Seismic Analysis and Design of Hospital Building-libre
Transcript of Seismic Analysis and Design of Hospital Building-libre
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SEISMIC ANALYSIS AND DESIGN OF MULTI STOREYED
HOSPITAL BUILDING
Submitted at the end of final semester by
K.Aslam
[Reg.No.11609103006]
In partial fulfillment for the award of the degree of
BACHELOR OF ENGINEERING
IN
CIVIL ENGINEERING
SRI VENKATESHWARA COLLEGE OF ENGINEERING & TECHNOLOGY
THIRUVALLUR
ANNA UNIVERSITY: CHENNAI 600 025
APRIL 2012
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CERTIFICATE
This is to certify that the project report entitled
“SEISMIC ANALYSIS AND DESIGN OF MULTI STROREYED HOSPITAL
BUILDING” is t he bonafied project work done by K.ASLAM (Reg.No.11609103006) in
partial fulfillment of the requirement for the award of Bachelor of Engineering Degree in
Civil Engineering under Sri Venkateswara College of Engineering & Technology during
the year 2011-2012.
Internal Guide
S.SANTHANA RAMAN,M.E,C.A.R(CSU)USA Mrs.GAYATRI PADHY,B.E
Dean& Project Guide Head of the Department Department of Civil Engineering. Department of Civil Engineering
S.V.C.E.T. . S.V.C.E.T.
External Guide
Dr.S.JUSTIN
Engineering Manager
SDDH,
EDRC, Larsen & Toubro,
Chennai.
Mr.UP.VIJAY Mr.M.RAMPRATHAP
Assistant Engineering Manager, Assistant Engineering Manager,
EDRC, Larsen & Toubro, EDRC, Larsen & Toubro,
Chennai. Chennai.
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ACKNOWLEDGEMENT
I take this oppurtunity to thank Mr.Bikram K.Naik [HR Manager, EDRC Division] and
Mr.Mukesh Kumar Singh [HR Manager P&OD] for giving me the oppurtunity to work with
Larsen & Toubro.
I thank Dr.S.Justin [Engineer Manager (SDDH),EDRC], Mr.UP.Vijay [Assitant Engineering
Manager] and Mr.M.Ramprathap [Assistant Engineering Manager] without them this project
would not have been possible. Their feedback, comments and suggestions were helpful
throughout the entire work.
I also thank all other Engineers of the Health and Leisure Division of B&F, L&T for guiding
me throughtout the program.
I thank Dr.Suresh Mohan Kumar M.Tech,Ph.D our Principal, for giving me the oppurtunity
to work with Larsen & Toubro Limited and I thank Mr.S.Santhanaraman M.E,C.A.R (CSU)
USA and Mrs.Gayatri Padhy,B.E. without them this project would not have been possible
throughout the entire work.
Last but not the least I thank my friends and family for their whole hearted support and
cooperation.
K.ASLAM
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ABSTRACT
Industrial training is an essential in the development of the practical and professional skills
required of an Engineer and as an aid to prospective employment undertaking the training in
a reputed firm adds to the advantage. The training was done with Larsen & Toubro, Chennai.
The work allotted during the Indutrial Training period was the Seismic Analysis and Design
of multistoryed New Teaching Hospital block at Agartala one of the projects undertaken by
L&T.
Earthquake Engineering was developed a lot from the early days and seismically analysing
the structures requires specialized explicit finite element analysis software,which divides the
element into very small slices and models the actual physics. The seismic analysis of the
proposed building was done in the software ETABS, version- 9.7, which is one of the most
advanced software in the structural design field. The loads applied on the structure was based
on IS:875(part I)-1987[dead load],IS:875(part II)-1987[live load], IS:875(part III)-1987[wind
load], IS:1893-2000 [Earthquake load]. Scale factor is calculated from the design base shear
(Vb) to the base shear calculated using fundamental time period (Ta).
Once the analysis was completed all the structural components were designed according to
Indian standard code IS:456-2000. Footing, columns, beams, slab, staircase and shear wallwere designed. Ductile detailing of the structural elements were done as per code IS:13920-
1993.
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LIST OF CONTENTS PAGE NO.
