 N/mm2 Yield Stress for secondary reinforcing steel.
FC 30 N/mm2 Concrete Yield Stress.
CLEAR 25 mm
40 mm
For beam members.
For column members
MINMAIN 10 mm Minimum main reinforcement bar size.
MAXMAIN 60 mm Maximum main reinforcement bar size.
MINSEC 8 mm Minimum secondary reinforcement bar size.
MAXSEC 12 mm Maximum secondary reinforcement bar size.
BRACING 0.0 BEAM DESIGN
A value of 1.0 means the effect of axial force will be taken into account for beam design.
COLUMN DESIGN
A value of 1.0 means the column is unbraced about major axis.
A value of 2.0 means the column is unbraced about minor axis.
A value of 3.0 means the column is unbraced about both axis.
RATIO 4.0 Maximum percentage of longitudinal reinforcement in columns.
RFACE 4.0 A value of 4.0 means longitudinal reinforcement in column is arranged equally along 4 faces.
A value of 2.0 invokes 2 faced distribution about major axis.
Section 9A1
9-35
Table 9A1.1 Indian Concrete Design IS13920 Parameters
Parameter
Name
Default Value Description
A value of 3.0 invokes 2 faced distribution about minor axis.
WIDTH ZD Width to be used for design. This value defaults to ZD as provided under MEMBER PROPERTIES.
DEPTH YD Total depth to be used for design. This value defaults to YD as provided under MEMBER PROPERTIES.
ELZ 1.0 Ratio of effective length to actual length of column about major axis.
ELY 1.0 Ratio of effective length to actual length of column about minor axis.
REINF 0.0 Tied column. A value of 1.0 will mean spiral reinforcement.
TORSION 0.0 A value of 0.0 means torsion to be considered in beam design.
A value of 1.0 means torsion to be neglected in beam design.
TRACK 0.0 BEAM DESIGN:
For TRACK = 0.0, output consists of reinforcement details at START, MIDDLE and END.
For TRACK = 1.0, critical moments are printed in addition to TRACK 0.0 output.
For TRACK = 2.0, required steel for intermediate sections defined by NSECTION are printed in addition to TRACK 1.0 output.
COLUMN DESIGN:
With TRACK = 0.0, reinforcement details are printed.
With TRACK = 1.0, column interaction analysis results are printed in addition to TRACK 0.0 output.
Concrete Design Per IS13920
Section 9A1
9-36
Table 9A1.1 Indian Concrete Design IS13920 Parameters
Parameter
Name
Default Value Description
With TRACK = 2.0, a schematic interaction diagram and intermediate interaction values are printed in addition to TRACK 1.0 output.
SPSMAIN 25 mm Minimum clear distance between main reinforcing bars in beam and column. For column centre to centre distance between main bars cannot exceed 300mm.
SFACE 0.0 Face of support location at start of beam. It is used to check against shear at the face of the support in beam design. The parameter can also be used to check against shear at any point from the start of the member.*
EFACE 0.0 Face of support location at end of beam. The parameter can also be used to check against shear at any point from the end of the member. (Note: Both SFACE and EFACE are input as positive numbers).*
ENSH 0.0 Perform shear check against enhanced shear strength as per Cl. 40.5 of IS456:2000.
ENSH = 1.0 means ordinary shear check to be performed ( no enhancement of shear strength at sections close to support)
For ENSH = a positive value(say x ), shear strength will be enhanced up to a distance x from the start of the member. This is used only when a span of a beam is subdivided into two or more parts. (Refer note after Table 8A.1 )
For ENSH = a negative value(say –y), shear strength will be enhanced up to a distance y from the end of the member. This is used only when a span of a beam is subdivided into two or more parts.(Refer note after Table 8A.1)
If default value (0.0) is used the program will calculate Length to Overall Depth ratio. If this ratio is greater than 2.5, shear strength will be enhanced at sections (<2d) close to support otherwise ordinary shear check will
Section 9A1
9-37
Table 9A1.1 Indian Concrete Design IS13920 Parameters
Parameter
Name
Default Value Description
be performed.
RENSH 0.0 Distance of the start or end point of the member from its nearest support. This parameter is used only when a span of a beam is subdivided into two or more parts. (Refer note after Table 8A.1)
EUDL None Equivalent u.d.l on span of the beam. This load value must be the unfactored load on span. During design the load value is multiplied by a factor 1.2. If no u.d.l is defined factored shear force due to gravity load on span will be taken as zero. No elastic or plastic moment will be calculated. Shear design will be performed based on analysis result.(Refer note)
GLD None Gravity load number to be considered for calculating equivalent u.d.l on span of the beam, in case no EUDL is mentioned in the input. This loadcase can be any static loadcase containing MEMBER LOAD on the beam which includes UNI, CON, LIN and TRAP member loading. CMOM member loading is considered only when it is specified in local direction. FLOOR LOAD is also considered.
The load can be primary or combination load. For combination load only load numbers included in load combination is considered. The load factors are ignored. Internally the unfactored load is multiplied by a factor 1.2 during design.
If both EUDL and GLD parameters are mentioned in the input mentioned EUDL will be considered in design
Note :
No dynamic (Response spectrum, 1893, Time History) and moving load cases are considered.
CMOM member loading in global direction is
Concrete Design Per IS13920
Section 9A1
9-38
Table 9A1.1 Indian Concrete Design IS13920 Parameters
Parameter
Name
Default Value Description
not considered.
UMOM member loading is not considered.
PLASTIC 0.0 Default value calculates elastic hogging and sagging moments of resistance of beam at its ends.
A value of 1.0 means plastic hogging and sagging moments of resistance of beam to be calculated at its ends.
IPLM 0.0 Default value calculates elastic/plastic hogging and sagging moments of resistance of beam at its ends.
A value of 1.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be ignored at start node of beam. This implies no support exists at start node.
A value of -1.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be considered at start node of beam. . This implies support exists at start node.
A value of 2.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be ignored at end node of beam. This implies no support exists at end node.
A value of -2.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be considered at end node of beam. . This implies support exists at end node. **
IMB 0.0 Default value calculates elastic/plastic hogging and sagging moments of resistance of beam at its ends.
A value of 1.0 means calculation of
Section 9A1
9-39
Table 9A1.1 Indian Concrete Design IS13920 Parameters
Parameter
Name
Default Value Description
elastic/plastic hogging and sagging moments of resistance of beam to be ignored at both ends of beam. This implies no support exist at either end of the member.
A value of -1.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be considered at both ends of beam. This implies support exist at both ends of the member.**
COMBINE 0.0 Default value means there will be no member combination.
A value of 1.0 means there will be no printout of sectional force and critical load for combined member in the output.
A value of 2.0 means there will be printout of sectional force for combined member in the output.
A value of 3.0 means there will be printout of both sectional force and critical load for combined member in the output. ***
HLINK Spacing of longitudinal bars measured to the
outer face
Longer dimension of the rectangular confining hoop measured to its outer face. It shall not exceed 300 mm as per Cl. 7.4.8. If hlink value as provided in the input file does not satisfy the clause the value will be internally assumed as the default one. This parameter is valid for rectangular column.
Bar combination has been introduced for detailing. Please refer section 8A1.6 for details.
* EFACE and SFACE command is not valid for member combination. ** IPLM and IMB commands are not valid for member combination. These commands are ignored for members forming physical member.
Concrete Design Per IS13920
Section 9A1
9-40
*** The purpose of COMBINE command is the following:
1. If a beam spanning between two supports is subdivided into many sub-beams this parameter will combine them into one member. It can also be used to combine members to form one continuous beam spanning over more than two supports.
2. When two or more members are combined during design plastic or elastic moments will be calculated at the column supports. At all the intermediate nodes (if any) this calculation will be ignored. Please note that the program only recognizes column at right angle to the beam. Inclined column support is ignored.
3. It will calculate sectional forces at 13 sections along the length of the combined member.
4. It will calculate critical loads (similar to that of Design Load Summary) for all active load cases during design. Beams will be combined only when DESIGN BEAM command is issued. The following lines should be satisfied during combination of members:
1. Members to be combined should have same sectional properties if any single span between two column supports of a continuous beam is subdivided into several members.
2. Members to be combined should have same constants (E, Poi ratio, alpha, density and beta angle)
3. Members to be combined should lie in one straight line. 4. Members to be combined should be continuous. 5. Vertical members (i.e. columns) cannot be combined. 6. Same member cannot be used more than once to form two different
combined members. 7. The maximum number of members that can be combined into one
member is 299.
Section 9A1
9-41
Note: Sectional forces and critical load for combined member output will only be available when all the members combined are successfully designed in both flexure and shear. ENSH and RENSH parameters will have to be provided (as and when necessary) even if physical member has been formed. The following lines show a standard example for design to be
performed in IS 13920.
STAAD SPACE
UNIT METER MTON
JOINT COORDINATES
…………………………………..
MEMBER INCIDENCES
…………………………………..
MEMBER PROPERTY INDIAN
…………………………………..
CONSTANTS
…………………….
SUPPORTS
…………………….
DEFINE 1893 LOAD
ZONE 0.05 I 1 K 1 B 1
SELFWEIGHT
JOINT WEIGHT
……………………….
LOAD 1 SEISMIC LOAD IN X DIR
1893 LOAD X 1
LOAD 2 SEISMIC LOAD IN Z DIR
1893 LOAD Z 1
LOAD 3 DL
MEMBER LOAD
…… UNI GY -5
LOAD 4 LL
Concrete Design Per IS13920
Section 9A1
9-42
MEMBER LOAD
……. UNI GY -3
LOAD COMB 5 1.5(DL+LL)
3 1.5 4 1.5
LOAD COMB 6 1.2(DL+LL+SLX)
1 1.2 3 1.2 4 1.2
LOAD COMB 7 1.2(DL+LL-SLX)
1 1.2 3 1.2 4 -1.2
LOAD COMB 8 1.2(DL+LL+SLZ)
2 1.2 3 1.2 4 1.2
LOAD COMB 9 1.2(DL+LL-SLZ)
2 1.2 3 1.2 4 -1.2
PDELTA ANALYSIS
LOAD LIST 5 TO 9
START CONCRETE DESIGN
CODE IS13920
UNIT MMS NEWTON
FYMAIN 415 ALL
FC 20 ALL
MINMAIN 12 ALL
MAXMAIN 25 ALL
TRACK 2.0 ALL
*** Unfactored gravity load on members 110 to 112 is 8 t/m (DL+LL) i.e. 78.46 New/mm
EUDL 78.46 MEMB 110 TO 112
** Members to be combined into one physical member
COMBINE 3.0 MEMB 110 TO 112
*** Plastic moment considered
PLASTIC 1.0 MEMB 110 TO 112
DESIGN BEAM 110 TO 112
DESIGN COLUMN ………
END CONCRETE DESIGN
FINISH
Section 9A1
9-43
9A1.6 Bar Combination
Initially the program selects only one bar to calculate the number
of bars required and area of steel provided at each section along
the length of the beam. Now two bar diameters can be specified to
calculate a combination of each bar to be provided at each section.
The syntax for bar combination is given below.
START BAR COMBINATION MD1 <bar diameter> MEMB <member list> MD2 <bar diameter> MEMB <member list> END BAR COMBINATION
MD2 bar diameter should be greater than MD1 bar diameter. The
typical output for bar combination is shown below:
OUTPUT FOR BAR COMBINATION
----------------------------------------------------------------------------
| M A I N R E I N F O R C E M E N T |
----------------------------------------------------------------------------
SECTION | 0.0- 2166.7 | 2166.7- 6500.0 | 6500.0- 8666.7 |
| mm | mm | mm |
----------------------------------------------------------------------------
TOP | 6-20í + 1-25í | 2-20í + 1-25í | 2-20í |
| in 2 layer(s) | in 1 layer(s) | in 1 layer(s) |
Ast Reqd| 2330.22 | 1029.90 | 582.55 |
Prov| 2376.79 | 1119.64 | 628.57 |
Ld (mm) | 940.2 | 940.2 | 940.2 |
----------------------------------------------------------------------------
BOTTOM | 4-20í | 2-20í | 2-20í |
| in 1 layer(s) | in 1 layer(s) | in 1 layer(s) |
Ast Reqd| 1165.11 | 582.55 | 582.55 |
Prov| 1257.14 | 628.57 | 628.57 |
Ld (mm) | 940.2 | 940.2 | 940.2 |
----------------------------------------------------------------------------
The beam length is divided into three parts, two at its ends and one
at span. Ld gives the development length to be provided at the two
ends of each section.
Concrete Design Per IS13920
Section 9A1
9-44
Sample example showing calculation of design shear force as per
Clause 6.3.3
For Beam No. 1 and 2
Section Width b 250 mm
Depth D 500 mm
Characteristic Strength of Steel fy 415 N/sq. mm Characteristic Strength of Concrete fck 20 N/sq. mm Clear Cover 25 mm Bar Diameter 12 mm Effective Depth d 469 mm Eudl w 6.5 N/sq. mm Length L 4000 mm Ast_Top_A 339.29 sq. mm Ast_Bot_A 226.19 sq. mm Ast_Top_B 226.19 sq. mm Ast_Bot_B 339.29 sq. mm
Section 9A1
9-45
Steps
Calculation of Simple Shear
Simple shear from gravity load on span =
Va = Vb = 1.2 * w * L / 2 = 15600N
Calculation of Moment Of Resistances Based On Area Of Steel Provided
Sagging Moment Of Resistance of End A Mu, as =
0.87 * fy * Ast_Bot_A * d * ( 1 - Ast_Bot_A * fy / b * d * fck)
= 36768130.05 N
Hogging Moment Of Resistance of End A Micah =
0.87 * fy * Ast_Top_A * d * ( 1 - Ast_Top_A * fy / b * d * fck)
= 54003057.45 N
Sagging Moment Of Resistance of End A Mu, bs =
0.87 * fy * Ast_Bot_B * d * ( 1 - Ast_Bot_B * fy / b * d * fck)
= 54003057.45 N
Hogging Moment Of Resistance of End A Mob =
0.87 * fy * Ast_Top_B * d * ( 1 - Ast_Top_B* fy / b * d * fck)
= 36768130.05 N
Calculation of Shear Force Due To Formation Of Plastic Hinge At Both Ends Of The Beam Plus The Factored Gravity Load On Span
FIG1: SWAY TO RIGHT
Vur,a = Va - 1.4 [ ( Mu,as + Mu,bh ) / L ] = -10137.69104 N Vur,b = Va + 1.4 [ ( Mu,as + Mu,bh ) / L ] = 41337.69104 N
Concrete Design Per IS13920
Section 9A1
9-46
FIG2: SWAY TO LEFT
Vul,a = Va + 1.4 [ ( Mu,ah + Mu,bs ) / L ] = 53402.14022 N
Vul,b = Va - 1.4 [ ( Mu,ah + Mu,bs ) / L ] = - 22202.14022 N Design Shear Force Shear Force From Analysis At End A , Va,anl = 11.56 N Design Shear Force At End A, Vu,a = Max ( Va,anl, Vur,a, Vul,a) = 53402.14022 N
Shear Force From Analysis At End B , Vb,anl = -6.44 N Design Shear Force At End B, Vu,b = Max ( Vb,anl, Vur,b, Vul,b) = 41337.69104 N
For Beam No. 3
Section Width b 300 mm
Depth D 450 mm
Characteristic Strength of Steel fy 415 N/sq. mm
Characteristic Strength of Concrete fck 20 N/sq. mm
Clear Cover 25 mm
Bar Diameter 12 mm
Effective Depth d 419 mm
Eudl w 6.5 N/sq. mm
Length L 3000 mm
Ast_Top_A 226.19 sq. mm
Ast_Bot_A 339.29 sq. mm
Ast_Top_B 452.39 sq. mm
Ast_Bot_B 226.19 sq. mm
Section 9A1
9-47
Calculation of Simple Shear
Simple shear from gravity load on span =
Va = Vb = 1.2 * w * L / 2 = 11700N
Calculation of Moment Of Resistances Based On Area Of Steel Provided
Sagging Moment Of Resistance of End A Mu,as =
0.87 * fy * Ast_Bot_A * d * ( 1 - Ast_Bot_A * fy / b * d * fck)
= 48452983 N
Hogging Moment Of Resistance of End A Mu,ah =
0.87 * fy * Ast_Top_A * d * ( 1 - Ast_Top_A * fy / b * d * fck)
= 32940364.5 N
Sagging Moment Of Resistance of End A Mu,bs =
0.87 * fy * Ast_Bot_B * d * ( 1 - Ast_Bot_B * fy / b * d * fck)
= 32940364.5 N
Hogging Moment Of Resistance of End A Mu,bh =
0.87 * fy * Ast_Top_B * d * ( 1 - Ast_Top_B* fy / b * d * fck)
= 63326721.3 N
Calculation of Shear Force Due To Formation Of Plastic Hinge At Both
Ends Of The Beam Plus The Factored Gravity Load On Span
FIG1: SWAY TO RIGHT
Vur,a = Va - 1.4 [ ( Mu,as + Mu,bh ) / L ] = -40463.862 N Vur,b = Va + 1.4 [ ( Mu,as + Mu,bh ) / L ] = 63863.862 N
Concrete Design Per IS13920
Section 9A1
9-48
Vul,a = Va + 1.4 [ ( Mu,ah + Mu,bs ) / L ] = 42444.3402 N
Vul,b = Va - 1.4 [ ( Mu,ah + Mu,bs ) / L ] = -15144.34 N Design Shear Force Shear Force From Analysis At End A , Va,anl = -10.31 N Design Shear Force At End A, Vu,a = Max ( Va,anl, Vur,a, Vul,a) = 42444.3402 N
Shear Force From Analysis At End B , Vb,anl = -23.81 N Design Shear Force At End B, Vu,b = Max ( Vb,anl, Vur,b, Vul,b) = 63863.862 N
9-49
Steel Design Per IS800
9B.1 Design Operations
STAAD contains a broad set of facilities for designing structural
members as individual components of an analyzed structure. The
member design facilities provide the user with the ability to carry
out a number of different design operations. These facilities may
be used selectively in accordance with the requirements of the
design problem. The operations to perform a design are:
Specify the members and the load cases to be considered in the
design.
Specify whether to perform code checking or member
selection.
Specify design parameter values, if different from the default
values.
Specify whether to perform member selection by optimization.
These operations may be repeated by the user any number of times
depending upon the design requirements. The entire ISI steel
section table is supported. Section 8B.13 describes the
specification of steel sections.
Section 9B
Steel Design Per IS800
Section 9B
9-50
9B.2 General Comments
This section presents some general statements regarding the
implementation of Indian Standard code of practice (IS:800-1984)
for structural steel design in STAAD. The design philosophy and
procedural logistics for member selection and code checking are
based upon the principles of allowable stress design. Two major
failure modes are recognized: failure by overstressing, and failure
by stability considerations. The flowing sections describe the
salient features of the allowable stresses being calculated an d the
stability criteria being used. Members are proportioned to resist
the design loads without exceeding the allowable stresses and the
most economic section is selected on the basis of least weight
criteria. The code checking part of the program checks stability
and strength requirements and reports the critical loading
condition and the governing code criteria. It is generally assumed
that the user will take care of the detailing requirements like
provision of stiffeners and check the local effects such as flange
buckling and web crippling.
9B.3 Allowable Stresses
The member design and code checking in STAAD are based upon
the allowable stress design method as per IS:800 (1984). It is a
method for proportioning structural members using design loads
and forces, allowable stresses, and design limitations for the
appropriate material under service conditions. It would not be
possible to describe every aspect of IS:800 in this manual. This
section, however, will discuss the salient features of the allowable
stresses specified by IS:800 and implemented in STAAD.
Appropriate sections of IS:800 will be referenced during the
discussion of various types of allowable stresses.
Section 9B
9-51
9B.3.1 Axial Stress
Tensile Stress
The allowable tensile stress, as calculated in STAAD as per IS:800
is described below.
The permissible stress in axial tension, at in MPa on the net
effective area of the sections shall not exceed
at = 0.6 fy
where,
fy = minimum yield stress of steel in Mpa
Compressive Stress
Allowable compressive stress on the gross section of axially
loaded compression members shall not exceed 0.6fy nor the
permissible stress ac calculated based on the following formula:
(Clause: 5.1.1)
f f
nccf
nyf
0 6.
[( ) ( ) ]
where,
ac = Permissible stress in axial compression, in Mpa
fy = Yield stress of steel, in Mpa
fcc = Elastic critical stress in compression = 2 E/2
E = Modulus of elasticity of steel, 2 X 105 Mpa
=l/r = Slenderness ratio of the member, ratio of the effective
length to appropriate radius of gyration
n = A factor assumed as 1.4.
Steel Design Per IS800
Section 9B
9-52
9B.3.2 Bending Stress
The allowable bending stress in a member subjected to bending is
calculated based on the following formula: (Clause: 6.2.1)
bt or bc = 0.66 fy
where,
bt = Bending stress in tension
bc = Bending stress in compression
fy = Yield stress of steel, in MPa
For an I-beam or channel with equal flanges bent about the axis of
maximum strength (z-z axis), the maximum bending compressive
stress on the extreme fibre calculated on the effective section shall
not exceed the values of maximum permissible bending compressive
stress. The maximum permissible bending compressive stress shall be
obtained by the following formula: (Clause: 6.2.2)
6.2.3) :(Clause
])f y(n
)f cb(n
[
1/n
f yf cb0.66σbc
where,
fy = Yield stress of steel, in Mpa
n = A factor assumed as 1.4.
fcb = Elastic critical stress in bending, calculated by the
following formula:
f k X k Yc
c [ ]
Section 9B
9-53
where,
X YIT
r DMP
yr 1
1
20 1 Y =
26.5x10
( / )
k1 = a coefficient to allow for reduction in thickness or
breadth of flanges between points of effective lateral
restraint and depends on , the ratio of the total area of
both flanges at the point of least bending moment to the
corresponding area at the point of greatest bending
moment between such points of restraint.
k2 = a coefficient to allow for the inequality of flanges, and
depends on , the ratio of the moment of inertia of the
compression flange alone to that of the sum of the moment
of the flanges each calculated about its own axis parallel to
the y-yaxis of the girder, at the point of maximum bending
moment.
1 = effective length of compression flange
ry = radius of gyration of the section about its axis of
minimum strength (y-y axis)
T = mean thickness of the compression flange, is equal to the
area of horizontal portion of flange divided by width.
D = overall depth of beam
c1 ,c2 = respectively the lesser and greater distances from the
section neutral axis to the extreme fibres.
9B.3.3 Shear Stress
Allowable shear stress calculations are based on Section 6.4 of IS:800 .
For shear on the web, the gross section taken into consideration consist
of the product of the total depth and the web thickness. For shear
parallel to the flanges, the gross section is taken as 2/3 times the total
flange area.
Steel Design Per IS800
Section 9B
9-54
9B.3.4 Combined Stress
Members subjected to both axial and bending stresses are
proportioned accordingly to section 7 of IS:800. All members
subject to bending and axial compression are required to satisfy
the equation of Section 7.1.1.(a) for intermediate points, and
equation of Section 7.1.1.(b) for support points.
For combined axial tension and bending the equation of Section
7.1.2. is required to be satisfied.
Cm coefficients are calculated according to the specifications of
Section 7.1.3. information regarding occurrence of sidesway can
be provided through the use of parameters SSY and SSZ. In the
absence of any user provided information, sidesway will be
assumed.
9B.4 Design Parameters
In STAAD implementation of IS:800, the user is allowed complete
control of the design process through the use of design parameters.
Available design parameters to be used in conjunction with IS:800
are listed in Table 7B.1 of this section along with their default
values and applicable restrictions. Users should note that when the
TRACK parameter is set to 1.0 and use in conjunction with this
code, allowable bending stresses in compression (FCY & FCZ),
tension (FTY & FTZ), and allowable shear stress (FV) will be
printed out in Member Selection and Code Check output in Mpa.
When TRACK is set to 2.0, detailed design output will be
provided.
9B.5 Stability Requirements
Slenderness ratios are calculated for all members and checked
against the appropriate maximum values. Section 3.7 of IS:800
Section 9B
9-55
summarizes the maximum slenderness ratios for different types of
members. In STAAD implementation of IS:800, appropriate
maximum slenderness ratio can be provided for each member. If
no maximum slenderness ratio is provided, compression members
will be checked against a maximum value of 180 and tension
members will be checked against a maximum value of 400.
9B.6 Truss Members
As mentioned earlier, a truss member is capable of carrying only
axial forces. So in design no time is wasted in calculating bending
or shear stresses, thus reducing design time considerably.
Therefore, if there is any truss member in an analysis (like bracing
or strut, etc.), it is wise to declare it as a truss member rather than
as a regular frame member with both ends pinned.
9B.7 Deflection Check
This facility allows the user to consider deflection as a criteria in
the CODE CHECK and MEMBER SELECTION processes. The
deflection check may be controlled using three parameters which
are described in Table 7B.1. Note that deflection is used in
addition to other strength and stabil ity related criteria. The local
deflection calculation is based on the latest analysis results.
9B.8 Code Checking
The purpose of code checking is to verify whether the specified
section is capable of satisfying applicable design code
requirements. The code checking is based on the IS:800 (1984)
requirements. Forces and moments at specified sections of the
members are utilized for the code checking calculations. Sections
may be specified using the BEAM parameter or the SECTION
command. If no sections are specified, the code checking is based
on forces and moments at the member ends.
Steel Design Per IS800
Section 9B
9-56
The code checking output labels the members as PASSed or
FAILed. In addition, the critical condition (applicable IS:800
clause no.), governing load case, location (distance from the start)
and magnitudes of the governing forces and moments are also
printed out.
9B.9 Member Selection
STAAD is capable of performing design operations on specified
members. Once an analysis has been performed, the program can
select the most economical section, that is, the lightest section,
which satisfies the applicable code requirements. The section
selected will be of the same type (I-Section, Channel etc.) as
originally specified by the user. Member selection may be
performed with all types of steel sections listed in Section 7B.13
and user provided tables. Selection of members, whose properties
are originally provided from user specified table, will be limited to
sections in the user provided table. Member selection can not be
performed on members whose cross sectional properties are
specified as PRISMATIC.
The process of MEMBER SELECTION may be controlled using
the parameters listed in Table 8B.1. It may be noted that the
parameters DMAX and DMIN may be used to specify member
depth constraints for selection. If PROFILE parameter is provided,
the search for the lightest section is restricted to that profile. Up to
three (3) profiles may be provided for any member with a section
being selected from each one.
9B.10 Member Selection By Optimization
Steel section selection of the entire structure may be optimized.
The optimization method utilizes a state-of-the -art numerical
technique which requires automatic multiple analysis. The user
may start without a specifically designated section. However, the
section profile type (BEAM, COLUMN, CHANNEL, ANGLE etc.)
must be specified using the ASSIGN command (see Chapter 6).
Section 9B
9-57
The optimization is based on member stiffness contributions and
corresponding force distributions. An optimum member size is
determined through successive analysis/design iterations. This
method requires substantial computer time and hence should be
used with caution.
9B.11 Tabulated Results of Steel Design
For code checking or member selection, the program produces the
result in a tabulated fashion. The items in the output table are
explained as follows:
a) MEMBER refers to the member number for which the design
is performed
b) TABLE refers to the INDIAN steel section name which has
been checked against the steel code or has been selected.
c) RESULT prints whether the member has PASSED or FAILed.
If the RESULT is FAIL, there will be an asterisk (*) mark in
front of the member number.
d) CRITICAL COND refers to the section of the IS:800 code
which governs the design.
e) RATIO prints the ratio of the actual stresses to allowable
stresses for the critical condition. Normally a value of 1.0 or
less will mean the member has passed.
f) LOADING provides the load case number which governs the
design.
g) FX, MY and MZ provide the axial force, moment in local y-
axis and moment in local z-axis respectively. Although
STAAD does consider all the member forces and moments
(except torsion) to perform design, only FX,MY and MZ are
printed since they are the ones which are of interest , in most
cases.
Steel Design Per IS800
Section 9B
9-58
h) LOCATION specifies the actual distance from the start of the
member to the section where design forces govern.
i) If the parameter TRACK is set to 1.0, the program will block
out part of the table and will print allowable bending stresses
in compression (FCY & FCZ) and tension (FTY & FTZ),
allowable axial stress in compression (FA), and allowable
shear stress (FV). When the parameter TRACK is set to 2.0
for all members parameter code values are as shown in Fig
8B.1.
STAAD.Pro CODE CHECKING - (ISA ) ***********************
|---------------------------------------------------------------------------|
| Y PROPERTIES |
|************* | IN CM UNIT |
| * |=============================| ===|=== ------------ |
|MEMBER 7 * | | | AX = 72.4 |
| * | ST ISLB400 | | --Z AY = 32.0 |
|DESIGN CODE * | | | AZ = 27.5 |
| IS-800 * =============================== ===|=== SY = 86.8 |
| * SZ = 965.3 |
| * |<---LENGTH (ME= 3.00 --->| RY = 3.1 |
|************* RZ = 16.3 |
| |
| 104.6( KN-METR) |
|PARAMETER |L1 STRESSES |
|IN NEWT MM | IN NEWT MM|
|--------------- + -------------|
| KL/R-Y= 95.4 | FA = 84.8 |
| KL/R-Z= 18.4 + fa = 1.6 |
| UNL = 3000.0 | FCZ = 116.6 |
| C = 400.0 + FTZ = 165.0 |
| CMY = 0.85 | FCY = 165.0 |
| CMZ = 0.85 + FTY = 165.0 |
| FYLD = 249.9 | L3 fbz = 108.4 |
| NSF = 0.9 +---+---+---+---+---+---+---+---+---+---| fby = 0.0 |
| DFF = 325.0 92.7 FV = 100.0 |
| dff = 4383.0 ABSOLUTE MZ ENVELOPE |
| (WITH LOAD NO.) |
| |
| MAX FORCE/ MOMENT SUMMARY ( KN-METR) |
| ------------------------- |
| |
| AXIAL SHEAR-Y SHEAR-Z MOMENT-Y MOMENT-Z |
| |
| VALUE -23.7 61.3 0.0 0.0 104.6 |
| LOCATION 0.0 0.0 0.0 0.0 0.0 |
| LOADING 3 1 0 0 1 |
| |
|***************************************************************************|
|* *|
|* DESIGN SUMMARY ( KN-METR) *|
|* -------------- *|
|* *|
|* RESULT/ CRITICAL COND/ RATIO/ LOADING/ *|
| FX MY MZ LOCATION |
| ====================================================== |
| PASS IS-7.1.2 0.667 1 |
| 9.62 T 0.0 -104.6 0.00 |
| |
| DEFLECTION * PASS |
| RATIO: 0.074 LOADING: 3 LOCATION: 0.67 |
|* *|
|***************************************************************************|
Section 9B
9-59
9B.12 Indian Steel Table
This is an important feature of the program since the program will
read section properties of a steel member directly from the latest
ISI steel tables (as published in ISI-800). These properties are
stored in memory corresponding to the section designation (e.g.
ISMB250, etc.). If called for, the properties are also used for
member design. Since the shear areas are built in to these tables,
shear deformation is always considered for these members.
Almost all ISI steel tables are available for input. A complete
listing of the sections available in the built -in steel section library
may be obtained using the tools of the graphical user interface.
Following are the descriptions of all the types of sections
available:
Rolled Steel Beams (ISJB, ISLB, ISMB and ISHB).
All rolled steel beam sections are available the way they are
designated in the ISI handbook., e.g. ISJB225, ISWB400, etc.
20 TO 30 TA ST ISLB325
NOTE:
In case of two identical beams, the heavier beam is designated
with an „A” on the end., e.g. ISHB400 A, etc.
1 TO 5 TA ST ISHB400A
Steel Design Per IS800
Section 9B
9-60
Rolled Steel Channels (ISJC, ISLC and ISMC)
All these shapes are available as listed in ISI section handbook.
Designation of the channels are per the scheme used by ISI.
10 TO 20 BY 2 TA ST ISMC125
12 TA ST ISLC300
Double Channels
Back to back double channels, with or without spacing between
them, are available. The letter D in front of the section name will
specify a double channel, e.g. D ISJC125, D ISMC75 etc.
21 22 24 TA D ISLC225
Rolled Steel Angles
Both rolled steel equal angles and unequal angles are available for
use in the STAAD implementation of ISI steel tables. The
following example with explanations will be helpful in
understanding the input procedure:
ISA 150 X 75 X 8 Angle symbol Thickness in mm Long leg length in mm Short leg length in mm
At present there is no standard way to define the local y and z axes
for an angle section. The standard section has local axis system as
illustrated in Fig.2.4 of this manual. The standard angle is
specified as:
51 52 53 TA ST ISA60X60X6
Section 9B
9-61
This specification has the local z-axis ( i.e., the minor axis
corresponding to the V-V axis specified in the steel tables. Many
engineers are familiar with a convention used by some other
programs in which the local y-axis is the minor axis. STAAD
provides for this convention by accepting the command:
54 55 56 TA RA ISA50X30X6 (RA denotes reverse angle)
Double Angles
Short leg back to back or long leg back to back double angles can
be specified by inputting the word SD or LD, respectively, in front
of the angle size. In case of an equal angle either LD or SD will
serve the purpose. For example,
14 TO 20 TA LD ISA50X30X5 SP 1.5
23 27 TA SD ISA75X50X6
Rolled Tees (ISHT, ISST, ISLT and ISJT)
All the rolled tee sections are available for input as they are
specified in the ISI handbook. Following example illustrates the
designated method.
1 2 5 8 TA ST ISNT100
67 68 TA ST ISST250
Pipes (Circular Hollow Sections)
To designate circular hollow sections from ISI tables, use PIP
followed by the numerical value of diameter and thickness of the
section in mm omitting the decimal section of the value provided
for diameter. Following example will illustrate the designation.
Steel Design Per IS800
Section 9B
9-62
10 15 TA ST PIP 213.2
(Specifies a 213 mm dia. pipe with 3.2 mm wall thickness)
Circular pipe sections can also be specified by providing the
outside and inside diameters of the section. For example,
1 TO 9 TA ST PIPE OD 25.0ID 20.0
(specifies a pipe with outside dia. of 25 and inside dia. of 20
in current length units)
Only code checking and no member selection will be performed if
this type of specification is used.
Tubes (Rectangular or Square Hollow Sections)
Designation of tubes from the ISI steel table is illustrated below. TUB 400 200 12.5 Tube Symbol Thickness in mm Height in mm Width in mm Example:
15 TO 25 TA ST TUB 160808
Tubes, like pipes, can also be input by their dimensions (Height,
Width and Thickness) and not by any table designations.
6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 is a tube that has a height
of 8, a width of 6, and a wall thickness of 0.5.
Section 9B
9-63
Note that only code checking and no member selection is
performed for TUBE sections specified this way.
Plate And Angle Girders (With Flange Plates)
All plate and angle grinders (with flange plates) are available as
listed in ISI section handbook. The following example with
explanations will be helpful in understanding the input procedure.
I 1000 12 A 400 12
A F
B E
C D
A Plate and angle girder symbol.
B Web plate width in mm.
C Web plate thickness in mm.
D Flange angle (Flange angle key below):
E Flange plate width in mm.
F Flange plate thickness in mm.
SYMBOL ANGLE(A X B X t)(all in mm)
A 150X150X18
B 200X100X15
C 200X150X18
E 200X200X18
Steel Design Per IS800
Section 9B
9-64
SINGLE JOIST WITH CHANNELS AND PLATES ON THE
FLANGES TO BE USED AS GIRDERS
All single joist with channel and plates on the flanges to be used
as girders are available as listed in ISI section handbook. The
following example with explanations will be helpful in
understanding the input procedure.
IW 450 350 X 10 20
A E
B D
C
A Joist Designation: IW450=ISWB450
B Top flange channel designation:
350=ISMC350
C Constant (always X).
