design of columns amd some parts
TRANSCRIPT
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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
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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
Development length required for 20 bar is 940mm
So provide 90o bend and then extend toa length of 600mm to get development length of
(415+160+600) mm=1175mm
Development length required for 16 bar is 752mm
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:
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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
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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
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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
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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.
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Fig: 12.1
Fig: 12.2
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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.
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Fig: 12.3
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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
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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
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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
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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
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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.
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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.