design of columns amd some parts

7/31/2019 Design of Columns Amd Some Parts

1/16

BEAM DESIGN

5.1.1Design Data

i) Beam size = 250mm x 425mm

ii) Grade of steel for main reinforcement = Fe 415

iii) Grade of concrete = M20

iv) Maximum size of main reinforcement = 16mm

v) Maximum size of shear reinforcement = 8mm

vi) Clear cover for beam = 25mm

5.1.2 Design of Beam

i) Effective depth of the beam section

d= 425-25-16/2 = 392mm

ii) Maximum steel reinforcement (As Per IS 456:2000, clause 26.5.1.1)

Ast=0 .04xbxd = .04x250x425 = 4250mm2

iii) Minimum steel reinforcement (As Per IS 456:2000, clause 26.5.1.1)

Ast = 0.85xbxd/fy = 0.85x300x412.5/415 = 253.46mm2

iv) For sagging moment (+ve) Ast and Asc are provided at the bottom face and top face of the

beam section respectively.

v) For hogging moment (-ve) Ast and Asc are provided at the top face and bottom face of the

beam section respectively.

vi) The maximum spacing of the vertical stirrup as per IS 456:2000, clause 26.5.1.5 should be

the least of the following.

a. 0.75d=0.75x412.5=309.38mm


2/16

b. 300 mm.

c. As calculated.

vii)Development length required for extreme beam column junction

development length available is 415mm

Development length required for 25 bar is 1175mm

So provide 90o bend and then extend toa length of 810mm to get development length of

(415+200+810) mm=1425mm


So provide 90o bend and then extend toa length of 600mm to get development length of

(415+160+600) mm=1175mm


So provide 90o bend and then extend to a length of 500mm to get development length

of (415+128+500) mm=1043mm

Beam design tables are given below:


3/16


4/16

DESIGN OF COLUMNS

6.1 DESIGN DATA

1. Column size =400x400

2. Grade of steel for reinforcement = Fe 415

3. Grade of concrete = M20

4. Maximum size of main reinforcement = 25 mm

5. Minimum size of shear reinforcement = 8 mm

6. Clear cover for column = 40 mm

6.2 DESIGN OF COLUMN

1. Minimum steel reinforcement (As per clause 26.5.3.1, IS-456)

Ast = 0.8 % of b x D

Ast,min =0.008 x 400 x 400 = 1280 mm

2. Maximum steel reinforcement (As per clause 26.5.1.1, IS-456)

Ast = 6 % of b x D

Ast,max 400 x 400 =0.06 x 400x 400 = 9600 mm

6.3 DESIGN TABLE:

Let us take d = 40 + (25/2) = 52.5 mm (Assuming 25 mm bar and clear cover of 40 mm)

Lateral dimension of column D=400mm

So d/D = 0.15

CHAPTER 6


5/16

Chart 46 of SP-16 is used for finding the % of longitudinal reinforcement of column in different

floor level.

Column design tables are given below:

S E C O N D F L O O R L E V E L

P u ( KN )M u (KN m )

A 4 0 A 4 0 '4 0 0 X 4 0 018 6 .9 5335 .97 1 0 .0 5 8 0 . 02 8 0 0 0 4 1 9 6 4

B40B40 '4 0 0 X 4 0 031 2 .9 2673 .63 7 0 .0 9 8 0 . 05 8 0 . 0 2 0 .4 6 4 0 4 1 9 6 4

C40C40 '4 0 0 X 4 0 034 5 .4 3569 .69 8 0 .1 0 8 0 . 05 4 0 . 0 1 0 .2 3 2 0 4 1 9 6 4

D40D40 '4 0 0 X 4 0 025 8 .5 2194 .94 5 0 .0 8 1 0 . 07 4 0 . 0 3 9 0 .7 8 1 24 8 4 1 9 6 4

Pt (%A s t R e

( m m C O L U M

C O L U M

D IM EN

D E SIG N V

N O . O F

A st

P r o v i d

F I R S T F L O O R L E V E L

P u (K N )M u (K N m )

A 4 1 - A 4 04 0 0 x 4 0 04 1 5 . 7 5 06 0 . 9 2 2 0 .1 3 0 0 . 04 8 0 0 0 4 1 9 6 4

B 4 1 - B 4 04 0 0 x 4 0 06 3 9 . 9 4 51 2 3 . 9 3 30 .2 0 0 0 . 09 7 0 . 0 4 0 . 8 1 2 8 0 4 1 9 6 4

C 4 1 - C 4 04 0 0 x 4 0 07 5 9 . 1 8 51 2 1 . 1 1 30 .2 3 7 0 . 09 5 0 . 0 3 9 0 .7 8 1 24 8 4 1 9 6 4