D Top flange plate thickness in mm.
NOTE: D is 0 for no plate.
E Bottom flange plate thickness in mm.
NOTE:
The heavier ISWB600 has been omitted, since the lighter
ISWB600 is more efficient.
Section 9B
9-65
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way STAAD
works for all codes.
Table 9B.1 Indian Steel Design - IS : 800 Parameters
Parameter
Name
Default Value Description
KY 1.0 K value in local y-axis. Usually, this is minor axis.
KZ 1.0 K value in local z-axis. Usually, this is major axis.
LY Member Length Length in local y-axis to calculate slenderness ratio.
LZ Member Length Same as above except in local z-axis (major).
FYLD 250 MPA
(36.25 KSI) Yield strength of steel.
NSF 1.0 Net section factor for tension members.
UNL Member Length Unsupported length for calculating allowable bending stress.
UNF 1.0 Same as above provided as a fraction of actual member length.
SSY 0.0 0.0 = Sidesway in local y-axis. 1.0 = No sidesway
SSZ 0.0 Same as above except in local z-axis.
CMY
CMZ
0.85 for sidesway and
calculated for no sidesway
Cm value in local y & z axes
MAIN 180 (Comp. Memb.)
Allowable Kl/r for slenderness calculations for compression members.
TMAIN 400 (Tension Memb)
Allowable Kl/r for slenderness calculations for tension members.
TRACK 0.0
0.0 = Suppress critical member stresses 1.0 = Print all critical member stresses 2.0 = Print expanded output. If there is
deflection check it will also print the governing load case number for deflection check whenever critical condition for design is not DEFLECTION. (see fig.8B.1)
Steel Design Per IS800
Section 9B
9-66
Table 9B.1 Indian Steel Design - IS : 800 Parameters
Parameter
Name
Default Value Description
DMAX 100.0 cm. Maximum allowable depth.
DMIN 0.0 cm. Minimum allowable depth.
RATIO 1.0 Permissible ratio of the actual to allowable stresses.
BEAM 3.0
0.0 = design only for end moments and those at locations specified by the SECTION command.
1.0 = calculate section forces at twelfth points along the beam, design at each intermediate location and report the critical location where ratio is maximum.
PROFILE - Search for the lightest section for the profile mentioned.
DFF None
(Mandatory for deflection check)
"Deflection Length" / Maxm. allowable local deflection
DJ1 Start Joint of member
Joint No. denoting starting point for calculation of "Deflection Length" (See Note 1)
DJ2 End Joint of member
Joint No. denoting end point for calculation of "Deflection Length" (See Note 1)
NOTES:
1) "Deflection Length" is defined as the length that is used for
calculation of local deflections within a member. It may be
noted that for most cases the "Deflection Length" will be equal
to the length of the member. However, in some situations, the
"Deflection Length" may be different. For example, refer to
the figure below where a beam has been modeled using four
joints and three members. Note that the "Deflection Length"
for all three members will be equal to the total length of the
beam in this case. The parameters DJ1 and DJ2 should be used
to model this situation. Also the straight line joining DJ1 and
DJ2 is used as the reference line from which local deflections
are measured. Thus, for all three members here, DJ1 should be
"1" and DJ2 should be "4".
Section 9B
9-67
D = Maximum local deflection for members1 2 and 3.
D
1
2 3
4
1
2 3
EXAMPLE : PARAMETERS
DFF 300. ALL
DJ1 1 ALL
DJ2 4 ALL
2) If DJ1 and DJ2 are not used, "Deflection Length" will default
to the member length and local deflections will be measured
from original member line.
3) The above parameters may be used in conjunction with other
available parameters for steel design.
9B.13 Column With Lacings And Battens
For columns with large loads it is desirable to build rolled sections
at a distance and inter-connect them. The joining of element
sections is done by two ways:
a) Lacing and b) Batten
Double channel sections (back-to-back and face-to-face) can be
joined either by lacing or by batten plates having rivetted or
welded connection.
Table 8B.2 gives the parameters that are required for Lacing or
batten design. These parameters will have to be provided in unit
NEW MMS along with parameters defined in Table 9B.1.
Steel Design Per IS800
Section 9B
9-68
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
Table 9B.2 Indian Concrete Design IS800 Parameters
Parameter
Name
Default Value Description
CTYPE 1 Type of joining
CTYPE = 1 implies single lacing with rivetted connection
CTYPE = 2 implies double lacing with rivetted connection
CTYPE = 3 implies single lacing with welded connection
CTYPE = 4 implies double lacing with welded connection
CTYPE = 5 implies batten with rivetted connection
CTYPE = 6 implies batten with welded connection
THETA 50 degree Angle of inclination of lacing bars. It should lie between 40 degree and 70 degree.
DBL 20 mm Nominal diameter of rivet
FVB 100 N/mm2 Allowable shear stress in rivet
FYB 300 N/mm2 Allowable bearing stress in rivet
WMIN 6 mm Minimum thickness of weld
WSTR 108 N/mm2 Allowable welding stress
EDIST 32 mm (Rivetted Connection)
25 mm (Welded Connection)
Edge Distance
Section 9B
9-69
Table 9B.2 Indian Concrete Design IS800 Parameters
Parameter
Name
Default Value Description
DCFR 0.0 0.0 implies double channel back-to-back.
1.0 Implies double channel face-to-face.
This parameter is used when member properties are defined through user provided table using GENERAL option.
COG 0.0 mm Centre of gravity of the channel. This parameter is used when member properties are defined through user provided table using GENERAL option.
SPA 0.0 mm Spacing between double channels. This parameter is used when member properties are defined through user provided table using GENERAL option.
Steel Design Per IS800
Section 9B
9-70
9-71
Steel Design Per IS802
9C.1 General Comments
This section presents some general statements regarding the
implementation of Indian Standard code of practice (IS:802-1995 –
Part 1) for structural steel design for overhead transmission line
towers in STAAD. The design philosophy and procedural logistics
for member selection and code checking are based upon the
principles of allowable stress design. Two major failure modes are
recognized: failure by overstressing, and failure by stability
considerations. The flowing sections describe the salient features
of the allowable stresses being calculated and the stability criteria
being used. Members are proportioned to resist the design loads
without exceeding the allowable stresses and the most economic
section is selected on the basis of least weight criteria. The code
checking part of the program checks stability and strength
requirements and reports the critical loading condition and the
governing code criteria.
9C.2 Allowable Stresses
The member design and code checking in STAAD are based upon
the allowable stress design method as per IS:802 (1995). It is a
method for proportioning structural members using design loads
and forces, allowable stresses, and design limitations for the
appropriate material under service conditions.
This section discusses the salient features of the allowable stresses
specified by IS:802 and implemented in STAAD.
Section 9C
Steel Design Per IS802
Section 9C
9-72
9C.2..1 Axial Stress
Tensile Stress
The allowable tensile stress, as calculated in STAAD as per IS:802
is described below.
The estimated tensile stresses on the net effective sectional area in
various members, multiplied by the appropriate factor of safety
shall not exceed minimum guaranteed yield stress of the material.
Thus, the permissible stress in axial tension, at in MPa on the net
effective area of the sections shall not exceed
at = fy
where,
fy = minimum yield stress of steel in Mpa
Compressive Stress
The estimated compressive stresses in various members multiplied
by the appropriate factor of safety shall not exceed the value given
by the formulae described below.
Condition 1: If
yFt
b
t
b 210
lim
CCr/KL
Stress Fa= yFCc
r/KL
2
11
2
N/mm2
CCr/KL
Section 9C
9-73
Stress Fa = 2
2
/ rKL
E N/mm2
Condition 2: If
lim
t
b
t
b
yF
378 when Fy is the N/mm2
formulae given in condition 1 shall be used substituting for Fy the
value Fcr given by:
Fcr = y
lim
F
t
b
t
b677.0
677.1
Condition 3:
t
b>
yF
378when Fy is the N/mm2 formulae given in
condition 1 shall be used substituting for Fy the value Fcr given by
Fcr = 2
t
b
65550
In which CC =
yF
E2
where,
Fa = allowable unit stress in compression, Mpa
Fy = minimum guaranteed yield stress of the material, Mpa
K = restraint factor,
L = unbraced length of the compression member in cm, and
R = appropriate radius of gyration in cm.
E = modulus of elasticity of steel in N/mm2
Steel Design Per IS802
Section 9C
9-74
r
KL = largest effective slenderness ratio of any unbraced segment
of the member,
b = distance from edge of the fillet to the extreme fibre in mm, and
t = thickness of flange in mm.
Note : The maximum permissible value of b/t for any type of steel
shall not exceed 25.
9C.3 Stability Requirements
Slenderness ratios are calculated for all members and checked
against the appropriate maximum values. Following are the default
values used in STAAD:
Compression Members:
Members Slenderness
value
Leg Members, ground wire peak member and lower
members of cross arms in compression 120
Other members carrying computed stress 200
Redundant members and those carrying nominal
stresses 250
Section 9C
9-75
Slenderness ratios of compression members are determined as
follows:
If ELA number given in the input for any particular member is
such that condition for L/r ratio to fall within the specified range
is not satisfied, STAAD goes on by the usual way of finding
slenderness ratio using K*L/r formula.
ELA NO.
Type of members
Value of KL/r
1 Leg sections or joint members bolted
at connections in both faces
L/r
2 Members with concentric loading at
both ends of the unsupported panel
with values of L/r up to and
including 120
L/r
3 Member with concentric loading at
one end and normal eccentricities at
the other end of the unsupported
panel for value of L/r up to and
including 120
30 + 0.75L/r
4 Members with normal framing
eccentricities at both ends of the
unsupported panel for values of L/r
up to and including 120
60 + 0.5L/r
5 Member unrestrained against
rotation at both ends of the
unsupported panel for value of L/r
from 120 to 200
L/r
6 Members partially restrained against
rotation at one end of the
unsupported panel for values of L/r
over 120 and up to and including 225
28.6 + 0.762L/r
7 Members partially restrained against
rotation at both ends of the
unsupported panel for values of L/r
over 120 and up to and including 250
46.2 + 0.615L/r
Steel Design Per IS802
Section 9C
9-76
Tension Members:
Slenderness ratio KL/r of a member carrying axial tension only,
shall not exceed 400.
9C.4 Minimum Thickness Requirement
As per Clause7.1 of IS: 802-1995 minimum thickness of different
tower members shall be as follows:
Members Minimum Thickness, mm
Galvanized Painted
Leg Members, ground wire peak
member and lower members of
cross arms in compression
5 6
Other members
4 5
9C.5 Code Checking
The purpose of code checking is to verify whether the specified
section is capable of satisfying applicable design code
requirements. The code checking is based on the IS:802 (1995)
requirements. Axial forces at two ends of the members are utilized
for the code checking calculations.
The code checking output labels the members as PASSed or
FAILed. In addition, the critical condition, governing load case,
location (distance from the start) and magnitudes of the governing
forces are also printed out. Using TRACK 9 option calculation
steps are also printed.
Section 9C
9-77
9C.5.1 Design Steps
The following are the steps followed in member design.
Step 1
Thickness of the member (maximum of web and flange
thicknesses) is checked against minimum allowable thickness,
depending upon whether the member is painted or galvanised.
Step 2
If the minimum thickness criterion is fulfilled, the program
determines whether the member is under compression or tension
for the loadcase under consideration. Depending upon whether the
member is under tension or compression the slenderness ratio of
the member is calculated. This calculated ratio is checked against
allowable slenderness ratio.
Step 3
If the slenderness criterion is fulfilled check against allowable
stress is performed. Allowable axial and tensile stresses are
calculated. If the member is under tension and there is no user
defined net section factor (NSF), the net section factor is
calculated by the program itself (Refer Section 8C.10). Actual
axial stress in the member is calculated. The ratio for actual stress
to allowable stress, if less than 1.0 or user defined value, the
member has passed the check.
Step 4
Number of bolts required for the critical loadcase is calculated.
Steel Design Per IS802
Section 9C
9-78
9C.6 Member Selection
STAAD is capable of performing design operations on specified
members. Once an analysis has been performed, the program can
select the most economical section, that is, the lightest section,
which satisfies the applicable code requirements. The section
selected will be of the same type (either angle or channel) as
originally specified by the user. Member selection may be
performed with all angle or channel sections and user provided
tables. Selection of members, whose properties are originally
provided from user specified table, will be limited to sections in
the user provided table.
The process of MEMBER SELECTION may be controlled using
the parameters listed in Table 8B.1. It may be noted that the
parameters DMAX and DMIN may be used to specify member
depth constraints for selection. If PROFILE parameter is provided,
the search for the lightest section is restricted to that profile. Up to
three (3) profiles may be provided for any member with a section
being selected from each one.
9C.7 Member Selection by Optimization
Steel section selection of the entire structure may be optimized .
The optimization method utilizes a state-of-the -art numerical
technique which requires automatic multiple analysis. The
optimization is based on member stiffness contributions and
corresponding force distributions.
An optimum member size is determined through successive
analysis/design iterations. This method requires substantial
computer time and hence should be used with caution.
Section 9C
9-79
9C.8 Tabulated Results of Steel Design
DETAILS OF CALCULATION
----------------------
CHECK FOR MINIMUM THICKNESS
---------------------------
TYPE : GALVANISED
MIN. ALLOWABLE THICKNESS : 5.0 MM
ACTUAL THICKNESS : 10.0 MM
RESULT : PASS
Steel Design Per IS802
Section 9C
9-80
CHECK FOR SLENDERNESS RATIO
---------------------------
VALUE OF L/r : 90.16
EQN. USED TO FIND KL/r : 60.0 + 0.5*L/r
ACTUAL VALUE OF KL/r : 105.08
ALLOWABLE KL/r : 120.00
RESULT : PASS
CALCULATION OF ALLOWABLE STRESS
--------------------------------
CRITICAL CONDITION : COMPRESSION
Cc : sqrt(2*3.141592*3.141592*E/fy) : 127.22
b : LENGTH OF LEG - WEB THICKNESS - ROOT RADIUS
: 150.0 - 10.0 - 11.0 : 129.0 MM
(b/t)lim : 210/sqrt(fy) : 13.28
(b/t)cal : 12.90
(b/t)cal <= (b/t)lim AND KL/r <= Cc
ALLOWABLE AXIAL COMP. STRESS : (1 -0.5*(KL/r/Cc)*(KL/r/Cc))*fy :
164.72 MPA
CHECK AGAINST PERMISSIBLE STRESS
--------------------------------
DESIGN AXIAL FORCE : 250000.00 N
ACTUAL AXIAL COMP. STRESS : 250000.00 / 2552.0 : 97.96 MPA
RESULT : PASS
BOLTING
-------
BOLT DIA : 16 MM
SHEARING CAP : 20.11 KN
BEARING CAP : 38.40 KN
BOLT CAP : 20.11 KN
NO. OF BOLTS REQD. : 13
Section 9C
9-81
9C.9 Parameter Table for IS 802
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
Table 9C.1 Indian Steel Design - IS 802 Parameters
Parameter
Name
Default Value Description
KY 1.0 K value in local y-axis. Usually, this is minor axis.
KZ 1.0 K value in local z-axis. Usually, this is major axis.
LY Member Length Unbraced length in local z-axis to calculate slenderness ratio.
LZ Member Length Unbraced length in local z-axis to calculate slenderness ratio.
FYLD 250 MPA Yield Strength of steel
MAIN 1.0 Type of member to find allowable Kl/r for slenderness calculations for members.
1.0 = Leg, Ground wire peak and lower members of cross arms in compression (KL/r = 120)
2.0 = Members carrying computed stress (KL/r = 200)
3.0 = Redundant members and members carrying nominal stresses (KL/r = 250)
4.0 = Tension members (KL/r = 400)
10.0 = Do not perform KL/r check
Any value greater than 10.0 indicates user defined allowable KL/r ratio. For this case KY and KZ values are must to find actual KL/r ratio of the member.
DMAX 100.0 cm. Maximum allowable depth.
DMIN 0.0 cm. Minimum allowable depth.
Steel Design Per IS802
Section 9C
9-82
Table 9C.1 Indian Steel Design - IS 802 Parameters
Parameter
Name
Default Value Description
TRACK 0.0 0.0 = Suppress critical member stresses
1.0 = Print all critical member stresses
2.0 = Print expanded output.
9.0 = Print design calculations along with expanded output.
LEG 1.0 This parameter is meant for plain angles.
0.0 = indicates the angle is connected by shorter leg
1.0 = indicates the angle is connected by longer leg
ELA 1.0 This parameter indicates what type of end conditions is to be used. Refer Section 8C.3.
NSF 1.0 Net section factor for tension members
CNSF 0.0 This parameter indicates whether user has defined NSF or the program will calculate it.
0.0 = User has defined NSF
1.0 = Program has to calculate it
DANGLE 0.0 This parameter indicates how the pair of angles are connected to each other. This is required to find whether the angle is in single or double shear and the net section factor.
0.0 = Double angle placed back to back and connected to each side of a gusset plate
1.0 = Pair of angle placed back-to-back connected by only one leg of each angle to the same side of a gusset plate�
DBL 12 mm Diameter of bolt for calculation of number of bolts and net section factor.
FVB 218 MPA Allowable shear stress in bolt
FYB 436 MPA Allowable bearing stress in bolt
Section 9C
9-83
Table 9C.1 Indian Steel Design - IS 802 Parameters
Parameter
Name
Default Value Description
GUSSET 5 mm Thickness of gusset plate.
Minimum of the thicknesses of the gusset plate and the leg is used for calculation of the capacity of bolt in bearing
NHL 0.0 mm Deduction for holes.
Default value is one bolt width plus 1.5 mm. If the area of holes cut by any straight, diagonal or zigzag line across the member is different from the default value, this parameter is to be defined.
9C.10 Calculation of Net Section Factor
The procedure for calculating net section factor for angle section is
described below.
Single angle connected by only one leg
Anet = A1 + A2 x K1
Where, A1 = net cross-sectional area of the connected leg
A2 = gross cross-sectional area of the unconnected leg
And K1 = A2 A13
A13
x
x
The area of a leg of an angle = Thickness of angle x (length of leg
– 0.5x thickness of leg)
Steel Design Per IS802
Section 9C
9-84
Pair of angles placed back-to-back connected by only one leg of
each angle to the same side of a gusset plate
Anet = A1 + A2 x K1
Where A1 = net cross-sectional area of the connected leg
A2 = gross cross-sectional area of the unconnected leg
And K1 = A2 A15
A15
x
x
The area of a leg of an angle = Thickness of angle x (length of leg
– 0.5x thickness of leg)
Double angles placed back to back and connected to each side
of a gusset plate
Anet = gross area – deduction for holes
Net Section Factor
For angle section it is the ratio of the net effective area, Anet to the
gross area.
For channel section net section factor is taken to be 1.0.
Section 9C
9-85
9C.11 Example Problem No. 28
A transmission line tower is subjected to different loading
conditions. Design some members as per IS-802 and show detailed
calculation steps for the critical loading condition.
Given: End Condition = Members with normal framing
eccentricities at both ends of the unsupported panel for
values of L/r up to and including 120
Diameter of the bolt = 16 mm
Thickness of the gusset plate = 8 mm
Net Section Factor is to be calculated.
Steel Design Per IS802
Section 9C
9-86
STAAD TRUSS
INPUT WIDTH 79
UNIT METER KN
JOINT COORDINATES
1 3 0 3; 2 1.2 27 1.2; 3 2.8 3 2.8; 4 2.6 6 2.6; 5 2.4 9 2.4; 6 2.2 12 2.2;
7 2 15 2; 8 1.8 18 1.8; 9 1.6 21 1.6; 10 1.4 24 1.4; 11 -3 0 3; 12 -1.2 27 1.2;
13 -2.8 3 2.8; 14 -2.6 6 2.6; 15 -2.4 9 2.4; 16 -2.2 12 2.2; 17 -2 15 2;
18 -1.8 18 1.8; 19 -1.6 21 1.6; 20 -1.4 24 1.4; 21 3 0 -3; 22 1.2 27 -1.2;
23 2.8 3 -2.8; 24 2.6 6 -2.6; 25 2.4 9 -2.4; 26 2.2 12 -2.2; 27 2 15 -2;
28 1.8 18 -1.8; 29 1.6 21 -1.6; 30 1.4 24 -1.4; 31 -3 0 -3; 32 -1.2 27 -1.2;
33 -2.8 3 -2.8; 34 -2.6 6 -2.6; 35 -2.4 9 -2.4; 36 -2.2 12 -2.2; 37 -2 15 -2;
38 -1.8 18 -1.8; 39 -1.6 21 -1.6; 40 -1.4 24 -1.4; 41 1.2 30 1.2;
42 -1.2 30 1.2; 43 1.2 30 -1.2; 44 -1.2 30 -1.2; 45 4.2 27 1.2; 46 7.2 27 1.2;
47 4.2 30 1.2; 48 4.2 27 -1.2; 49 7.2 27 -1.2; 50 4.2 30 -1.2; 51 -4.2 27 1.2;
52 -7.2 27 1.2; 53 -4.2 30 1.2; 54 -4.2 27 -1.2; 55 -7.2 27 -1.2;
56 -4.2 30 -1.2; 57 1.2 33 1.2; 58 -1.2 33 1.2; 59 1.2 33 -1.2;
60 -1.2 33 -1.2; 61 0 35 0;
MEMBER INCIDENCES
1 1 3; 2 3 4; 3 4 5; 4 5 6; 5 6 7; 6 7 8; 7 8 9; 8 9 10; 9 10 2; 10 11 13;
11 13 14; 12 14 15; 13 15 16; 14 16 17; 15 17 18; 16 18 19; 17 19 20; 18 20 12;
19 13 3; 20 14 4; 21 15 5; 22 16 6; 23 17 7; 24 18 8; 25 19 9; 26 20 10;
27 12 2; 28 11 3; 29 1 13; 30 13 4; 31 3 14; 32 14 5; 33 15 4; 34 15 6;
35 16 5; 36 16 7; 37 17 6; 38 17 8; 39 18 7; 40 18 9; 41 19 8; 42 19 10;
43 20 9; 44 20 2; 45 12 10; 46 21 23; 47 23 24; 48 24 25; 49 25 26; 50 26 27;
51 27 28; 52 28 29; 53 29 30; 54 30 22; 55 3 23; 56 4 24; 57 5 25; 58 6 26;
59 7 27; 60 8 28; 61 9 29; 62 10 30; 63 2 22; 64 1 23; 65 21 3; 66 3 24;
67 23 4; 68 4 25; 69 5 24; 70 5 26; 71 6 25; 72 6 27; 73 7 26; 74 7 28;
75 8 27; 76 8 29; 77 9 28; 78 9 30; 79 10 29; 80 10 22; 81 2 30; 82 31 33;
83 33 34; 84 34 35; 85 35 36; 86 36 37; 87 37 38; 88 38 39; 89 39 40; 90 40 32;
91 23 33; 92 24 34; 93 25 35; 94 26 36; 95 27 37; 96 28 38; 97 29 39; 98 30 40;
99 22 32; 100 21 33; 101 31 23; 102 23 34; 103 33 24; 104 24 35; 105 25 34;
106 25 36; 107 26 35; 108 26 37; 109 27 36; 110 27 38; 111 28 37; 112 28 39;
113 29 38; 114 29 40; 115 30 39; 116 30 32; 117 22 40; 118 33 13; 119 34 14;
120 35 15; 121 36 16; 122 37 17; 123 38 18; 124 39 19; 125 40 20; 126 32 12;
127 31 13; 128 11 33; 129 33 14; 130 13 34; 131 34 15; 132 35 14; 133 35 16;
134 36 15; 135 36 17; 136 37 16; 137 37 18; 138 38 17; 139 38 19; 140 39 18;
141 39 20; 142 40 19; 143 40 12; 144 32 20; 145 32 44; 146 12 42; 147 2 41;
148 22 43; 149 42 41; 150 41 43; 151 43 44; 152 44 42; 153 12 41; 154 42 2;
155 22 41; 156 43 2; 157 43 32; 158 44 22; 159 12 44; 160 32 42; 161 41 47;
162 47 45; 163 45 2; 164 47 46; 165 46 45; 166 41 45; 167 43 50; 168 50 48;
169 48 22; 170 50 49; 171 49 48; 172 43 48; 173 47 50; 174 46 49; 175 45 48;
176 41 50; 177 50 46; 178 43 47; 179 47 49; 180 22 50; 181 2 47; 182 22 45;
183 2 48; 184 47 48; 185 50 45; 186 45 49; 187 48 46; 188 42 53; 189 53 51;
190 51 12; 191 53 52; 192 52 51; 193 42 51; 194 44 56; 195 56 54; 196 54 32;
197 56 55; 198 55 54; 199 44 54; 200 53 56; 201 52 55; 202 51 54; 203 42 56;
204 56 52; 205 44 53; 206 53 55; 207 32 56; 208 12 53; 209 32 51; 210 12 54;
211 53 54; 212 56 51; 213 51 55; 214 54 52; 215 44 60; 216 42 58; 217 41 57;
218 43 59; 219 60 59; 220 59 57; 221 57 58; 222 58 60; 223 44 58; 224 42 60;
225 42 57; 226 41 58; 227 44 59; 228 43 60; 229 43 57; 230 41 59; 231 60 57;
232 59 58; 235 33 3; 236 13 23; 237 34 4; 238 14 24; 239 35 5; 240 15 25;
241 36 6; 242 16 26; 243 37 7; 244 17 27; 245 38 8; 246 18 28; 247 39 9;
248 19 29; 249 40 10; 250 20 30; 251 32 2; 252 22 12; 253 44 41; 254 43 42;
Section 9C
9-87
255 60 61; 256 58 61; 257 57 61; 258 59 61;
MEMBER PROPERTY INDIAN
1 TO 18 46 TO 54 82 TO 90 145 TO 148 215 TO 218 TA LD ISA200X150X18 SP 0.01
19 TO 26 28 TO 45 55 TO 62 64 TO 81 91 TO 98 100 TO 125 127 TO 144 155 156 -
159 160 223 224 229 230 235 TO 250 TA ST ISA150X150X10
27 63 99 126 149 TO 154 157 158 161 TO 214 219 TO 222 225 TO 228 231 232 251 -
252 TO 258 TA ST ISA80X50X6
CONSTANTS
E 2.05e+008 ALL
POISSON 0.3 ALL
DENSITY 76.8195 ALL
ALPHA 6.5e-006 ALL
SUPPORTS
1 11 21 31 FIXED
UNIT METER KG
LOAD 1 VERT
SELFWEIGHT Y -1
JOINT LOAD
61 FX 732
46 49 52 55 FX 153
61 FX 1280 FY -1016 FZ 160
46 49 52 55 FX 9006 FY -7844 FZ 1968
2 12 22 32 FX 4503 FY -3937 FZ 1968
LOAD 2 GWBC
SELFWEIGHT Y -1
JOINT LOAD
61 FX 549
46 49 52 55 FX 1148
61 FX 515 FY -762 FZ 2342
46 49 52 55 FX 6755 FY -5906
2 12 22 32 FX 3378 FY -2953
LOAD 3 LEFT PCBC
SELFWEIGHT Y -1
JOINT LOAD
61 FX 549
46 49 52 55 FX 1148
61 FX 960 FY -762
46 49 FX 6755 FY -5906
52 55 FX 4211 FY -4551 FZ 13293
2 12 22 32 FX 3378 FY -2953
LOAD 4 RIGHT PCBC
SELFWEIGHT Y -1
JOINT LOAD
61 FX 549
46 49 52 55 FX 1148
61 FX 960 FY -762
52 55 FX 6755 FY -5906
46 49 FX 4211 FY -4551 FZ 13293
2 12 22 32 FX 3378 FY -2953
PERFORM ANALYSIS
UNIT NEW MMS
PARAMETER
CODE IS802
Steel Design Per IS802
Section 9C
9-88
LY 2800 MEMB 28 LZ 2800 MEMB 28
MAIN 1.0 MEMB 1
ELA 4 MEMB 1
CNSF 1.0 MEMB 28
DBL 16 ALL
GUSSET 8 ALL
TRACK 9 ALL
CHECK CODE MEMB 1 28
FINISH
Output of design result
Section 9C
9-89
DETAILS OF CALCULATION ---------------------- CHECK FOR MINIMUM THICKNESS --------------------------- TYPE : PAINTED MIN. ALLOWABLE THICKNESS : 6.0 MM ACTUAL THICKNESS : 18.0 MM RESULT : PASS CHECK FOR SLENDERNESS RATIO --------------------------- VALUE OF L/r : 48.49 EQN. USED TO FIND KL/r : 60.0 + 0.5*L/r ACTUAL VALUE OF KL/r : 84.25 ALLOWABLE KL/r : 120.00 RESULT : PASS CALCULATION OF ALLOWABLE STRESS --------------------------------- CRITICAL CONDITION : COMPRESSION Cc : sqrt (2*3.141592*3.141592*E/fy) : 127.24 b : LENGTH OF LEG - WEB THICKNESS - ROOT RADIUS : 200.0 - 18.0 - 13.5 : 168.5 MM (b/t)lim : 210/sqrt(fy) : 13.28 (b/t)cal : 9.36 (b/t)cal <= (b/t)lim AND KL/r <= Cc ALLOWABLE AXIAL COMP. STRESS : (1- 0.5*(KL/r/Cc)*(KL/r/Cc))*fy :
195.15 MPA CHECK AGAINST PERMISSIBLE STRESS -------------------------------- LOAD NO. : 1 DESIGN AXIAL FORCE : 1742002.38 N ACTUAL AXIAL COMP. STRESS :1742002.38 / 11952.0 : 145.75 MPA RESULT : PASS
Steel Design Per IS802
Section 9C
9-90
BOLTING ------- BOLT DIA : 16 MM SHEARING CAP : 87.66 KN BEARING CAP : 55.81 KN BOLT CAP : 55.81 KN NO. OF BOLTS REQD. : 32
Section 9C
9-91
DETAILS OF CALCULATION ---------------------- CHECK FOR MINIMUM THICKNESS --------------------------- TYPE : PAINTED MIN. ALLOWABLE THICKNESS : 6.0 MM ACTUAL THICKNESS : 10.0 MM RESULT : PASS CHECK FOR SLENDERNESS RATIO --------------------------- VALUE OF L/r : 95.56 EQN. USED TO FIND KL/r : K*L/r ACTUAL VALUE OF KL/r : 95.56 ALLOWABLE KL/r : 400.00 RESULT : PASS CALCULATION OF ALLOWABLE STRESS --------------------------------- CRITICAL CONDITION : TENSION ALLOWABLE AXIAL TENSILE STRESS : 249.94 MPA CHECK AGAINST PERMISSIBLE STRESS -------------------------------- LOAD NO. : 3 DESIGN AXIAL FORCE : 112909.27 N ACTUAL AXIAL TENSILE STRESS : 112909.27 / ( 2903.0*0.801 ) : 48.53 MPA RESULT : PASS BOLTING ------- BOLT DIA : 16 MM SHEARING CAP : 43.83 KN BEARING CAP : 55.81 KN BOLT CAP : 43.83 KN NO. OF BOLTS REQD. : 3 ********** END OF TABULATED RESULT OF DESIGN ***********
Steel Design Per IS802
Section 9C
9-92
9-93
Design Per Indian Cold Formed
Steel Code
9D.1 General
Provisions of IS:801-1975, including revisions dated May, 1988,
have been implemented. The program allows design of single
(non-composite) members in tension, compression, bending, shear,
as well as their combinations. Cold work of forming strengthening
effects has been included as an option.
9D.2 Cross-Sectional Properties
The user specifies the geometry of the cross-section by selecting
one of the section shape designations from the Gross Section
Property Tables from IS:811-1987 (Specification for cold formed
light gauge structural steel sections).
The Tables are currently available for the following shapes:
Channel with Lips
Channel without Lips
Angle without Lips
Z with Lips
Hat
Shape selection may be done using the member property pages of
the graphical user interface (GUI) or by specifying the section
designation symbol in the input file.
Section 9D
Design Per Indian Cold Formed Steel Code
Section 9D
9-94
The properties listed in the tables are gross section properties.
STAAD.Pro uses unreduced section properties in the structure
analysis stage. Both unreduced and effective section properties are
used in the design stage, as applicable.
9D.3 Design Procedure
The following two design modes are available:
1. Code Checking
The program compares the resistance of members with the applied
load effects, in accordance with IS:801-1975. Code checking is
carried out for locations specified by the user via the SECTION
command or the BEAM parameter. The results are presented in a
form of a PASS/FAIL identifier and a RATIO of load effect to
resistance for each member checked. The user may choose the
degree of detail in the output data by setting the TRACK
parameter.
2. Member Selection
The user may request that the program search the cold formed steel
shapes database (IS standard sections) for alternative members that
pass the code check and meet the least weight criterion. In
addition, a minimum and/or maximum acceptable depth of the
member may be specified. The program will then evaluate all
database sections of the type initially specified (i.e., channel,
angle, etc.) and, if a suitable replacement is found, presents design
results for that section. If no section satisfying the depth
restrictions or lighter than the initial one can be found, the
program leaves the member unchanged, regardless of whether it
passes the code check or not.
The program calculates effective section properties in accordance
with Clause 5.2.1.1. Cross-sectional properties and overall
slenderness of members are checked for compliance with
Section 9D
9-95
Clause 6.6.3, Maximum Effective Slenderness Ratio for
members in Compression
Clause 5.2.3, Maximum Flat Width Ratios for Elements in
Compression
Clause 5.2.4, Maximum Section Depths.
The program will check member strength in accordance with
Clause 6 of the Standard as follows:
Members in tension
Resistance is calculated in accordance with Clauses 6.1
Members in bending and shear
Resistance calculations are based on Clauses:
a) 6.4.1 Shear stress in webs,
b) 6.4.2 Bending stress in webs
c) 6.4.3 Combined Bending and Shear in Webs.
Members in compression
Resistance calculations are based on Clauses:
a) 6.2 Compression on flat unstiffened element,
b) 6.6.1.1 Shapes not subject to torsional-flexural buckling,
c) 6.6.1.2 Singly-symmetric sections and nonsymmetrical
shapes of open cross section or intermittently fastened
singly-symmetrical components of built-up shapes having
Q = 1.0 which may be subject to torsional-flexural
buckling,
Design Per Indian Cold Formed Steel Code
Section 9D
9-96
d) 6.6.1.3 Singly-symmetric sections and nonsymmetrical
shapes or intermittently fastened singly-symmetrical
components of built-up shapes having Q < 1.0 which may
be subject to torsional-flexural buckling,
e) 6.8 Cylindrical Tubular Sections.
Members in compression and bending
Resistance calculations are based on Clauses:
a) All clauses for members in compression
&
b) 6.3 Laterally Unsupported Members,
c) 6.7.1 Doubly-symmetric shapes or Shapes not subjected
to torsional or torsional-flexural buckling
d) 6.7.2. Singly-symmetric shapes or Intermittently fastened
singly-symmetric components of built-up shapes having
Q=1.0 which may be subjected to torsional-flexural
buckling
e) 6.7.3. Singly-symmetric shapes or Intermittently fastened
singly-symmetric components of built-up shapes having
Q<1.0 which may be subjected to torsional-flexural
buckling.
Input for the coefficients of uniform bending must be provided by
the user.
Section 9D
9-97
The following table contains the input parameters for specifying
values of design variables and selection of design options. Note:
Once a parameter is specified, its value stays at that specified
number till it is specified again. This is the way STAAD works
for all codes.
COLD FORMED STEEL DESIGN PARAMETERS
Parameter
Name
Default
Value Description
BEAM 1.0 When this parameter is set to 1.0 (default), the adequacy of the member is determined by checking a total of 13 equally spaced locations along the length of the member. If the BEAM value is 0.0, the 13 location check is not conducted, and instead, checking is done only at the locations specified by the SECTION command (See STAAD manual for details. For TRUSS members only start and end locations are designed.