1.0 INTRODUCTION 1
1.1 New Teaching Hospital Building 1
1.2 Larsen & Toubro 2
1.2.1 Vision and Mission 2
2.0 FEATURES OF PROJECT 2
3.0 INTRODUCTION TO ETABS 3
3.1 Modeling Features 3
3.2 Analysis Features 4
4.0 LOAD CALCULATION 5
4.1 General data 5
4.2 Dead load 5
4.2.1 Typical Floor slab 5
4.2.2 Terrace Floor slab 5
4.3 Live load 5
4.4 Wall load 6
4.4.1 Member load due to 230mm thick exterior wall 6
4.4.2 Member load due to 100mm thick interior wall 6
4.5 Static check for load combintion 6
4.5.1 Plinth level 6
4.5.2 Floor level 7
4.5.3 Static check for dead and live load combination. 8
4.6 Wind load calculation 9
4.6.1 Basic wind speed 9
4.6.2 Design wind speed 9
4.6.3 Design wind pressure 9
4.6.4 Wind force 10
4.7 Seismic load calculation 13
4.7.1 Zone factor 14
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4.7.2 Response reduction factor 14
4.7.3 Importance factor 14
4.7.4 Seismic weight 14
4.7.5 Soil classification 15
4.7.6 Seismic base shear calculation 16
4.7.8 Analysis 17
4.7.9 Scale factor calculation 18
5.0 MODELLING AND ANALYSIS OF THE BUILDING 23
5.1 Basic Grid system 23
5.2 Define Geometry 23
5.3 Define material Property 24
5.4 Define frame section 24
5.5 Define Wall or Slab section 25
5.6 Define Diaphram 26
5.7 Define Response Spectrum Function 26
5.8 Response Spectrum Function 26
5.9 Define Static load cases 26
5.10 Define load combination 28
5.11 Output 30
6.0 DESIGN OF FOUNDATION 36
6.1 General 36
6.2 Design of Isolated footing 36
6.3 Design of typical isolated footing 37
6.3.1 Design Parameters 37
6.3.2 Bending moment in X direction 38
6.3.3 Bending moment in Y direction 39
6.3.4 Check for one way shear 39
6.3.5 Check for two way shear 39
6.3.6 Transfer of forces at column base 40
6.4 Foundation detailing 40
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7.0 COLUMN DESIGN 41
7.1 General 41
7.2 Column design 42
7.2.1 Design Parameters 42
7.2.2 Design of bending moment 42
7.2.3 Reinforcement provided 43
7.2.4 Design Parameters 43
7.2.5 Design of bending moment 44
7.2.6 Calculation of reinforcement 44
7.3 Column detailing 45
8.0 BEAM DESIGN 46
8.1 General 46
8.2 Beam design 47
8.2.1 Design Parameters 47
8.2.2 Bending moment calculation 47
8.2.3 Shear Reinforcement 48
8.2.4 Shear Reinforcement at mid span 48
8.2.5 Design of Hanger bars 49
8.2.6 Development Length 49
8.2.7 Check for deflection 49
8.3 Beam Detailing 50
9.0 DESIGN OF SLAB 51
9.1 Design of one way and two way slab 51
9.2 Design of typical two way slab 53
9.2.1 Design parameters 53
9.2.2 Design of moments 53
9.2.3 Reinforcement calculation 54
9.2.4 Check for depth 54
9.2.5 Check for shear 54
9.2.6 Check for deflection 55
9.3 Reinforcement details 55
9.4 Slab detailing 56
10. DESIGN OF STAIRCASE 57
10.1 General 57
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10.2 Design parameters 59
10.3 Load acting on stairs 59
10.4 Design of waist slab type staircase 59
10.5 Reinforcement provided 60
10.6 Staircase detailing 60
11. DESIGN OF SHEARWALL 61
11.1 General 61
11.2 Wall dimensions 61
11.3 Check for boundary element 62
11.4 Fixing boundary element 62
11.5 Determination of minimum steel 62
11.6 Shear reinforcement 63
11.7 Flexural strength 63
11.8 Transverse reinforcement 64
11.9 Shear wall detailing 64
12. Conclusion 65
13. References 66
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LIST OF SYMBOLS
Asc = Area of Compression Steel
Ast = Area of tension steel
A sv = Area of shear reinforcement
Ag = Gross area of concrete
b = Breadth of the section
B.M = Bending Moment
C/C = Center to Center
d = Effective depth
d’ = Depth of compression reinforcement.
DL = Dead load
D = Over all depth
Df = Depth of flange
EL = Earthquake load
f ck = Characteristic Strength of concrete
f y = Characteristic Strength of steel
I = Importance Factor (IS: 1893-1987)
L = Clear Span
L.L = Live Load
k 1 = Modification Factor (IS: 456-2000)
K1 = Risk Factor (IS 875:-1987) part III
K2 = Topography factor (IS 875-1987) part III
Ld = Development Length
Leff = Effective length
Lx = Length of span in x direction
Ly = Length of span in x direction
M.F = Modification factor
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M.R = Moment of Resistance
Mu = Ultimate Moment
Mu limit = Limiting moment of reinforcement of a section
Pu = Axial load on a compression member
Pt = Percentage of reinforcement
R.C.C = Reinforcement cement concrete
R = Response Reduction factor (IS: 1893-1987) part-III
S = Spacing of reinforcement
S.F = Shear force
T = Torsion moment
Vu = Shear force
WL = Wind load
Zp = Plastic section modulus (IS: 456-2000)
Z = Zone factor (IS: 1893-1987)-part III
τc = Critical shear stress in concrete
τv = Nominal shear stress in concrete
φ = Nominal diameter of bars
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LIST OF TABLES PAGE NO.
1. Value of Topography Factor K2 11
2. Wind load calculation 11
3. Wind forces from Analysis (X Direction) 12
4. Wind forces from Analysis (Y Direction) 12
5. Seismic zone 14
6. Base shear in X-direction using ETABS model 17
7. Base shear in Y-direction using ETABS model 18
8. Base shear in X-direction using ETABS model 19
9. Base shear in Y-direction using ETABS model 20
10. Period Vs Sa/g 20
11. Seismic weight output 22
12. Load combination 28
13. Moment coefficients 54
14. Reinforcement provided 54
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LIST OF FIGURES PAGE NO.
1. Location map 01
2. Panel drawing 07
3. Axial load from Analysis 09
4. Plan & Elevation 10
5. Soil classification 15
6. Response spectra for soft soil 22
7. The new model initialization form. 23
8. Building Plan Grid System and Storey Data Definition 23
9. Material property data form 24
10. Define Frame Properties form 24
11. Section properties and Reinforcement details. 25
12. Define wall or slab section 25
13. Define Diaphragms 26
14. Define response spectrum function. 26
15. Response spectrum function graph 27
16. Define static load case 27
17.
Define load combinations 28
18. Model output 30
19. Bending moment diagram from Analysis 31
20. Shear force diagram from Analysis 32
21. Diaphragm 33
22.