D 4 1 - D 4 04 0 0 x 4 0 05 2 7 . 7 3 01 0 8 . 0 6 40 .1 6 5 0 . 08 4 0 . 0 3 0 . 6 9 6 0 4 1 9 6 4

N O . O F

C O L U

D IM EN

D E SIG N VC O LU P t (

A s t R e

( m m

A st

P r o v i


6/16

CHAPTER 9

HOW TO MAKE BUILDINGS DUCTILE FOR GOOD SEISMIC

PERFORMANCE

12.1 Construction Materials:

Concrete is the material that has been popularly used in building construction particularly over the

last four decades. Cement concrete is made of crushed stone pieces (called aggregates), sand,

cement and water mixed in appropriate proportions. Concrete is much stronger than masonry under

compressive loads, but again its behavior in tension is poor. The properties of concrete critically

depend on the amount of water used in making concrete; too much too little water, both can cause

havoc. In general, both masonry and concrete are brittle, and fall suddenly.

Steel is used in masonry and concrete buildings as reinforcement bars of diameter from 6mm to

40mm. reinforcing steel can carry both tensile and compressive loads. Moreover , steel is a ductile

material. This important property of ductility enables steel bars to undergo large elongation before

breaking.

Concrete is used in buildings along with steel reinforcement bars. This complete material is called

reinforced cement concrete or simply reinforced concrete (RC). The amount and location of steel

in a member should be such that the failure of the member is by steel reaching its strength in

tension before concrete reaches its strength in compression. This type of failure is ductile failure,

and hence is preferred over a failure where concrete fails first in compression. Therefore, contrary

to common thinking, providing too much steel in RC buildings can be harmful even.

By using the routine design codes (meant for design against non-earthquake effects), designers

may not be able to achieve a ductile structure. Special design provisions are required to helpdesigners improve the ductility of the structure. Such provisions are usually put together in the

form of a special seismic design code, e.g., IS:13920-1993 for RC structure. These codes also

ensure that adequate ductility is provided in the members where damage is expected.

12.2 Beams

CHAPTER 12


7/16

Beams in RC buildings have two sets of steel reinforcement, namely: (a) long straight bars (called

longitudinal bars) placed along its length, and (b) closed loops of small diameter steel bars (called

stirrups) placed vertically at regular intervals along its full length.

Designing a beam involves the selection of its material properties (i.e. grades of steel bars and

concrete) and shape and size; these are usually selected as a part of an overall design strategy ofthe whole building. And, the amount and distribution of steel to be provided in the beam must be

determined by performing design calculation as per IS 456:2000 and IS 13920:1993.

The Indian ductile detailing code IS 13920:1993 prescribes that:-

a. At least two bars go through the full length of the beam at the top as well as the bottom of

the beam.

b. At the ends of the beams, the amount of steel provided at the bottom is at least half at that

at top.

The IS 13920:1993 prescribes the following requirements related to stirrups in R.C.C. beams.

(a) The diameter of stirrups must be at least 6mm; in beams more than 5m long, it must be

atleast 8mm.

(b) Both ends of the vertical stirrup should be bent into a 135 0 hook and extended sufficiently

beyond this hook to ensure that the stirrup does not open out in an earthquake.

(c) The spacing of vertical stirrups in any portion of the beam should be determined fromcalculations.

(d) The maximum spacing of stirrup is less than half the depth of the beam.

(e) For a length of twice the depth of the beam from the face of the column, and even more

stringent spacing of stirrups is specified, namely half the spacing mention in (d).

The IS 13920:1993 prescribes that laps of longitudinal bars in beams:-

(a) Made away from the face of the column, and

(b) Not made at locations where they are likely to stretch by large amounts and yield.

Moreover, at the locations of laps, vertical stirrups should be provided at a closer spacing.


8/16

Fig: 12.1

Fig: 12.2


9/16

12.3 COLUMNS

The Indian Standard IS 13920:1993 prescribes following details for earthquake-resistant columns.

(a) Closely spaced ties must be provided at the two ends of the column over a length not less

than larger dimension of the column, one-sixth the column height or 450mm.

(b)Over the distance specified in item (a) above and below a beam-column junction, the

vertical spacing of ties in columns should not exceed D/4 for where D is the smallest

dimension of the column (e.g., in a rectangular column, D is the length of the small side).

This spacing need not be less than 75mm nor more than 100mm. At other locations, ties

are spaced as per calculations but not more than D/2.

(c)The length of tie beyond the 1350 bends must be at least 10 times diameter of steel bar used

to make the closed tie; this extension beyond the bend should not be less than 75mm.