CMZ 1.0 Coefficient of equivalent uniform bending z. See IS:801-1975, 6.7. Used for Combined axial load and bending design. Values range from 0.4 to 1.0.
CMY 0.85 Coefficient of equivalent uniform bending y. See IS:801-1975, 6.7. Used for Combined axial load and bending design. Values range from 0.4 to 1.0.
CWY 0.85 Specifies whether the cold work of forming strengthening effect should be included in resistance computation. See IS:801-1975, 6.1.1
Values: 0 – effect should not be included
1 – effect should be included
FLX 1 Specifies whether torsional-flexural buckling restraint is provided or is not necessary for the member. See IS:801-1975, 6.6.1
Values:
0 – Section not subject to torsional flexural buckling 1 – Section subject to torsional flexural buckling
Design Per Indian Cold Formed Steel Code
Section 9D
9-98
COLD FORMED STEEL DESIGN PARAMETERS
Parameter
Name
Default
Value Description
FU 450 MPa (4588.72 kg/cm2)
Ultimate tensile strength of steel in current units.
FYLD 353.04 MPa
(3600.0 kg/cm2)
Yield strength of steel in current units.
KX 1.0 Effective length factor for torsional buckling. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.
KY 1.0 Effective length factor for overall buckling about the local Y-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.
KZ 1.0 Effective length factor for overall buckling in the local Z-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.
LX Member length
Unbraced length for twisting. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.
LY Member length
Effective length for overall buckling in the local Y-axis. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.
Section 9D
9-99
COLD FORMED STEEL DESIGN PARAMETERS
Parameter
Name
Default
Value Description
LZ Member length
Effective length for overall buckling in the local Z-axis. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.
MAIN 0 0 – Check slenderness ratio
0 – Do not check slenderness ratio
NSF 1.0 Net section factor for tension members DMAX
2540.0 cm. Maximum allowable depth. It is input in the current units of
length.
RATIO 1.0 Permissible ratio of actual to allowable stresses
TRACK 0 This parameter is used to control the level of detail in which the design output is reported in the output file. The allowable values are: 0 - Prints only the member number, section name, ratio, and
PASS/FAIL status. 1 - Prints the design summary in addition to that printed by
TRACK 1 2 - Prints member and material properties in addition to that
printed by TRACK 2. TSA 1 Specifies whether webs of flexural members are adequately
stiffened to satisfy the requirements of IS:801-1975, 5.2.4.
Values:
0 – Do not comply with 5.2.4
1 – Comply with 5.2.4
Design Per Indian Cold Formed Steel Code
Section 9D
9-100
Section 10
Japanese Codes
;alksdf;lkajf
10-1
Concrete Design Per AIJ
10A.1 Design Operations
STAAD has the capabilities of performing concrete design based
on the AIJ standard for structural calculation of Reinforced
Concrete Structures (1985 edition). Design for a member involves
calculation of the amount of reinforcement required for the
member. Calculations are based on the user specified properties
and the member forces obtained from the analysis. In addition, the
details regarding placement of the reinforcement on the cross
section are also reported in the output.
10A.2 Section Types for Concrete Design
The following types of cross sections for concrete members can be
designed.
For Beams Prismatic (Rectangular & Square)
For Columns Prismatic (Rectangular, Square and Circular)
10A.3 Member Dimensions
Concrete members which will be designed by the program must
have certain section properties input under the MEMBER
PROPERTY command. The following example shows the required
input:
Section 10A
Concrete Design Per AIJ
Section 10A
10-2
UNIT MM
MEMBER PROPERTY
1 3 TO 7 9 PRISM YD 450. ZD 250.
11 13 PR YD 350.
In the above input, the first set of members are rectangular (450
mm depth and 250mm width) and the second set of members, with
only depth and no width provided, will be assumed to be circular
with 350mm diameter. It is absolutely imperative that the user not
provide the cross section area (AX) as an input.
10A.4 Slenderness Effects and Analysis Consideration
Slenderness effects are extremely important in designing
compression members. Slenderness effects result in additional
forces being exerted on the column over and above those obtained
from the elastic analysis. There are two options by which the
slenderness effects can be accommodated.
The first option is to compute the secondary moments through an
exact analysis. Secondary moments are caused by the interaction
of the axial loads and the relative end displacements of a member.
The axial loads and joint displacements are first determined from
an elastic stiffness analysis and the secondary moments are then
evaluated.
The second option is to approximately magnify the moments from
the elastic analysis and design the column for the magnified
moment. It is assumed that the magnified moment is equivalent to
the total moment comprised of the sum of primary and secondary
moments.
STAAD provides facilities to design according to both of the
above methods. To utilize the first method, the command PDELTA
ANALYSIS must be used instead of PERFORM ANALYSIS in the
Section 10A
10-3
input file. The user must note that to take advantage of this
analysis, all the combinations of loading must be provided as
primary load cases and not as load combinations. This is due to the
fact that load combinations are just algebraic combinations of
forces and moments, whereas a primary load case is revised during
the P-delta analysis based on the deflections. Also, note that the
proper factored loads (like 1.5 for dead load etc.) should be
provided by the user. STAAD does not factor the loads
automatically. The second method mentioned above is utilized by
providing the magnification factor as a concrete design parameter
(See the parameter MMAG in Table 9A.1). The column is designed
for the axial load and total of primary and secondary biaxial
moments if the first method is used and for the axial load and
magnified biaxial moments if the second method is used.
10A.5 Beam Design
Beams are designed for flexure, shear and torsion. Program
considers 12 equally spaced sections of the beam member.
However this number can be redefined by NSECTION parameter.
All these sections are designed for flexure, shear and torsion for
all the load cases and print out the design results for most critical
load case.
Design for Flexure
Reinforcement for positive and negative moments are calculated
on the basis of section properties provided by the user. Program
first try to design the section for =0 and pt = balanced
reinforcement ratio. If allowable moment is lower than the actual
moment program increases value for same pt and checks the
satisfactory conditions. If conditions are not satisfied this
procedure continues until reaches to 1.0 and then pt value is
increased keeping = 1.0. This procedure continues until pt
reaches to its maximum value( 2 % ). But if the allowable moment
for pt = maximum value and = 1.0 is lower than the actual
moment the program gives message that the section fa ils.
This program automatically calculates the Bar size and no. of bars
needed to design the section. It arranges the bar in layers as per
Concrete Design Per AIJ
Section 10A
10-4
the requirements and recalculate the effective depth and redesign
the sections for this effective depth.
Notes:
Beams are designed for MZ only. The moment MY is not
considered in flexure design
MMAG parameter can be used to increase design moment
1.4 cm. is added to the clear cover to take stirrup size into
consideration for flexure design.
STAAD beam design procedure is based on the local practice
and considering the fact that Japan is a high seismic zone area.
Design for Shear
Shear design of beam is done for Qy value. The update effective
depth is used for allowable shear stress calculation. Allowable
shear stress of concrete is automatically calculated from design
load type (permanent or temporary) and given density of concrete.
Program calculates required Bar size and spacing of stirrups. Pw is
calculated for design Bar size and spacing and all the necessary
checking is done.
For seismic load it is needed to increase shear force 1.5 times the
actual value and this can be done utilizing SMAG parameter.
Notes:
SMAG parameter can be used if its needed to increase the
Design Shear Force without changing Design Moment.
Stirrups are always assumed to be 2-legged
Governing density to determine Light weight or Normal
Weight Concrete is 2.3 kg/sq. cm
Section 10A
10-5
Example of Input Data for Beam Design
UNIT KG CM
START CONCRETE DESIGN
CODE JAPAN
FYMAIN SRR295 ALL
FYSEC SRR295 ALL
FC 350 ALL
CLEAR 2.5 MEM 2 TO 6
TRACK 1.0 MEMB 2 TO 9
DESIGN BEAM 2 TO 9
END CONCRETE DESIGN
Design for Torsion
Torsion design for beam is optional. If TORSION parameter value
is 1.0, program design that beam for torsion. Program first checks
whether extra reinforcement is needed for torsion or not. If
additional reinforcement is needed, this additional pt is added to
flexure pt and additional Pw is added to shear design Pw.
10A.6 Column Design
Columns are designed for axial force, MZ moment, MY moment
and shear force. Both the ends of the members are designed for all
the load cases and the loading which produces largest amount of
reinforcement is called as critical load. If Track 0 or Track 1 is
used, design results will be printed for critical load only. But if
Track 2 is used user can get details design results of that member.
Pt needed for minimum axial force, maximum axial force,
maximum MZ, maximum MY among all the load cases for both the
ends will be printed. If MMAG parameter is used, the column
moments will be multiplied by that value. If SMAG parameter is
used, column shear force will be multiplied by that value.
Column design is done for Rectangular, Square and Circular
sections. For rectangular and square sections Pt value is calculated
Concrete Design Per AIJ
Section 10A
10-6
separately for MZ and MY, while for circular sections Pg value is
calculated for MZ and MY separately.
Column design for biaxial moments is optional. If BIAXIAL
parameter value 1.0, program will design the column for biaxial
moments. Otherwise column design is always uniaxial type.
Steps involved :
1) Depending on the axial force zone is determined for Pt = 0.0 .
2) If the column is in "zone A", design is performed by
increasing Pt and checking allowable load for that known Pt
and known actual eccentricity of the column.
3) If the column is in "zone B" or in "zone C", xn is calculated
for given P and Pt and checking is done for allowable moment,
if allowable moment is less than the actual moment, program
increases Pt and this procedure continues until the column
design conditions are satisfied or the column fails as the
required Pt is higher than Pt maximum value.
4) If the column is in tension, design is done by considering
allowable tensile stress of steel only.
5) If biaxial design is requested program solve the following
interaction equation
0.1Mzcap
Mz
Mycap
My
where, = 1.0+1.66666666 (ratio-0.2), ratio = P/Pcap &
1.0 2.0, Mycap, Mzcap & Pcap represents section
capacity
6) If the interaction equation is not satisfied program increases Pt
and calculates Pcap, Mycap and Mzcap and solve the
interaction equation again and this process continues until the
Section 10A
10-7
eqn. is satisfied or the column fails as Pt exceeds its maximum
limit.
7) If biaxial design is not requested program assumes that
interaction equation is satisfied ( if uniaxial design is
performed successfully ).
8) If the interaction equation is satisfied program determines bar
size and calculates no. of bars and details output is written.
Example of Input Data for Column Design
UNIT KGS CMS
START CONCRETE DESIGN
CODE JAPAN
FYMAIN SRR295 ALL
FC 210 ALL
CLEAR 2.5 MEMB 2 TO 6
DESIGN COLUMN 2 TO 6
END CONCRETE DESIGN
10A.7 Slab/Wall Design
To design a slab or a wall, it must first be modelled using finite
elements and analysed. The command specifications are in
accordance with Chapter 2 and Chapter 6 of the Technical
Reference Manual.
Elements are designed for the moments Mx and My. These
moments are obtained from the element force output (see Chapter
2 of the Technical Reference Manual). The reinforcement required
to resist the Mx moment is denoted as longitudinal reinforcement
and the reinforcement required to resist the My moment is denoted
as transverse reinforcement.
Concrete Design Per AIJ
Section 10A
10-8
The longitudinal bar is the layer closest to the exterior face of the
slab or wall. The following parameters are those applicable to slab
and wall design:
1. FYMAIN Yield stress for reinforcing steel - transverse and
longitudinal.
2. FC Concrete grade
3. CLEAR Distance from the outer surface of the element to
the edge of the bar. This is considered the same on
both top and bottom surfaces of the element.
4. MINMAIN Minimum required size of longitudinal/transverse
reinforcing bar
The other parameters shown in Table 9A.1 are not applicable to
slab or wall design.
LONG.
TRANS.
X
Y
Z
M
MM
Mx
y
x
y
10A.8 Design Parameters
The program contains a number of parameters which are needed to
perform the design. Default parameter values have been selected
such that they are frequently used numbers for conventional design
requirements. These values may be changed to suit the particular
design being performed. Table 9A.1 contains a complete list of the
available parameters and their default values. It is necessary to
declare length and force units as centimeters and Kilograms before
performing the concrete design. Note: Once a parameter is
specified, its value stays at that specified number till it is
specified again. This is the way STAAD works for all codes.
Section 10A
10-9
Table 10A.1 Japanese Concrete Design Parameters
Parameter
Name
Default Value Description
FYMAIN SR235 Steel grade. Acceptable values for steel grade and their associated yield stress values are shown in the next table. Program automatically calculates yield stress value depending on design load type (permanent or temporary).
FYSEC SR235 Same as FYMAIN except this is for secondary steel.
FC 210 Kg/cm2 Compressive Strength of Concrete.
CL 3.0 cm Clear cover for Beam.
CLS 4.0 cm Clear side cover for Column.
MINMAIN 10 mm Minimum main reinforcement bar size.
MINSEC 10 mm Minimum secondary reinforcement bar size.
MAXMAIN 41.0 cm Maximum main reinforcement bar size
MAXSEC 41.0 cm Maximum secondary reinforcement bar size.
SFACE 0.0 Face of support location at start of beam.
EFACE 0.0 Face of support location at end of beam. (Note: Both SFACE & EFACE are input as positive numbers).
REINF 0.0 Tied Column. A value of 1.0 will mean spiral.
MMAG 1.0 Design moment magnification factor
SMAG 1.0 Design shear magnification factor
LONG 0.0 Value to define design load type 0 = Permanent Loading 1 = Temporary Loading
BIAXIAL 0.0 Value to define biaxial or uniaxial design type for Column 0 = uniaxial design only 1 = design for biaxial moments
TORSION 0.0 Value to request for torsion design for beam 0 = torsion design not needed 1 = torsion design needed
Concrete Design Per AIJ
Section 10A
10-10
Table 10A.1 Japanese Concrete Design Parameters
Parameter
Name
Default Value Description
WIDTH ZD Width of concrete member. This value defaults to ZD as provided under MEMBER PROPERTIES.
DEPTH YD Depth of concrete member. This value defaults to YD as provided under MEMBER PROPERTIES.
NSECTION 12 Number of equally-spaced sections to be considered in finding critical moments for beam design.
TRACK 0.0 BEAM DESIGN:
0.0 = Critical section design results. 1.0 = Five section design results & design
forces. 2.0 = 12 section design results & design forces. COLUMN DESIGN:
1.0 = Detail design results for critical load case only.
2.0 = Design results for minimum P, maximum P, maximum MZ and maximum MY among all load cases for both ends.
Table of permissible Steel Grades and associated Yield Stresses
for FYMAIN and FYSEC parameters. (Default values in Kg/Cm^2)
Steel Grade Design Load Type Design Load Type
Long Term Short Term
SR235
SRR235
SDR235
22.76
34.14
SR295
SRR295
22.76 42.67
SD295A
SD295B
SDR295
28.45
42.67
SDR345
SD345
31.29 49.78
SD390 31.29 56.89
10-11
Steel Design Per AIJ
10B.1 General
This section presents some general statements regarding the
implementation of the “Architectural Institute of Japan” (AIJ)
specifications for structural steel design (1986 edition) in STAAD.
The design philosophy and procedural logistics are based on the
principles of elastic analysis and allowable stress design. Facilities
are available for member selection as well as code checking. Two
major failure modes are recognized: failure by overstressing an d
failure by stability considerations. The following sections describe
the salient features of the design approach.
Members are proportioned to resist the design loads without
exceedance of the allowable stresses or capacities and the most
economical section is selected on the basis of the least weight
criteria. The code checking part of the program also checks the
slenderness requirements and the stability criteria. Users are
recommended to adopt the following steps in performing the steel
design:
Specify the geometry and loads and perform the analysis.
Specify the design parameter values if different from the
default values.
Specify whether to perform code checking or member
selection.
Section 10B
Steel Design Per AIJ
Section 10B
10-12
10B.2 Analysis Methodology
Elastic analysis method is used to obtain the forces and moments
for design. Analysis is done for the primary and combination
loading conditions provided by the user. The user is allowed
complete flexibility in providing loading specifications and in
using appropriate load factors to create necessary loading
situations. Depending upon the analysis requirements, regular
stiffness analysis or P-Delta analysis may be specified. Dynamic
analysis may also be performed and the results combined with
static analysis results.
10B.3 Member Property Specifications
For specification of member properties of standard Japanese steel
shapes, the steel section library available in STAAD may be used.
The next section describes the syntax of commands used to assign
properties from the built-in steel table. Members properties may
also be specified using the User Table facility. For more
information on these facilities, refer to the STAAD Technical
Reference Manual.
10B.4 Built-in Japanese Steel Section Library
The following information is provided for use when the built-in
steel tables are to be referenced for member property specification.
These properties are stored in a database file. If called for, these
properties are also used for member design. Since the shear areas
are built into these tables, shear deformation is always considered
for these members during the analysis. An example of member
property specification in an input file is provided at the end of this
section.
Section 10B
10-13
A complete listing of the sections available in the built -in steel
section library may be obtained using the tools of the graphical
user interface.
Following are the descriptions of different types of sections.
I shapes
I shapes are specified in the following way:
Note : While specifying the web thickness, the portion after the
decimal point should be excluded.
Example: 1 TO 9 TA ST I300X150X11
12 TO 15 TA ST I350X150X9
H shapes
H shapes are specified as follows:
Note: While specifying the web thickness, the portion after the decimal
point should be excluded.
Example: 1 TO 8 TA ST H200X100X4
13 TO 17 TA ST H350X350X12
I 250 X 125 X 10
Web thickness (mm)
Nominal width of flange (mm)
Section-type (I)
Nominal height (mm)
H 600 X 200 X 11
Web thickness (mm)
Nominal width of flange (mm)
Section-type (H)
Nominal height (mm)
Steel Design Per AIJ
Section 10B
10-14
T shapes
T shapes are specified as follows:
Note : While specifying the web thickness, the portion after the
decimal point should be excluded
Example: 20 TO 25 TA ST T250X19
Channels
Channel sections are specified as follows.
Example: 25 TO 34 TA ST C125X65X6
46 TO 49 TA ST C200X90X8
Double Channels
Back to back double channels, with or without a spacing in
between them, are available. The letter D in front of the section
name is used to specify a double channel.
17 TO 27 TA D C300X90X10
45 TO 76 TA D C250X90X11 SP 2.0
In the above commands, members 17 to 27 are a back to back
double channel C300X90X10 with no spacing in between.
T 250 X 16
Flange thickness (mm)
Section-type (T)
Nominal width of flange (mm)
C 300 X 90 X 10
Web thickness (mm)
Nominal width of flange (mm)
Section-type (C)
Nominal height (mm)
Section 10B
10-15
Members 45 to 76 are a double channel C250X90X11 with a
spacing of 2 length units.
Angles
Two types of specification may be used to describe an angle. The
standard angle specification is as follows.
The letter L (signifying that the section is an angle) is followed by
the length of the legs and then the thickness of the leg, all in
millimetres. The word ST signifies that the section is a STandard
angle meaning that the major principal axis coincides with the
local YY axis specified in Chapter 1 of Section 1.5.2 of the User's
Manual.
Example: 1 4 TA ST L150X90X9
If the minor principal axis coincides with the local YY axis
specified in Chapter 2 of the User's Manual, the word RA (Reverse
Angle) should be used instead of ST as shown below.
7 TO 23 TA RA L90X75X9
Double angles
Short leg back to back and long leg back to back double angles
may be specified by using the words SD or LD in front of the
angle size. In the case of an equal angle, either SD or LD will
serve the purpose. The spacing between the angles may be
specified by using the word SP after the angle size followed by the
value of the spacing.
L 125 X 90 X 10
Thickness (mm)
Length of shorter side (mm)
Section-type (L)
Length of longer side (mm)
Steel Design Per AIJ
Section 10B
10-16
8 TO 25 TA SD L100X65X7 SP 2.0
36 TO 45 TA LD L300X90X11 SP 3.0
The first example indicates a short legs back to back double angle
comprised of 100X65X7 angles separated by 2 length units. The
latter is a long legs back to back double angle comprised of
300X90X11 angles separated by 3 length units.
Tubes
Tube names are input by their dimensions. For example,
6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5
is a tube that has a height of 8 length units, width of 6 length units
and a wall thickness of 0.5 length units. Only code checking, no
member selection can be performed on TUBE sections.
Pipes (Circular Hollow sections)
Circular hollow sections may be provided by specifying the word
PIPE followed by the outside and inside diameters of the section.
For example,
1 TO 9 TA ST PIPE OD 25.0 ID 20.0
specifies a pipe with outside diameter of 25 length units and an
inside diameter of 20 length units. Only code checking, no member
selection, can be performed on PIPE sections.
Section 10B
10-17
Sample Input file containing Japanese shapes
STAAD SPACE
UNIT KIP FEET
JOINT COORD
1 0 0 0 12 11 0 0
MEMB INCIDENCE
1 1 2 11
UNIT INCH
MEMBER PROPERTY JAPANESE
* H-SHAPE
1 TA ST H200X100X4
* I SHAPE
2 TA ST I250X125X10
* T SHAPE
3 TA ST T200X19
* CHANNEL
4 TA ST C125X65X6
* DOUBLE CHANNEL
5 TA D C200X90X8
* REGULAR ANGLE
6 TA ST L100X75X7
* REVERSE ANGLE
7 TA RA L90X75X9
* DOUBLE ANGLE - LONG LEG BACK TO BACK
8 TA LD L125X75X7 SP 2.0
* DOUBLE ANGLE - SHORT LEG BACK TO BACK
9 TA SD L300X90X11 SP 1.5
* TUBE
10 TA ST TUBE DT 3.0 WT 2.5 TH 0.25
* PIPE
11 TA ST PIPE OD 3.0 ID 2.5
PRINT MEMBER PROPERTIES
FINISH
Steel Design Per AIJ
Section 10B
10-18
10B.5 Member Capacities
As mentioned before, member design and code checking in
STAAD are based upon the allowable stress design method. It is a
method for proportioning structural members using design loads
and forces, allowable stresses, and design limitations for the
appropriate material under service conditions. The basic measure
of member capacities are the allowable stresses on the member
under various conditions of applied loading such as allowable
tensile stress, allowable compressive stress etc. These depend on
several factors such as cross sectional properties, slenderness
factors, unsupported width to thickness ratios and so on. Explained
here is the procedure adopted in STAAD for calculating such
capacities.
Design Capabilities
All types of available shapes like H-Shape, I-Shape, L-Shapes,
CHANNEL, PIPE, TUBE, Prismatic section etc. can be used as
member property and STAAD will automatically adopt the design
procedure for that particular shape if Steel Design is requested.
STEEL TABLE available within STAAD or UPTABLE facility can
be used for member property.
Methodology
For steel design, STAAD compares the actual stresses with the
allowable stresses as required by AIJ specifications. The design
procedure consist of following three steps.
1) Calculation of sectional properties
Program extract sectional properties like sectional area ( A ),
Moment of Inertia about Y axis and Z axis ( Iyy, Izz) from in-
built Japanese Steel Table and calculates Zz, Zy, iy, iz using
appropriate formula. For calculation of i ( radius of gyration
needed for bending ), program calculates moment of inertia ( Ii
)and sectional area ( Ai ) for 1/6th section and then uses
following formula:
Section 10B
10-19
Ai
Iii
Please note, that the above mentioned procedure for
calculation of i is applicable for I shape, H shape and Channel
sections.
2) Calculation of actual and allowable stresses
Program calculates actual and allowable stresses by following
methods:
i) Axial Stress:
Actual tensile stresses ( FT ) = Force / ( A NSF ),
NSF = Net Section Factor for tension
Actual compressive stress ( FC ) = Force / A
Allowable tensile stress ( ft ) = F / 1.5 (For Permanent
Case)
= F ( For Temporary Case )
Allowable compressive stress
when /F x / x4.1 )fc( 2
when / /F x 77.2 2
= fc 1.5 (For Temporary Case )
where, )xF6/(.E2 =F) , =3 / 2 + 2 / 3 ( / )2
ii) Bending Stress:
Actual bending stress for My for compression
( Fbcy) = My / Zcy
Actual bending stress for Mz for compression
( Fbcz) = Mz / Zcz
Actual bending stress for My for tension
( Fbty ) = My / Zcy Or ( Fbty ) = My / Zty
Actual bending stress for Mz for tension
( Fbtz ) = Mz / Zcz Or (Fbtz ) = Mz / Ztz
Steel Design Per AIJ
Section 10B
10-20
where, Zcy , Zcz are section modulus for compression and
Zty, Ztz are section modulus for tension
Allowable bending stress for My
(fbcy) = ft
Allowable bending stress for Mz
(fbcz) = { 1-.4 (lb / i )2 / (C 2)}ft max
= 900/ ( lb h / Af )
For Temporary case, fbcz = 1.5 (fbcz for Permanent
Case)
where, C = 1.75 -1.05(M2/M1)+0.3(M2/M1)2
Allowable bending stress for My ( fbty) = ft
Allowable bending stress for Mz ( fbtz) = fbcz
iii) Shear Stress
Actual shear stresses are calculated by following formula :
qy = Qy / Aww,
Where, Aww = web shear area = product of depth and web
thickness
qz = Qz / Aff ,
Where, Aff = flange shear area = 2/3 times total flange
areas
Allowable shear stress ( fs ) = Fs / 1.5 , Fs = F / 3
3) Checking design requirements:
User provided RATIO value (default 1.0) is used for checking
design requirements
The following conditions are checked to meet the AIJ
specifications. For all the conditions calculated value should not
be more than the value of RATIO. If for any condition value
exceeds RATIO , program gives the message that the section fails.
Conditions:
i) Axial tensile stress ratio = FT / ft
ii) Axial compressive stress ratio = FC / fc
iii) Combined compression &
bending ratio = FC/fc+Fbcz/fbcz+Fbcy/fbcy
Section 10B
10-21
iv) Combined compression &
bending ratio = (Fbtz+Fbty-FC) / ft
v) Combined tension & bending ratio = (FT+Fbtz+Fbty) / ft
vi) Combined tension & bending ratio = Fbcz/fbcz+Fbcy/fbcy-
FT/ft
vii) Shear stress ratio for qy = qy / fs
viii) Shear stress ratio for qz = qz / fs
New Output Format ( TRACK -- 3 )
One new output format has been introduced which provides details
step by step information of Steel Design for guiding load case
only. If Section command is used before Parameter command this
output will provide details information for all the sections
specified by Section Command.
Please note, that this output format is available only when Beam
parameter value is 0 and Track parameter value is 3. If section
command is not used design information will be printed for two
ends only. If Member Truss option is used no Shear Design
information will be printed.
Example:
SECTION 0.0 0.25 0.5 0.75 1.0 ALL
PARAMETER
CODE JAPAN
BEAM 0.0 ALL
TMP 0.0 MEMB 1 to 4
TMP 1.0 MEMB 5 to 8
TRACK 3 ALL
CHECK CODE ALL
FINISH
Allowable stress for Axial Tension
Allowable axial stress in tension is calculated per section 5.1 (1)
of the AIJ code. In members with axial tension, the tensile load
must not exceed the tension capacity of the member. The tension
Steel Design Per AIJ
Section 10B
10-22
capacity of the member is calculated on the basis of the member
area. STAAD calculates the tension capacity of a given member
based on a user supplied net section factor (NSF-a default value of
1.0 is present but may be altered by changing the input value, see
Table 8B.1) and proceeds with member selection or code checking.
Allowable stress for Axial Compression
The allowable stress for members in compression is determined
according to the procedure of section 5.1 (3). Compressive
resistance is a function of the slenderness of the cross -section
(Kl/r ratio) and the user may control the slenderness value by
modifying parameters such as KY, LY, KZ and LZ. In the absence
of user provided values for effective length, the actual member
length will be used. The slenderness ratios are checked against the
permissible values specified in Chapter 11 of the AIJ code.
Allowable stress for Bending
The permissible bending compressive and tensile stresses are
dependent on such factors as length of outstanding legs, thickness
of flanges, unsupported length of the compression flange (UNL,
defaults to member length) etc. The allowable stresses in bending
(compressive and tensile) are calculated as per the criteria of
Clause 5.1 (4) of the code.
Allowable stress for Shear
Shear capacities are a function of web depth, web thickness etc.
The allowable stresses in shear are computed according to Clause
5.1 (2) of the code.
10B.6 Combined Loading
For members experiencing combined loading (axial force, bending
and shear), applicable interaction formulas are checked at different
locations of the member for all modelled loading situations.
Members subjected to axial tension and bending are checked using
the criteria of clause 6.2. For members with axial compression and
bending, the criteria of clause 6.1 is used.
Section 10B
10-23
10B.7 Design Parameters
The user is allowed complete control over the design process
through the use of parameters mentioned in Table 9B.1 of this
chapter. These parameters communicate design decisions from the
engineer to the program. The default parameter values have been
selected such that they are frequently used numbers for
conventional design. Depending on the particular design
requirements of the situation, some or all of these parameter
values may have to be changed to exactly model the physical
structure. Note: Once a parameter is specified, its value stays at
that specified number till it is specified again. This is the way
STAAD works for all codes.
Table 10B.1 - Japanese Steel Design Parameters
Parameter
Name
Default Value Description
KY 1.0 K value in local y-axis. Usually, this is the minor axis.
KZ 1.0 K value in local z-axis. Usually, this is the major axis.
LY Member Length
Length in local y-axis to calculate slenderness ratio.
LZ Member Length
Same as above except in z-axis
FYLD 235 MPA Yield strength of steel in Megapascal.
NSF 1.0 Net section factor for tension members.
UNL Member Length
Unsupported length for calculating allowable bending stress.
UNF 1.0 Same as above provided as a fraction of actual member length.
SSY 0.0 0.0 = Sidesway in local y-axis. 1.0 = No sidesway
Steel Design Per AIJ
Section 10B
10-24
Table 10B.1 - Japanese Steel Design Parameters
Parameter
Name
Default Value Description
SSZ 0.0 Same as above except in local z-axis.
MAIN 0.0 0.0 = check for slenderness 1.0 = suppress slenderness check
TRACK 0.0 0.0 = Suppress critical member stresses 1.0 = Print all critical member stresses 2.0 = Print expanded output
DMAX 100 cm Maximum allowable depth for member.
DMIN 0.0 cm Minimum allowable depth for member.
TMP 0 (Permanent
Load)
0 = Permanent Loading 1 = Temporary Loading
RATIO 1.0 Permissible ratio of the actual to allowable stresses.
BEAM 0.0 0.0 = design only for end moments or those at locations specified by the SECTION command.
1.0 = calculate moments at twelfth points along the beam, and use the maximum Mz location for design.
DFF None (Mandatory for
deflection check)
"Deflection Length" / Maxm. allowable local deflection
DJ1 Start Joint of member
Joint No. denoting starting point for calculation of "Deflection Length" (See Note 1)
DJ2 End Joint of member
Joint No. denoting end point for calculation of "Deflection Length" (See Note 1)
NOTE:
1) "Deflection Length" is defined as the length that is used for
calculation of local deflections within a member. It may be
noted that for most cases the "Deflection Length" will be equal
to the length of the member. However, in some situations, the
"Deflection Length" may be different. For example, refer to
the figure below where a beam has been modeled using four
joints and three members. Note that the "Deflection Length"
Section 10B
10-25
for all three members will be equal to the total length of the
beam in this case. The parameters DJ1 and DJ2 should be used
to model this situation. Also the straight line joining DJ1 and
DJ2 is used as the reference line from which local deflections
are measured. Thus, for all three members here, DJ1 should be
"1" and DJ2 should be "4".
D = Maximum local deflection for members1, 2 and 3.
D
1
2 3
4
1
2 3
EXAMPLE : PARAMETERS
DFF 300. ALL
DJ1 1 ALL
DJ2 4 ALL
2) If DJ1 and DJ2 are not used, "Deflection Length" wil l default
to the member length and local deflections will be measured
from original member line.
3) The above parameters may be used in conjunction with other
available parameters for steel design.
10B.8 Code Checking
The purpose of code checking is to check whether the provided
section properties of the members are adequate to carry the forces
transmitted to it by the loads on the structure. The adequacy is
checked per the AIJ requirements.
Code checking is done using forces and moments at specified
sections of the members. If the BEAM parameter for a member is
set to 1, moments are calculated at every twelfth point along the
beam, and the maximum moment about the major axis is used.
When no sections are specified and the BEAM parameter is set to
zero (default), design will be based on the forces at the start and
end joints of the member. The code checking output labels the
members as PASSed or FAILed. In addition, the critical condition,
governing load case, location (distance from start joint) and
magnitudes of the governing forces and moments are also printed.
Steel Design Per AIJ
Section 10B
10-26
10B.9 Member Selection
The member selection process basically involves determination of
the least weight member that PASSes the code checking procedure
based on the forces and moments obtained from the most recent
analysis. The section selected will be of the same type as that
specified initially. For example, a member specified initially as a
channel will have a channel selected for it. Selection of members
whose properties are originally provided from a user table will be
limited to sections in the user table. Member selection cannot be
performed on TUBES, PIPES or members listed as PRISMATIC.
Sample Input data for Steel Design
UNIT METER
PARAMETER
CODE JAPAN
NSF 0.85 ALL
UNL 10.0 MEMBER 7
KY 1.2 MEMBER 3 4
RATIO 0.9 ALL
TRACK 1.0 ALL
CHECK CODE ALL
SELECT ALL
Section 11
Mexican Codes
11-1
Concrete Design Per MEX NTC 1987
11A.1 Design Operations
STAAD has the capabilities for per forming concrete design. It will
calculate the reinforcement needed for the specified concrete
section. All the concrete design calculations are based on the
current: Complementary Technical Standards for the Design and
Construction of Concrete Structures – Nov. 1987. (Normas
Técnicas Complementarias para Diseño y construcción de
Estructuras de Concreto) of the Mexican Construction Code for the
Federal District –Aug. 1993 (Reglamento de Construcciones para
el Distrito Federal).
11A.2 Section Types for Concrete Design
The following types of cross sections can be defined for concrete
design.
For Columns Prismatic (Rectangular, Square and Circular)
For Beams Prismatic (Rectangular & Square), Trapezoidal
and T-shapes
For Slabs Finite element with a specified thickness
Section 11A
Concrete Design Per Mexican Code
Section 11A
11-2
11A.3 Member Dimensions
Concrete members which will be designed by the program must
have certain section properties input under the MEMBER
PROPERTY command. The following example shows the required
input:
UNIT CM
MEMBER PROPERTY
13 TO 79 PRISM YD 40. ZD 20. IZ 53333 IY 13333
11 13 PR YD 20.
14 TO 16 PRIS YD 24. ZD 48. YB 18. ZB 12.
17 TO 19 PR YD 24. ZD 18. ZB 12.
In the above input, the first set of members are rectangular (40 cm
depth and 20 cm width) and the second set of members, with only
depth and no width provided, will be assumed to be circular with 20
cm diameter. Note that no area (AX) is provided for these members.
For concrete design, this property must not be provided. If shear areas
and moments of inertias are not provided, the program calculates
these values from YD and ZD. Notice that in the above example the
IZ and IY values provided are actually 50% of the values calculated
using YD and ZD. This is a conventional practice which takes int o
consideration revised section parameters due to cracking of section.
Section 11A
11-3
Note that the third and the fourth set of members in the above
example represent a T-shape and a TRAPEZOIDAL shape
respectively. Depending on the properties (YD, ZD, YB, ZB, etc.)
provided, the program will determine whether the section is
rectangular, trapezoidal or T-shaped and the BEAM design will be
done accordingly.
11A.4 Design Parameters
The program contains a number of parameters which are needed to
perform design by the Mexican code. Default parameter values
have been selected such that they are frequently used numbers for
conventional design requirements. These values may be changed to
suit the particular design being performed. Table 3.1 is a complete
list of the available parameters and their default values.