Plan showing slab details 34
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23. Plan showing beam and column ID 35
24. Types of footing 36
25. Pressure diagram 38
26. Footing detailing 40
27. Types of column 41
28. Column detailing 45
29. Beam detailing 50
30.
Types of Slab 51
31. Load distribution in two way slab 53
32. R.C Details of Slabs 55
33. Slab detailing 56
34. Types of staircase 58
35.
Detailing of staircase 60
36. Shear wall diagram 61
37. Shear wall detailing. 64
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1.0 INTRODUCTION
1.1 NEW TEACHING HOSPITAL BUILDING:
Figure1-location map
The New teaching hospital block located at Agartala. The total build up area of the hospital
building is 12596.67 square meter and having five floors (G+5). The Hospital building
consists of various divisions like Ortho ward,Orthopedic ward, Opthamal ward, ENT ward,
major and minor operation theaters, out patient ward, seminar halls for medical students,
scanning and X-ray centre and medicine store room etc. The building located at seismic
prone zone (zone factor V). The building has designed according to the Earthquake resistant
considerations.
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1.2 LARSEN & TOUBRO LIMITED
1.2.1 Vision and Mission
The design and execution of New teaching hospital block were awarded to Larsen & Toubro
Limited (L&T) is an Indian multinational conglomerate company headquarted in Mumbai,
India. The company has four main sectors; Technology, Engineering, Construction and
Manufacturing. L&T has an international presence with a global spread of office and
factories further, supplemented by a comprehensive marketing and distribution network. The
firm has more than 60 units in 25 countries. Domestic business with in India dominates, but
the company steadily growing it’s global operations with a focus on China and Middle East.The company was founded in Mumbai in 1938 by Danish Engineers, Mr.Henning Hlock-
Larsen and Seren Kristian Toubro. In 1944 ECC was incorporated by the partners; presently
ECC(Engineering Construction & Contracts Division of L&T) is the largest contruction
organization. L&T covers various disciplines of construction- Civil, Mechanical,
Instrumentation and Electrical.
The design wing of L&T, EDRC division provides consultancy design and total Engineering
solutions to customers. It carries out both residential and commercial projects. The training
work was carried out in the EDRC division of L&T.
2.0 FEATURES OF PROJECT
The project consists of Seismic Analysis and Design of New Teaching Hospital block (NTH)
located at Agartala. The architectural drawings of NTH were done in the Auto CAD 2010 and
the structural modeling was done by using ETABS software. The concrete mix used for all
the structural member is M 30 and steel is Fe 500. The load combination were taken to obtain
the maximum design loads, bending moments and shear forces. The structural element
designs were carried as per IS:456-2000 for the load combinations. Earthquake resistant
design detailing of the structure was done as per IS:13920-1993.
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3.0 INTRODUCTION TO ETABS:
ETABS is sophisticated software for analysis and design program developed specifically for
buildings systems. ETABS version-9.7 features an in intuitive and powerful graphical
interface coupled with unmatched modeling, analytical, and design procedures, all integrated
using common database. Although quick and easy for simple structures, ETABS can also
handle the largest and most complex building models, including a wide range of nonlinear
behaviors, making it the tool of choice for structural engineers in the building industry.
3.1 MODELING FEATURES
The ETABS building is idealized as an assemblage of area, line and point objects. Those
objects are used to represent wall, floor, column, beam, brace and link / spring physical
members. The basic frame geometry is defined with reference to a simple three-dimensional
grid system. With relatively simple modeling techniques, very complex framing situations
may be considered.
The building may be unsymmetrical and non-regulator in plan, Torsional behavior of the
floors and understory compatibility of the floors are accurately reflected in the results. Thesolution enforces complete three-dimensional displacement compatibility, making it possible
to capture tubular effects associated with the behavior of tall structures having relatively
closely spaced columns.
Semi-rigid floor diaphragms may be modeled to capture the effects of in plane floor
deformations. Floor objective may span between adjacent levels to create sloped floors
(ramps), which can be useful for modeling parking garage structures.
3.2 ANALYSIS FEATURES
Static analysis for user specified vertical and lateral floor on story loads are possible. If floor
elements with plate bending capability are modeled, vertical uniform loads on the floor are
transferred to the beams and columns through bending of the floor elements.
The program can automatically generate lateral wind and seismic load patterns to meet the
requirements of various building codes. Three dimensional mode shapes and frequencies,
model participation factors, direction factors and participating mass percentage are evaluated
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using Eigen vector or Ritz-vector analysis-Delta analysis effects may be included with static
or dynamic analysis.
Response spectrum analysis, linear time history analysis, nonlinear analysis and static
nonlinear analysis are possible. The static nonlinear capabilities also allow you to perform
incremental construction analysis, so that forces that arise as a result of construction sequence
are included. Results from the various static load cases may be combined with each other or
with the results from the dynamic response dynamic response spectrum or time history
method.
Output may be viewed graphically, displayed in tabular output, the types of output include
reactions, member forces, mode shapes, participation factors, static and dynamic story
displacements and story shears inter story drifts and joint displacements, time history traces
and more.