10/16

Fig: 12.3


11/16

12.1 CONCLUSION

This project aims at the structural design of a multistoried office cum commercial building in

Guwahati City. The first phase of the project was to plan a building according to the existing

Guwahati Metropolitan Development Authority (GMDA) bye-laws. The planning of the building

has been done to arrange the location of various rooms and their sizes so that it fulfills the

functional requirements of the intended purpose.

After the planning stage, estimation of the various loads, viz. gravity and seismic loads are carried

out. During this stage, analysis has been done by approximate methods such has moment

distribution and portal methods to yield the various bending moments, shear forces and axial loads

acting at the various section at different levels. The result of these computations are then subjected

to load combination procedure, the main objective of which is to give the worst combination that

can be accepted as the design values i.e. that values for which the various components of the

structure has to be designed.

The design phase consisted of designing of the various components that constitutes the structure

such as beams, columns, slabs, staircases, chajja/sunshade, lintels and footing. The final output is

in the form of reinforcement detailing of the various constituent parts as they are essential for the

execution of the actual construction work. Ductile detailing has been incorporated as per

IS 13920 : 1993

CHAPTER 13


12/16

SCOPE FOR FUTURE STUDY

There is immense scope of future study in the field of Structural Design of Multistoreyed Building

that has been dealt with in this project work. These include

Study of the cost estimate.

3-D Seismic Analysis with the aid of computer programming.

Use of ready-made computer package programs for analysis, design, plotting, detailing and

specification writing.

CHAPTER 14


13/16

ANNEXER A

LIST OF REFERRED INDIAN STANDARDS AND CLAUSES

IS: 875 (Part II) 1987 Code of Practice for Design Loads (other than earthquake) for

Building and Structures

Clause. 3.1.2

IS: 1893 (Part II)- 2002- Criteria for Earthquake Resistant Design of Structures

Part 1 General Provisions and Buildings.

Clause 6.4.2

Clause 7.3.1

Clause 7.3.2

Clause 7.4.2

Clause 7.5.3

Clause 7.6.1

Table 2

Table 6

Table 7


14/16

Fig. 2

IS: 456-2000-Plain and Reinforced Concrete-Code of Practice

Clause 23.2.1

Clause 26.2.1

Clause 26.3.2

Clause 26.4.1

Clause 26.5.1.1

Clause 26.5.1.5

Clause 26.5.1.6

Clause 26.5.2.1

Clause 26.5.2.1

Clause 26.5.3.1 (a)

Clause 26.5.3.2 (c)

Clause D-1.1

Clause D-1.8

Clause D-1.9

Clause D-2.1

Table 26

DESIGN AID TO IS: 456-1978 [SP: 16]

Chart 11

Chart 12

Chart 13

Chart 14

Chart 15

Chart 44

Table 2

Table 37

Table 61

Table 62


15/16

Table 96

IS: 13920-1993- Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic

Forces.

Clause 3.4

Clause 5.1

Clause 5.2

Clause 5.3

Clause 6.2.1

Clause 6.2.2

Clause 6

Clause 6.2.12.3 Clause 6.2.4

ANNEXER B

LIST OF REFERRED BOOKS AND REPORTS

1. Jain, Ashok K. (2006) Reinforced Concrete Limit State Design, 6

th

Edition, NemChand & Bros., Roorkee.

2. Pillai, S Unnikrishna and Menon, Devdas (2005), Reinforced Concrete Design,

Second Edition, Tata McGraw-Hill, New Delhi.

3. Ramamrutham, S (2006), Design of Reinforced Concrete Structures, Sixteenth

Edition, Dhanpat Rai Publishing Company (P) Ltd., New Delhi.

4. Sinha, S.N., (2005), Reinforced Concrete Resign, Second Edition, Tata McGraw-

Hill, New Delhi.

5. Saran, Swami (2006), Analysis and Design of Substructures-Limit State Design,

Second Edition, Oxford & IBH published Co. Pvt.Ltd., New Delhi.


16/16

6. Shah, Dr. H.J. and Jain, Dr. Sudhir K, Design Example of a Six Storey Building,

Document No. II TK-GSDMA-EQ26-V3.0, IITK-GSDMA Project on Building

Codes.

7. Ramamrutham, S and Narayan, R (2003), Theory of Structures, Seventh Editing,Dhanpat Rai Publishing Company (P) Ltd., New Delhi.

8. Guide Lines for Guwahati Metropolitan Development Authority (GMDA),

Guwahati. (Building Permission)

9. Design of a five storeyed RCC office building, by Devish Mazumdar (03/09), in

2006-2007, under the guidance of Dr. Palash Jyoti Hazarika, Dr. Diganta Goswami

and Dr. Jayanta Pathak.

design of columns amd some parts

Documents