The manual describes the commands required to provide these
parameters in the input file. For example, the values of SFACE
and EFACE (parameters that are used in shear design), the
distances of the face of supports from the end nodes of a beam, are
assigned values of zero by default but may be changed depending
on the actual situation. Similarly, beams and columns are designed
for moments directly obtained from the analyses without any
magnification. The factors MMAGx and MMAGy may be used for
magnification of column moments. For beams, the user may
generate load cases which contain loads magnified by the
appropriate load factors. Note: Once a parameter is specified, its
value stays at that specified number till it is specified again.
This is the way STAAD works for all codes.
Concrete Design Per Mexican Code
Section 11A
11-4
Table 11A.1 – Mexican Concrete Design Parameters
Parameter Default Description
Name Value
FYMAIN 4200Kg/cm2 Yield Stress for main reinforcing steel
FYSTIRR 4200Kg/cm2 Yield Stress for stirrup reinforcing steel
FC 200Kg/cm2 Compressive Strength of Concrete
clear_cover_top 3cm Clear cover for top reinforcement
clear_cover_bottom 3cm Clear cover for bottom reinforcement
clear_cover_side 3cm Clear cover for side reinforcement
MINMAIN** No 2.5 bar Minimum main reinforcement bar size (Number 2 -18)
MINSEC** No 2.5 bar Minimum secondary reinforcement bar size (Number 2 -18)
MAXMAIN** No 12 bar Maximum main reinforcement bar size (Number 2 -18)
SFACE 0
Face to support location of start of beam. If specified, for shear force at start is computed at a distance of SFACE+d from the start joint of the member. Positive number
EFACE 0
Face to support location of end of beam. If specified, for shear force at start is computed at a distance of
EFACE+d from the start joint of the member. Positive number.
REINF 0 Tied Column. A value of 1 will mean spiral.
AMAGx
AMAGy 1
A factor by which the column design moments will be
magnified
WIDTH *ZD Width of concrete member. This value defaults to ZD
as provided under MEMBER PROPERTIES
DEPTH *YD Depth of concrete member. This value defaults to YD
as provided under MEMBER PROPERTIES
NSECTION 12 Number of equally-spaced sections to be considered in
finding critical moments for beam design
Section 11A
11-5
Table 11A.1 – Mexican Concrete Design Parameters
Parameter Default Description
Name Value
TRACK 0
Beam Design
0 = Critical Moment will not be printed out with
beam design report.
1 = will mean a print out.
2 = will print out required steel areas for all intermediate sections specified by NSECTION.
Column Design
0 = will print out detailed design results.
1 = will mean a print out column interation analysis results in addition to TRACK 0 output.
2 = will print out a schematic interaction diagram and intermediate interaction values in addition to all of the above.
BARTYPE 2 0: IMPERIAL (No 3 to 18) 1: METRIC (4.2 to 60mm)
2: MEXICAN (No 2 to 18)
DIM_PRECAUTION TRUE TRUE: Precautions are taken to assure dimensions FALSE: Not precautions taken - Section reduction to
section 1.5 NTC Concrete
EXPOSED_SOIL_ WEATHER
FALSE Exposition to soil or weather to define cover and min Steel reinforcement
CONC_CLAS 1 Concrete class according to 1.4.1d) to define Modulus of Elasticity
LIGHT_CONC FALSE Light Concrete to define development multipliers according to table 3.1 NTC
COLD_FORM_BAR FALSE Cold formed Bar to define development multipliers according to table 3.1 NTC
DUCTILE_SEISMIC _DESIGN
TRUE DUCTILE FRAMES ACCORDING TO SECTION 5. Some design conditions are considered (not including, for the time being, geometric or confinment ones)
DIAM_AG *2 cm MAXIMUM DIAM AGGREGATE
BEARED_PERIM TRUE Slab beared perimeter. To calculate min steel required
according to 2.1.2
Concrete Design Per Mexican Code
Section 11A
11-6
Table 11A.1 – Mexican Concrete Design Parameters
Parameter Default Description
Name Value
DIRECT_COMP TRUE Beam Loads and reactions in direct compression Cl-2.1.5.a.I 2nd paragraph
PHI 90 degrees Stirrups angle with the axis of the element
TORSIONAL_
EQUILIBRIUM
FALSE Beam needed for torsional equilibrium Cl.2.1.6a) 2nd
paragraph
Pfact 1.0 Part of the longitudinal steel considered to reduce
shear. 0(zero) is on the safe side. Value between 1 and 0.
ZB 0.0 IDEM ACI
YB 0.0 IDEM ACI
EIT *198000 Kg/cm2
CONCRETE MODULUS OF ELASTICITY
* These values must be provided in the current unit system being used. ** When using metric bars for design, provide values for these parameters in actual „mm„ units instead of the bar number. The following metric bar sizes are available: 4.2mm, 6 mm, 8 mm, 10 mm, 12 mm, 16 mm, 20 mm, 25 mm, 32 mm, 40 mm, 50 mm and 60 mm.
11A.5 Beam Design
Beams are designed for flexure, shear and torsion. For all these
forces, all active beam loadings are prescanned to locate the
possible critical sections. The total number of sections considered
is 12 (twelve) unless this number is redefined with an NSECTION
parameter. All of these equally spaced sections are scanned to
determine moment and shear envelopes.
Design for Flexure
Reinforcement for positive and negative moments are calculated
on the basis of the section properties provided by the user. If the
section dimensions are inadequate to carry the applied load, that is
if the required reinforcement is greater than the maximum
allowable for the cross section, the program reports that beam fails
in maximum reinforcement. Rectangular sections are also designed
with compression reinforcement.
Section 11A
11-7
Effective depth is chosen as Total depth - (Clear cover + diameter
of stirrup + half the dia. of main reinforcement), and a tr ial value
is obtained by adopting proper bar sizes for the stirrups and main
reinforcements. The relevant clauses in Sections 1.5, 1.6, 2.1.1 -2-
5, 3.10 and 5.2.2 of NTC Concrete are utilized to obtain the actual
amount of steel required as well as the maximum allowable and
minimum required steel. These values are reported as ROW,
ROWMX and ROWMN in the output and can be printed using the
parameter TRACK 1.0 (see Table 10A.1). In addition, the
maximum, minimum and actual bar spacing are also printed.
It is important to note that beams are designed for flexural moment
MZ only. The moment MY is not considered in the flexural design.
Design for Shear
Shear reinforcement is calculated to resist both shear forces and
torsional moments. Shear forces are calculated at a distance
(d+SFACE) and (d+EFACE) away from the end nodes of the beam.
SFACE and EFACE have default values of zero unless provided
under parameters (see Table 10A.1). Note that the value of the
effective depth "d" used for this purpose is the update value and
accounts for the actual c.g. of the main reinforcement calculated
under flexural design. Clauses 2.1.5-6 and 5.2.4 of NTC Concrete
are used to calculate the reinforcement for shear forces and
torsional moments. Based on the total stirrup reinforcement
required, the size of bars, the spacing, the number of bars and the
distance over which they are provided are calculated. Stirrups due
to geometric conditions are assumed to be 2-legged, due to design
conditions could be 2 or 4-legged.
Design for Anchorage
In the output for flexural design, the anchorage details are also
provided. At any particular level, the START and END coordinates
of the layout of the main reinforcement is described along with the
information whether anchorage in the form of a hook or
continuation is required or not at these START and END points.
Note that the coordinates of these START and END points are
obtained after taking into account the anchorage requirements.
Concrete Design Per Mexican Code
Section 11A
11-8
Anchorage length is calculated on the basis of the Clauses
described in Section 3.1 of NTC concrete. In case the program
selects 2 different diameters for the main or compression
reinforcement, only the anchorage for the largest diameter is
analyzed.
Output
Section 11A
11-9
ACTUAL OUTPUT FROM DESIGN
=====================================================================
BEAM NO. 1 DESIGN RESULTS - FLEXURE PER CODE NTC FOR THE DESIGN AND
CONSTRUCTION OF CONCRETE STRUCTURES,DDF LEN - 525.00(cm) FY - 4200. FC -
250. SIZE - 30.00 X 80.00(cm)
LEVEL HEIGHT BAR INFO FROM TO ANCHOR
(cm) (cm) (cm) STA END
_____________________________________________________________________ 1
4. 8 - -NUM, 5 0. 39. YES NO 1 4. 1 - -NUM,
4 0. 39. 2 8. 3 - -NUM, 5 0.
39. YES NO |------------------------------------------------------------
----| | CRITICAL MOMENT=5978000.50 Kg cm AT 0.00 (cm)LOAD 1|
| REQD STEEL= 24.41 (cm2)ROW=0.0109 ROWMX=0.0190 ROWMN=0.0026 |
| REQD COMP STEEL= 0.00 (cm2) |
| MAX/MIN/ACTUAL BAR SPACING= 24.14/ 3.18/ 3.45 (cm) |
| COMP MAX/MIN/ACTUAL BAR SPACING= 0.00/ 0.00/ 0.00 (cm) |
| BASIC/REQD. DEVELOPMENT LENGTH = 40.07/ 39.08(cm) |
|----------------------------------------------------------------| Cracked
Moment of Inertia Iz at above location = 1015658.4 cm^4 3 77. 10 - -
NUM, 4 0. 45. YES NO 4 73. 9 - -NUM, 4 0.
45. YES NO |-------------------------------------------------------------
---| | CRITICAL MOMENT=5978000.50 Kg cm AT 0.00 (cm)LOAD 1|
| REQD STEEL= 24.17 (cm2)ROW=0.0107 ROWMX=0.0190 ROWMN=0.0026 |
| REQD COMP STEEL= 0.00 (cm2) |
| MAX/MIN/ACTUAL BAR SPACING= 24.46/ 2.54/ 2.72 (cm) |
| COMP MAX/MIN/ACTUAL BAR SPACING= 0.00/ 0.00/ 0.00 (cm) |
| BASIC/REQD. DEVELOPMENT LENGTH = 32.00/ 44.81(cm) |
|----------------------------------------------------------------|Cracked Moment
of Inertia Iz at above location = 1008728.7 cm^4 REQUIRED REINF. STEEL SUMMARY :
-------------------------------
SECTION REINF STEEL(+VE/-VE) MOMENTS(+VE/-VE) LOAD(+VE/-VE)
( CM ) (SQ. CM ) (KG -CM )
0.00 24.67/ 24.67 5978000./ 5978000.50 0/ 0
525.00 24.67/ 24.67 5978000./ 5978000.50 0/ 0
B E A M N O. 1 D E S I G N R E S U L T S – SHEAR
AT START SUPPORT - Vu=41850.00 Kg Vc= 6074.49 Kg Vs=44719.39 Kg
Tu= 0.00 Kg cm Tc= 0.00 Kg cm Ts= 0.00 Kg cm LOAD 0
NO STIRRUPS ARE REQUIRED FOR TORSION.
REINFORCEMENT IS REQUIRED FOR SHEAR.
PROVIDE NUM. 2.5 2-LEGGED STIRRUPS AT 7.(cm) C/C FOR 176.(cm)
ADDITIONAL LONGITUDINAL STEEL REQD. FOR TORSIONAL RESISTANCE = 0.00 (cm2)
AT END SUPPORT - Vu=37450.00 Kg Vc= 6074.49 Kg Vs=39219.39 Kg
Tu= 0.00 Kg cm Tc= 0.00 Kg cm Ts= 0.00 Kg cm LOAD 0
NO STIRRUPS ARE REQUIRED FOR TORSION.
REINFORCEMENT IS REQUIRED FOR SHEAR.
PROVIDE NUM. 2.5 2-LEGGED STIRRUPS AT 8.(cm) C/C FOR 176.(cm)
ADDITIONAL LONGITUDINAL STEEL REQD. FOR TORSIONAL RESISTANCE = 0.00 (cm2)
Concrete Design Per Mexican Code
Section 11A
11-10
11A.6 Column Design
Columns design in STAAD per the Mexican code is performed for
axial force and uniaxial as well as biaxial moments. All active
loadings are checked to compute reinforcement. The loading which
produces the largest amount of reinforcement is called the critical
load. Column design is done for square, rectangular and circular
sections. For rectangular and circular sections, reinforcement is
always assumed to be equally distributed on all faces. This means that
the total number of bars for these sections will always be a multiple
of four (4). If the MMAGx & -MMAGy parameters are specified, the
column moments are multiplied by the corresponding MMAG value to
arrive at the ultimate moments on the column. Minimum eccentricity
conditions to be satisfied according to section 2.1.3.a are checked.
Method used: Bresler Load Contour Method
Known Values: Pu, Muy, Muz, B, D, Clear cover, Fc, Fy
Ultimate Strain for concrete : 0.003
Steps involved :
1. Assume some reinforcement. Minimum reinforcement (1% for
ductile design or according to section 4.2.2 ) is a good amount
to start with.
2. Find an approximate arrangement of bars for the assumed
reinforcement.
3. Calculate PNMAX = Po, where Po is the maximum axial load
capacity of the section. Ensure that the actual nominal load on
the column does not exceed PNMAX. If PNMAX is less than
the axial force Pu/FR, (FR is the strength reduction factor)
increase the reinforcement and repeat steps 2 and 3. If the
reinforcement exceeds 6% (or 4% for ductile design), the
column cannot be designed with its current dimensions.
4. For the assumed reinforcement, bar arrangement and axial
load, find the uniaxial moment capacities of the column for the
Section 11A
11-11
Y and the Z axes, independently. These values are referred to
as MYCAP and MZCAP respectively.
5. Solve the Interaction Bresler equation:
Mny Mnz
+
Mycap Mycap
Where a = 1.24. If the column is subjected to uniaxial moment: a =1
6. If the Interaction equation is satisfied, find an arrangement
with available bar sizes, find the uniaxial capacities and solve
the interaction equation again. If the equation is satisfied now,
the reinforcement details are written to the output file.
7. If the interaction equation is not satisfied, the assumed
reinforcement is increased (ensuring that it is under 6% or 4%
respectively) and steps 2 to 6 are repeated.
By the moment to check shear and torsion for columns the sections
have to be checked as beams and the most strict of both shear and
torsion reinforcement adopted.
11A.7 Column Interaction
The column interaction values may be obtained by using the
design parameter TRACK 1.0 or TRACK 2.0 for the column
member. If a value of 2.0 is used for the TRACK parameter, 12
different Pn-Mn pairs, each representing a different point on the
Pn-Mn curve are printed. Each of these points represents one of
the several Pn-Mn combinations that this column is capable of
carrying about the given axis, for the actual reinforcement that the
column has been designed for. In the case of circular columns, the
values are for any of the radial axes. The values printed for the
TRACK 1.0 output are:
Concrete Design Per Mexican Code
Section 11A
11-12
P0 = Maximum allowable pure axial load on the column (moment zero).
Pnmax = Maximum allowable axial load on the column.
P_bal = Axial load capacity of balanced strain condition.
M_bal = Uniaxial moment capacity of balanced strain condition.
E_bal = M_bal / P_bal = Eccentricity of balanced strain condition.
M0 = Moment capacity at zero axial load.
P_tens = Maximum permissible tensile load on the column.
Des. Pn = Pu/FR where FR is the Strength Reduction Factor and Pu is the axial
load for the critical load case.
Des.Mnx = Mux*MMAGx/FR where FR is the Strength Reduction Factor and Mu
is the bending moment for the appropriate axis for the critical load case.
Mu = (Mux.Mmagx)²+ (Muy.Mmagy)²
e/h = (Mn/Pn)/h where h is the length of the column
11A.8 Column Design Output
The next table illustrates different levels of the column design
output.
Section 11A
11-13
The output is generated without any TRACK specification:
====================================================================
COLUMN NO. 1 DESIGN PER - AXIAL + BENDING
FY -4200.0 FC - 294.1 Kg/cm2 CIRC SIZE 100.0(cm)DIAMETER
AREA OF STEEL REQUIRED = 128.506
BAR CONFIGURATION REINF PCT. LOAD LOCATION PHI
----------------------------------------------------------
46 - NUMBER 6 1.669 1 END 0.700
(EQUALLY SPACED)
TRACK=1 generates the following additional output:
COLUMN INTERACTION: MOMENT ABOUT Z/Y -AXIS (Kg-cm )
--------------------------------------------------------
P0 Pn max P-bal. M-bal. e-bal.(cm)
2095196.38 2095196.38 727411.12 29235398.00 40.2
M0 P-tens. Des.Pn 'Des.Mn e/h
20606994.00 -550620.00 0.00 20000000.00 NaN
--------------------------------------------------------
TRACK=2 generates the following output in addition to all the above:
Pn Mn Pn Mn
| 1934027.38 5373253.50 967013.69 27278232.00
P0 |* 1772858.50 11408365.00 805844.75 28658428.00
| * 1611689.50 16296947.00 644675.81 29473708.00
Pn,max|__* 1450520.62 20083028.00 483506.84 28901764.00
| * 1289351.62 23117562.00 322337.91 27205616.00
Pn | * 1128182.62 25462606.00 161168.95 24433192.00
NOMINAL| *
AXIAL| *
COMPRESSION| *
Pb|-------*Mb
| *
___________|____*_______
| * M0 Mn,
| * BENDING
P-tens|* MOMENT
11A.9 Slab Design
Slab are designed per Mexican NTC specifications. To design a
slab, it must be modeled using finite elements.
Element design will be performed only for the moments MX and
MY at the center of the element. Design will not be performed for
FX, FY, FXY, MXY. Also, design is not performed at any other
point on the surface of the element. Shear is checked with Q.
A typical example of element design output is shown below. The
reinforcement required to resist Mx moment is denoted as
Concrete Design Per Mexican Code
Section 11A
11-14
longitudinal reinforcement and the reinforcement required to resist
My moment is denoted as transverse reinforcement. The
parameters FYMAIN, FC, CLEAR, DIM_PRECAUTION, and
EXPOSED_SOIL_WEATHER listed in Table 3.1 are relevant to
slab design. Other parameters mentioned are not used in slab
design.
ELEMENT DESIGN SUMMARY ----------------------
ELEMENT LONG. REINF MOM-X /LOAD TRANS. REINF MOM-Y /LOAD
(SQ.CM/M ) (T -M /M ) (SQ.CM/M ) (T -M /M )
1 TOP : Longitudinal direction - Only minimum steel required.
1 BOTT: Transverse direction - Only minimum steel required.
1 TOP : 2.239 0.00 / 0 3.252 983.00 / 1
BOTT: 3.758 983.00 / 1 1.684 0.00 / 0
1 SHEAR CAPACITY 3794.73 Kg ***PASS***
11-15
Steel Design per Mexican Code
11B.1 General
The program is based in: Complementary Technical Standards for
the Design and Construction of Steel Structures – Dec. 1987.
(Normas Técnicas Complementarias para Diseño y construcción de
Estructuras Metálicas) of the Mexican Construction Code for the
Federal District –Aug. 1993 (Reglamento de Construcciones para
el Distrito Federal).
The design philosophy considered is that of the Load Cases and
Resistance Method or Limit States Design usually known as Load
and Resistance Factor Design (LRFD).
Structures are designed and proportioned taking into consideration
the limit states at which they would become unfit for their
intended use. Two major categories of limit-state are recognized--
ultimate and serviceability. The primary considerations in ultimate
limit state design are strength and stability, while that in
serviceability is deflection. Appropriate load and resistance factors
are used so that a uniform reliability is achieved for all steel
structures under various loading conditions and at the same time
the chances of limits being surpassed are acceptably remote.
In the STAAD implementation of the Mexican Standards for steel
structures, members are proportioned to resist the design loads
without exceeding the limit states of strength, and stability. It
allows to check deformation to verify serviceability.
Accordingly, the most economic section is selected on the basis of
the least weight criteria as augmented by the designer in
Section 11B
Steel Design Per Mexican Code
Section 11B
11-16
specification of allowable member depths, desired section type, or
other such parameters. The code checking portion of the program
checks that main code requirements for each selected section are
met and identifies the governing criteria.
The following sections describe the salient features of the Mexican
specifications as implemented in STAAD steel design. A brief
description of the fundamental concepts is presented here.
11B.2 Limit States Design Fundamentals
The primary objective of the Limit States Design Specification is
to provide a uniform reliability for all steel structures under
various loading conditions.
The Limit States Design Method uses separate factors for each
load and resistance. Because the different factors reflect the degree
of uncertainty of different loads and combinations of loads and of
the accuracy of predicted strength, a more uniform reliability is
possible.
The method may be summarized by the inequality
Yi Qi < Rn FR
On the left side of the inequality, the required strength is the
summation of the various load effects, Qi, multiplied by their
respective load factors, yi. The design strength, on the right side,
is the nominal strength or resistance, Rn, multiplied by a
resistance factor, FR.
In the STAAD implementation of the Mexican Standards, it is
assumed that the user will use appropriate load factors and create
the load combinations necessary for analysis. The design portion
of the program will take into consideration the load effects (forces
and moments) obtained from analysis. In calculation of resistances
of various elements (beams, columns etc.), resistance (nominal
strength) and applicable resistance factor will be automatically
considered.
Section 11B
11-17
11B.3 Member End Forces and Moments
Member end forces and moments in the member result from loads
applied to the structure. These forces are in the local member
coordinate system. the following figures show the member end
actions with their directions.
Steel Design Per Mexican Code
Section 11B
11-18
11B.4 Section Classification
The Limit States Design specification allows inelastic deformation
of section elements. Thus local buckling becomes an important
criterion. Steel sections are classified as compact (type 2),
noncompact (type 3), or slender element(type 4), sections
depending upon their local buckling characteristics, besides
sections type 1 are able for plastic design. This classification is a
function of the geometric properties of the section. The design
procedures are different depending on the section class. STAAD is
capable of determining the section classification for the standard
shapes and design accordingly.
11B.5 Member in Axial Tension
The criteria governing the capacity of tension members is based on
two limit states. The limit state of yielding in the gross section is
intended to prevent excessive elongation of the member. The
second limit state involves fracture at the section with th e
minimum effective net area. The net section area may be specified
by the user through the use of the parameter NSF (see Table
10B.1), that always refers to the gross section. STAAD calculates
the tension capacity of a given member based on these two limit
states and proceeds with member selection or code check
accordingly.
In addition to the tension resistance criterion, the user defines if
tension members are required to satisfy slenderness limitations
which are a function of the nature of use of the member (main load
resisting component, bracing member, etc.). In both the member
selection and code checking process, STAAD immediately does a
slenderness check on appropriate members before continuing with
other procedures for determining the adequacy of a given member.
Section 11B
11-19
11B.6 Axial Compression
The column strength equations take into account inelastic
deformation and other recent research in column behavior. Two
equations governing column strength are available, one for
inelastic buckling and the other for elastic or Euler buckling. Both
equations include the effects of residual stresses and initial out -of-
straightness. Compression strength for a particular member is
calculated by STAAD according to the procedure outlin ed in
Section 3.2 of the NTC. For slender elements, the procedure
described in Section 2.3.6.NTC is also used.
The procedures of Section 3.2 of the Commentaries, design helps
and examples of the Complementary Technical Standards for the
Design and Construction of Steel Structures (de los Comentarios,
ayudas de diseño y ejemplos de las Normas Técnicas
Complementarias para el Diseño y Construcción de Estructuras
Metálicas, DDF (Comentarios - Julio 1993) were implemented for
the determination of design strength for these limit states.
Effective length for calculation of compression resistance may be
provided through the use of the parameters KY, KZ and/or LY,
LZ. If not provided, the entire member length will be taken into
consideration.
In addition to the compression resistance criterion, compression
members are required to satisfy slenderness limitations which are a
function of the nature of use of the member (main load resisting
component, bracing member, etc.). In both the member selection
and code checking process, STAAD immediately does a
slenderness check on appropriate members before continuing with
other procedures for determining the adequacy of a given member.
Steel Design Per Mexican Code
Section 11B
11-20
11B.7 Flexural Design Strength
In the Limit States Design Method, the flexural design strength of
a member is determined mainly by the limit state of lateral
torsional buckling. Inelastic bending is allowed and the basic
measure of flexural capacity is the plastic moment capacity of the
section.
The flexural resistance is a function of plastic moment capacity,
actual laterally unbraced length, limiting laterally unbraced length,
buckling moment and the bending coefficient. The limiting
laterally unbraced length Lu and flexural resistance Mr are
functions of the section geometry and are calculated as per the
procedure of Section 3.3.2 of the NTC.
The purpose of bending coefficient Cb is to account for the
influence of the moment gradient on lateral-torsional buckling.
This coefficient can be specified by the user through the use of
parameter CB or CBy (see Table 10B.1) or may be calculated by
the program (according to LRDF USA specification) if CB is
specified as 0.0. In the absence of the parameter CB, a default
value of 1.0 will be used.
To specify laterally unsupported length, either of the parameters
UNL and UNF (see Table 10B.1) can be used.
It is taken into account the reduction of flexural resistance due to
slender web according to section 4.5.8 of the NTC
For the sections where the web and flange are slender the LRDF
USA specification was used.
Section 11B
11-21
Stress areas due to bending about y axis (MY)
Notes: the local X axis goes into the page; the Global Y axis is
vertical upwards; the shaded area indicates area under
compression; the area not shaded indicates area under tension.
Stress areas due to bending about Z axis (MZ)
Steel Design Per Mexican Code
Section 11B
11-22
11B.8 Design for Shear
The procedure of Sect. 3.3.3 of the NTC is used in STAAD to
design for shear forces in members. Besides combined bending and
shear is checked according to section 3.3.4 of the NTC,
considering also the limits for stiffeners of the web according to
sections 4.5.6/7 of the NTC. Shear in wide flanges and channel
sections is resisted by the area of the web/s..
11B.9 Combined Compression Axial Force and Bending
The interaction of flexure and axial forces in singly and doubly
symmetric shapes is governed by formulas of the Section 3.4 of
the NTC. These interaction formulas cover the general case of
biaxial bending combined with axial force. They are also valid for
uniaxial bending and axial force.
It is considered that the frames are part of structures that have
shear walls or rigid elements so that the lateral displacements of a
floor could be disregarded. The program has included for mulas to
include structures with lateral displacements in the future
considering for B2 the columns individually and not the complete
floor analysis.
It is taken into account if the elements have transverse loads and if
the ends are angularly restrained.
11B.10 Combined Tension Axial Force and Bending
Based on Section 3.5 4 of the NTC.
Section 11B
11-23
11B.11 Design Parameters
Design per Mexican Standards is requested by using the CODE.
Other applicable parameters are summarized in Table 10B.1. These
parameters communicate design decisions from the engineer to the
program and thus allow the engineer to control the design process
to suit an application's specific needs.
The default parameter values have been selected such that they are
frequently used numbers for conventional design. Depending on
the particular design requirements, some or all of these parameter
values may be changed to exactly model the physical structure.
The parameters DMAX and DMIN may only be used for member
selection only.
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
Steel Design Per Mexican Code
Section 11B
11-24
TABLA 11B.1. DESIGN PARAMETERS ACCORDING TO MEXICAN
STANDARS - STEEL
Parameter Default Description
Name Value
KX 1.0 K value for flexural-torsional buckling
KY 1.0 K value in local Y axis- Usually minor axis
KZ 1.0 K value in local Z axis- Usually major axis
LX Member length Length for flexural-torsional buckling
LY Member length Length to calculate slenderness ratio for buckling
about local Y axis.
LZ Member length Length to calculate slenderness ratio for buckling about local Z axis.
FYLD 2530 kg/cm2 Minimum Yield strength of steel
FU 4230 Kg/cm2 Ultimate tensile strength of steel
NSF 1 Net section factor for tension members
UNT Member length Unsupported length (L) of the top* flange for calculating flexural strength . Will be used only if compression is in the top flange.
UNB Member length Unsupported length (L) of the bottom* flange for calculating flexural strength . Will be used only if compression is in the bottom flange.
STIFF Member length Spacing of stiffeners for beams for shear design
Cb y Cby 1 Coefficient C defined per section 3.3.2.2. If Cb is set to 0.0 it will be calculated by the program according to LRFD USA (CbMex=1/CbUSA). Any other value will be directly used in the design.
TRACK 0 0 = Suppress all design strengths
1 = Print all design strengths
2 = Print expanded design output
DMAX 114 cm Maximum allowable depth
DMIN 0.0 cm Minimum allowable depth
RATIO 1.0 Permissible ratio of actual load effect and design
strength
BEAM 0 0: Design at ends and those locations specified by SECTION command.
1: Design at ends and at every y cada 1/12th point along member length
Rigid_to_H_Loads TRUE Defines if the structure has elements to bear the wind load ( shear walls, wind trusses or bracing
Section 11B
11-25
TABLA 11B.1. DESIGN PARAMETERS ACCORDING TO MEXICAN
STANDARS - STEEL
Parameter Default Description
Name Value
rigid elements ) that restrict lateral displacements
and allow to disregard slenderness effects.
IRREG 0 Variable defined for the whole structure indicating if it is regular or irregular according
to section 3.4 of the NTC. IRREG=1 for columns being part of irregular structures.
I_NO_OXIG 0 Defined for I shapes or tubes
Curve Definition according to NTC.3.2.2.1a) I_NO_OXIG.= 0 implies n=1.4 laminated I shapes, tubes or built up with 3 or 4 welded plates obtained from wider plates cuts with oxygen. I_NO_OXIG.= 1 implies n=1 I shapes, tubes or built up with 3 or 4 welded plates
n is defined by the program
IMAIN_MEM 0 IMAIN_MEM=0 MAIN MEMBER IMAIN_MEM=1 Secondary and wind trusses
Ccomb 1 Cfactor for combined forces when there are transverse loads in the members. Section 3.4.3.3.ii NTC Ccomb=1 If members ends are restricted
angularly. Ccomb=0.85 If members ends are not restricted angularly.
DUCTILE_SEISMIC
_DESIGN
TRUE DUCTILE FRAMES ACCORDING TO
SECTION 11. Main design conditions are considered (not including, at the moment, geometric ones)
KX 1.0 K value for flexural-torsional buckling
KY 1.0 K value in local Y axis- Usually minor axis
KZ 1.0 K value in local Z axis- Usually major axis
LX Member length Length for flexural-torsional buckling
LY Member length Length to calculate slenderness ratio for buckling
about local Y axis.
LZ Member length Length to calculate slenderness ratio for buckling about local Z axis.
FYLD 2530 kg/cm2 Minimum Yield strength of steel
FU 4230 Kg/cm2 Ultimate tensile strength of steel
Steel Design Per Mexican Code
Section 11B
11-26
TABLA 11B.1. DESIGN PARAMETERS ACCORDING TO MEXICAN
STANDARS - STEEL
Parameter Default Description
Name Value
NSF 1 Net section factor for tension members
UNT Member length Unsupported length (L) of the top* flange for calculating flexural strength . Will be used only
if compression is in the top flange.
UNB Member length Unsupported length (L) of the bottom* flange for calculating flexural strength . Will be used only
if compression is in the bottom flange.
STIFF Member length Spacing of stiffeners for beams for shear design
Cb y Cby 1 Coefficient C defined per section 3.3.2.2. If Cb is set to 0.0 it will be calculated by the program according to LRFD USA (CbMex=1/CbUSA). Any other value will be directly used in the design.
TRACK 0 0 = Supress all design strengths
1 = Print all design strengths
2 = Print expanded design output
DMAX 114 cm Maximum allowable depth
DMIN 0.0 cm Minimum allowable depth
RATIO 1.0 Permissible ratio of actual load effect and design
strength
BEAM 0 0: Design at ends and those locations specified by SECTION command.
1: Design at ends and at every y cada 1/12th point along member length
Rigid_to_H_Loads TRUE Defines if the structure has elements to bear the wind load ( shear walls, wind trusses or bracing rigid elements ) that restrict lateral displacements and allow to disregard slenderness effects.
IRREG 0 Variable defined for the whole structure indicating if it is regular or irregular according to section 3.4 of the NTC. IRREG=1 for columns being part of irregular structures.
I_NO_OXIG 0 Defined for I shapes or tubes Curve Definition according to NTC.3.2.2.1a) I_NO_OXIG.= 0 implies n=1.4
laminated I shapes, tubes or built up with 3 or 4 welded plates obtained from wider plates cuts with oxygen.
Section 11B
11-27
TABLA 11B.1. DESIGN PARAMETERS ACCORDING TO MEXICAN
STANDARS - STEEL
Parameter Default Description
Name Value
I_NO_OXIG.= 1 implies n=1
I shapes, tubes or built up with 3 or 4 welded plates n is defined by the program
IMAIN_MEM 0 IMAIN_MEM=0 MAIN MEMBER
IMAIN_MEM=1 Secondary and wind trusses
Ccomb 1 Cfactor for combined forces when there are transverse loads in the members. Section
3.4.3.3.ii NTC Ccomb=1 If members ends are restricted angularly. Ccomb=0.85 If members ends are not restricted angularly.
DUCTILE_SEISMIC _DESIGN
TRUE DUCTILE FRAMES ACCORDING TO SECTION 11. Main design conditions are considered (not including, at the moment, geometric ones)
* Top and Bottom represent the positive and negative side of the local Y axis (local
Z axis if SET Z UP is used.
Note: For deflection check, parameters DFF, DJ1 and DJ2 from Table 2.1 may be
used. All requirements remain the same.
11B.12 Code Checking and Member Selection
Both code checking and member selection options are available in
STAAD Mexican Standards implementation.
Steel Design Per Mexican Code
Section 11B
11-28
11B.13 Tabulated Results of Steel Design
Results of code checking and member selection are presented in a
tabular format.
CRITICAL COND refers to the section of the Mexican NTC which
governed the design.
If the TRACK is set to 1.0, member design strengths will be
printed out.
Section 12
Russian Codes
12-1
Concrete Design Per Russian Code (SNiP 2.03.01-84*)
12A.1 General
Russian Code SNiP 2.03.0184* “Plain concrete and concrete
structures” is based on the method of limit states. Code SNiP
2.03.0184* defines two groups of limit states.
Analysis according to the first group of limit states is performed to
avoid the following phenomena:
brittle, plastic or other type of failure,
loss by structure of stable form or position,
fatigue failure,
failure due to the action of load actions and unfavourable
environmental effects.
Analysis according to the second group of limit states is performed
to avoid the following phenomena:
excessive and longterm opening of cracks if they are allowed
according to service conditions,
excessive displacements.
Analysis of structures for the first group of limit states is
performed with the use of the maximum (design) loads and
actions. Analysis of structures for the second group of limit states
is made in accordance with the operational (normative) loads and
actions. Ratio between design and normative loads is called
reliability coefficient for loads which is determined according to
SNiP 2.01.07.-85 “Loads and actions”.
Section 12A
Concrete Design Per Russian Code
Section 12A
12-2
Reliability coefficient n for destination according to SNiP
2.01.07.-85 shall be considered in determination of loads and their
combinations.
Program STAAD/Pro makes it possible to calculate reinforcement
for concrete members according to codes of many countries round
the World and Russian Code SNiP 2.03.0184* inclusive.
Algorithms for calculation of reinforcement of concrete linear
(beams, columns) and 2D (two dimensional) (slabs, walls, shells)
members are incorporated in program STAAD/Pro. Not only Code
SNiP 2.03.0184* but also the “Guide for design of plain concrete
and reinforced concrete structures from normal weight and
lightweight concrete (to SNiP 2.03.0184)” have been used in
creation of these algorithms.
It is possible using program STAAD/Pro to calculate
reinforcement for beams of rectangular or T section and for
columns of rectangular or circular section (Fig.1).
Figure 1 - Notation of dimensions for rectangular, circular and T sections
Flange of T-shape beams may be situated at the top zone of the
section if the angle BETA=00, or at the bottom zone of the section,
if BETA=1800.