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4.0 LOAD CALCULATIONS
4.1 GENERAL DATA
Structure = G + 5
Floor height ( First Floor to Fifth Floor) = 4.0 m
Grade of concrete (for all structural elements) = M 30
Unit weight of concrete = 25kN/m3
Unit weight of cement mortar = 24kN/m3
Unit weight of water = 10kN/m3
Unit weight of Brick = 20kN/m3
4.2 DEAD LOAD (As per IS 875 part I)
4.2.1 TYPICAL FLOOR SLAB:
Self-weight of slab (150mm thick) = 3.75 kN/m2
Floor Finish = 1.5 kN/m2
Total Load = 5.25 kN/m2
4.2.2 TERRACE FLOOR SLAB:
Self-weight of slab (150mm thick) = 3.75 kN/m2
Terrace (Roof finish + Water proofing) = 3.20 kN/m2
Total Load = 6.95 kN/ m2
4.3 LIVE LOAD (As per IS 875 part II)
Living room, Toilet & Bath room = 3.00 kN/m2
Recreation Room and Pantry = 3.00 kN/m2
Store and Laundry = 4.00 kN/m2
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Corridors & stair case = 4.00 kN/m2
Terrace Floor = 1.5 kN/m2
ICU = 3.00 kN/m2
Lounge = 3.00 kN/m2
Nurse station = 3.00 kN/m2
Operation Theatres = 3.00 kN/m2
Dining room = 4.00 kN/m2
Waiting room = 4.00 kN/m2
4.4 WALL LOAD
4.4.1 Member load due to 230mm thick exterior wall
Wall thickness = 230 mm
Floor Height = 4000 mm
Beam Depth = 750 mm
(0.23 × (4-0.75) × 20) = 15kN/m
4.4.2 Member load due to 230mm thick interior wall
Wall thickness = 115 mm
Floor Height = 4000 mm
Beam Depth = 750 mm
(0.115 × (4-0.75) × 20 = 7.5 kN/m
4.5 STATIC CHECK FOR LOAD COMBINATION (D.L + L.L)
4.5.1 PLINTH LEVEL
Beam size = 300×750mm
Self-weight of beam (B1) = 25×0.75 ×0.3×3.42
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= 19.24kN/m
Self-weight of beam (B2) = 25× 0.75 ×0.3×4.28
= 24.08kN/m
Self-weight of beam (B3) = 25× 0.75 ×0.3×3.60
= 20.25kN/m
Self-weight of beam (B4) = 25× 0.75 ×0.3×4.95
= 27.85kN/m
Wall load on beam (B2, B3 & B4) = (0.115×(4-0.75)×20
= 7.5kN/m
Column size = 750×750mm
Self-weight of column C1 =25× (4-0.75) ×0.75×0.75
= 45.70kN
Total Load at Plinth level = 159.62 kN/m
.
Figure 2-Panel drawing
4.5.2 FLOOR LEVEL
Beam size = 300×750mm
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Self-weight of beam (B1) = 25× 0.75 ×0.3×3.42
= 19.24kN/m
Self-weight of beam (B2) = 25× 0.75×0.3×4.28
= 24.08kN/m
Self-weight of beam (B3) = 25× 0.75 ×0.3×3.60
= 20.25kN/m
Self-weight of beam (B4) = 25× 0.75 ×0.3×4.95
= 27.85kN/m
Self-weight of Slab = 25× 0.15×9.23×7.02
= 242.98kN/m
Column size = 750×750mm
Self-weight of column =25× (4-0.75) ×0.75×0.75
= 45.70kN
Wall load on beam (B2, B3 & B4) = 0.115×(4-0.75) ×20
= 7.5kN/m
Live load on Slab = 5.5×9.23×7.02
= 356.37kN/m2
4.5.3 STATIC CHECK FOR DEAD AND LIVE LOAD COMBINATION
Total dead load = 2417.72kN/m
Total dead Imposed load = 157.50kN/m
Total live load (Floors+ Terrace) = 2138.22kN/m
Total load = 4713.44 kN/m
Axial load from Analysis = 4737.58 kN/m
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Figure 3- Axial load from software
4.6 WIND LOAD CALCULATION
Wind is air in motion relative to the surface of the earth. The primary cause of wind is traced
to earth’s rotation and differences in terrestrial radiation. The radiation effects are primarily
responsible for convection either upwards or downwards. The wind generally blows
horizontal to the ground at high wind speeds. Since vertical components of atmospheric
motion are relatively small, the term ‘wind’ denotes almost exclusively the horizontal wind,
vertical winds are always identified as such. The wind speed is assessed with the aid of
anemometers or anemographs.
4.6.1BASIC WIND SPEED:
Basic wind speed is based on peak gust velocity averaged over a short time interval of about
three seconds and corresponds to mean heights above ground level in an open terrain. Basic
wind speed given in figure1 in IS 875(part):1987.
4.6.2 DESIGN WIND SPEED:
The basic wind speed for any site is obtained from figure and shall be modified to include the
following effects to get design wind velocity at any height shall be modified to include the
following effects to get design wind velocity at any height(Vz) for the chosen structure:
Vz = Vb× k 1×k 2× k 3
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The suggested life period to be assumed in design and the corresponding k 1 factors for
different structures for different class of structures given in table 1, IS 875(part):1987. k 2 is
the terrain, Height and structure size factor given in table 2, IS 875(part):1987. k 3 is the
topography factor given in table 3, IS 875(part):1987.
4.6.3 DESIGN WIND PRESSURE:
The design wind pressure at any height above mean ground level shall be obtained by the
following relationship between wind pressure and wind velocity
Pz = 0.6×Vz2
4.6.4 WIND FORCES:
The value of force coefficient apply to the building or structure as a whole and multiplied by
effective frontal area of the building by design wind pressure, Pz gives the total wind load on
that particular building or structure. The force coefficients are given in two mutually
perpendicular directions relative to reference axis of the structural member. They are
designed as Cpn and Cpt, give the normal and transverse, respectively to the reference plane.
