COLLEGE OF ENGINEERING DEPARTMENT OF CIVIL & ARCHITECTURAL ENGINEERING

CVEN 220 : ANALYSIS OF STRUCTURES

WAEL I. ALNAHHAL, Ph. D., P. Eng

Spring, 2015

Introduction & Loads

Introduction

Structure refers to a system of connected parts used to support load, such as Buildings, Bridges, towers, . etc.

OBJECTIVES OF STRUCTURAL ENGINEERING

Structural engineering is the science and art of designing and making, with economy and elegance, buildings, bridges, frameworks, and other structures so that they can safely resist the forces to which they may be subjected.

STRUCTURAL ENGINEERING PROCESS

Determine types & magnitudes of loads Determine structural context geometric and geological information cost / schedule / height/ limitations / etc. Generate alternate structural systems Analyze one or more alternatives Select and perform detailed design Implement (usually done by contractor)

A typical structural engineering project

Revised structural

design

No

Planning

Preliminary structural design

Structural analysis

Load estimation

Safety/serviceability

Construction

Yes

Government

Consultant

Contractor

Structural Elements

Tie Rods

Beams

Type of Beams

Beams

Columns

Columns

Type of Structure

Trusses

Cables and Arches

Cables and Arches

Frames Frames members are subjected to axial, shear and

moment

Frames

Braced Rigid

Cable Suspended Structure

Cable Stayed Bridge

Surface Structures

Loads Codes a) General Building Codes Specify the requirement of minimum design load on structures 1. ASCE 2. UBC 3. IBC

Loads Codes b) Design Code Used to establish the requirement for the actual structural design 1. ACI 2. AISC 3. AASHTO

Other Code EuroCode EN 1990 Eurocode : Basis of Structural Design EN 1991 Eurocode 1: Actions on structures EN 1992 Eurocode 2: Design of concrete structures EN 1993 Eurocode 3: Design of steel structures EN 1994 Eurocode 4: Design of composite steel

and concrete structures.

Other Code EuroCode

EN 1995 Eurocode 5: Design of timber structures EN 1996 Eurocode 6: Design of masonry structures EN 1997 Eurocode 7: Geotechnical design EN 1998 Eurocode 8: Design of structures for

earthquake resistance EN 1999 Eurocode 9: Design of aluminium

structures

Types of loads

Dead loads

Live loads

Dynamic loads (e.g., trains, equipment)

Wind loads

Earthquake loads

Thermal loads

Settlement loads

Dead Load Consist of the weight of the various structural members and weight of any object that permanently attached to the structure

Dead Load

Dead Load

Dead Load

10cm

20cm

3m

1.0m 1.0m

The floor beam used to support the 2 m width of lightweight plain concrete slab having thickness of 10 cm. The slab serve as a portion of the ceiling for the floor below, and therefore its bottom is coated with plaster. Furthermore, an 3m high, 20 cm thick lightweight solid concrete is directly over the top flange of the beam. Determine the loading on the beam measured per one meter of the length of the beam Solution From Table 1-3 Lightweight concrete 0.015 kN/m2 per (mm)

15 kN/m3

0.24 kN/m2 Plaster on tile or concrete From Table 1-2 Masonry, Lightweight solid concrete 16.5kN/m3

------------------------------------------------------------ Total load = 13.38 kN/m

Concrete Slab (15)(0.1)(2)(1) = 3kN/m Plaster Ceiling (0.24)(2)(1) = 0.48 kN/m Block Wall (16.5)(0.2)(3) = 9.9 kN/m

Example 2 - Dead Loads

A typical 87.5 mm floor of an office building consists of a normal weight concrete slab. The floor has ceramic tiles above it (0.48 kN/m2 ) and a channel suspended ceiling system with 13 mm gypsum board underneath it. If mechanical and electrical fixtures will contribute 0.24 kN/m2 to the system, what is the total dead load to be supported?