Section 12A
12-3
12A.2 Input Data
Entry of data of cross-sections of beams and columns is made by
the use of MEMBER PROPERTIES command, and thicknesses of
2D members are entered by ELEMENT PROPERTY command.
Example:
UNIT MM
MEMBER PROPERTIES
* Columns of rectangular cross-section
1 TO 16 PRI YD 350. ZD 350.
* Columns of circular cross-section
17 TO 22 PRI YD 350.
* Beams of T cross-section
23 TO 40 PRI YD 450. ZD 550. YB 230. ZB 200.
UNIT METER
ELEMENT PROPERTY
41 TO 100 THICKNESS 0.14
101 TO 252 THICKNESS 0.16
* Flange of T beams is located at the bottom zone of
cross-section
BETA 180. MEMB 23 TO 40
Commands for calculation of reinforcement are located in the
input data file after the command of analysis and as a rule, after
output commands to print results of calculation.
Example:
* Command of analysis PERFORM ANALYSIS
.
.* Output command to print results of calculation
(according to user’s judgment)
.
Concrete Design Per Russian Code
Section 12A
12-4
* Command of loading and their combinations
considered in design
LOAD LIST 1 5 TO 9
* Command to start reinforcement calculation procedure
START CONCRETE DESIGN
CODE RUSSIAN
.* List of parameters being used in reinforcement
calculation
.
.
BCL 20. MEMB 17 TO 22
CL1 0.04 MEMB 1 TO 40
DD2 10. MEMB 23 TO 40
CRA 0.036 MEMB 41 TO 252
.
.
.
* Command of beam reinforcement calculation
DESIGN BEAM 23 TO 40
* Command of column reinforcement calculation
DESIGN COLUMN 1 TO 22
* Command of calculation 2D elements (slabs, walls,
shells)
DESIGN ELEMENT 41 TO 252
* Command of interruption reinforcement calculation
END CONCRETE DESIGN
In tables 1, 2 and 3 information about parameters used for
calculation of reinforcement for beams, columns and 2D (two
dimensional) members is presented. Values of parameters do not
depend on UNIT command. In the file of input data only such
parameters have to be taken, the values of which differ from
determined in the program.
Section 12A
12-5
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
Table 1- Names of parameters for Concrete design according to Russian Code
СНиП 2.03.0184* for beams.
No. Parameter
name
Default
value Description
1 NLT 1 Number of long-term loading case
2 RCL 3
Class of longitudinal reinforcement:
RCL = 1, if class of reinforcement is A-I;
RCL = 2, if class of reinforcement is A-II;
RCL = 3, if class of reinforcement is A-III;
RCL = 33, if class of reinforcement is A-IIIb;
RCL = 4, if class of reinforcement is A-IV;
RCL = 5, if class of reinforcement is A-V;
RCL = 6, if class of reinforcement is A-VI;
RCL = 7, if class of reinforcement is A-VII;
RCL = 77, if class of reinforcement is K-7;
RCL = 8, if class of reinforcement is B-II;
RCL = 9, if class of reinforcement is Bp-II;
RCL = 10, if class of reinforcement is Bp-I;
RCL = 19, if class of reinforcement is K-19
3 USM 1. Total product of service conditions coefficients for
longitudinal reinforcement (s)
4 UB2 0.9 Specific service conditions coefficient for concrete
(b2)
5 DD1 16. Diameter of longitudinal reinforcement bars in
beam tension zone
6 DD2 16. Diameter of shear reinforcement bars for beam;
7 BCL 15. Compression class of concrete
8 UBM 1. Product of service conditions coefficients for
concrete, except UB2 (b)
9 TEM 0.
Parameter of concrete hardening conditions:
TEM=0, for natural hardening conditions;
TEM=1, for steam hardening conditions
10 CL1 0.05 Distance from top/bottom fiber of beam cross
Concrete Design Per Russian Code
Section 12A
12-6
No. Parameter
name
Default
value Description
section to the center of longitudinal reinforcement
bar;
11 CL2 0.05 Distance from left/right side of beam cross section
to the center of longitudinal reinforcement bar
12 WST 0.4 Ultimate width of short-term crack
13 WLT 0.3 Ultimate width of long-term crack
14 SSE 0
Limit state parameter for beam design
SSE=0, if calculation of reinforcement
amount must be carried out according to the
requirements of load carrying capacity (the
first limit state);
SSE=1, if calculation of reinforcement
amount must be carried out according to the
cracking requirements (the second limit
state)
15 RSH 1
Class of shear reinforcement:
RSH = 1, if class of reinforcement is A-I;
RSH = 2, if class of reinforcement is A-II;
RSH = 3, if class of reinforcement is A-III;
RSH = 33, if class of reinforcement is A-
IIIb;
RSH = 4, if class of reinforcement is A-IV;
RSH = 5, if class of reinforcement is A-V;
RSH = 6, if class of reinforcement is A-VI;
RSH = 7, if class of reinforcement is A-VII;
RSH = 77, if class of reinforcement is K-7;
RSH = 8, if class of reinforcement is B-II;
RSH = 9, if class of reinforcement is Bp-II;
RSH = 10, if class of reinforcement is Bp-I;
RSH = 19, if class of reinforcement is K-19
16 FWT ZD
Design width of beam top flange. Use for beam
design only with default value provided as ZD in
member properties.
17 FWB ZB
Design width of beam bottom flange. Use for beam
design only with default value provided as ZB in
member properties.
Section 12A
12-7
No. Parameter
name
Default
value Description
18 DEP YD
Design depth of beam section. Use for beam
design only with default value provided as YD in
member properties.
19 SFA 0. Face of support location at the start of the beam.
Use for beam design only.
20 EFA 0. Face of support location at the end of the beam.
Use for beam design only.
21 NSE 13
Number of equally-spaced sections for beam
design. Use for beam design only. Upper limit is
equal to 20.
Table 2 - Names of parameters for Concrete design according to Russian Code
СНиП 2.03.0184* for columns
No. Parameter
name
Default
value Description
1 NLT 1 Number of long-term loading case
2 RCL 3
Class of longitudinal reinforcement:
RCL = 1, if class of reinforcement is A-I;
RCL = 2, if class of reinforcement is A-II;
RCL = 3, if class of reinforcement is A-III;
RCL = 33, if class of reinforcement is A-IIIb;
RCL = 4, if class of reinforcement is A-IV;
RCL = 5, if class of reinforcement is A-V;
RCL = 6, if class of reinforcement is A-VI;
RCL = 7, if class of reinforcement is A-VII;
RCL = 77, if class of reinforcement is K-7;
RCL = 8, if class of reinforcement is B-II;
RCL = 9, if class of reinforcement is Bp-II;
RCL = 10, if class of reinforcement is Bp-I;
RCL = 19, if class of reinforcement is K-19
3 USM 1. Total product of service conditions coefficients for
longitudinal reinforcement (s)
4 UB2 0.9 Specific service conditions coefficient for concrete
(b2)
5 DD1 16. Minimum diameter of longitudinal reinforcement
Concrete Design Per Russian Code
Section 12A
12-8
No. Parameter
name
Default
value Description
bars for column
6 DD2 16. Maximum diameter of longitudinal reinforcement
bars for column
7 BCL 15. Compression class of concrete
8 UBM 1. Product of service conditions coefficients for
concrete, except UB2 (b)
9 TEM 0.
Parameter of concrete hardening conditions:
TEM=0, for natural hardening conditions;
TEM=1, for steam hardening conditions
10 CL1 0.05 Distance from edge of column cross section to the
center of longitudinal reinforcement bar
11 ELY 1. Column's length coefficient to evaluate
slenderness effect in local Y axis
12 ELZ 1. Column's length coefficient to evaluate
slenderness effect in local Z axis
Тable 3 - Names of parameters for Concrete design according to Russian Code
(SNiP 2.03.01-84*) for slabs and/or walls
No. Parameter
name
Default
value Description
1 NLT 1 Number of long-term loading case
2 RCL 3
Class of longitudinal reinforcement:
RCL = 1, if class of reinforcement is A-I;
RCL = 2, if class of reinforcement is A-II;
RCL = 3, if class of reinforcement is A-III;
RCL = 33, if class of reinforcement is A-
IIIb;
RCL = 4, if class of reinforcement is A-IV;
RCL = 5, if class of reinforcement i s A-V;
RCL = 6, if class of reinforcement is A-VI;
RCL = 7, if class of reinforcement is A-VII;
RCL = 77, if class of reinforcement is K-7;
RCL = 8, if class of reinforcement is B-II;
RCL = 9, if class of reinforcement is Bp-II;
RCL = 10, if class of reinforcement is Bp-I;
Section 12A
12-9
No. Parameter
name
Default
value Description
RCL = 19, if class of reinforcement is K-19
3 USM 1. Total product of service conditions coefficients
for longitudinal reinforcement (s)
4 UB2 0.9 Specific service conditions coefficient for
concrete (b2)
5 SDX 16. Diameter of reinforcing bars located in the first
local (X) direction of slab/wall
6 SDY 16. Diameter of reinforcing bars located in the
second local (Y) direction of slab/wall
7 BCL 15. Compression class of concrete
8 UBM 1. Product of service conditions coefficients for
concrete, except UB2 (b)
9 TEM 0.
Parameter of concrete hardening conditions:
TEM=0, for natural hardening conditions;
TEM=1, for steam hardening conditions
10 CL 0.05
Distance from top/bottom face of slab/wall
element to the center of longitudinal reinforcing
bars located in first local (X) direction. (Main
thickness of top/bottom concrete cover for
slab/wall element)
11 CRA 0.05
Distance from top/bottom face of slab/wall
element to the center of transverse reinforcing
bars located in second local (Y) direction
(Secondary thickness of top/bottom concrete
cover for slab/wall)
12 WST 0.4 Ultimate width of short-term crack
13 WLT 0.3 Ultimate width of long-term crack
14 STA 0
Parameter of limit state for slab/wall design:
STA=0, if calculation of nonsymmetrical
reinforcement must be carried out according
to the requirements of load carrying capacity
(the first limit state);
STA=1, if calculation of symmetrical
reinforcement must be carried out according
to the requirements of load carrying capacity
(the first limit state);
Concrete Design Per Russian Code
Section 12A
12-10
No. Parameter
name
Default
value Description
STA=2, if calculation of nonsymmetrical
reinforcement must be carried according to
the cracking requirements (the second limit
state);
STA=3, if calculation of symmetrical
reinforcement must be carried according to
the cracking requirements (the second limit
state)
15 SELX 0. Design length of wall member to evaluate
slenderness effect in local X axis
16 SELY 0. Design length of wall member to evaluate
slenderness effect in local Y axis
17 MMA 0
Design parameter of slab/wall reinforcement:
MMA=0, if reinforcement calculation must
be applied by stresses in local axis;
MMA=1, if reinforcement calculation must
be applied by principal stresses
18 MMB 1
Design parameter of slab/wall reinforcement:
MMB=0, if the effect of additional
eccentricity is not taken into account;
MMB=1, if the effect of additional
eccentricity is taken into account
12A.3 Beams
Reinforcement for beams of rectangular and T cross-section can be
calculated. In calculation of longitudinal reinforcement bending
moment about local axis Z loc and torsional moments are
considered, but influence of longitudinal forces and bending
moments in relation to local axis Yloc is ignored. In calculation of
transverse reinforcement shear forces parallel to local axis Yloc and torsional moments are taken into account.
Section 12A
12-11
Reinforcement for beams can be calculated either from conditions
of strength or from conditions of open crack width limitation (see
parameter SSE).
Parameters SFA and ЕFA are considered only in calculation of
transverse reinforcement.
In general case calculation of reinforcement for beams is carried
out two times – according to strength conditions and according to
conditions of open crack width limitation. In reinforcement
calculations from conditions of strength design values of load have
to be taken and in calculations from conditions of crack width
limitation – characteristic (normative) load values are used. Both
calculations can be carried out in one session with the use multiple
analysis possibility of the program STAAD.Pro.
In most cases calculation of reinforcement is carried out with
account only of a part of loadings. In such cases command LOAD
LIST is used, in which numbers of loads considered in calculation
are indicated. Number of permanent and long-term loads equal to
parameter NLT must be included into the list of considered loads.
It has to be noted, that values of parameters DD1 and DD2 have
influence not only on the width of opened crack but also in som e
cases, on design and normative reinforcement resistances.
Parameter BCL can be equal to any value of concrete compression
strength class given in SNiP 2.03.0184* and to any intermediate
value as well.
It should be remembered, that accuracy of results of calculation of
transverse reinforcement increases with the value of parameter
NSE.
Parameters SFA and ЕFA are considered only in calculations of
transverse reinforcement. Beam 1 is shown in Figure 2 with rigid
intervals the lengths of which are: at the start of the beam 0.3m
and at the end – 0.2m. In modeling of the beam the following
command can be used.
Concrete Design Per Russian Code
Section 12A
12-12
MEMBER OFFSET
1 START 0.3 0 0
1 END -0.2 0 0
Figure 2 - Diagram of a beam with rigid intervals
When command MEMBER OFFSET is used forces corresponding
to the beam the length of which is equal to the distance between
points a and b are calculated and then used in calculation of
reinforcement. In such case it is necessary to take into account
default values of parameters SFA and ЕFA equal to zero.
When command MEMBER OFFSET is not used forces
corresponding to the beam the length of which is equal to the
distance between points 10 and 11 are calculated and then used in
calculation of reinforcement. In this case it is necessary to
consider values of parameters SFA=0.3 and ЕFA=0,2 in
reinforcement calculation.
In both cases calculated quantity of transverse reinforcement will
be the same. Calculated quantity of longitudinal reinforcement in
the second case will be greater.
For beam the following output is generated:
beam number;
method of calculation (according to conditions of strength
or limitations of opened crack width);
length and cross-sectional dimensions;
distance from resultant of forces acting in bottom/top
reinforcement to bottom/top edge of the section;
Section 12A
12-13
distance from the side edge of cross-section of the beam
web to the centroid of longitudinal bars located at this
edge;
concrete class;
class of longitudinal and transverse reinforcement;
assumed in calculations bar diameters of longitudinal and
transverse reinforcement;
calculation results of longitudinal and transverse
reinforcement (in two tables).
In nine columns of the first table the following results are
presented:
Section distance of the section from the “start” of the
beam, мм
As cross-sectional area of longitudinal
reinforcement in the bottom zone of cross-
section of the beam, if angle BETA=0, or in the
top zone, if BETA=180 , sq.cm
As cross-sectional area of longitudinal
reinforcement in the top zone of cross-section of
the beam , if angle BETA=0, or in the top zone,
if BETA=180 , sq.cm
Moments (/) values of bending moments, determining cross-
sectional areas of longitudinal reinforcement As
and As , kNm
Load. N. (/) numbers of loading versions, determining cross-
sectional areas of longitudinal reinforcement
Acrc1 short-term opened crack width*, mm
Acrc2 long-term opened crack width*, mm
* Opened crack width is presented only in the case when calculation is
performed according to conditions limiting opened crack width.
Concrete Design Per Russian Code
Section 12A
12-14
In ten columns of second table the following results are presented:
Section distance of the section from the “start” of the
beam, mm
Qsw intensity of transverse reinforcement, kN/m
Asw cross-sectional area of transverse bars, sq.cm, if
their step is 10, 15, 20, 25 or 30 cm
Q value of shear force parallel to the local axis, kN
T value of torsional moment, kNm
Load N. number of loading version, determining intensity
of transverse reinforcement
An example of output of calculation results is presented below.
BEAM NO. 23 DESIGN RESULTS
(by limitation of crack width)
Length 6000 mm.
Section: BF1= 550 mm, B= 200 mm, HF1=220 mm, H=450 mm.
Distance from top/bottom surface of beam to center of longitudinal
reinforcement 40 mm.
Distance from side surface of beam to center of longitudinal
reinforcement 30 mm.
Concrete class В25.0 (Rb=13.05 MPa; Rbt=0.94 MPa; Gb2=0.9).
Class of longitudinal reinforcement АIII (Rs=365.0 MPa;
Rsc=365.0 MPa).
Diameter of longitudinal reinforcement bars D=16 mm.
Class of shear reinforcement АI (Rsw=175.0 MPa).
Diameter of shear reinforcement bars Dw=10 mm.
Section 12A
12-15
L O N G I T U D I N A L R E I N F O R C E M E N T
Section As- As+ Moments( -/+) Load.N.(-/+) Acrc1 Acrc2
mm sq.cm kNm mm mm
0.
10.92 0.41 152.
/ 2. 6 / 4 0.237 0.121
500.
4.74 0.41 60.
/ 0. 5 / 0 0.294 0.157
1000.
1.13 1.13 5.
/ 17. 4 / 6 0.000 0.000
1500.
1.13 6.41 8.
/ 75. 4 / 6 0.295 0.147
2000.
1.13 9.24 11.
/ 115. 4 / 6 0.298 0.149
2500.
1.13 11.53 14.
/ 139. 4 / 6 0.271 0.134
3000.
1.19 12.16 18.
/ 144. 4 / 6 0.263 0.127
3500.
1.41 10.86 21.
/ 132. 4 / 6 0.277 0.130
4000.
1.63 8.28 24.
/ 103. 4 / 6 0.296 0.129
4500.
1.95 4.54 27.
/ 56. 4 / 6 0.299 0.093
5000.
3.23 0.58 39.
/ 9. 5 / 3 0.293 0.157
5500.
0.74 0.41 124.
/ 0. 5 / 0 0.271 0.142
6000.
16.89 0.41 226.
/ 0. 5 / 0 0.155 0.078
Concrete Design Per Russian Code
Section 12A
12-16
S H E A R R E I N F O R C E M E N T
Section Qsw Asw, cm^2, if Sw= Q T Load
mm kN/m 10cm 15cm 20cm 25cm 30cm kN kNm N.
0. 251.3 1.44 2.15 2.87 3.59 4.31 203.9 0.0 6
500. 251.3 1.44 2.15 2.87 3.59 4.31 168.9 0.0 6
1000. 174.5 1.00 1.50 1.99 2.49 2.99 133.9 0.0 6
1500. 63.9 0.36 0.55 0.73 0.91 1.09 98.9 0.0 6
2000. Minimum detailing requirements ! 63.9 0.0 6
2500. Minimum detailing requirements ! 28.9 0.0 6
3000. Minimum detailing requirements ! 12.7 0.0 5
3500. Minimum detailing requirements ! 47.7 0.0 5
4000. Minimum detailing requirements ! 82.7 0.0 5
4500. 95.0 0.55 0.82 1.09 1.37 1.64 117.7 0.0 5
5000. 242.5 1.39 2.08 2.77 3.46 4.16 152.7 0.0 5
5500. 302.5 1.73 2.59 3.46 4.32 5.19 187.7 0.0 5
6000. 302.5 1.73 2.59 3.46 4.32 5.19 216.1 0.0 5
Here Minimum detailing requirements! means that reinforcement is
not required according to calculation.
122A.4 Columns
Reinforcement for columns of rectangular or circular cross -section
can be calculated. Flexibility of columns can be evaluated in two
ways. In the case of usual analysis (command PERFORM
ANALYSIS) flexibility is assessed by parameters ELY and ELZ,
values of which should conform with recommendation of the Code
SNiP 2.03.0184*. If PDELTA (analysis according to deformed
diagram) or NONLINEAR (nonlinear geometry) analysis is
performed, values of parameters ELY and ELZ should be close to
zero, for example ELY = ELZ=0.01.
Longitudinal reinforcement for columns is calculated only from
condition of strength. Longitudinal forces and bending moments in
Section 12A
12-17
relation to local axes Yloc and Z loc are taken into account in
longitudinal reinforcement calculations.
For rectangular columns the following output is generated:
column number;
column length and cross-sectional dimensions;
distance of centroid of each longitudinal bar from the
nearest edge of the cross-section;
concrete class;
longitudinal reinforcement class;
range of longitudinal reinforcement bar diameters assumed
in calculation;
diameter of longitudinal reinforcement bars obtained in
calculation;
total quantity of longitudinal bars;
quantity of longitudinal bars at each cross-section edge,
directed parallel to the local axis Yloc ;
quantity of longitudinal bars at each cross-section edge,
directed parallel to the local axis Z loc .
In nine columns of the table under the heading LONGITUDINAL
REINFORCEMENT the following output is presented:
Section distance of the section from the “start” of the
column, mm
Astot total cross-sectional area of longitudinal
reinforcement, sq.cm
Asy cross-sectional area of longitudinal
reinforcement bars at each edge of section,
directed parallel to the local axis Yloc , sq.cm
Asz cross-sectional area of longitudinal
reinforcement bars at each edge of section,
directed parallel to the local axis Z loc , sq.cm
Percent reinforcement percentage in the section
Nx, Mz, My respective values of longitudinal force and
bending moments in relation to the local axes
Z loc and Yloc , determining cross-sectional area
Concrete Design Per Russian Code
Section 12A
12-18
of longitudinal reinforcement
Load.N. number of loading version, determining cross-
sectional area of longitudinal reinforcement
An example of output of calculation results is presented below.
COLUMN NO. 97 DESIGN RESULTS
(rectangular section)
Length 4000 mm.
Section: B= 350 mm, H=350 mm.
Distance from edge of column cross section to center of each
longitudinal
reinforcement bar 40 mm.
Concrete class В25.0 (Rb=13.05 МPa; Gb2=0.9).
Class of longitudinal reinforcement АIII (Rs=365.0 МPa;
Rsc=365.0 МPa).
Diameter range of longitudinal reinforcement bars:
Dmin=16 mm . . . Dmax=32 mm
Diameter of longitudinal reinforcement bars from calculation d=20
mm.
Total number of reinforcement bars Ntot=6.
Number of longitudinal bars at each section edge parallel to the
local Y axis Nyy =2.
Number of longitudinal bars at each section edge parallel to the
local Z axis Nzz =3.
L O N G I T U D I N A L R E I N F O R C E M E N T
Section Astot Asy Asz Per cent Nx Mz My Load
m sq.cm sq.cm sq.cm % kN kNm kN m N.
0.
16.42
3.01
6.20
1.34
285.5
81.9
0.0
6
4000.
15.35
3.01
5.67
1.25
397.3
95.3
0.0
5
Section 12A
12-19
Diameter of longitudinal reinforcement bars, total quantity of
longitudinal bars as well as quantity of longitudinal bars at each
edge of the section obtained from calculation should be considered
as recommendation. In this case arrangement of reinforcement in
the section depends on the orientation of the local axes and is as
follows:
or
Calculated values of reinforcement cross-sectional areas are
presented in the table and they may differ from recommended on
the lower side.
When it is not possible according to detailing provisions to arrange
in the column longitudinal reinforcement determined from
calculation additional message is derived.
For columns of circular section the following output is generated:
column number;
column length and diameter of cross-section;
distance of centroid of each longitudinal bar to the edge of
cross-section;
longitudinal reinforcement class;
assumed in calculation range of diameters of longitudinal
reinforcement bars;
diameter of longitudinal reinforcement bars obtained from
calculation;
quantity of longitudinal bars.
Concrete Design Per Russian Code
Section 12A
12-20
In seven columns of the table under the heading LONGITUDINAL
REINFORCEMENT the following results are presented:
Section distance of the section from the “start” of the
column, mm
Astot total cross-sectional area of longitudinal
reinforcement, sq.cm
Per cent percentage of longitudinal reinforcement
Nx, Mz, My respective values of longitudinal force and
bending moments in relation to local axis Z loc
and Yloc , determining cross-sectional area of
longitudinal reinforcement
Load. N. number of loading version, determining cross-
sectional area of longitudinal reinforcement
An example of output of calculation results for a column of
circular section is presented below.
COLUMN NO. 80 DESIGN RESULTS
(circular section)
Length 4000 mm.
Diameter: Dс= 350 mm.
Distance from edge of column cross section to center of each
longitudinal
reinforcement bar 50 mm.
Concrete class В20.0 (Rb=10.35 МPa; Gb2=0.9).
Class of longitudinal reinforcement АIII (Rs=365.0 МPa;
Rsc=365.0 МPa).
Diameter range of longitudinal reinforcement bars:
Dmin=16 mm . . . Dmax=32 mm
Diameter of longitudinal reinforcement bars from calculation
D=20 mm.
Total number of reinforcement bars Ntot =7.
Section 12A
12-21
L O N G I T U D I N A L R E I N F O R C E M E N T
Section Astot Per cent Nx Mz My Load. N.
mm sq.cm % kN kNm kNm
0. 17.96 1.87 195.1 59.8 0.0 5
4000. 21.86 2.27 195.1 80.2 0.0 5
Diameter of longitudinal reinforcement bars, total quantity of
longitudinal bars as well as quantity of longitudinal bars at each
edge of the section should be considered as recommendation.
Arrangement of reinforcement in section in this case is shown
below:
Calculated cross-sectional areas of reinforcement presented in the
table may differ from recommended on the lower side.
When according to detailing provisions it is not possible to arrange
in the column longitudinal reinforcement obtained from
calculation additional message is derived.
12A.5 2D (two dimensional) element (slabs, walls, shells)
In general case calculation of reinforcement for 2D members is
carried out two times – according to conditions of strength and
conditions of limiting opened width of cracks. If reinforcement is
calculated according to conditions of strength, design values of
loads have to be used, and for conditions of limiting crack width –
characteristic (normative) loads are employed. Both calculations
can be made in one session taking advantage of multiple analysis
possibility of the program STAAD.Pro.
Concrete Design Per Russian Code
Section 12A
12-22
Symmetric or nonsymmetric reinforcement of 2D members is
calculated according to conditions of strength or according to
conditions of limiting opened crack width (see for example STA).
In reinforcement calculation for 2D members it is necessary to pay
attention to arrangement of local axes of member and direction of
reinforcement (see for example CL and CRA).
An example of output of calculation results is presented bellow.
SLAB/WALL DESIGN RESULTS
(by stresses in local axes for limitation of crack width)
Element Asx Mx Nx Load. N. Asy My Ny Load N.
sq.cm/m kNm/m kN/m (X) sq.cm/m kNm/m kN/m (Y)
60 TOP 0.00 - 4.9 0.0 1 0.00 - 4.5 0.0 1
BOT 3.53 - 9 .9 0.0 3 3.46 - 8.9 0.0 3
61 TOP 0.00 - 5 .3 0.0 1 0.00 - 4.7 0.0 1
BOT 3.87 - 10.7 0.0 3 3.65 - 9.4 0.0 3
62 TOP 0.00 - 5 .6 0.0 1 0.00 - 4.8 0.0 1
BOT 4.10 - 11.2 0.0 3 3.77 - 9.6 0.0 3
Section 12A
12-23
Here:
Element number of finite element, TOP “top” zone of
member, BOT “bottom” zone of member (“top”
zone of member is determined by positive direction of
local axis Z loc see Fig.2)
Asx intensity of reinforcing in the first direction (parallel
to the local axis X loc ), sq.cm/m
Mx distributed bending moment in respect to the local
axis Yloc , kNm/m
Nx distributed longitudinal force directed parallel to the
axis X loc , kNm/m
Load N.(X) number of loading version, determining intensity of
reinforcing in the first direction
Asy intensity of reinforcing in the second direction
(parallel to the local axis Yloc ), sq.cm/m
My distributed bending moment in respect to the local
axis X loc kNm/m
Ny distributed longitudinal force directed parallel to the
local axis Yloc kN/m
Load N.(Y) number of loading version, determining intensity of
reinforcing in the second direction
Concrete Design Per Russian Code
Section 12A
12-24
Figure 2 - Local coordinate system of 2D member and notation of forces
12-25
Steel Design Per Russian Code SNIP 2.23-81* (Edition 1990)
12B.1 General
Design Code SNiP “Steel Structures” as majority of modern codes
is based on the method of limit states. The following groups of
limit states are defined in the Code.
The first group is concerned with losses of general shape
and stability, failure, qualitative changes in configuration
of structure. Appearance of non-allowable residual
deformations, displacements, yielding of materials or
opening of cracks.
The second group is concerned with states of structures
making worse normal their service or reducing durability
due to not allowable deflections, deviations, settlements,
vibrations, etc.
Analysis of structures for the first limit state is performed using
the maximum (design) loads and actions, which can cause failure
of structures.
Analysis of structures for the second limit state is performed using
service (normative) loads and actions. Relation between design
and normative loads is referred to as coefficient of load reliability,
which is defined in SNiP 2.01.07.- 85 “Loads and Actions”.
Coefficient of reliability for destination GAMA n according to
SNiP 2.01.07.- 85 shall be taken in to account determining loads or
their combinations.
Section 12B
Steel Design Per Russian Code
Section 12B
12-26
In this version of the program only members from rolled, tube and
roll-formed assortment sections and also from compound such as
double angles of T-type sections, double channels are presented.
Design of other members of compound section will be presented in
other versions of the program.
Economy of selected section is indicated by ratio (RATIO) /Ryyc
presented in calculation results. A section is economical when said
ratio equals to 0,9 – 0,95.
12B.2 Axial tension members
Stress in a section of axial tension member shall not exceed design
strength Ry of selected steel multiplied by coefficient of service
conditions c (KY and KZ), table 6 of SNiP 2.01.07. - 81*.
Slenderness of tension member (CMM) shall not exceed
slenderness limit indicated in table 20 of SNiP 2.01.07. - 81*
(default value u=200, but another value can be defined). Net
section factor (ratio Anet/Agross (NSF)) is used for tension member
to allow for reduction of design cross-section area.
12B.3 Axial compression members
All axial compression members are calculated as long bars, i.e.,
with allowance for slenderness (=l0/imin). Calculation is
performed in accordance with the clause 5.3 of SNiP 2.01.07. -
81*, buckling coefficient is determined by formula 8-10.
Effective bar lengths (within and out of plane) taking in to account
role and location of the bar in the structure, as well as fixation of
ends (l0=l), are determined according to requirements of chapter
6 or addition 6 to SNiP 2.01.07.- 81* and are set by specification
of members. Slenderness of compression members (CMN) shall
not exceed limit values given in table 19 of SNiP 2.01.07.- 81*.
Value of coefficient being used in table 19 is taken within limits
from 0,5 to 1,0. Limit slenderness value depends on stress acting
in the member, section area, buckling coefficient and design
resistance of steel.
Section 12B
12-27
Since slenderness can be different in various planes the greatest
slenderness is assumed in calculations.
12B.4 Flexural members
Members subjected to the action of bending moments and shear
forces are called flexural members.
Calculation of flexural members consists of verification of
strength, stability and deflection.
Normal and tangential stresses are verified by strength calculation
of members. Normal stresses are calculated in the outermost
section fibres. Tangential stresses are verified in the neutral axis
zone of the same section. If normal stresses do not exceed design
steel strength and tangential stresses do not exceed design value of
steel shear strength Rss then according to clause 5.14 of SNiP
2.01.07.- 81* principal stresses are checked.
General stability of member subjected to bending in one plane are
calculated in accordance with clause 5.15 of SNiP 2.01.07. - 81*,
and subjected to bending in two planes – in accordance with
“Guide to design of steel structures” (to SNiP 2.01.07. - 81*).
Coefficient b value is determined according to appendix 7 of
SNiP 2.01.07.- 81*. Additional data about load (concentrated or
distributed), numbers of bracing restrains of compression flanges,
location of applied load are required. For closed sections it is
assumed that coefficient b=1,0.
Simply supported (non-continuous) beams can be calculated in
elastic as well as in elastic-plastic state according to requirements
of clause 5.18 of SNiP 2.01.07.- 81*. Calculation can be selected
by specification of structure in input data.
Steel Design Per Russian Code
Section 12B
12-28
Stiffness of flexural members is verified comparing input value of
deflection limit (through parameter DFF) with maximum
displacement of a section of flexural member allowing for load
reliability coefficient, which is specified, in input data. Limit
values of deflection are determined in accordance with SNiP
2.01.07.- 85 “Loads and Actions. Addition chapter 10. Deflections
and displacements”. Verification of deflection is performed only in
the case of review (CHECK) problem.
12B.5 Eccentrical compression/tension members
Eccentrical compression or tension members are subjected to
simultaneous action of axial force and bending moment. Bending
moment appears due to eccentrical application of longitudinal
force or due to transverse force.
Stress in eccentrical compression/tension members is obtained as a
sum of stresses due to axial force and bending.
Following the requirements of clause 5.25 of SNiP 2.01.07.- 81*
resistance of eccentrical compression/tension member taking into
consideration condition Ry<530 MPa, <0,5Rs and N/(AnRy)>0,1 is
calculated by formula 49, and in other cases-by formula 50.
Calculations of stability verification are performed according to
requirements of clauses 5.27, 5.30, 5.32 or 5.34.
Calculation for strength of eccentrical tension members is made
according to formula 50 of SNiP 2.01.07.- 81*.
When reduced relative eccentricity m ef>20 eccentrical compression
members are calculated as flexural members (N=0), when m ef<20
strength by formula 49 is not verified (clause 5.24).
Section 12B
12-29
12B.6 Input Data
Program STAAD/Pro gives opportunity to verify sections of steel
structures by codes of many countries including and Russian Code
SNiP 2.01.07.- 81*. Algorithms for selection and review of
sections for steel members according to assortments and databases
of the main rolled steel producers from given countries and
according to international standards as well are included in
STAAD/Pro program. In this program version only assortment
sections can be utilized.
Typical sections of members being checked and selected according
to SNiP 2.01.07.- 81* are presented in tables 1 and 2.
Table 1. Typical sections
No
. Section Section type Designation form
1 I-beam (GOST 8239-89)
ST I12
2 Regular I-beam (GOST 26020-
83) ST B1-10
3 Broad-flanged I-beam (GOST
26020-83) ST SH1-23
4 Column I-beam (GOST 26020-
83) ST K1-20
5 Channel (GOST 8240-89)
ST C14
Steel Design Per Russian Code
Section 12B
12-30
Table 1. Typical sections
No
. Section Section type Designation form
6 Equal legs angle (GOST 8509-
89)
ST L100x100x7
RA L100x100x7
7 Unequal legs angle (GOST
8510-89)
ST L125x80x10
RA L125x80x10
8 Pipes (welded and for gas
piping)
ST PIP102x5.5
or
ST PIPE OD 0.102 ID
0.055
9 Roll-formed square and
rectangular tubes
ST TUB160x120x3
or
ST TUBE TH 0.003
WT 0.12 DT 0.16
Section 12B
12-31
Table 2. Compound sections
No
. Section Section type Designation form
1 Double channels
D C14 SP 0.01
(SP – clear distance
between channel walls)
2 Double equal legs angles
LD L100x100x7 SP
0.01
(SP – clear distance
between angle walls)
5 Double unequal legs angles with
long legs back to back
LD L125x80x10 SP
0.01
(SP – clear distance
between angle walls)
6 Double unequal legs angles with
short legs back to back
SD L125x80x10 SP
0.01
(SP – clear distance
between angle walls)
7 Tee with flange at the top
T I12
T B1-10
T SH1-23
T K1-20
Flange of Tee beams is at the top part of cross-section if angle
BETA = 0, or at the bottom part if BETA = 180.
For entry of cross-sectional dimensions command MEMBER
PROPERTIES RUSSIAN is used.