Fn = Cpn× Pz×l×b
Ft= Cpt × Pz× l×b
Basic wind speed at Agartala (As per IS 875-1987) = 50km/s (Vb)
Terrain category (clause 5.3.2.1) = 2
Building class (B=36m, W=53.0) (clause 5.3.2.2) = C
Risk coefficient (K1) (Assume 100 years Life period) = 1.08
Topography factor (K3)(clause 5.3.2.3) = 1
a=53.0m a=53.0m
b=36m h=28.0m
Fig4.A- Plan Fig 4.B- Elevation
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In X-direction (a/b) = 1.47 In Y-direction (b/a) = 0.68
In X-direction (h/b) = 0.78 In Y-direction (h/a) = 0.53
Width of building in X-direction = 53.0m
Width of building in Y-direction = 36m
1. Value of Topography Factor (k 2) - Table 1
Force coefficient in X-direction = 1.075(from code IS 875-1987(part3))
Force coefficient in Y-direction = 1.20(from code IS 875-1987(part 3))
Design speed Vz = Vb× K1 × K2 × K3
2. Wind load calculation-Table 2
Story Height(m) K 2 Vz(km/s) Pz=0.6Vz2(kN)
Load X in
direction(kN)
Load in Y
direction(kN)
FIRST 4.0 0.930 50.22 1.513 351.32 577.36
SECOND 8.0 0.930 50.22 1.513 234.21 384.91
THIRD 12.0 0.950 51.30 1.579 244.43 401.69
FOURTH 16.0 0.979 52.87 1.677 259.60 426.63
FIFTH 20.0 1.000 54.00 1.749 270.75 444.95
TERRACE 24.0 1.016 54.86 1.805 139.71 229.60
Total 1500.02 2465.14
Height(m) K2
10 0.93
15 0.9720 1.00
30 1.04
50 1.10
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3. Wind forces from Analysis – Table 3
Story Point Load FX
(kN)
FY
(kN)
FZ
(kN)
MX
(kN-m)
MY
(kN-m)
MZ
(kN-m)
BASE 1 WINDPX -3.94 -0.36 -11.44 0.304 -15.199 0.071
BASE 3 WINDPX -5.17 0.35 1.63 -1.013 -16.898 -0.036
BASE 58 WINDPX -0.22 -7.95 -30.13 0.341 -0.544 0.041
BASE 59 WINDPX -0.35 10.82 42.97 -0.494 -0.649 0.05
BASE 96 WINDPX -6.44 -0.43 119.41 1.174 -18.245 0.121
BASE 115 WINDPX -6.22 0.15 -13.46 -0.426 -19.163 -0.216
BASE 379 WINDPX -27.28 -0.03 -107.35 0.097 -2.789 0
BASE 380 WINDPX -27.92 0 -33.24 0.012 -2.75 0
BASE 184 WINDPX -4.39 -0.13 -1.19 0.179 -0.241 -0.001
BASE 191 WINDPX 3.41 -0.67 -16.6 0.358 -0.051 0.007
BASE 200 WINDPX -3.12 0.06 -2.57 0.054 -0.102 0.002
BASE 201 WINDPX 4.55 -0.78 23.06 0.423 -0.029 -0.007
Summation WINDPX 1500.02
4. Wind forces from software-Table 4
Story Point Load FX
(kN)
FY
(kN)
FZ
(kN)
MX
(kN-m)
MY
(kN-m)
MZ
(kN-m)
BASE 1 WINDPY -1.01 -6.36 -33.52 23.774 -3.106 -0.198
BASE 3 WINDPY -1.36 -9.92 -34.13 31.666 -3.66 -0.205
BASE 5 WINDPY -1.94 -6.61 -39.98 25.27 -4.641 -0.171
BASE 73 WINDPY -18.29 -0.3 -62.8 0.695 -0.976 -0.097
BASE 74 WINDPY 5.39 -65.76 -255.22 6.363 -0.504 0.21
BASE 117 WINDPY -0.6 -2.1 -224.58 0 0 0
BASE 119 WINDPY 0.75 -2.38 -229.76 0 0 0
BASE 374 WINDPY 20.31 -0.44 94.16 1.313 1.667 0
BASE 375 WINDPY 20.38 -0.46 105.38 1.36 1.582 0.001
BASE 197 WINDPY 2.35 0.3 -4.6 0.196 0.157 -0.002
BASE 199 WINDPY -19.47 -1.77 31.28 0.924 -0.613 0.034
BASE 200 WINDPY -3.02 0.32 -5.15 0.212 -0.177 0.003
BASE 201 WINDPY 14.03 -2.17 77.89 1.349 0.306 -0.02
Summation WINDPY 2465.14
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4.7 SEISMIC LOAD CALCULATION (Based on code IS 1893-2002)
During an earthquake, ground motions develop in a random manner both horizontally and
vertically in all directions radiating from the epicenter. The ground motions develop
vibrations in the structure inducing inertial forces on them. Hence structures located in
seismic zones should be suitably designed and detailed to ensure strength, serviceability and
stability with acceptable levels of safety under seismic forces.
The satisfactory performance of a large number of reinforced concrete structures subject to
severe earthquake in various parts of the world has demonstrated that it is possible to design
structures to successfully withstand the destructive effects of major earthquakes.
The Indian standard codes IS: 1893-1984 and IS: 13920-1993 have specified the minimum
design requirements of earthquake resistant design probability of occurrence of earthquakes,
the characteristics of the structure and the foundation and the acceptable magnitude of
damage.