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87.5 mm thick concrete Slab

Example 2 - Dead Loads

Solution: The floor must then support:

Concrete (87.5 x 10-3) x 24000 2.1 kN/m2 Ceramic tiles (Manufacturer or AISCM) 0.48 kN/m2 13-mm Gypsum board (AISCM) 0.04 kN/m2

Mechanical/electrical fixtures 0.24 kN/m2 Total 2.86 kN/m2

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Live Loads

Loads that are caused by the occupancy and use of the structure. They include:

Weight of occupants and furniture Weight of moveable partitions Crane rated capacity Construction loads

Refer to Applicable Building Code for minimum values.

Note minimum distributed and concentrated load requirements

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Summary of Typical Values of Distributed Live Load

No Occupancy or Use Live Load (psf) (kPa)

1. Hotel guest rooms, School classrooms, private apartments, hospital private rooms

40 1.92

2. Offices 50 2.40 3. Assembly halls, fixed seat library reading rooms 60 2.87 4. Corridors, above first floor in schools, libraries,

and hospitals 80 3.83

5. Assembly areas; theater lobbies; dining rooms and restaurants; office building lobbies main floor; retail stores assembly hall; movable seats

100 4.79

6. Wholesale stores; all floors light manufacturing; light storage warehouses

125 6.00

7. Armories and drill halls; stage floors; library stack rooms

150 7.18

8. Heavy manufacturing; sidewalks and driveways subject to trucking; heavy storage warehouses

250 11.97

Wind Load

2 ) (N/m q = 0.613 K K K V 2 I z zt d

pressure Wind

z

V I Kz Kzt

The velocity of the wind measured 10 m above the ground Importance factor depends upon nature of the building The velocity pressure coefficient which is function of height a factor that account for wind speed increases due to hills and

escarpments for flat ground Kzt=1.0 Kd a factor account for direction of wind when subjected to load combination

Wind Load

(N/m2 ) p = qGC p qh (GC ) pi

pressure for Enclosed Building Wind

Wind Load

(N/m2 ) q = 0.613 K K K V 2 I z zt d

pressure Wind

z

Design wind pressure for Signs F = qhGC p Af

Wind Load

Snow Load

F = 0.7CeCt Ipg

Earthquake Load

Earthquake Loads

Structure loaded when base is shaken

Response of structure is dependent on the frequency of motion

When frequencies match with natural frequency of structure - resonance

Load Example: Earthquake Load

Base Motion

Earthquake Load

Earthquake Load

Settlement

Hydrostatic and Soil Pressure

Other natural Loads

Structural Design

LRFD (Load and resistance factor design)

Load combination example:

1.4 Dead Load

1.2 Dead Load +1.6 Live Load

1.2 Dead Load +1.6 Live Load + 0.5 Snow Load

1.2 Dead Load + 1.5 Eq. Load + 0.5 Live Load

Load Paths in Structures

Load Path is the term used to describe the path by which loads are transmitted to the foundations

Different structures have different load paths

Some structures have only one path

Some have several (redundancy good)

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A building structure safely transmits loads down to Earth

Load Path in Framed Structure

Slide Number 1IntroductionOBJECTIVES OF STRUCTURAL ENGINEERINGSTRUCTURAL ENGINEERING PROCESSA typical structural engineering projectSlide Number 6BeamsSlide Number 8Slide Number 9Slide Number 10Cables and ArchesCables and ArchesSlide Number 13Slide Number 14FramesCable Suspended StructureSlide Number 17Cable Stayed BridgeSlide Number 19Surface StructuresSlide Number 21Slide Number 22Slide Number 23Slide Number 24Types of loadsSlide Number 26Slide Number 27Slide Number 28Dead LoadExample 2 - Dead LoadsExample 2 - Dead LoadsLive LoadsSummary of Typical Values of Distributed Live LoadWind LoadWind LoadSlide Number 36Slide Number 37Slide Number 38Earthquake LoadEarthquake LoadsLoad Example: Earthquake LoadSlide Number 42SettlementHydrostatic and Soil PressureStructural DesignLoad Paths in StructuresSlide Number 47Load Path in Framed StructureSlide Number 49Slide Number 50Slide Number 51Slide Number 52