Steel Design Per Russian Code
Section 12B
12-32
Example
UNITS METER
MEMBER PROPERTY RUSSIAN
* I-beam
1 TO 6 TABLE ST B1-10
* Channel
7 TO 11 TABLE ST C14
* Unequal legs angle
12 TO 30 TABLE RA L125x80x10
* Round assortment pipe
31 TO 46 TABLE ST PIP102x5.5
* Round pipe of cross-sectional dimensions defined by
client
47 TO 60 TABLE ST PIPE OD 0.102 ID 0.055
* Square tube from assortment
61 TO 68 TABLE ST TUB120x120x3
* Rectangular tube of cross-sectional dimension defined
by client
69 TO 95 TABLE ST TUBE TH 0.003 WT 0.12 DT 0.16
* Double channel (distance between walls 10 мм)
96 TO 103 TABLE D C14 SP 0.01
* Double unequal legs angles with short legs back to
back (distance between walls 10 мм)
104 TO 105 TABLE SD L125x80x10 SP 0.01
* Member of Tee section
106 TO 126 TABLE T SH1-23
* Flange of T-beams at the bottom of cross-section
BETA 180. MEMB 116 TO 126
* Orientation of the local angle axes in relation to the
global axes of the structure
BETA RANGLE MEMB 12 TO 30
Commands of output data for check and selection of sections are
located after commands of analysis and, as a rule, after output
command to print results of calculation.
Section 12B
12-33
Example
* Command of analysis
PERFORM ANALYSIS
* Command of loadings and their combinations
considered in design
LOAD LIST 1 5 TO 9
* Command to start design according to Russian Code
PARAMETER
CODE RUSSIAN
* List of parameters used in checking and selecting
.
BEAM 1. ALL (obligatory parameter) .
LY 4. MEMB 1 TO 4
LZ 4. MEM 1 TO 4
MAIN 1. ALL
SGR 3. ALL
SBLT 0 ALL
* Parameter of output amount of information on
calculation results
TRACK 2. ALL
.
* Command to start section check procedure
CHECK CODE ALL
* Command to start section selection procedure
SELECT ALL
.
* Command of output to print content of assortment
tables
PRINT ENTIRE TABLE
* Command of output to print summary of steel according
to sections
STEEL TAKE OFF
* Command of output to print summary of steel according
to members and sections
STEEL MEMBER TAKE OFF
Steel Design Per Russian Code
Section 12B
12-34
Information on parameters, data used for check and selection of
sections in design of steel structures according to Russian Code is
presented in table 3.
In this version of calculation according to requirements of SNiP
2.01.07.- 81* there is common database of equal legs angles and
unequal legs angles, therefore solution of section selection
problem may give equal legs angle as well as unequal legs angle
irrespective of set at the beginning. The same is and with
rectangular and square tubes.
Values of parameters do not depend on command UNIT. Only
these values of parameters, which differ from, defined in the
program need to be included in the input data file.
Review of sections (command CHECK) can be performed
according to the first and the second group of limit states.
Selection of section (command SELECT) can be performed only
according to the first group of limit states with subsequent
recalculation and verification of selected section with allowance
for deflection.
Calculation for the first group of limit states involves selection of
members according to strength and stability. Parameters CMN and
CMM give opportunity to set slenderness limit for compression
and tension members respectively for their stability calculation, or
refuse consideration of slenderness by setting default parameters.
In this case selection of sections will be performed with
consideration only of strength check.
Check for deflection performed by setting parameter DFF
(maximum allowable relative deflection value) different from set
in the program.
In the case of application of steel not defined by SNiP and/or
GOST it is necessary to set their design strength by parameters
UNL and PY.
Section 12B
12-35
In determination of steel parameters SBLT and MAIN shall be
approved (see table 4). Note: Once a parameter is specified, its
value stays at that specified number till it is specified again.
This is the way STAAD works for all codes.
Table 3. Names of parameters for Steel design according
to Russian Code (SNiP II – 23 – 81*, edition 1990)
No. Parameter
name Description
Default
value
1 KY
Coefficient of effective length in
respect to local axis Y (in plane
XZ)
1.0
2 KZ
Coefficient of effective length in
respect to local axis Z (in plane
XY)
1.0
3 LY
[m]
Effective length in respect to local
axis Y (in plane XZ)
Default is selected member's
length
Member
length
4 LZ
[m]
Effective length in respect to local
axis Z (in plane XY)
Default is selected member's
length
Member
length
5 SBLT
Number of lateral bracing
restraints along the span:
SBLT = 0, if beam not
fixed;
SBLT = 1, one restraint in
the middle of the span;
SBLT = 2, 3, etc. number
of uniformly spaced
lateral supports along the
span
0
6 NSF
Net section factor for tension
members or web section area
weakening factor for bending
members
1.0
Steel Design Per Russian Code
Section 12B
12-36
Table 3. Names of parameters for Steel design according
to Russian Code (SNiP II – 23 – 81*, edition 1990)
No. Parameter
name Description
Default
value
7 MAIN
Standard of steel grade (GOST):
MAIN = 1, if Standard of
steel grade is
GOST27772-88;
MAIN = 2, if Standard of
steel grade is
GOST10705-80;
MAIN = 3, if Standard of
steel grade is
GOST10706-76;
MAIN = 4, if Standard of
steel grade is GOST8731-
87;
MAIN = 5, if Standard of
steel grade is TY14-3-567-
76
1
8 DFF
Allowable limit of relative local
deflection (Member
length/Deflection Ratio):
Default value 0 is valid if design
is applied without deflection
limitation.
Set for deflection check only
0.
Section 12B
12-37
Table 3. Names of parameters for Steel design according
to Russian Code (SNiP II – 23 – 81*, edition 1990)
No. Parameter
name Description
Default
value
9 SGR
Steel grade (STAL):
SGR = 1, if Steel grade is
C235;
SGR = 2, if Steel grade is
C245;
SGR = 3, if Steel grade is
C255;
SGR = 4, if Steel grade is
C275;
SGR = 5, if Steel grade is
C285;
SGR = 6, if Steel grade is
C345;
SGR = 7, if Steel grade is
C345K;
SGR = 8, if Steel grade is
C375;
SGR = 9, if Steel grade is
C390;
SGR = 10, if Steel grade is
C390K;
SGR = 11, if Steel grade is
C440;
SGR = 12, if Steel grade is
C590;
SGR = 13, if Steel grade is
C590K;
SGR = 14, if Steel grade is
BCT3KP;
SGR = 15, if Steel grade is
BCT3PC;
SGR = 16, if Steel grade is
BCT3CP;
SGR = 17, if Steel grade is
20;
1
Steel Design Per Russian Code
Section 12B
12-38
Table 3. Names of parameters for Steel design according
to Russian Code (SNiP II – 23 – 81*, edition 1990)
No. Parameter
name Description
Default
value
SGR = 18, if Steel grade is
16G2AF
10 СMM
Slenderness limit value for tension
members:
СMM = 0, if
slenderness is
suppressed;
СMM = 2, if
ultimate
slenderness value
is "150";
СMM = 2, if
ultimate
slenderness value
is "200";
СMM = 3, if
ultimate
0
Section 12B
12-39
Table 3. Names of parameters for Steel design according
to Russian Code (SNiP II – 23 – 81*, edition 1990)
No. Parameter
name Description
Default
value
slenderness value
is "250";
СMM = 4, if
ultimate
slenderness value
is "300";
СMM = 5, if
ultimate
slenderness value
is "350";
СMM = 6, if
ultimate
slenderness value
is "400
Set slenderness limit value not
equal to "0" for design with
evaluation of buckling effect
11 CMN
Slenderness limit value for
compression members:
СMN = 0, if
slenderness is
suppressed;
СMN = 1, if
slenderness limit
value is "120";
СMN = 2, if
slenderness limit
value is "210-
60a";
СMN = 3, if
slenderness limit
value is "220-
40a";
СMN = 4, if
slenderness limit
0
Steel Design Per Russian Code
Section 12B
12-40
Table 3. Names of parameters for Steel design according
to Russian Code (SNiP II – 23 – 81*, edition 1990)
No. Parameter
name Description
Default
value
value is "220";
СMN = 5, if
slenderness limit
value is "180-
60a";
СMN = 6, if
slenderness limit
value is "210-
60a";
СMN = 7, if
slenderness limit
value is "210-
60a";
СMN = 8, if
slenderness limit
value is "200";
СMN = 9, if
slenderness limit
value is "150";
Set slenderness limit value not
equal to "0" for design with
evaluation of buckling effect
12 LEG
Type and position of loading on
beam:
LEG = 1, for loading
concentrated in the middle
span;
LEG = 2, for loading
concentrated in the quarter
of the span;
LEG = 3, for loading
concentrated at the end of
bracket;
LEG = 4, for loading
uniformly distributed on
4
Section 12B
12-41
Table 3. Names of parameters for Steel design according
to Russian Code (SNiP II – 23 – 81*, edition 1990)
No. Parameter
name Description
Default
value
beam;
LEG = 5, for loading
uniformly distributed on
bracket
13 CB
Place of loading on beam:
CB = 1, for loading on
top flange;
CB = 2, for loading on
bottom flange
1
14 TRACK
Output parameter:
TRACK = 0, for
suppressed output
information;
TRACK = 1, for
extended output
information;
TRACK = 2, for
advanced output
information
0
15 TB
Indication of elastic or elastic-
plastic calculation:
TB = 0, for elastic
calculation
TB = 1, for elastic-plastic
calculation
Set for members under bending or
non-axial compression/tension
only.
0
16 RATIO Ratio between design and
characteristic loads values 1.0
Steel Design Per Russian Code
Section 12B
12-42
Table 3. Names of parameters for Steel design according
to Russian Code (SNiP II – 23 – 81*, edition 1990)
No. Parameter
name Description
Default
value
17 DMAX
[m] Maximum allowable section depth 1.
18 DMIN
[m] Minimum allowable section depth 0.
19 BEAM
Member design parameter:
BEAM = 0, Design
members for forces at
their ends or at the
sections defined by
SECTION command;
BEAM = 1, Calculate the
major axis moment Mz at
13 points along the beam
and design beam at the
location of maximum Mz;
BEAM = 2, Same as
BEAM=1, but additional
checks are carried out at
beam ends and at critical
inter mediate section;
BEAM = 3, Calculate
forces at 13 points and
perform design checks at
all locations including the
ends
1
20 GAMC1 Specific service condition
coefficient for buckling design 1.0
21 GAMC2 Specific service condition
coefficient for strength design 1.0
22 PY
[MPa]
Design steel strength (yield
strength):
If parameters MAIN according to
Standard of steel grade (GOST)
0
Section 12B
12-43
Table 3. Names of parameters for Steel design according
to Russian Code (SNiP II – 23 – 81*, edition 1990)
No. Parameter
name Description
Default
value
and by SGR according to Steel
grade (STAL) are not defined
23 UNL
[MPa]
Design steel strength (ultimate
strength):
If parameters MAIN according to
Standard of steel grade (GOST)
and by SGR according to Steel
grade (STAL) are not defined
0
Steel Design Per Russian Code
Section 12B
12-44
Table 4. Steel types for design of steel structures
according to SNiP 2.01.07.- 81* (table 51 and 51a)
Parameter
SGR Steel
Parameter
MAIN GOST
For members
*
1 C235 1 GOST
27772-88
GT, F
2 C245 1 “ GT, F
3 C255 1 “ GT, F
4 C275 1 “ GT, F
5 C285 1 “ GT, F
6 C345 1 “ GT, F
7 C345K 1 “ GT, F
8 C375 1 “ GT, F
9 C390 1 “ F
10 C390K 1 “ F
11 C440 1 “ F
12 C590 1 “ F
13 C590К 1 “ F
14 BSt3kp 2 GOST
10705-
80*
Tube
15 BSt3ps 2
3
GOST
10705-
80*
GOST
10706-
76*
Tube
16 BSt3sp 2
3
GOST
10705-
80*
GOST
10706-
76*
Tube
17 20 4 GOST
8731-87
Tube
18 16G2АF 5 TY 14-3-
567-76
Tube
*GT – members from sheet and roll-formed tubes
F – rolled section steel
Section 12B
12-45
12B.7 Section selection and check results
Output of selection and check results are given in suppressed,
extended and advanced forms. Form of output results depends on
value of parameter TRACK.
Results are presented in tables. Three versions of output results are
possible: suppressed – results according the critical strength
condition (TRACK=0), extended - results according to all check
conditions (TRACK=1) and advanced – complete information on
results of member design (TRACK=2).
In tables of results common data for all TRACKs are indicated:
(TRACK=2).
In tables of results common data for all TRACKs are indicated:
number of member;
type and number of cross-section;
result obtained (ACCEPTED – requirements are met, FAILURE –
are not met);
abbreviated name of normative document (code, standard) (SNiP);
number of check clause;
safety of strength (ratio between design and normative values);
number of the most unfavorable loading;
value of longitudinal force acting in the member with subscript
indicating its direction (“C” – compression, “P” – tension);
bending moments in relation to local member axes Z and Y;
distance to section, in which the most unfavorable combination of
forces acts.
Steel Design Per Russian Code
Section 12B
12-46
In suppressed form (TRACK=0) results are presented according to
the critical check for given member with indication of SNiP clause
number, according to which strength safety of the member is
minimum.
Example of output with TRACK=0 of calculation results of a
member is given below.
ALL UNITS ARE - KN METE
==============================================================
MEMBER CROSS RESULT/ CRITICAL COND/ RATIO/ LOADING/
SECTION NO. FX MZ MY LOCATION
==============================================================
1 B1-30 PASS SNiP- 5.12 0.73 2
0.000E+00 -8.750E+01 0.000E+00 4.167E+00
In extended form (TRACK=1) results are presented on the
basis of all required by SNiP checks for given stress state.
Example of output with TRACK=1 of calculation results of a
member is given below.
ALL UNITS ARE - KN METE
==============================================================
MEMBER CROSS RESULT/ CRITICAL COND/ RATIO/ LOADING/
SECTION NO. FX MZ MY LOCATION
==============================================================
1 B1-30 PASS SNiP- 5.12 0.73 2
0.000E+00 -8.750E+01 0.000E+00 4.167E+00
1 B1-30 PASS SNiP- 5.12 0.06 2
0.000E+00 -8.750E+01 0.000E+00 4.167E+00
1 B1-30 PASS SNiP- 5.14 0.97 2
0.000E+00 -8.750E+01 0.000E+00 4.167E+00
1 B1-30 PASS SNiP- 5.15 0.84 2
0.000E+00 -8.750E+01 0.000E+00 4.167E+00
* 1 B1-30 FAIL SNiP- DISPL 1.59 2
0.000E+00 -8.750E+01 0.000E+00 4.167E+00
Section 12B
12-47
In advanced form (TRACK=2) in addition to tabled results
supplementary information is presented.
Material characteristics:
Steel;
Design resistance;
Elasticity modulus;
Section characteristics:
Length of member;
Section area;
Net area;
Inertia moment (second moment of area) (I);
Section modulus (W);
First moment of area (S);
Radius of gyration;
Effective length;
Slenderness;
Results are presented in two columns, Z and Y respectively.
Design forces:
Longitudinal force;
Moments;
Shear force.
Signs “+” and “-“ indicate direction of acting longitudinal force,
bending moments and shear forces in accordance with sign rules
assumed in program STAAD.
Check results in advanced form are presented with values of
intermediate parameters by formulas in analytical and numerical
expression with indication of SNiP clause.
Example of output with TRACK=2 of calculation results of a
member is given in the next page.
Steel Design Per Russian Code
Section 12B
12-48
ALL UNITS ARE - KN METE
========================================================================
MEMBER CROSS RESULT/ CRITICAL COND/ RATIO/ LOADING/
SECTION NO. FX MZ MY LOCATION
========================================================================
1 B1-30 PASS SNiP- 5.12 0.73 2
0.000E+00 -8.750E+01 0.000E+00 4.167E+00
1 B1-30 PASS SNiP- 5.12 0.06 2
0.000E+00 -8.750E+01 0.000E+00 4.167E+00
1 B1-30 PASS SNiP- 5.14 0.97 2
0.000E+00 -8.750E+01 0.000E+00 4.167E+00
1 B1-30 PASS SNiP- 5.15 0.84 2
0.000E+00 -8.750E+01 0.000E+00 4.167E+00
* 1 B1-30 FAIL SNiP- DISPL 1.59 2
0.000E+00 -8.750E+01 0.000E+00 4.167E+00
MATERIAL DATA
Steel = C285
Modulus of elasticity = 206.E+06 KPA
Design Strength (Ry) = 280.E+03 KPA
SECTION PROPERTIES (units - m)
Member Length = 1.00E+01
Gross Area = 4.19E-03
Net Area = 4.19E-03
z-axis y-axis
Moment of inertia (I) : 633.E-07 390.E-08
Section modulus (W) : 428.E-06 557.E-07
First moment of area (S) : 240.E-06 415.E-07
Radius of gyration (i) : 123.E-03 305.E-04
Effective Length : 100.E-01 333.E-02
Slenderness : 0.00E+00 0.00E+00
DESIGN DATA (units -kN,m)SNiP II-23-81*/1998
Axial force : 0.00E+00
z-axis y-axis
Moments : -875.E-01 0.00E+00
Shear force : 0.00E+00 -150.E-01
CRITICAL CONDITIONS FOR EACH CLAUSE CHECK
F.(28) M/Wmin=-875.0E-01/ 4.28E-04= 204.6E+03
F.(29) (QY*SZ)/(IZ*TW)=-150.0E-01* 2.40E-04/ 6.33E-05* 5.80E-03= 980.9E+01
RS*GAMAC= 162.4E+03
F.(33) SQRT(SIGMz**2+3*TAUzy**2)<=1.15*RY*GAMAC
-312.5E+03**2+3* 980.9E+01**2<=1.15* 280.0E+03* 100.0E-02
313.0E+03<= 322.0E+03
TAUzy<=RS*GAMAC
980.9E+01<= 162.4E+03
F.(34) M/(FIB*Wmin)=-875.0E-01/ 8.75E-01* 4.28E-04= 234.0E+03
RY*GAMAC= 280.0E+03
ACTUAL SECTION DISPLACEMENT = 6.349E-02 M
MAXIMUM MEMBER DEFLECTION = 6.349E-02 M Loading No. 2
ULTIMATE ALLOWABLE DEFLECTION VALUE = 4.000E-02 M
Conventional notations assumed in presentation of results: “+”, “ -
“, “/”, “*”,”**”, “SQRT”, their respective meanings – addition,
subtraction, division, multiplication, raising to the second power
(squared) and square root. Conventional notations of stresses,
coefficients and characteristics of steel resistance comply with
accepted in SNiP, only Greek letters are changed by their names
(e.g. , с-GAMAC; -ALFA; -BETA, -ETA, -FI, etc.).
Section 13
South African
Codes
13-1
Concrete Design Per SABS 0100-1
13A.1 Design Operations
STAAD has the capability for performing design of concrete
beams and columns according to the South African code SABS
0100-1. The 2000 revision of the code is currently implemented.
Design can be performed for beams (flexure, shear and torsion)
and columns (axial load + biaxial bending). Given the width and
depth (or diameter for circular columns) of a section, STAAD will
calculate the required reinforcement.
13A.2 Design Parameters
The program contains a number of parameters which are needed to
perform and control the design to SABS 0100-1. These parameters
not only act as a method to input required data for code
calculations but give the engineer control over the actual design
process. Default values of commonly used parameters for
conventional design practice have been chosen as the basis. Table
12A.1 contains a complete list of avai lable parameters with their
default values. Note: Once a parameter is specified, its value
stays at that specified number till it is specified again. This is
the way STAAD works for all codes.
Section 13A
South African Concrete Code Per SABS 0100-1
Section 13A
13-2
Table 13A.1 – South African Concrete Design-SABS 0100-1 -Parameters Parameter Default Description Name Value FYMAIN *450 N/mm2 Yield Stress for main reinforcement FYSEC *450N/mm2 Yield Stress for secondary reinforcement a.
Applicable to shear bars in beams FC * 30N/mm2 Concrete Yield Stress / cube strength MINMAIN 8mm Minimum main reinforcement bar size
Acceptable bar sizes: 6 8 10 12 16 20 25 28 32 36 40 50 60
MINSEC 8mm Minimum secondary bar size a. Applicable to shear reinforcement in beams
MAXMAIN 50mm Maximum required reinforcement bar size Acceptable bars are per MINMAIN above.
CLT 20mm Clear Cover for outermost top reinforcement CLB 20mm Clear Cover for outermost bottom
reinforcement CLS 20mm Clear Cover for outermost side
reinforcement TRACK 0.0 0.0 = Critical Moment will not be printed with
beam design report. Column design gives no detailed results. 1.0 = For beam gives min/max steel % and spacing. For columns gives a detailed table of output with additional moments calculated. 2.0 = Output of TRACK 1.0 List of design sag/hog moments and corresponding required steel area at each section of member
WIDTH *ZD Width of concrete member. This value default is as provided as ZD in MEMBER PROPERTIES.
DEPTH *YD Depth of concrete member. This value default is as provided as YD in MEMBER PROPERTIES.
Section 13A
13-3
Table 13A.1 – South African Concrete Design-SABS 0100-1 -Parameters Parameter Default Description Name Value BRACE 0.0 0.0 = Column braced in both directions.
1.0 = Column braced about local Y direction only 2.0 = Column unbraced about local Z direction only 3.0 = Column unbraced in both Y and Z directions
ELY 1.0 Member length factor about local Y direction for column design.
ELZ 1.0 Member length factor about local Z direction for column design.
* Provided in current unit system
13A.3 Member Dimensions
Concrete members that are to be designed by STAAD must have
certain section properties input under the MEMBER PROPERTIES
command. The following example demonstrates the required
input:
UNIT MM
MEMBER PROPERTIES
*RECTANGULAR COLUMN 300mm WIDE X 450mm DEEP
1 3 TO 7 9 PRISM YD 450. ZD 300.
*CIRCULAR COLUMN 300mm diameter
11 13 PR YD 300.
* T-SECTION - FLANGE 1000.X 200.(YD-YB)
* - STEM 250(THICK) X 350.(DEEP)
14 PRISM YD 550. ZD 1000. YB 350. ZB 250.
South African Concrete Code Per SABS 0100-1
Section 13A
13-4
In the above input, the first set of members are rectangular
(450mm depth x 300mm width) and the second set of members,
with only depth and no width provided, will be assumed to be
circular with 300mm diameter. Note that area (AX) is not provided
for these members. If shear area areas (AY & AZ ) are to be
considered in analysis, the user may provide them along with YD
and ZD. Also note that if moments of inertias are not provided, the
program will calculate them from YD and ZD. Finally a T section
can be considered by using the third definition above.
13A.4 Beam Design
Beam design includes flexure, shear and torsion. For all types of
beam action, all active beam loadings are scanned to create
moment and shear envelopes and locate the critical sections. The
total number of sections considered is thirteen. From the critical
moment values, the required positive and negative bar pattern is
developed. Design for flexure is carried out as per clause no.
4.3.3.4.
Shear design as per SABS 0100 clause 4.3.4 has been followed and
the procedure includes computation of critical shear values. From
these values, stirrup sizes are calculated with proper spacing. If
torsion is present, the program will also consider the provisions of
SABS 0100 clause 4.3.5. Torsional reinforcement is separately
reported.
Section 13A
13-5
A TRACK 2 design output is presented below .
B E A M N O. 4 D E S I G N R E S U L T S
M20 Fe450 (Main) Fe450 (Sec.)
LENGTH: 7500.0 mm SIZE: 380.0 mm X 715.0 mm COVER: 25.0 mm
DESIGN LOAD SUMMARY (KN MET)
--------------------------------------------------------------------
SECTION |FLEXURE (Maxm. Sagging/Hogging moments)| SHEAR
(in mm) | MZ Load Case MX Load Case | VY P Load Case
--------------------------------------------------------------------
0.0 | 135.75 5 -3.44 5 | 152.06 50.62 4
| -295.92 4 |
625.0 | 189.16 5 -3.43 5 | 133.95 48.87 4
| -236.52 4 |
1250.0 | 231.25 5 -3.41 5 | 115.84 47.12 4
| -188.44 4 |
1875.0 | 262.01 5 -3.40 5 | 97.73 45.37 4
| -151.68 4 |
2500.0 | 281.46 5 -3.39 5 | 79.61 43.63 4
| -126.24 4 |
3125.0 | 289.59 5 -3.37 5 | 61.50 41.88 4
| -112.12 4 |
3750.0 | 286.39 5 -3.36 4 | -62.13 40.13 5
| -109.32 4 |
4375.0 | 271.88 5 -3.37 4 | -80.25 41.88 5
| -117.84 4 |
5000.0 | 246.05 5 -3.39 4 | -98.36 43.63 5
| -137.68 4 |
5625.0 | 208.89 5 -3.40 4 | -116.47 45.37 5
| -168.84 4 |
6250.0 | 160.42 5 -3.41 4 | -134.58 47.12 5
| -211.33 4 |
6875.0 | 100.62 5 -3.43 4 | -152.70 48.87 5
| -265.13 4 |
7500.0 | 29.50 4 -3.44 4 | -170.81 29.63 4
| -330.25 5 |
SUMMARY OF REINF. AREA FOR FLEXURE DESIGN (Sq.mm)
--------------------------------------------------------------------
SECTION | TOP | BOTTOM | STIRRUPS
(in mm) | Reqd./Provided reinf. | Reqd./Provided reinf. | (2 legged)
--------------------------------------------------------------------
0.0 | 1232.70/1256.64( 4-20í )| 543.40/ 565.50( 5-12í )| 8í @ 425 mm
625.0 | 960.90/ 981.74( 2-25í )| 754.32/ 791.70( 7-12í )| 8í @ 510 mm
1250.0 | 751.24/ 791.70( 7-12í )| 937.49/ 942.48( 3-20í )| 8í @ 510 mm
1875.0 | 596.52/ 603.18( 3-16í )| 1075.72/1206.36( 6-16í )| 8í @ 510 mm
2500.0 | 543.40/ 565.50( 5-12í )| 1165.13/1206.36( 6-16í )| 8í @ 510 mm
3125.0 | 543.40/ 565.50( 5-12í )| 1203.00/1206.36( 6-16í )| 8í @ 220 mm
3750.0 | 543.40/ 565.50( 5-12í )| 1188.08/1206.36( 6-16í )| 8í @ 220 mm
4375.0 | 543.40/ 565.50( 5-12í )| 1120.87/1206.36( 6-16í )| 8í @ 220 mm
5000.0 | 543.40/ 565.50( 5-12í )| 1003.50/1005.30( 5-16í )| 8í @ 220 mm
5625.0 | 668.18/ 678.60( 6-12í )| 839.38/ 904.80( 8-12í )| 8í @ 220 mm
6250.0 | 849.99/ 904.80( 8-12í )| 632.84/ 678.60( 6-12í )| 8í @ 220 mm
6875.0 | 1089.94/1206.36( 6-16í )| 543.40/ 565.50( 5-12í )| 8í @ 220 mm
7500.0 | 1397.16/1407.42( 7-16í )| 543.40/ 565.50( 5-12í )| 8í @ 220 mm
--------------------------------------------------------------------
TORSION REINFORCEMENT: Not required
South African Concrete Code Per SABS 0100-1
Section 13A
13-6
13A.5 Column Design
Columns are designed for axial force and biaxial bending at the
ends. All active loadings are tested to calculate reinforcement. The
loading which produces maximum reinforcement is called the
critical load and is displayed. The requirements of SABS 0100-1
clause 4.7 are followed, with the user having control on the
effective length in each direction by using the ELZ and ELY
parameters as described in table 12A.1. Bracing conditions are
controlled by using the BRACE parameter. The program will then
decide whether or not the column is short or slender and whether it
requires additional moment calculations. For biaxial bending, the
recommendations of 4.7.4.4 of the code are considered.
Column design is done for square, rectangular and circular
sections. For rectangular and square sections, the reinforcement is
always assumed to be arranged symmetrically. This causes slightly
conservative results in certain cases. Table 12A.3 shows typical
column design results.
Using parameter TRACK 1.0, the detailed output below is
obtained. TRACK 0.0 would merely give the bar configuration,
required steel area and percentage, column size and critical load
case.
Section 13A
13-7
TABLE 12A.3 -COLUMN DESIGN OUTPUT
=======================================================================
C O L U M N N O. 1 D E S I G N R E S U L T S
M20 Fe450 (Main) Fe450 (Sec.)
LENGTH: 3660.0 mm CROSS SECTION: 750.0 mm X 460.0 mm COVER:40.0mm
** GUIDING LOAD CASE: 4 END JOINT: 1 SHORT COLUMN
DESIGN FORCES (KNS-MET)
-----------------------
DESIGN AXIAL FORCE (Pu) : 915.6
About Z About Y
INITIAL MOMENTS : 0.00 0.00
MOMENTS DUE TO MINIMUM ECC. : 18.31 18.31
SLENDERNESS RATIOS : 7.96 4.88
ADDITION MOMENTS (Maddz and Maddy) : 0.00 0.00
TOTAL DESIGN MOMENTS : 555.13 21.91
REQD. STEEL AREA : 3349.20 Sq.mm.
REQD. CONCRETE AREA: 114451.62 Sq.mm.
MAIN REINFORCEMENT : Provide 32 - 12 dia. (1.05%, 3619.20 Sq.mm.)
(Equally Distributed)
TIE REINFORCEMENT : Provide 8 mm dia. rectangular ties @ 140 mm c/c
SECTION CAPACITY BASED ON REINFORCEMENT REQUIRED (KNS-MET)
----------------------------------------------------------
Puz : 2160.42 Muz1 : 570.23 Muy1 : 563.74
South African Concrete Code Per SABS 0100-1
Section 13A
13-8
13-9
Steel Design Per SAB Standard SAB0162–1: 1993
13B.1 General
The South African Steel Design facility in STAAD is based on the
SAB Standard SAB0162-1: 1993, Limit States Design of Steel
Structures. A steel section library consisting of South African
Standards shapes is available for member property specification.
The design philosophy embodied in this specification is based on
the concept of limit state design. Structures are designed and
proportioned taking into consideration the limit states at which
they would become unfit for their intended use. Two major
categories of limit-state are recognized - ultimate and
serviceability. The primary considerations in ultimate limit state
design are strength and stability, while that in serviceability is
deflection. Appropriate load and resistance factors are used so that
a uniform reliability is achieved for all steel structures under
various loading conditions and at the same time the chances of
limits being surpassed are acceptably remote.
In the STAAD implementation, members are proportioned to resist
the design loads without exceeding the limit states of strength,
stability and serviceability. Accordingly, the most economic
section is selected on the basis of the least weight criteria as
augmented by the designer in specification of allowable member
depths, desired section type, or other such parameters. The code
checking portion of the program checks whether code requirements
for each selected section are met and identifies the governing
criteria.
Section 13B
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-10
The following sections describe the salient features of the STAAD
implementation of SAB0162-1: 1993. A detailed description of the
design process along with its underlying concepts and assumptions
is available in the specification document.
13B.2 Analysis Methodology
Elastic analysis method is used to obtain the forces and moments
for design. Analysis is done for the primary and combination
loading conditions provided by the user. The user is allowed
complete flexibility in providing loading specifications and using
appropriate load factors to create necessary loading situations.
Depending upon the analysis requirements, regular stiffness
analysis or P-Delta analysis may be specified. Dynamic analysis
may also be performed and the results combined with static
analysis results.
13B.3 Member Property Specifications
For specification of member properties, the steel section library
available in STAAD may be used. The next section describes the
syntax of commands used to assign properties from the built -in
steel table. Member properties may also be specified using the
User Table facility. For more information on these facilities, refer
to the STAAD Technical Reference Manual.
13B.4 Built-in Steel Section Library
The following information is provided for use when the built -in
steel tables are to be referenced for member property specification.
These properties are stored in a database file. If called for, the
properties are also used for member design. Since the shear areas
are built into these tables, shear deformation is always considered
during the analysis of these members.
Section 13B
13-11
I Shapes
The following example illustrates the specification of I- shapes.
1 TO 15 TABLE ST IPE-AA100
H shapes
Designation of H shapes in STAAD is as follows.
For example,
18 TO 20 TABLE ST 152X37UC
PG shapes
Designation of PG shapes in STAAD is as follows.
100 TO 150 TABLE ST 720X200PG
Channel Sections (C & MC shapes)
C and MC shapes are designated as shown in the following
example.
3 TABLE ST 127X64X15C
Double Channels
Back to back double channels, with or without spacing between
them, are specified by preceding the section designation by the
letter D. For example, a back to back double channel section
PFC140X60 without spacing in between should be specified as:
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-12
100 TO 150 TABLE D PFC140X60
A back to back double channel section 140X60X16C with spacing
0.01unitlength in between should be specified as:
100 TO 150 TABLE D 140X60X16C SP 0.01
Note that the specification SP after the section designation is used
for providing the spacing. The spacing should always be provided
in the current length unit.
Angles
To specify angles, the letter L succeeds the angle name. Thus, a
70X70 angle with a 25mm thickness is designated as 70X70X8L.
The following examples illustrate angle specifications.
100 TO 150 TABLE ST 70X70X8L
Note that the above specification is for “standard” angles. In this
specification, the local z-axis (see Fig. 2.6 in the Technical
Reference Manual) corresponds to the Y‟-Y‟ axis shown in the
CSA table. Another common practice of specifying angles assumes
the local y-axis to correspond to the Y‟-Y‟ axis. To specify angles
in accordance with this convention, the reverse angle designation
facility has been provided. A reverse angle may be specified by
substituting the word ST with the word RA. Refer to the following
example for details.
100 TO 150 TABLE RA 45X45X3L
The local axis systems for STANDARD and REVERSE angles are
shown in Fig. 2.6 of the STAAD Technical Reference manual.
Section 13B
13-13
Double Angles
To specify double angles, the specification ST should be
substituted with LD (for long leg back to back) or SD (short leg
back to back). For equal angles, either SD or LD will serve the
purpose. Spacing between angles may be provided by using the
word SP followed by the value of spacing (in current length unit)
after section designation.
100 TO 150 TABLE LD 50X50X3L 3 TABLE LD 40X40X5L SP 0.01
The second example above describes a double angle section
consisting of 40X40X5 angles with a spacing of 0.01 length units.
Tees
Tee sections obtained by cutting W sections may be specified by
using the T specification instead of ST before the name of the W
shape. For example:
100 TO 150 TABLE T IPE-AA180
will describe a T section cut from a IPE-AA180 section.
Rectangular Hollow Sections
These sections may be specified in two possible ways. Those
sections listed in the SAB tables may be specified as follows.
100 TO 150 TABLE ST TUB60X30X2.5
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-14
In addition, any tube section may be specified by using the DT(for
depth), WT(for width), and TH(for thickness) specifications. For
example:
100 TO 150 TABLE ST TUBE TH 3 WT 100 DT 50
will describe a tube with a depth of 50mm, width of 100mm. and a
wall thickness of 3mm. Note that the values of depth, width and
thickness must be provided in current length unit.
Circular Hollow Sections
Sections listed in the SAB tables may be provided as follows:
100 TO 150 TABLE ST PIP34X3.0CHS
In addition to sections listed in the SAB tables, circular hollow
sections may be specified by using the OD (outside diameter) and
ID (inside diameter) specifications.
Pipe symbol
Thickness
PIP34X3.0
Diameter
Width
Tube symbol
Height
Thickness
TUB60X30X2.5
Section 13B
13-15
For example:
100 TO 150 TABLE ST PIPE OD 50 ID 48
will describe a pipe with an outside diameter of 50 length units
and inside diameter of 48 length units. Note that the values of
outside and inside diameters must be provided in terms of current
length unit.
Sample input file to demonstrate usage of South African shapes is
shown below.