Determination of design earthquake forces is computed by the following methods,
1) Equivalent static lateral loading.
2)
Dynamic Analysis.
In the first method, different partial safety factors are applied to dead, live, wind earthquake
forces to arrive at the design ultimate load. In the IS: 456-2000 code, while considering
earthquake effects, wind loads assuming that both severe wind and earthquake do not act
simultaneously. The American and Australian code recommendations are similar but with
different partial safety factors.
The dynamic analysis involves the rigorous analysis of the structural system by studying the
dynamic response of the structure by considering the total response in terms of component
modal responses.
4.7.1 ZONE FACTOR (Z):
The values of peak ground acceleration given in units ‘g’ for the maximum
considered earthquake.
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The value of (Z/2) corresponds to design basis earthquake damage control in limit
state.
Based on history of seismic activities seism tectonic understanding the entire country
has been divided in to four zones. The zone factor from table 2(IS 1893:2002)
Seismic zone II III IV V
Seismic Intensity Low Moderate Severe Very severe
Z 0.10 0.16 0.24 0.36
Zone factor values- Table 5
4.7.2 RESPONSE REDUCTION FACTOR (R):
R is the response reduction factor and controls the permitted damage in design basis
earthquake.
The minimum value of R is 3 and maximum is 5 however to use higher values of R
special ductile detailing requirements are must and the designer is accepting more
damages but in the controlled manner. The Response reduction factor from table 7(IS
1893:2002)
4.7.3 IMPORTANCE FACTOR (I):
I is the importance factor and permitted damage could be reduced by setting the value
of I more than ‘1’.
For the buildings like ‘HOSPITALS’, communication and community buildings the
value is 1.5 from table 6 (IS 1893:2002).
4.7.4 SEISMIC WEIGHT (W):
Seismic weight of the building is measured in Newton. Seismic weight includes the
dead loads (that of floor, slabs, finishes, columns, beams, water tanks, permanent
machines etc.
Seismic weight includes only a part of Imposed loads, for example 25% to 50% of
imposed loads for buildings from table 8 (IS 1893:2002).
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4.7.5 SOIL CLASSIFICATION:
Sa/g is the lateral acceleration to be established in m/s2. For 5 present of damping
three different types of curves are recommended in IS 1893:2002 for different
stiffness of supporting media-Rock, Medium soil and Soft soil.
The classification of soil is based on the average shear velocity for 30m of rock or soil
layers or based on average Standard Penetration Test (SPT) values for top 30m.
Fi
Figure 5- soil classification graph
Zone factor of the building (Z) = 0.36 (Zone V)
Importance of the building (I) = 1.5 (Post Earth quake service needed)
Response reduction factor (R) = 5 (Ductile shear walls with SMRF system)
Soil type = Soft soil
Width of building in X-direction = 53.0m
Width of building in Y-direction = 36m
Height of the building = 28m
Seismic weight of the building = 177309kN
0
0.5
1
1.5
2
2.5
3
0 0.5 1 1.5 2 2.5 3 3.5 4
Period (s)
S p e c t r a l A c c e l e r a t i o n C o e f f i c i
e n t ( S a / g )
Type I (Rock, or Hard Soil)
Type II (Medium Soil)
Type III (Soft Soil)
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4.7.6 SEISMIC BASESHEAR CALCULATION:
The design base shear is the sum of lateral forces applied at all levels that are finally
transferred to the ground.
Vb = Ah× W
Ah = (ZI/2R)(Sa/ g)
Fundamental Natural Time period (without infill)
Ta = 0.075(h) 0.75
Ta (X-Direction) = 0.913
Ta (Y-Direction) = 0.913
Sa/g = 1.67/T = 1.83
Ah (X-Direction) = 0.099
Ah (Y-Direction) = 0.099
Fundamental Natural Time period (with infill)
Ta = (0.09×h)/√d
Ta (X-Direction) = 0.420 & Ta (Y-Direction) = 0.346
Sa/g = 2.5
Ah (X-Direction) = 0.135 &Ah (Y-Direction) = 0.135
Base shear (without infill)
Base shear (X direction) (Ah×W) = 17554kN
Base shear (Y direction) (Ah×W) = 17554kN
Base shear (with infill)
Base shear (X direction) (Ah×W) = 23937kN
Base shear (Y direction)(Ah×W) = 23937kN
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Average base shear
Base shear in X-direction using Code = 20746kN
Base shear in Y-direction using Code = 20746kN
Base shear in X-direction using ETABS model = 6760kN
Base shear in Y-direction using ETABS model = 6173.94kN
4.7.7 ANALYSIS
Analysis options are set before the analysis, the analysis is performed with a scale factor 1.
The number of modes is initially set as 1.5 after anlysis. If the cumulative mass participation
factor is less than 95 percentage, then it is modified accordingly with base shear values
obtained for the earth quake load case the new scale factor is calculated and again the model
is analysed for the new scale factor. It can be observed that the base shear value calculated
from the code and by the software with the new scale factor are the same.