STAAD PLANE START JOB INFORMATION ENGINEER DATE 30-Mar-05 END JOB INFORMATION UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 9 0 0; 3 0 6 0; 4 3 6 0; 5 6 6 0; 6 9 6 0; 7 0 10.5 0; 8 9 10.5 0; 9 2.25 10.5 0; 10 6.75 10.5 0; 11 4.5 10.5 0; 12 1.5 11.4 0; 13 7.5 11.4 0; 14 3 12.3 0; 15 6 12.3 0; 16 4.5 13.2 0; MEMBER INCIDENCES 1 1 3; 2 3 7; 3 2 6; 4 6 8; 5 3 4; 6 4 5; 7 5 6; 8 7 12; 9 12 14; 10 14 16; 11 15 16; 12 13 15; 13 8 13; 14 9 12; 15 9 14; 16 11 14; 17 11 15; 18 10 15; 19 10 13; 20 7 9; 21 9 11; 22 10 11; 23 8 10; MEMBER PROPERTY SAFRICAN 1 TABLE ST IPE-AA100 2 TABLE T IPE120 3 TABLE ST 152X23UC 4 TABLE T 152X23UC 5 TABLE ST 812X200PG 6 TABLE T 812X200PG 7 TABLE ST 178X54X15C 8 TABLE D 178X54X15C 9 TABLE D 178X54X15C SP 0.1 10 TABLE ST 25X25X5L 11 TABLE RA 25X25X5L 12 TABLE LD 25X25X5L 13 TABLE SD 25X25X5L 14 TABLE LD 25X25X5L SP 0.1 15 TABLE SD 25X25X5L SP 0.1
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-16
16 TABLE ST TUB40X2.5SHS 17 TABLE ST TUBE TH 0 WT 0 DT 50 18 TABLE ST TUBE TH 0.02 WT 100 DT 50 20 TABLE ST PIP48X2.0CHS 21 TABLE ST PIPE OD 0.5 ID 0.48 PRINT MEMBER PROPERTIES FINISH
13B.5 Section Classification
The SAB specification allows inelastic deformation of section
elements. Thus, local buckling becomes an important criterion.
Steel sections are classified as plastic (Class 1), compact (Class 2),
non compact (Class 3) or slender element (Class 4) sections
depending upon their local buckling characteristics (See Clause
11.2 and Table 1 of SAB0162-1:1993). This classification is a
function of the geometric properties of the section. The design
procedures are different depending on the section class. STAAD
determines the section classification for the standard shapes and
user specified shapes. Design is performed for sections that fall
into the category of Class 1,2 or 3 sections only. Class 4 sections
are not designed by STAAD.
13B.6 Member Resistances
The member resistances are calculated in STAAD according to the
procedures outlined in section 13 of the specification. These
depend on several factors such as members‟ unsupported lengths,
cross-sectional properties, slenderness factors, unsupported width
to thickness ratios and so on. Note that the program automatically
takes into consideration appropriate resistance factors to calculate
member resistances. Explained here is the procedure adopted in
STAAD for calculating the member resistances.
All the members are checked against allowable slenderness ratio as
per Cl.10.2 of SAB0162-1: 1993.
Section 13B
13-17
Axial Tension
The criterion governing the capacity of tension members is based
on two limit states. The limit state of yielding in the gross section
is intended to prevent excessive elongation of the member. The
second limit state involves fracture at the section with the
minimum effective net area. The net section area may be specified
by the user through the use of the parameter NSF (see Table 3B.1).
STAAD calculates the tension capacity of a member based on
these two limits states per Cl.13.2 of SAB0162-1: 1993.
Parameters FYLD, FU and NSF are applicable for these
calculations.
Axial Compression
The compressive resistance of columns is determined based on
Clause 13.3 of the code. The equations presented in this section of
the code assume that the compressive resistance is a function of
the compressive strength of the gross section (Gross section Area
times the Yield Strength) as well as the slenderness factor (KL/r
ratios). The effective length for the calculation of compression
resistance may be provided through the use of the parameters KX,
KY, KZ, LX, LY and LZ (see Table 3B.1). Some of the aspects of
the axial compression capacity calculations are:
1. For frame members not subjected to any bending, and for truss
members, the axial compression capacity in general column
flexural buckling is calculated from Cl.13.3.1 using the
slenderness ratios for the local Y-Y and Z-Z axis. The
parameters KY, LY, KZ and LZ are applicable for this.
2. For single angles, asymmetric or cruciform sections are
checked as to whether torsional-flexural buckling is critical.
But for KL/r ratio exceeding 50,as torsional flexural buckling
is not critical, the axial compression capacities are calculated
by using Cl.13.3. The reason for this is that the South African
code doesn‟t provide any clear guidelines for calculating this
value. The parameters KY, LY, KZ and LZ are applicable for
this.
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-18
3. The axial compression capacity is also calculated by taking
flexural-torsional buckling into account. Parameters KX and
LX may be used to provide the effective length factor and
effective length value for flexural-torsional buckling. Flexural-
torsional buckling capacity is computed for single channels,
single angles, Tees and Double angles.
4. While computing the general column flexural buckling
capacity of sections with axial compression + bending, the
special provisions of 13.8.1(a), 13.8.1(b) and 13.8.1(c) are
applied. For example, Lambda = 0 for 13.8.1(a), K=1 for
13.8.1(b), etc.)
Bending
The laterally unsupported length of the compression flange for the
purpose of computing the factored moment resistance is specified
in STAAD with the help of the parameter UNL. If UNL is less
than one tenth the member length (member length is the distance
between the joints of the member), the member is treated as being
continuously laterally supported. In this case, the moment
resistance is computed from Clause 13.5 of the code. If UNL is
greater than or equal to one-tenth the member length, its value is
used as the laterally unsupported length. The equations of Clause
13.6 of the code are used to arrive at the momen t of resistance of
laterally unsupported members. Some of the aspects of the bending
capacity calculations are:
1. The weak axis bending capacity of all sections except single
angles is calculated as
For Class 1 & 2 sections, Phi*Py*Fy
For Class 3 sections, Phi*Sy*Fy
Where Phi = Resistance factor = 0.9
Py = Plastic section modulus about the local Y axis
Sy = Elastic section modulus about the local Y axis
Fy = Yield stress of steel
Section 13B
13-19
2. For single angles sections are not designed by STAAD, as the
South African code doesn‟t provide any clear guidelines for
calculating this value.
3. For calculating the bending capacity about the Z-Z axis of
singly symmetric shapes such as Tees and Double angles,
SAB0162-1: 1993 stipulates in Clause 13.6(b), page 31, that a
rational method.
Axial compression and bending
The member strength for sections subjected to axial compression
and uniaxial or biaxial bending is obtained through the use of
interaction equations. In these equations, the additional bending
caused by the action of the axial load is accounted for by using
amplification factors. Clause 13.8 of the code provides the
equations for this purpose. If the summation of the left hand side
of these equations exceeds 1.0 or the allowable value provided
using the RATIO parameter (see Table 3B.1), the member is
considered to have FAILed under the loading condition.
Axial tension and bending
Members subjected to axial tension and bending are also designed
using interaction equations. Clause 13.9 of the code is used to
perform these checks. The actual RATIO is determined as the
value of the left hand side of the critical equation.
Shear
The shear resistance of the cross section is determined using the
equations of Clause 13.4 of the code. Once this is obtained, the
ratio of the shear force acting on the cross section to the shear
resistance of the section is calculated. If any of the ratios (for both
local Y & Z axes) exceed 1.0 or the allowable value provided
using the RATIO parameter (see Table 3B.1), the section is
considered to have failed under shear. The code also requires that
the slenderness ratio of the web be within a certain limit (See
Cl.13.4.1.3, page 29 of SABS 0162-1:1993). Checks for safety in
shear are performed only if this value is within the allowable limit.
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-20
Users may by-pass this limitation by specifying a value of 2.0 for
the MAIN parameter.
13B.7 Design Parameters
The design parameters outlined in table below may be used to
control the design procedure. These parameters communicate
design decisions from the engineer to the program and thus allow
the engineer to control the design process to suit an application's
specific needs.
The default parameter values have been selected such that they are
frequently used numbers for conventional design. Depending on
the particular design requirements, some or all of these parameter
values may be changed to exactly model the physical structure.
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way
STAAD works for all codes.
South African steel design parameters
Parameter
Name
Default Value Description
Kt 1.0 K value for flexural torsional buckling
Ky 1.0 K value in local Y-axis, usually minor axis
Kz 1.0 K value in local Z-axis, usually major axis
Lt Member length Length for flexural torsional buckling
Ly Member length Length in local Y axis for slenderness
value KL/r
Lz Member length Length in local Z axis for slenderness value
KL/r
Fyld 300Mpa Yield strength of steel
Fu 345Mpa Ultimate strength of steel
NSF 1.0 Net section factor for tension members
Section 13B
13-21
South African steel design parameters
Parameter
Name
Default Value Description
UNT Member Length
Unsupported length in bending
compression of top flange for calculating
moment resistance
UNB Member Length
Unsupported length in bending
compression of bottom flange for
calculating moment resistance
Main 0
Flag for controlling slenderness check
0 - For Check for slenderness.
1 - For Do not check for slenderness
Cb 1.0
Greater than 0.0 and less than 2.5,Value of
Omega_2 (C1.13.6) to be used for
calculation
Equal to 0.0: Calculate Omega_2
Ssy 0
Sidesway parameter
0 - Sideway about local Y-axis.
1 - No sideway about local Y-axis.
Ssz 0
Sidesway parameter
0 - Sideway about local Z-axis.
1 - No sideway about local Z-axis.
Cmy 1.0
1 - Do not calculate Omega-1 for local Y
axis.
2 - Calculate Omega-1 for local Y axis
Cmz 1.0
1 - Do not calculate Omega-1 for local Z
axis.
2 - Calculate Omega-1 for local Z axis
Track 0
Track parameter
0 = Print the design output at the minimum
detail level.
1 = Print the design output at the
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-22
South African steel design parameters
Parameter
Name
Default Value Description
intermediate detail level.
2 = Print the design output at maximum
detail level
Dmax 1000 Maximum allowable depth
Dmin 0 Minimum required depth
Ratio 1.0
Permissible ratio of applied load to section
capacity
Used in altering the RHS of critical
interaction equations
Beam 0
0 - Perform design at ends and those
locations specified in the section command.
1 - Perform design at ends and 1/12th
section locations along member length.
Dff 0 Default is 0 indicating that deflection
check is not performed
Dj1 0
Start node of physical member for
determining deflected pattern for deflection
check and should be set along with DFF
parameter
Dj2 0
End node of physical member for
determining deflected pattern for deflection
check and should be set along with DFF
parameter
13B.8 Code Checking
The purpose of code checking is to determine whether the current
section properties of the members are adequate to carry the forces
obtained from the most recent analysis. The adequacy is checked
as per the SAB0162-1: 1993 requirements.
Section 13B
13-23
Code checking is done using forces and moments at specified
sections of the members. If the BEAM parameter for a member is
set to 1 (which is also its default value), moments are calculated at
every twelfth point along the beam. When no section locations are
specified and the BEAM parameter is set to zero, design will be
based on member start and end forces only. The code checking
output labels the members as PASSed or FAILed. In addition, the
critical condition, governing load case, location (di stance from the
start joint) and magnitudes of the governing forces and moments
are also printed. Using the TRACK parameter can control the
extent of detail of the output.
PARAMETER CODE SAB0162 MAIN 1 all LY 4 MEMB 1 LZ 4 MEMB 1 UNL 4 MEMB 1 CB 0 MEMB 1 TO 23 CMZ MEMB 2 1 TO 23 CMY MEMB 2 1 TO 23 SSY 0 MEMB 1 TO 23 SSZ 0 MEMB 1 TO 23 FU 450000 MEMB 1 TO 23 BEAM 1 ALL NSF 0.85 ALL KY 1.2 MEMB 3 4 RATIO 1.0 ALL TRACK 2 ALL FYLD 300000 1 TO 23 CHECK CODE ALL FINISH
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-24
13B.9 Member Selection
The member selection process involves determination of the least
weight member that PASSes the code checking procedure based on
the forces and moments of the most recent analysis. The section
selected will be of the same type as that specified initially. For
example, a member specified initially as a channel will have a
channel selected for it. Selection of members whose properties are
originally provided from a user table will be limited to sections in
the user table. Member selection cannot be performed on members
listed as PRISMATIC.
13B.10 Tabulated Results of Steel Design
Results of code checking and member selection are presented in a
tabular format. The term CRITICAL COND refers to the section of
the SAB0162-1: 1993 specification, which governed the design.
If the TRACK parameter is set to 1.0, the output will be displayed
as follows:
**************************************
STAAD.PRO CODE CHECKING
(SOUTHAFRICAN STEEL/SAB-0162-01(1993))
**************************************
ALL UNITS ARE - KNS MET (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
* 1 ST PFC140X60 (SOUTHAFRICAN SECTIONS)
FAIL SAB-13.9 4.321 1
-20.00 0.00 82.53 0.00
|---------------------------------------------------------------------|
| FACTORED RESISTANCES FOR MEMBER- 1 UNIT - KN,M PHI = 0.90 |
| MRZ= 14.35 MRY= 3.86 |
| CR= 58.41 TR= 425.81 VR= 123.85 |
|---------------------------------------------------------------------|
Factored member resistances will be printed out. Following is a
description of some of the items printed out.
MRZ= Factored moment of resistance in z direction
Section 13B
13-25
MRY= Factored moment of resistance in z direction
CR = Factored compressive resistance for column
TR= Factored tensile capacity
VR= Factored shear resistance
Further details can be obtained by setting TRACK to 2.0. A typical
output of track 2.0 parameter is as follows.
**************************************
STAAD.PRO CODE CHECKING
(SOUTHAFRICAN STEEL/SAB-0162-01(1993))
**************************************
ALL UNITS ARE - KNS MET (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
* 1 ST PFC140X60 (SOUTHAFRICAN SECTIONS)
FAIL SAB-13.9 4.321 1
-20.00 0.00 82.53 0.00
MEMBER PROPERTIES (UNIT = CM)
-----------------------------
CROSS SECTION AREA = 1.95E+01 MEMBER LENGTH = 4.50E+02
IZ = 6.05E+02 SZ = 8.64E+01 PZ = 4.24E+02
IY = 6.91E+01 SY = 1.73E+01 PY = 1.52E+02
MATERIAL PROPERTIES (UNIT = MPA)
--------------------------------
FYLD = 248.2 FU = 285.4
SECTION CAPACITIES (UNIT - KN,M)
---------------------------------
CRY = 5.841E+01 CRZ = 2.947E+02
CTORFLX = 2.021E+02
TENSILE CAPACITY = 4.258E+02 COMPRESSIVE CAPACITY = 5.841E+01
FACTORED MOMENT RESISTANCE : MRY = 3.859E+00 MRZ = 1.435E+01
FACTORED SHEAR RESISTANCE : VRY = 1.238E+02 VRZ = 1.168E+02
MISCELLANEOUS INFORMATION
--------------------------
NET SECTION FACTOR FOR TENSION = 1.000
KL/RY = 239.051 KL/RZ = 80.789 ALLOWABLE KL/R = 300.000
UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 4.500
OMEGA-1 (Y-AXIS) = 1.00 OMEGA-1 (Z-AXIS) = 1.00 OMEGA-2 = 1.00
SHEAR FORCE (KNS) : Y AXIS = 0.000E+00 Z AXIS = 3.526E+01
SLENDERNESS RATIO OF WEB (H/W) = 2.00E+01
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-26
Following is a description of some of the items printed out.
CRY Factored compressive resistance for column buckling
about the local y axis
CRZ Factored compressive resistance for column buckling
about the local z axis
CTORFLX Factored compressive resistance against torsional
flexural buckling
TENSILE
CAPACITY
Factored tensile capacity
COMPRESSIVE
CAPACITY
Factored compressive capacity
FACTORED MOMENT
RESISTANCE
MRY = Factored moment of resistance in y direction
MRZ = Factored moment of resistance in z direction
FACTORED SHEAR
RESISTANCE
VRY = Factored shear resistance in y direction
VRZ = Factored shear resistance in z direction
13B.11 Verification Problems
In the next few pages are included 3 verification examples for
reference purposes.
Section 13B
13-27
Verification Problem No. 1
Objective: - To determine the capacity of a South African I-
section column in axial compression. Column is
braced at its ends for both axes.
Design Code: - South African steel design code (SAB:0162-
1(1993))
Reference: - Example 4.3.4.1, page 4.18, Structural Steel
Design to SAB:0162-1(1993)(Limit state Design)
by Greg Parrott, 1st edition, Shades Technical
publication
Given: - FYLD = 300Mpa
Length = 6000mm
Comparison: -
Solution Design Strength (kN)
Theory 1516
STAAD 1516
Difference No
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-28
****************************************************
* *
* STAAD.Pro *
* Version Bld *
* Proprietary Program of *
* Research Engineers, Intl. *
* Date= *
* Time= *
* *
* USER ID: *
****************************************************
1. STAAD PLANE
2. START JOB INFORMATION
3. ENGINEER DATE
4. END JOB INFORMATION
5. INPUT WIDTH 79
6. ***********************************************
7. * STAAD.PRO GENERATED COMMENT *
8. ***********************************************
9. *1 0 0 0,2 0 6 0
10. ***********************************************
11. UNIT METER KN
12. JOINT COORDINATES
13. 1 0 0 0; 2 0 6 0
14. MEMBER INCIDENCES
15. 1 1 2
16. MEMBER PROPERTY SAFRICAN
17. 1 TABLE ST 356X67UB
18. DEFINE MATERIAL START
19. ISOTROPIC MATERIAL1
20. E 2.0E+008
21. POISSON 0.3
22. DENSITY 76.977
23. ISOTROPIC STEEL
24. E 2.00E+008
25. POISSON 0.3
26. DENSITY 76.8195
27. ALPHA 1.2E-005
28. DAMP 0.03
29. END DEFINE MATERIAL
30. UNIT MMS KN
31. CONSTANTS
32. MATERIAL STEEL MEMB 1
33. UNIT METER KN
34. SUPPORTS
35. 1 FIXED
36. LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1
37. JOINT LOAD
38. 2 FY -1500
39. PERFORM ANALYSIS
P R O B L E M S T A T I S T I C S
-----------------------------------
NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 2/ 1/ 1
ORIGINAL/FINAL BAND-WIDTH= 1/ 1/ 3 DOF
TOTAL PRIMARY LOAD CASES = 1, TOTAL DEGREES OF FREEDOM = 3
SIZE OF STIFFNESS MATRIX = 0 DOUBLE KILO-WORDS
REQRD/AVAIL. DISK SPACE = 12.0/ 3978.5 MB
40. PARAMETER
41. CODE SAB0162
42. LZ 6 ALL
43. LY 3 ALL
44. FU 450000 ALL
45. BEAM 1 ALL
46. NSF 0.85 ALL
47. TRACK 2 ALL
48. FYLD 300000 ALL
49. CHECK CODE ALL
Section 13B
13-29
**************************************
STAAD.PRO CODE CHECKING
(SOUTHAFRICAN STEEL/SAB-0162-01(1993))
**************************************
ALL UNITS ARE - KNS MET (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
1 ST 356X67UB (SOUTHAFRICAN SECTIONS)
PASS SAB-13.8 0.989 1
1500.00 0.00 0.00 0.00
MEMBER PROPERTIES (UNIT = CM)
-----------------------------
CROSS SECTION AREA = 8.55E+01 MEMBER LENGTH = 6.00E+02
IZ = 1.95E+04 SZ = 1.07E+03 PZ = 1.21E+03
IY = 1.36E+03 SY = 1.57E+02 PY = 2.43E+02
MATERIAL PROPERTIES (UNIT = MPA)
--------------------------------
FYLD = 300.0 FU = 345.0
SECTION CAPACITIES (UNIT - KN,M)
---------------------------------
CRY = 1.516E+03 CRZ = 2.038E+03
CTORFLX = 1.516E+03
TENSILE CAPACITY = 1.918E+03 COMPRESSIVE CAPACITY = 1.516E+03
FACTORED MOMENT RESISTANCE : MRY = 6.561E+01 MRZ = 1.992E+02
FACTORED SHEAR RESISTANCE : VRY = 5.903E+02 VRZ = 6.461E+02
MISCELLANEOUS INFORMATION
--------------------------
NET SECTION FACTOR FOR TENSION = 0.850
KL/RY = 75.220 KL/RZ = 39.730 ALLOWABLE KL/R = 200.000
UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 6.000
OMEGA-1 (Y-AXIS) = 1.00 OMEGA-1 (Z-AXIS) = 1.00 OMEGA-2 = 1.00
SHEAR FORCE (KNS) : Y AXIS = 0.000E+00 Z AXIS = 0.000E+00
SLENDERNESS RATIO OF WEB (H/W) = 3.65E+01
50. FINISH
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-30
Verification Problem No. 2
Objective:- To determine the capacity of a South African I-section
beam in bending. The beam has torsional and simple
lateral rotational restraint at the supports, and the
applied point load provides effective lateral restraint at
the point of application is braced at its ends for both
axes.
Design Code: - South African steel design code (SAB:0162-
1(1993))
Reference: - Example 4.5, page 4.37, Structural Steel Design to
SAB:0162-1(1993)(Limit state Design) by Greg Parrott,
1st edition, Shades Technical publication
Given: - FYLD = 300Mpa
Comparison: -
Solution Design Strength (kN-m)
Theory 353.4
STAAD 353.3
Difference Small
Section 13B
13-31
****************************************************
* *
* STAAD.Pro *
* Version Bld *
* Proprietary Program of *
* Research Engineers, Intl. *
* Date= *
* Time= *
* *
* USER ID: *
****************************************************
1. STAAD PLANE
2. START JOB INFORMATION
3. ENGINEER DATE
4. END JOB INFORMATION
5. INPUT WIDTH 79
6. UNIT METER KN
7. JOINT COORDINATES
8. 1 0 0 0; 2 10 0 0; 3 7 0 0
9. MEMBER INCIDENCES
10. 1 1 3; 2 3 2
11. MEMBER PROPERTY SAFRICAN
12. 1 2 TABLE ST 406X67UB
13. DEFINE MATERIAL START
14. ISOTROPIC MATERIAL1
15. E 2.0E+008
16. POISSON 0.3
17. DENSITY 76.977
18. ISOTROPIC STEEL
19. E 2.00E+008
20. POISSON 0.3
21. DENSITY 76.8195
22. ALPHA 1.2E-005
23. DAMP 0.03
24. END DEFINE MATERIAL
25. UNIT MMS KN
26. CONSTANTS
27. MATERIAL STEEL MEMB 1 2
28. UNIT METER KN
29. SUPPORTS
30. 1 3 PINNED
31. LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1
32. MEMBER LOAD
33. 1 CON GY -104 4
34. 1 UNI GY -26.4
35. 2 UNI GY -7.2
36. PERFORM ANALYSIS
P R O B L E M S T A T I S T I C S
-----------------------------------
NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 3/ 2/ 2
ORIGINAL/FINAL BAND-WIDTH= 2/ 2/ 5 DOF
TOTAL PRIMARY LOAD CASES = 1, TOTAL DEGREES OF FREEDOM = 5
SIZE OF STIFFNESS MATRIX = 1 DOUBLE KILO-WORDS
REQRD/AVAIL. DISK SPACE = 12.0/ 3978.5 MB
37. PARAMETER
38. CODE SABS0162
39. CB 0 ALL
40. UNL 4 MEMB 1
41. FU 450000 ALL
42. BEAM 1 ALL
43. NSF 0.85 ALL
44. FYLD 300000 ALL
45. TRACK 2 ALL
46. CHECK CODE MEMB 1
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-32
**************************************
STAAD.PRO CODE CHECKING
(SOUTHAFRICAN STEEL/SAB-0162-01(1993))
**************************************
ALL UNITS ARE - KNS MET (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
1 ST 406X67UB (SOUTHAFRICAN SECTIONS)
PASS SHEAR 0.244 1
0.00 0.00 32.40 7.00
MEMBER PROPERTIES (UNIT = CM)
-----------------------------
CROSS SECTION AREA = 8.55E+01 MEMBER LENGTH = 7.00E+02
IZ = 2.43E+04 SZ = 1.19E+03 PZ = 1.35E+03
IY = 1.36E+03 SY = 1.52E+02 PY = 2.37E+02
MATERIAL PROPERTIES (UNIT = MPA)
--------------------------------
FYLD = 300.0 FU = 345.0
SECTION CAPACITIES (UNIT - KN,M)
---------------------------------
CRY = 4.532E+02 CRZ = 2.016E+03
CTORFLX = 4.532E+02
TENSILE CAPACITY = 1.918E+03 COMPRESSIVE CAPACITY = 4.532E+02
FACTORED MOMENT RESISTANCE : MRY = 6.399E+01 MRZ = 3.533E+02
FACTORED SHEAR RESISTANCE : VRY = 6.420E+02 VRZ = 6.075E+02
MISCELLANEOUS INFORMATION
--------------------------
NET SECTION FACTOR FOR TENSION = 0.850
KL/RY = 175.514 KL/RZ = 41.522 ALLOWABLE KL/R = 300.000
UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 4.000
OMEGA-1 (Y-AXIS) = 1.00 OMEGA-1 (Z-AXIS) = 1.00 OMEGA-2 = 1.75
SHEAR FORCE (KNS) : Y AXIS = 0.000E+00 Z AXIS = -1.565E+02
SLENDERNESS RATIO OF WEB (H/W) = 4.33E+01
47. FINISH
Section 13B
13-33
Verification Problem No. 3
Objective: - To determine the elastic shear capacity of a South
African I-section which is simply supported over the
span of 8 m
Design Code: - South African steel design code (SAB:0162-1(1993))
Reference: - Example 4.6.5, page 4.54, Structural Steel Design to
SAB:0162-1(1993)(Limit state Design) by Greg Parrott,
1st edition, Shades Technical publication
Given: - FYLD = 300Mpa
Comparison: -
Solution Design Strength (kN)
Theory 687.1
STAAD 687.1
Difference No
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-34
****************************************************
* *
* STAAD.Pro *
* Version Bld *
* Proprietary Program of *
* Research Engineers, Intl. *
* Date= *
* Time= *
* *
* USER ID: *
****************************************************
1. STAAD PLANE
2. START JOB INFORMATION
3. ENGINEER DATE
4. END JOB INFORMATION
5. INPUT WIDTH 79
6. UNIT METER KN
7. JOINT COORDINATES
8. 1 0 0 0; 2 8 0 0
9. MEMBER INCIDENCES
10. 1 1 2
11. MEMBER PROPERTY SAFRICAN
12. 1 TABLE ST 457X67UB
13. DEFINE MATERIAL START
14. ISOTROPIC MATERIAL1
15. E 2E+008
16. POISSON 0.3
17. DENSITY 76.977
18. ISOTROPIC STEEL
19. E 2E+008
20. POISSON 0.3
21. DENSITY 76.8195
22. ALPHA 1.2E-005
23. DAMP 0.03
24. END DEFINE MATERIAL
25. UNIT MMS KN
26. CONSTANTS
27. MATERIAL STEEL MEMB 1
28. UNIT METER KN
29. SUPPORTS
30. 1 2 PINNED
31. LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1
32. MEMBER LOAD
33. 1 UNI GY -70
34. PERFORM ANALYSIS
P R O B L E M S T A T I S T I C S
-----------------------------------
NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 2/ 1/ 2
ORIGINAL/FINAL BAND-WIDTH= 1/ 1/ 2 DOF
TOTAL PRIMARY LOAD CASES = 1, TOTAL DEGREES OF FREEDOM = 2
SIZE OF STIFFNESS MATRIX = 0 DOUBLE KILO-WORDS
REQRD/AVAIL. DISK SPACE = 12.0/ 3978.4 MB
35. PARAMETER
36. CODE SABS0162
37. FU 450000 ALL
38. BEAM 1 ALL
39. FYLD 300000 ALL
40. TRACK 2 ALL
41. CHECK CODE ALL
Section 13B
13-35
**************************************
STAAD.PRO CODE CHECKING
(SOUTHAFRICAN STEEL/SAB-0162-01(1993))
**************************************
ALL UNITS ARE - KNS MET (UNLESS OTHERWISE NOTED)
MEMBER TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/
FX MY MZ LOCATION
=======================================================================
* 1 ST 457X67UB (SOUTHAFRICAN SECTIONS)
FAIL CLASS 4 SECT 2.000
0.00 0.00 0.00
MEMBER PROPERTIES (UNIT = CM)
-----------------------------
CROSS SECTION AREA = 8.55E+01 MEMBER LENGTH = 8.00E+02
IZ = 2.94E+04 SZ = 1.30E+03 PZ = 1.47E+03
IY = 1.45E+03 SY = 1.53E+02 PY = 2.37E+02
MATERIAL PROPERTIES (UNIT = MPA)
--------------------------------
FYLD = 300.0 FU = 345.0
SECTION CAPACITIES (UNIT - KN,M)
---------------------------------
CRY = 0.000E+00 CRZ = 0.000E+00
CTORFLX = 0.000E+00
TENSILE CAPACITY = 2.257E+03 COMPRESSIVE CAPACITY = 0.000E+00
FACTORED MOMENT RESISTANCE : MRY = 4.123E+01 MRZ = 0.000E+00
FACTORED SHEAR RESISTANCE : VRY = 6.871E+02 VRZ = 5.730E+02
MISCELLANEOUS INFORMATION
--------------------------
NET SECTION FACTOR FOR TENSION = 1.000
KL/RY = 194.263 KL/RZ = 43.142 ALLOWABLE KL/R = 200.000
UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 8.000
OMEGA-1 (Y-AXIS) = 1.00 OMEGA-1 (Z-AXIS) = 1.00 OMEGA-2 = 1.00
SHEAR FORCE (KNS) : Y AXIS = 0.000E+00 Z AXIS = 2.800E+02
SLENDERNESS RATIO OF WEB (H/W) = 5.04E+01
42. FINISH
South African Steel Code Per SAB Standard SAB0162–1: 1993 Section 13B
13-36
Section 14
American Aluminum Code
14-1
Design Per American Aluminum Code
14.1 General
STAAD is currently equipped with the facilities to perform design
based on the specifications for Aluminum Structures. The
requirements of the Allowable Stress Design, Sixth edition,
October 1994, have been implemented.
The various issues related to the implementation of this code in
STAAD are explained below.
14.2 Member Properties
In order to do this design in STAAD, the members in the structure
must have their properties specified from Section VI of the above-
mentioned manual. The section names are mentioned in Tables 5
through 28 of that manual. All of those tables except Table 10
(Wing Channels) and Table 20 (Bulb Angles) are available in
STAAD.
Described below is the command specification for various
sections:
Standard single section
memb-list TA ST section-name
Section 14
Design Per American Aluminum Code
Section 14
14-2
Example
1 TO 5 TA ST CS12X11.8
9 TA ST I8.00X13.1
11 33 45 67 TA ST LS8.00X8.00X0.625
18 TA ST 1.50PipeX160
15 TA ST T(A-N)6.00X8.00X11.2
23 25 29 TA ST 20X12RectX.500Wall
Double channel back-to-back
memb-list TA BACK section-name SPACING value
Example
3 TA BACK C(A-N)7X3.61 SPACING 1.5
5 TA BACK C15X17.33 SP 0.75
Double channel front-to-front
memb-list TA FRONT section-name SPACING value
Example
2 TA FRONT CS12X10.3 SP 1.0
4 TA FR CS10X10.1 SP 0.5
Section 14
14-3
Double angle long leg back-to-back
memb-list TA LD section-name SPACING value
Example
14 TA LD LS4.00X3.00X0.375 SP 1.5
Double angle short leg back-to-back
memb-list TA SD section-name SPACING value
Example
12 TA SD L3.5X3X0.5 SP 0.25
13 TA SD L8X6X0.75 SP 1.0
14.3 Design Procedure
The design is done according to the rules specified in Sections 4.1,
4.2 and 4.4 on pages I-A-41 and I-A-42 of the Aluminum code.
The allowable stresses for the various sections are computed
according to the equations shown in Section 3.4.1 through 3.4.21
on pages I-A-27 through I-A-40. The adequacy of the member is
checked by calculating the value of the left -hand side of equations
4.1.1-1, 4.1.1-2, 4.1.1-3, 4.1.2-1, 4.4-1 and 4.4-2. This left-hand
side value is termed as RATIO. If the highest RATIO among these
equations turns out to be less than or equal to 1.0, the member is
declared as having PASSed. If it exceeds 1.0, the member has
FAILed the design requirements.
Design Per American Aluminum Code
Section 14
14-4
The check for torsion per Clause 4.3 for open sections is currently
not done.
14.4 Design Parameters
The following are the parameters for specifying the values for
variables associated with the design. Note: Once a parameter is
specified, its value stays at that specified number till it is
specified again. This is the way STAAD works for all codes.
Table 14.1 Aluminum Design Parameters
Parameter Default Description
Name Value
ALLOY 34 This variable can take on a value from 1 through 40. The default value represents the alloy 6061-T6. See Table 12A.2 in the following pages for a list of values for this parameter and the alloy they represent. Table 3.3-1 in Section I-B of the Aluminum specifications provides information on the properties of the various alloys.
PRODUCT 1 This variable can take on a value from 1 through 4. They represent: 1 - All 2 - Extrusions 3 - Drawn Tube 4 - Pipe The default value stands for All. The PRODUCT parameter finds mention in Table 3.3-1 in Section I-B of the Aluminum specifications.
ALCLAD 0 This variable can take on a value of either 0 or 1. 0 - Material used in the section is not an Alclad. 1 - Material used in the section is an Alclad.
Section 14
14-5
Table 14.1 Aluminum Design Parameters
Parameter Default Description
Name Value
WELD 0 In Table 3.4-2 in Section I-A of the Aluminum specifications, it is mentioned that the value of coefficients Kt and Kc are dependent upon whether or not, the location of the section where design is done is within 1.0 inch of a weld. The WELD parameter is used in STAAD for this purpose. The values that can be assigned to this parameter are: 0 - Region is farther than 1.0in from a weld 1 - Region is within 1.0in from a weld
STRUCTURE 1 In Table 3.4-1 in Section I-A of the Aluminum specifications, it is mentioned that the value of coefficients nu, ny and na are dependent upon whether the structure being designed is a building or a bridge. Users may convey this information to STAAD using the parameter STRUCTURE. The values that can be assigned to this parameter are: 1 - Buildings and similar type structures 2 - Bridges and similar type structures
DMAX 1000 in. Maximum depth permissible for the section during member selection. This value must be provided in the current units.
DMIN 0.0 in Minimum depth required for the section during member selection. This value must be provided in the current units.
UNL Member length
Distance between points where the compression flange is braced against buckling or twisting. This value must be provided in the current units. This value is used to compute the allowable stress in bending compression.
KY 1.0 Effective length factor for overall column buckling in the local Y-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the allowable stress in axial compression.
Design Per American Aluminum Code
Section 14
14-6
Table 14.1 Aluminum Design Parameters
Parameter Default Description
Name Value
LY Member length
Effective length for overall column buckling in the local Y-axis. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the allowable stress in axial compression.
KZ 1.0 Effective length factor for overall column buckling in the local Z-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the allowable stress in axial compression.
LZ Member length
Effective length for overall column buckling in the local Z-axis. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the allowable stress in axial compression.
KT 1.0 Effective length factor for torsional buckling. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the allowable stress in axial compression. See Equation 3.4.7.2-6 on page I-A-28 of the Aluminum specifications for details.
LT Member length
Unbraced length for twisting. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the allowable stress in axial compression. See Equation 3.4.7.2-6 on page I-A-28 of the Aluminum specifications for details.
STIFF Member length
Spacing in the longitudinal direction of shear stiffeners for stiffened flat webs. It is input in the current units of length. See section 3.4.21 on page I-A-40 of the Aluminum specifications for information regarding this parameter.
Section 14
14-7
Table 14.1 Aluminum Design Parameters
Parameter Default Description
Name Value
SSY 0.0 Factor that indicates whether or not the structure is subjected to sidesway along the local Y axis of the member. The values are: 0 - Sidesway is present along the local Y-axis of the member 1 - There is no sidesway along the local Y-axis of the member. The sidesway condition is used to determine the value of Cm explained in Section 4.1.1, page I-A-41 of the Aluminum specifications.