6. Base shear in X-direction using ETABS model- Table 6
Story Point Load FX
(kN)
FY
(kN)
FZ
(kN)
MX
(kN-m)
MY
(kN-m)
MZ
(kN-m)
BASE 1 SPECX 21.12 6.06 51.23 23.359 78.266 0.911
BASE 3 SPECX 26.97 8.54 30.56 25.089 86.532 1.435
BASE 5 SPECX 29.62 3.71 63.14 11.368 90.891 1.676
BASE 7 SPECX 161.37 34.86 772.61 1.607 14.971 0.587
BASE 8 SPECX 190.16 4.52 19.77 0.66 20.901 0.464
BASE 9 SPECX 161.54 29.35 759.54 1.607 15.034 0.604
BASE 62 SPECX 36.09 4.51 13.19 12.545 100.706 1.788
BASE 66 SPECX 10.92 1.08 12.92 0 0 0
BASE 115 SPECX 26.77 4.34 63.2 12.201 80.561 2.515
BASE 1591 SPECX 0.11 6.7 0.93 0 0 0
BASE 1592 SPECX 0.82 6.79 5.12 0 0 0
BASE 1594 SPECX 2.23 7.86 15.27 0 0 0
BASE 1595 SPECX 0.08 5.91 11.84 0 0 0
Sum 6760
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7.Base shear in Y-direction using ETABS model- Table 7
Story Point Load FX
(kN)
FY
(kN)
FZ
(kN)
MX
(kN-m)
MY
(kN-m)
MZ
(kN-m)
BASE 1 SPECY 5.67 14.41 91.79 52.89 17.692 1.018
BASE 3 SPECY 6.92 25.76 92.27 77.876 19.551 2.137
BASE 5 SPECY 8.2 18.87 118.39 65.448 21.629 1.569
BASE 7 SPECY 66.6 69.75 520.95 6.717 4.599 0.125
BASE 159 SPECY 0.34 39.45 118.78 5.311 0.793 0.009
BASE 160 SPECY 0.15 68.93 307.44 6.871 0.433 0.001
BASE 172 SPECY 11.22 0.16 77.79 0 0 0
BASE 174 SPECY 60.13 0.3 402.37 0 0 0
BASE 1587 SPECY 0.19 105.15 76.18 0 0 0
BASE 1588 SPECY 0.1 107.69 219.67 0 0 0
BASE 1591 SPECY 0.01 54.74 65.87 0 0 0
BASE 1592 SPECY 0.2 65.62 205.77 0 0 0
BASE 1594 SPECY 0.47 98.15 299.42 0 0 0
BASE 1595 SPECY 0.03 46.88 222.45 0 0 0
Sum 6173.94
4.7.8 SCALE FACTOR CALCULATION
Summation of support reaction gives the seismic weight of the building. Base shear in
X direction calculated as per the code. ETABS did the dynamic analysis and total base shear
in X and Y direction are found from results. The ratio of base shear obtained from code to
that obtained from dynamic analysis gives the shear force in X and Y direction. Since thespectra value for different time period is calculated manually the base shear values might not
be the same values obtained from manual calculations. Thus the new scale factor is calculated
and the structure reanalyzed to obtain the new base shear values.
Base shear (from Analysis)
Base shear in X-direction using Code = 20746kN
Base shear in Y-direction using Code = 20746kN
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Base shear in X-direction using ETABS model = 6760kN
Base shear in Y-direction using ETABS model = 6173.94kN
Scale Factor (Vbx/ Vbx') = 3.07
Scale Factor (Vby/ Vby') = 3.36
8. Base shear in X-direction using ETABS model-Table 8
Story Point Load FX
(kN)
FY
(kN)
FZ
(kN)
MX
(kN-m)
MY
(kN-m)
MZ
(kN-m)
BASE 1 SPECX 64.85 18.61 157.27 71.713 240.277 2.796
BASE 3 SPECX 82.81 26.2 93.83 77.024 265.653 4.404
BASE 5 SPECX 90.92 11.39 193.85 34.901 279.036 5.146
BASE 7 SPECX 495.42 107.03 2371.91 4.934 45.96 1.803
BASE 115 SPECX 82.19 13.33 194.02 37.458 247.321 7.72
BASE 117 SPECX 21.32 6.37 714.21 0 0 0
BASE 119 SPECX 23.94 6.78 724.44 0 0 0
BASE 121 SPECX 13.81 5.94 40.5 0 0 0
BASE 442 SPECX 340.62 9.65 1323.44 8.414 34.379 0.113
BASE 1587 SPECX 0.81 99.15 997.9 0 0 0
BASE 1588 SPECX 0.68 87.3 1162.35 0 0 0
BASE 1591 SPECX 0.32 20.57 2.86 0 0 0
BASE 1592 SPECX 2.52 20.84 15.73 0 0 0
BASE 1594 SPECX 6.84 24.14 46.89 0 0 0
BASE 1595 SPECX 0.26 18.13 36.35 0 0 0
Sum 20753.07
9. Base shear in Y-direction using ETABS model-Table 9
Story Point Load FX
(kN)
FY
(kN)
FZ
(kN)
MX
(kN-m)
MY
(kN-m)
MZ
(kN-m)
BASE 1 SPECY 19.05 48.43 308.4 177.711 59.445 3.419
BASE 3 SPECY 23.25 86.57 310.02 261.662 65.691 7.179
BASE 5 SPECY 27.56 63.42 397.8 219.907 72.672 5.271
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BASE 7 SPECY 223.79 234.38 1750.39 22.57 15.453 0.422
BASE 119 SPECY 10.08 20.21 2062.4 0 0 0
BASE 121 SPECY 4.34 22.2 24.92 0 0 0
BASE 123 SPECY 2.91 62.47 11.13 156.838 5.821 0.665
BASE 440 SPECY 210.17 7.31 1056.86 14.678 17.001 0.01
BASE 442 SPECY 216.26 17.22 1617.36 21.921 16.802 0.136
BASE 1592 SPECY 0.67 220.5 691.38 0 0 0
BASE 1594 SPECY 1.58 329.78 1006.05 0 0 0
BASE 1595 SPECY 0.09 157.52 747.42 0 0 0
Sum 20744.37
Base shear in X-direction using Code = 20746 kN
Base shear in Y-direction using Code = 20746 kN
Base shear in X-direction using ETABS model = 20753.07 kN
Base shear in Y-direction using ETABS model = 20744.37 kN
10. Period Vs Sa/g- Table 10
Period
(seconds) Sa /g
Acceleration
(m2 /s)
0 1.000 0.530
0.1 2.500 1.324
0.2 2.500 1.324
0.3 2.500 1.324
0.4 4.175 2.212
0.5 3.340 1.769
0.6 2.783 1.474
0.7 2.386 1.264