SSZ 0.0 Factor that indicates whether or not the structure is subjected to sidesway along the local Z axis of the member. The values are: 0 - Sidesway is present along the local Z-axis of the member 1 - There is no sidesway along the local Z-axis of the member. The sidesway condition is used to determine the value of Cm explained in Section 4.1.1, page I-A-41 of the Aluminum specifications.
TRACK 2 This parameter is used to control the level of detail in which the design output is reported in the output file. The allowable values are: 1 - Prints only the member number, section name,
ratio, and PASS/FAIL status. 2 - Prints the design summary in addition to that
printed by TRACK 1 3 - Prints the member properties and alloy properties in addition to that printed by TRACK 2. 4 - Prints the values of variables used in design in
addition to that printed by TRACK 3.
Design Per American Aluminum Code
Section 14
14-8
Table 14.1 Aluminum Design Parameters
Parameter Default Description
Name Value
BEAM 0.0 If this parameter is set to 1.0, the adequacy of the member is determined by checking a total of 13 equally spaced locations along the length of the member. If the BEAM value is 0.0, the 13 location check is not conducted, and instead, checking is done only at the locations specified by the SECTION command (See STAAD manual for details). If neither the BEAM parameter nor any SECTION command is specified, STAAD will terminate the run and ask the user to provide one of those 2 commands. This rule is not enforced for TRUSS members.
14.5 Code Checking
The purpose of code checking is to determine whether the initially
specified member properties are adequate to carry the forces
transmitted to the member due to the loads on the structure. Code
checking is done at the locations specified by either the SECTION
command or the BEAM parameter described above.
It is done with the aid of the command “CHECK CODE”
described in the main STAAD Technical Reference Manual.
Example Problem 1 in the Getting Started and Examples Manual
for STAAD provides an example on the usage of the CHECK
CODE command.
14.6 Member Selection
The member selection process involves the determination of the
least weight member that PASSes the code checking procedure
based on the forces and moments of the most recent analysis. The
section selected will be of the same type as that specified initially.
For example, a member specified initially as a channel will have a
channel selected for it. It is done with the aid of the command
“SELECT MEMBER” described in the main STAAD Technical
Section 14
14-9
Reference Manual. Example Problem 1 in the Getting Started and
Examples Manual for STAAD provides an example on the usage of
the SELECT MEMBER command.
Sample input data for Aluminum Design
PARAMETER
CODE ALUMIMUM
BEAM 1 ALL
KY 1.2 MEMB 3 4
ALLOY 35 ALL
PRODUCT 2 ALL
TRACK 3 ALL
SELECT ALL
ALCLAD 1 ALL
STRUCT 1 ALL
CHECK CODE ALL
Design Per American Aluminum Code
Section 14
14-10
Table 14.2 - ALLOY PARAMETER :
Values and Corresponding Names
1 1100-H12
2 1100-H14
3 2014-T6
4 2014-T6510
5 2014-T6511
6 2014-T651
7 3003-H12
8 3003-H14
9 3003-H16
10 3003-H18
11 3004-H32
12 3004-H34
13 3004-H36
14 3004-H38
15 5005-H12
16 5005-H14
17 5005-H32
18 5005-H34
19 5050-H32
20 5050-H34
21 5052-H32
22 5052-H34
23 5083-H111
24 5086-H111
25 5086-H116
26 5086-H32
27 5086-H34
28 5454-H111
29 5454-H112
30 5456-H111
31 5456-H112
32 6005-T5
33 6105-T5
Section 14
14-11
34 6061-T6
35 6061-T6510
36 6061-T6511
37 6061-T651
38 6063-T5
39 6063-T6
40 6351-T5
Design Per American Aluminum Code
Section 14
14-12
Section 15
American Transmission Tower Code
15-1
Steel Design per ASCE 10-97
15A.1 General Comments
The design of structural steel members in accordance with the
specifications of ASCE Standard 10-97 – Design of Latticed Steel
Transmission Structures is now implemented. This code is meant
to supercede the older edition of the code, available under the
name ASCE Publication 52. However, in the interests of backward
compatibility, both codes are currently accessible in STAAD.Pro.
To access the ASCE 52 code, use the commands
PARAMETER CODE ASCE 52
To access the ASCE 10-97 code, use the commands
PARAMETER CODE ASCE
In general, the concepts followed in MEMBER SELECTION and
CODE CHECKING procedures are similar to that of the AISC
based design. It is assumed that the user is familiar with the basic
concepts of steel design facilities available in STAAD. Please
refer to Section 2 of the STAAD Technical Reference Manual for
detailed information on this topic. This section specifically
addresses the implementation of steel design based on ASCE 10-
97.
Design is available for all standard sections listed in the AISC
ASD 9th
edition manual, namely, Wide Flanges, S, M, HP, Tees,
Channels, Single Angles, Double Angles, Tubes and Pipes. Design
Section 15A
Steel Design Per ASCE 10-97
Section 15A
15-2
of HSS sections (those listed in the 3 rd edition AISC LRFD
manual) and Composite beams (I shapes with concrete slab on top)
is not suppported.
15A.2 Allowable Stresses per ASCE 10 - 97
Member selection and code checking operations in th e STAAD
implementation of ASCE 10-97 are done to resist loads at stresses
approaching yielding, buckling, fracture and other limiting
conditions specified in the standard. Those stresses are referred to
in the standard as Design Stresses. The appropriate sections of the
ASCE standard where the procedure for calculating the design
stresses is explained are as follows.
Design Axial Tensile Stress
Design tensile stresses are calculated on the basis of the procedure
described in section 3.10. The NSF parameter (see the Parameters
table shown later in this section) may be used if the section area
needs to be reduced to account for bolt holes.
Design Axial Compressive Stress
Design compressive stress calculation is based on the procedures
of section 3.6 through 3.9. For angle members under compression,
the procedures of sections 3.7 and 3.8 have been implemented.
Capacity of the section is computed for column buckling and
wherever applicable, torsional buckling. The user may control the
effective lengths for buckling using the LT, LY, LZ and/or KT,
KY, KZ parameters (see the Parameters table shown later in this
section).
Design Bending Compressive Stress
Calculations for design bending compressive stress about the
major axis and minor axis are based on the procedures of section
3.14. Procedures outlined in sections 3.14.1 through 3.14.6 have
been implemented.
Section 15A
15-3
Design Bending Tensile Stress
Calculations for design bending tensile stress about the major and
minor axis are based on the procedures of section 3.14.2.
Design Shear Stress
Calculation of the design shear stress is based on the procedure
outlined in section 3.15 of the ASCE 10-97. The procedure of
section 3.15.2 is followed for angles and the procedure of section
3.15.1 is followed for all other sect ions.
15A.3 Critical Conditions used as criteria to determine Pass/Fail status
These are Clause 3.4 for slenderness limits, Clause 3.12 for Axial
Compression and Bending, Clause 3.13 for Axial Tension and
Bending, Clause 3.9.2 for Maximum w/t ratios and Clause 3.15 for
Shear.
15A.4 Design Parameters
Design per ASCE (10-97) must be initiated by using the command
CODE ASCE. This command should be the first command after the
PARAMETER statement. Other applicable parameters are
summarized in the table shown later in this section. These
parameters may be used to control the design process to suit
specific modeling needs. The default parameter values have been
selected such that they are frequently used numbers for
conventional design.
15A.5 Code Checking and Member Selection
Both code checking and member selection options are available in
the ASCE 10-97 implementation. For general information on these
Steel Design Per ASCE 10-97
Section 15A
15-4
options, refer to sections 2 and 5 of the STAAD Technical
Reference Manual.
Table of Steel Design Parameters for ASCE 10-97
Parameter Name
Default Value
Description
KY 1.0 Effective length factor (K) for compression buckling about the Y-axis (minor axis)
KZ 1.0 Effective length factor (K) for compression buckling about the Z-axis (major axis)
KT 1.0 Effective length coefficient for warping restraint (clause 3.14.4, pg 11)
LY Member Length
Length to calculate slenderness ratio for buckling about the Y-axis (minor axis)
LZ Member Length
Length to calculate slenderness ratio for buckling about the Z-axis (major axis)
LT Member Length
Effective length for warping.
FYLD 36.0 KSI Yield Strength of steel NSF 1.0 Net section factor for tension members UNL Member
Length Unsupported length of member for calculation of allowable bending stress
UNF 1.0 Same as UNL, but provided as a fraction of the member length
TRACK 0.0 0.0 = Suppresses printing of allowable stresses 1.0 = Prints all allowable stresses
DMAX 45.0 in. Maximum allowable depth for member selection DMIN 0.0 in. Minimum allowable depth for member selection RATIO 1.0 Permissible ratio that determines the cut off point for
pass/fail status. A value below this quantity indicates PASS while a value greater than this quantity indicates FAILURE.
BEAM 1.0 0.0 = Perform design at beam ends and section locations specified according to the SECTION command 1.0 = Perform design at the ends and eleven
intermediate sections of the beam
Section 15A
15-5
Table of Steel Design Parameters for ASCE 10-97
Parameter Name
Default Value
Description
MAIN 2 Parameter that indicates the member type for the purpose of calculating the KL/R ratio (SEE CLAUSE 3.4, PAGE 3, ASCE 10-97) = 10 : DO NOT PERFORM THE KL/R CHECK = 1 : LEG MEMBER KL/R <= 150 = 2 : COMPRESSION MEMBER KL/R <= 200 = 3 : TENSION MEMBER KL/R <= 500 = 4 : HANGAR MEMBERS KL/R <= 375 (Clause 4C.4, page 43) = 5 : REDUNDANT MEMBERS KL/R <= 250
ELA 4 Indicates what type of end conditions are to be used from among Equations 3.7-4 thru 3.7-7 to determine the KL/R ratio. ELA=1 : EQN.3.7-4, Page 4
(VALID FOR LEG MEMBERS ONLY) ELA=2 : EQN.3.7-5, Page 4 ELA=3 : EQN.3.7-6, Page 4 ELA=4 : EQN.3.7-7, Page 5
ELB 1 Indicates what type of end conditions are to be used from among Equations. 3.7-8 thru 3.7-10 and 3.7-12 thru 3.7-14 to determine the KL/R ratio. ELB=1 : EQN.3.7-8, Page 5, EQN.3.7-12, Page 5 ELB=2 : EQN.3.7-9, Page 5, EQN.3.7-13, Page 5 ELB=3 : EQN.3.7-10, Page 5, EQN.3.7-14,Page 5
Steel Design Per ASCE 10-97
Section 15A
15-6
Table of Steel Design Parameters for ASCE 10-97
Parameter Name
Default Value
Description
LEG 0.0 This parameter is meant for plain angles. 0.0 = indicates that the angle is connected by both legs and allowable stress in axial tension is 1.0FYLD. 1.0 = indicates that the angle is connected only by the shorter leg and allowable tensile stress is computed per clause 3.10.2 as 0.9FYLD. 2.0 = indicates that the angle is connected by the longer leg.
DBL 0.75 in. Diameter of bolt for calculation of number of bolts required and the net section factor.
FYB 36 KSI Yield strength of bolt. FVB 30 KSI Shear strength of bolt. NHL
0 Number of bolt holes on the cross section that should be used to determine the net section factor for tension capacity.
Notes:
All values must be provided in the current unit system.
Once a parameter is specified, its value stays at that specified number
till it is specified again. This is the way STAAD works for all codes.
15-7
Steel Design per ASCE Manuals and Reports
15B.1 General Comments
This document presents some general statements regarding the
implementation of the Steel Design per ASCE Manuals and
Reports on Engineering Practice No. 52 – Guide for Design of
Steel Transmission Towers, Second Edition. The design
philosophy and procedural logistics for member selection and code
checking is based upon the principles of allowable stress design.
Two major failure modes are recognized: failure by overstressing
and failure by stability considerations.
The following sections describe the salient features regarding the
process of calculation of the relevant allowable stresses and the
stability criteria being used. Members are proportioned to resist
the design loads without exceeding the allowable stresses and the
most economical section is selected based on the least weight
criteria. The code checking part of the program also checks the
slenderness requirements, the minimum metal thickness
requirements and the width-thickness requirements. It is generally
assumed that the user will take care of the detailing requirements
like provision of stiffeners and check the local effects like flange
buckling, web crippling, etc. It general, it may be noted that the
concepts followed in MEMBER SELECTION and CODE
CHECKING procedures are similar to that of the AISC based
design. It is assumed that the user is familiar with the basic
concepts of Steel Design facilities available in STAAD. Please
refer to Section 3 of the STAAD Technical Reference Manual for
detailed information on this topic. This document specifically
addresses the implementation of steel design based on ASCE Pub.
52.
Section 15B
Steel Design Per ASCE Manuals and Reports
Section 15B
15-8
15B.2 Allowable Stresses per ASCE (Pub. 52)
The member design and code checking in the STAAD
implementation of ASCE (Pub. 52) is based upon the allowable
stress design method. Appropriate sections of this publication are
referenced below.
Allowable Axial Tensile Stress
Allowable tensile stresses are calculated on the basis of the
procedure described in section 4.10. The NSF parameter (Table
1.1) may be used if the net section area needs to be used.
Allowable Axial Compressive Stress
Allowable compressive stress calculation is based on the
procedures of section 4.6 through 4.9. For angle members under
compression, the procedures of sections 4.7 and 4.8 have been
implemented. Capacity of the section is computed for column
buckling and wherever applicable, torsional buckling. The user
may control the effective lengths for buckling using the LX, LY,
LZ and/or KX, KY, KZ parameters (Table 1.1).
Allowable Bending Compressive Stress
Calculations for allowable bending compressive stress about the
major axis and minor axis are based on the procedures of section
4.14. Procedures outlined in sections 4.14.1 through 4.14.6 have
been implemented.
Allowable Bending Tensile Stress
Calculations for allowable bending tensile stress about the major
and minor axis are based on the procedures of section 4.14.2.
Allowable Shear Stress
Calculation of the allowable shear stress is based on the procedure
outlined in section 4.15 of the ASCE Pub. 52. The procedure of
Section 15B
15-9
section 4.15.2 is followed for angles and the procedure of section
4.15.1 is followed for all other sections.
Critical Conditions used as criteria to determine Pass/Fail
status
These are Clause 4.4 for slenderness limits, Equation 4.12-1 for
Axial Compression and Bending, Equation 4.13-1 for Axial
Tension and Bending, Clause 4.9.2 for Maximum w/t ratios and
Clause 4.15 for Shear.
15B.3 Design Parameters
Design per ASCE (Pub. 52) must be initiated by using the
command CODE ASCE. This command should be the first
command after the PARAMETER statement. Other applicable
parameters are summarized in Table 1.1. These parameters may be
used to control the design process to suit specific modeling needs.
The default parameter values have been selected such that they are
frequently used numbers for conventional design.
15B.4 Code Checking and Member Selection
Both code checking and member selection options are available in
the ASCE Pub. 52 implementation. For general information on
these options, refer to section 3 of the STAAD Technical
Reference Manual. For information on specification of these
commands, refer to section 6.
Steel Design Per ASCE Manuals and Reports
Section 15B
15-10
15B.5 Parameter Definition Table
Table 15B.1 - Steel Design Parameters for ASCE (PUB. 52) Based Design
Parameter Name
Default Value
Description
KY 1.0 Effective length factor (K) for compression buckling about the Y-axis (minor axis)
KZ 1.0 Effective length factor (K) for compression buckling about the Z-axis (major axis)
KT 1.0 Effective length coefficient for warping restraint (clause 4.14.4, pg 36)
LY Member Length
Length to calculate slenderness ratio for buckling about the Y-axis (minor axis)
LZ Member Length
Length to calculate slenderness ratio for buckling about the Z-axis (major axis)
LT Member Length
Effective length for warping.
FYLD 36.0 KSI Yield Strength of steel NSF 1.0 Net section factor for tension members UNL Member
Length Unsupported length of member for calculation of allowable bending stress
UNF 1.0 Same as UNL, but provided as a fraction of the member length
TRACK 0.0 1.0 = Suppresses printing of allowable stresses 1.0 = Prints all allowable stresses
DMAX 45.0 in. Maximum allowable depth for member selection DMIN 0.0 in. Minimum allowable depth for member selection RATIO 1.0 Permissible ratio that determines the cut off point for
pass/fail status. A value below this quantity indicates PASS while a value greater than this quantity indicates FAILURE.
Section 15B
15-11
Table 15B.1 - Steel Design Parameters for ASCE (PUB. 52) Based Design
Parameter Name
Default Value
Description
BEAM 0.0 2.0 = Perform design using the section locations specified according to the SECTION command 3.0 = Perform design at the ends and eleven intermediate sections of the beam
MAIN 2 Parameter that indicates the member type for the purpose of calculating the KL/R ratio (SEE CLAUSE 4.4, PAGE 25) = 10 : DO NOT PERFORM THE KL/R CHECK = 1 : LEG MEMBER KL/R <= 150 = 2 : COMPRESSION MEMBER KL/R <= 200 = 3 : TENSION MEMBER KL/R <= 500 = 4 : HANGAR MEMBERS KL/R <= 375 (Clause 4C.4, page 43) = 5 : REDUNDANT MEMBERS KL/R <= 250
ELA 4 Indicates what type of end conditions are to be used From among Equations 4.7-4 thru 4.7-7 to determine the the KL/R ratio. ELA=1 : EQN.4.7-4, Page 26
(VALID FOR LEG MEMBERS ONLY) ELA=2 : EQN.4.7-5, Page 27 ELA=3 : EQN.4.7-6, Page 27 ELA=4 : EQN.4.7-7, Page 27
ELB 1 Indicates what type of end conditions are to be used From among Equations. 4.7-8 thru 4.7-10 to determine the KL/R ratio. ELB=1 : EQN.4.7-8, Page 27, EQN.4.7-12, Page 28 ELB=2 : EQN.4.7-9, Page 27, EQN.4.7-13, Page 28 ELB=3 : EQN.4.7-10, Page 27, EQN.4.7-14,Page28
Steel Design Per ASCE Manuals and Reports
Section 15B
15-12
Table 15B.1 - Steel Design Parameters for ASCE (PUB. 52) Based Design
Parameter Name
Default Value
Description
LEG 0.0 This parameter is meant for plain angles. 3.0 = indicates that the angle is connected by both legs and allowable stress in axial tension is 1.0FYLD. 4.0 = indicates that the angle is connected only by the shorter leg and allowable tensile stress is computed per clause 4.10.2 as 0.9FYLD. 5.0 = indicates that the angle is connected by the longer leg.
DBL 0.75 in. Diameter of bolt for calculation of number of bolts required and the net section factor.
FYB 36 KSI Yield strength of bolt. FVB 30 KSI Shear strength of bolt. NHL
0 Number of bolt holes on the cross section that should be used to determine the net section factor for tension capacity.
Notes:
All values must be provided in the current unit system.
Note: Once a parameter is specified, its value stays at that
specified number till it is specified again. This is the way STAAD
works for all codes.
Section 16
American Steel Design Per A.P.I. Code
16-1
Steel Design Per A.P.I.
16.1 Design Operations
STAAD contains a broad set of facilities for the design of
structural members as individual components of an analyzed
structure. The member design facilities provide the user with the
ability to carry out a number of different design operations. These
facilities may be used selectively in accordance with the
requirements of the design problem. The operations to perform a
design are:
Specify the members and the load cases to be considered in the
design;
Specify whether to perform code checking or member
selection;
Specify design parameter values, if different from the default
values; and
Specify design parameters to carry out punching shear checks.
These operations may be repeated by the user any number of times
depending upon the design requirements, but care should be taken
when coupled with manipulation of the punching shear LEG
parameter.
The basic process is:-
a. Define the STAAD model geometry, loading and analysis.
b. Define the API code parameters with LEG 1.0.
c. Run the analysis and API design which creates the Geometry
file and give preliminary design results.
d. Check and modify the Geometry file as necessary.
Section 16
Steel Design Per A.P.I.
Section 16
16-2
e. Reset the LEG parameter to 2.0 and re-run the analysis to read
the modified Geometry file for the final design results.
16.2 Allowables per API Code
For steel design, STAAD compares the actual stresses with the
allowable stresses as defined by the American Petroleum Institute
(API-RP2A) Code. The 20th edition of API Code, as published in
1993, is used as the basis of this design (except for tension stress).
16.2.1 Tension Stress
Allowable tension stresses, as calculated in STAAD, are based on
the API Code, clause (3.2.1-1).
Allowable tension stress on the net section
Ft = 0.60Fy
16.2.2 Shear Stress
Beam Shear Stress
Allowable beam shear stress on the gross section must conform to
(3.2.4-2):
Fv = 0.4 Fy
The maximum applied beam shear stress is:
fv = V / 0.5 A (3.2.4-1)
Torsional Shear Stress
Allowable torsional shear stress
Fvt = 0.4 Fy (3.2.4-4)
Section 16
16-3
Fvt is the maximum torsional shear stress per (3.2.4-3).
16.3 Stress due to Compression
The allowable compressive stress on the gross section of axially
loaded compression members is calculated based on the formula
3.2.2-1 in the API Code, when the largest effective slenderness
ratio
r
Kl is less than Cc =
yF
E22 . If r
Kl exceeds Cc the
allowable compressive stress is increased as per formula (3.2.2 -2)
of the Code.
For t
D > 60 the lesser of Fxe or Fxc are substituted for Fxy .
Fxe = the elastic local buckling stress calculated with C, the critical
elastic buckling coefficient = 0.3 (3.2.2-3)
Fxc = the inelastic local buckling stress, (3.2.2-4)
16.4 Bending Stress
The allowable bending stress for tension and compression for a
symmetrical member loaded in the plane of its minor axis, as given
in Section 3.2.3 is:
a) Fb = 0.75 Fy
provided t
D
yF
1500 (Imperial Units)
b) Fb =
Et
DFy74.184.0 Fy
Steel Design Per A.P.I.
Section 16
16-4
where
yF
1500 <
t
D <
yF
3000 (Imperial Units)
c) Fb =
Et
DFy58.072.0 Fy
where
yF
3000 <
t
D 300 (Imperial Units)
16.5 Combined Compression and Bending
Members subjected to both axial compression and bending stresses
are proportioned to satisfy API formula 3.3.1-1 and 3.3.1-2 when
a
a
F
f is greater than 0.15, otherwise formula 3.3.1-3 applies. It
should be noted that during code checking or member selection, if
a
a
F
f exceeds unity, the program does not compute the second
3.3.1-1/2.
16.6 Design Parameters
The program contains a large number of parameter names which
are required to perform design and code checks. These parameter
names, with their default values, are listed in Table 12.1. These
parameters communicate design decisions from the engineer to the
program. (Also see section 5.44.1).
The default parameter values have been selected such that they are
frequently used numbers for conventional design. Depending on
the particular design requirements for an analysis, some or all of
these parameter values may have to be changed to exactly model
the physical structure. For example, by default the KZ value (k
value in local z-axis) of a member is set to 1.0, wile in the real
Section 16
16-5
structure it may be 1.5. In that case, the KZ value in the program
can be changed to 1.5, as shown in the input instruction (Section
5). Similarly, the TRACK value of a member is set to 0.0, which
means no allowable stresses of the member will be printed. If the
allowable stresses are to be printed, the TRACK value must be set
to 1.0.
Notes: The parameter names DMAX and DMIN are only used for
member selection. Once a parameter is specified, its value stays at
that specified number till it is specified again. This is the way
STAAD works for all codes.
Table 16.1- American (API) Steel Design Parameters
Parameter
Name
Default
Value
Description
KY 1.0 K value in local y-axis. Usually, this is minor axis.
KZ 1.0 K value in local z-axis. Usually, this is major axis.
LY Member Length
Length in local Y-axis to calculate slenderness ratio.
LZ Member Length
Length in local Z-axis to calculate slenderness ratio.
FYLD 36 KSI Yield strength of steel.
NSF 1.0 Net section factor for tension members.
UNL Member Length
Unsupported length for calculating allowable bending stress
UNF 1.0 Same as above provided as a fraction of actual member length
CB 1.0 Cb value as used in Section 1.5 of AISC 0.0 = Cb value to be calculated Any other value will mean the value to be used in design
MAIN 0.0 1.0 = Main member
2.0 = Secondary member
SSY 0.0 0.0 = Sidesway in local y-axis
Steel Design Per A.P.I.
Section 16
16-6
Table 16.1- American (API) Steel Design Parameters
Parameter
Name
Default
Value
Description
1.0 = No sidesway
SSZ 0.0 Same as above except in local z-axis
CMY
CMZ
0.85 for sidesway*
and calculated for no sidesway
Cm value in local y & z axes
TRACK 0.0 1.0 = Print all critical member stresses
100.0 = Suppress all checks except punching shear
DMAX 0.0 Maximum allowable depth
DMIN 0.0 Minimum allowable depth
RATIO Permissible ratio of the actual to allowable stresses
WELD 1 for closed sections
2 for open sections
Weld type, as explained in section 3.1.1.
1 = Welding is one side only except for wide flange or tee sections, where the web is always assumed to be welded on both sides.
2 = Welding is both sides. For closed sections like pipe or tube, the welding will be only on one side.
BEAM 1.0 0.0 = design only for end moments or those at locations specified by the SECTION command.
= calculate moments at twelfth points along the beam, and use the maximum Mz location for design.
WMIN 1.16 in. Minimum thickness
WSTR 0.4 X FLYD Allowable welding stress
LEG 1.0
2.0
To write out external parameters file.
To read in the external parameters file.
Section 16
16-7
16.7 Code Checking
The purpose of code checking is to ascertain whether the provided
section properties of the members are adequate as per API. Code
checking is done using the forces and moments at specific sections
of the members. If no sections are specified, the program uses the
start and end forces for code checking.
When code checking is selected, the program calculates and prints
whether the members have passed or failed the checks, the critical
condition of API code (like any of the API specifications for
compression, tension, shear, etc.), the value of the ratio of the
critical condition (overstressed for value more than 1.0 or an y
other specified RATIO value), the governing load case, and the
location (distance from the start of the number of forces in the
member) where the critical condition occurs.
Code checking can be done with any type of steel section listed in
Section 2.2, American Steel Design, of the Technical Reference
manual.
16.8 Member Selection
STAAD is capable of performing design operations on specified
members. Once an analysis has been performed, the program can
select the most economical section, i.e. the lightest section which
fulfills the code requirements for the specified member. The
section selected will be of the same type section as originally
designated for the member being designed. Member selection can
also be constrained by the parameters DMAX and DMIN which
limits the maximum and minimum depth of the members.
Member selection can be performed with all types of hollow steel
sections.
Steel Design Per A.P.I.
Section 16
16-8
Selection of members whose properties are originally input from a
user created table will be limited to sections in the user table.
Member selection cannot be performed on members whose section
properties are input as prismatic.
16.9 Truss Members
As mentioned earlier, a truss member is capable of carrying only
axial force. So in design, no time is wasted calcula ting the
allowable bending or shear stresses, thus reducing design time
considerably. Therefore, if there is any truss member in an
analysis (like bracing or strut, etc.), it is wise to declare it as a
truss member rather than as a regular frame member wi th both
ends pinned.
16.10 Punching Shear
For tubular members, punching shear may be checked in
accordance with the American Petroleum Institute (API) RP 2A –
20th Edition Section 4. The parameter PUNCH is used to identify
joint types for each end of the member where the punching shear
check is required. The PUNCH parameter is only read in from the
external geometry file. The external geometry file is described in
section 12.13. The PUNCH parameter is not specified within the
STAAD input file (the file with the .std extension).
Type of Joint and Geometry Req. Value of Parameter
PUNCH
K (overlap) 1.0
K (gap) 2.0
T & Y 3.0
CROSS 4.0
CROSS (with/diaphragms) 5.0
Section 16
16-9
Note: A value representing joint type and geometry must be
provided for parameter PUNCH, in the external file. On the first
run where no external table is present, LEG must equal 1.0.
16.11 Generation of the Geometry File
Automatic selection of the chord and brace members is performed
with the parameter LEG 1.0.
Two tubular members are used by the program to identify the
chord member. The chord members must be collinear (5 degree
tolerance).
The chord member must have a greater diameter and thickness
than the brace member being considered.
The punching shear check is performed on the joint treating it as a
T/Y joint. The yield stress of the brace is used. In the 50%
strength check the brace and chord yield are assumed to be the
same.
The major moment axis Mz is taken as In Plane Bending (IPB).
To change this, the parameter SWAP 1 should be used in the
external geometry file.
Note: The in-plane/out-of-plane correspondence can be set by
using the BETA angle.
If the punching shear cannot be performed at the joint for the
member being considered, a message is written to the output file
<filename>.ANL.
If a punching shear check is performed with the parameter LEG
1.0 used, then the geometry data used to perform the check is
written to the default external output file APIPUN.
The default external output/input file name can be changed by
using the command line:-
Steel Design Per A.P.I.
Section 16
16-10
CODE API <filename>.
This external output data file can be edited and used as an external
input file to re-perform the check using the parameter PUNCH 1.0
to 5.0.
This external input file allows can/stub geometry data to be
specified and chords to be assigned geometry where they could not
be identified in the Automatic selection.
The parameter LEG 2.0 must be used to read an external input file
where the default name is APIPUN.
The yield strength of the brace is used in the punching shear
check. This can be changed in the external geometry file. The
user should ensure that the correct cord member has been selected
for the check.
16.12 Chord Selection and Qf Parameter
Qf is a factor to account for the presence of nominal longitudinal
stress in the chord. When calculating Q f for the joints, the
moments used in the chord stress calculation will be from the
computer node results and not the representative moments
underneath the brace. If the moment varies significantly a long the
chord, it is more accurate to use the actual chord moment in the
middle of the brace foot print. The tests reported in Reference I1
were performed with a constant moment along the chord. Thus for
a local joint check, the local chord moment (under the brace)
should be used.
STAAD calculates Qf based on the moment at the chord member.
The chord member can be selected automatically by initial
screening by the program (based on geometry and independent of
loading) or specified by the user in the External file.
1 Ref I: Boone, TJ, Yura, JA and Hoadley, PW, Ultimate Strength if Tubular Joints – Chord
Stress Effects, OTC 4828, 1984
Section 16
16-11
In the automatic selection of the chord two collinear members (5
degree tolerance) are used to identify the chord. The chord is then
selected from one of the two members based on the larger diameter
then thickness or then by the minimum framing angle; for T joints
the first member modeled will be selected as the chord.
The user should confirm that the chord either be assigned by the
program or the user is representative of the local chord moment for
the brace in question.
16.13 External Geometry File
An example of the external geometry file is shown below:
BRACE CHORD PUNCH D T d T GAP FYLD THETAT TW SWAP
209 211 3 17.992 0.984 12.752 0.787 0.000 50.00 0.00 0.000 0
209 210 3 17.992 0.984 12.752 0.787 0.000 50.00 0.00 0.000 0
212 202 3 17.992 0.787 12.752 0.787 0.000 50.00 0.00 0.000 0
The parameters used in the external file are defined as follows:
Table 16.2 – External File
Parameter Description
PUNCH Parameter for punching shear (See Section 12.10)
BRACE Member number of brace CHORD Member number of chord D Chord Diameter in inches T Chord Thickness in inches d Brace Diameter in inches T Brace Thickness in inches GAP Gap in inches (must be negative for overlap
K-joint) FYLD Local yield strength used for joint in KIPS THETAT Angle of through brace in overlap K-joint in
Steel Design Per A.P.I.
Section 16
16-12
Table 16.2 – External File
Parameter Description
Degrees TW Used in overlap K-joint, taken as the lesser of
the weld throat thickness or thickness t of the thinner brace in inches
SWAP If parameter SWAP 0 is used then major moment Mz is taken for In Plane Bending (IPB). SWAP 1 uses the minor moment My as the IPB.
Notes:
For overlap K-joints, the through brace is assumed to be the
same diameter as the brace being checked.
If any of the parameters for diameter and thickness specified
in the external file are less than that for members being
checked, then the member properties specified in the STAAD
file shall be used.
The member diameter and thickness should be used in API
equation (4.1-1); in this check it has been assumed that the
yield strength of the chord and brace members are the same. The geometry file name is currently limited to eight characters
(4 if an extension as .txt is used).
The overall process of performing punching shear checks consists
of two steps. These steps are explained in section 12.16.
16.14 Limitations
The parameter SELECT 1.0 should not be used while carrying out
punching shear checks. It can be used in initial runs for member
selection.
No classification of the joint is performed using the loading.
No hydrostatic checks are performed.
Section 16
16-13
16.15 Tabulated Results of Steel Design
For code checking or member selection, the program produces the
results in a tabulated fashion. The items in the output table are
explained as follows:
a) Member refers to the member number for which the
design is performed.
b) TABLE refers to AISC steel section name which has been
checked against the steel code or has been selected.
c) RESULTS prints whether the member has PASSed or
FAILed. If the RESULT is FAIL, there will be an asterisk
(*) mark on front of the member.
d) CRITICAL COND refers to the section of the AISC code
which governs the design.
e) RATIO prints the ratio of the actual stresses to allowable
stresses for the critical condition. Normally a value of 1.0
or less will mean the member has passed.
f) LOADING provides the load case number which governed
the design.
g) FX, MY, and MZ provide the axial force, moment in local
Y-axis, and the moment in local Z-axis respectively.
Although STAAD does consider all the member forces
and moments (except torsion) to perform design, only FX,
MY and MZ are printed since they are the ones which are
of interest, in most cases.
h) LOCATION specifies the actual distance from the start of
the member to the section where design forces govern.
i) If the parameter TRACK is set to 1.0, the program will
block out part of the table and will print the allowable
bending stressed in compression (FCY & FCZ) and
tension (FTY & FTZ), allowable axial stress in
compression (FA), and allowable shear stress (FV).
Steel Design Per A.P.I.
Section 16
16-14
16.16 The Two-Step Process
The overall procedure for performing the code check per the API
code is as follows:
Step 1 – Creating the geometry data file. This is done by
specifying the name of the geometry data file alongside the
command line CODE API. If a file name is not specified, STAAD
automatically assigns the file name APIPUN to the geometry data
file. The parameter instructions in the .std file should contain the
LEG parameter and it should be assigned the value 1.0.
Example Reading External Geometry File
UNIT INCHES KIPS
PARAMETERS
* All joint data will be written to external file GEOM1 for
punching shear.
CODE API GEOM1
LEG 1.0
* Joints to be considered as T and Y, i.e. PUNCH is set to 3.0.
FYLD 50.0 ALL
TRACK 1.0 ALL
RATIO 1.0 ALL
BEAM 1.0 ALL
CHECK CODE ALL
After ensuring that your STAAD input file contains the above
data, run the analysis. Once the analysis is completed, you will
find that a file by the name GEOM1 has been created and is
located in the same folder as the one where your .std file is
located. (In case you did not specify a file name - GEOM1 shown
in the earlier example - STAAD will create the file named
APIPUN.
Section 16
16-15
Step 2 – The geometry data file (GEOM 1 or otherwise) should be
inspected and modified as required such as changing the PUNCH
values and local section properties for the punching shear checks.
Modify the .std file so it reruns the code check process by reading
the instructions of the GEOM file. This message is conveyed by
changing the value of the LEG parameter to 2.0. After making this
change, a re-analysis will result in the program using the
information in the geometry data file (GEOM1, APIPUN, or
otherwise) for performing the code check.
Example Reading an existing Joint Geometry Data File,
GEOM1
UNIT INCHES KIPS
PARAMETERS
* All joint data will be read from the external file GEOM1 for
punching shear.
CODE API GEOM1
LEG 2.0
FYLD 50.0 ALL
TRACK 1.0 ALL
RATIO 1.0 ALL
BEAM 1.0 ALL
CHECK CODE ALL
Steel Design Per A.P.I.
Section 16
16-16