0.8 2.088 1.106
0.9 1.856 0.983
1 1.670 0.885
1.1 1.518 0.804
1.2 1.392 0.737
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1.3 1.285 0.681
1.4 1.193 0.632
1.5 1.113 0.590
1.6 1.044 0.5531.7 0.982 0.520
1.8 0.928 0.491
1.9 0.879 0.466
2 0.835 0.442
2.1 0.795 0.421
2.2 0.759 0.402
2.3 0.726 0.3852.4 0.696 0.369
2.5 0.668 0.354
2.6 0.642 0.340
2.7 0.619 0.328
2.8 0.596 0.316
2.9 0.576 0.305
3 0.557 0.2953.1 0.539 0.285
3.2 0.522 0.276
3.3 0.506 0.268
3.4 0.491 0.260
3.5 0.477 0.253
3.6 0.464 0.246
3.7 0.451 0.2393.8 0.439 0.233
3.9 0.428 0.227
4 0.418 0.221
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Figure 6-Response spectra for Soft soil sites
11. Seismic weight output-Table 11
Story Point Load FX
(kN)
FY
(kN)
FZ
(kN)
MX
(kN-m)
MY
(kN-m)
MZ
(kN-m)
BASE 1 SISWT 27.65 21.32 2497.5 -34.428 42.726 0.476
BASE 3 SISWT 6.31 19.1 4190.33 -33.679 12.518 -0.08
BASE 5 SISWT 0.11 19.9 3577.2 -33.288 3.005 0.052
BASE 72 SISWT -17.8 -13.2 2293.75 19.13 -29.645 -0.359
BASE 73 SISWT 55.84 -1.31 243.8 1.129 2.512 -0.173
BASE 74 SISWT -57.53 62.27 545.42 -4.294 -3.983 0.017
BASE 148 SISWT -13.74 -31.27 3478.73 54.117 -21.508 0.292
BASE 149 SISWT -15.04 -14.49 1985.17 20.963 -23.614 0.588
BASE 410 SISWT 21.85 53.21 477.07 -2.793 2.787 -0.171
BASE 416 SISWT -0.1 22.94 277.04 1.069 0.413 -0.059
BASE 198 SISWT 34.07 -1.58 56.5 0.839 1.065 -0.028
BASE 199 SISWT -33.99 -1.54 56.36 0.832 -1.057 0.028
BASE 200 SISWT -7.72 0.22 -8.62 0.142 -0.455 0
Sum 177309.1
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5.0 MODELING AND ANALYSIS OF THE BUILDING
The primary purpose of structural analysis in building structure is to establish the distribution
of internal forces and moment over the whole or part of the structure and to identify the
critical design conditions at all sections the geometry is commonly idealised by considering
the structure to make up of linear elements. Here the structural analysis is carried out by
ETABS
5.1 BASIC GRID SYSTEM:
Begin creating the grid system by clicking the File menu > New model command or the New
model icon. The form shown in figure below wil display. Select the No option on that form
the next figure will display.
Figure 7-The new model initialization form.
5.2 DEFINE GEOMETRY:
The Building Plan Grid System and Storey Data form is used to specify horizontal and
vertical grid line spacing, storey data, storey elevation and units. They automatically add the
structural objects with appropriate properties to the model.
Figure 8- Building Plan Grid System and Storey Data Definition
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5.3 DEFINE MATERIAL PROPERTY:
The material properties of each object in the model is specified in the appropriate form. The
material used is concrete, the grade of concrete, the properties of concrete such as Mass per
unit volume, Modulus of Elasticity of concrete,Poisson ratio are specified and for steel yield
strength is specified.
Figure 9- Material property data form.
5.4 DEFINE FRAME SECTION:
Assign the frame section such as Column and Beam. Select the section property as Rectangle
and define the depth,width and reinfprcement details,cover provisions.similarly for various
sections like circular,pipe, steel joist sections aiso assigned with suitable data.
Figure 10- Define Frame Properties form.
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Figure 11- Section properties and Reinforcement details.
5.5 DEFINE WALL OR SLAB SECTION:
Assign the slab or wall section then assign the section name,thickness,material used,type and
reinforcement details.
Figure 12- Define wall or slab section
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5.6 DEFINE DIAPHRAM:
The lateral loads can be in the form of wind or seismic loads, the loads are automatically
calculated from the dimensions and properties of the structure based on built-in options for a
variety of building codes. For Rigid diaphragm systems, the wind loads applied at the
geometric centers of each rigid floor diaphragm.
Figure 13-Define Diaphragms
5.7 DEFINE RESPONSE SPECTRUM FUNCTION:
Functions are defined to describe how a load varies as a function of period, time or
frequency.
Figure 14- Define response spectrum function.
5.8 RESPONSE SPECTRUM FUNCTIONS
Response spectrum functions are pseudo spectral acceleration versus period functions for usein response spectrum analysis. In this program the acceleration values to be normalized; that
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is, the functions themselves are not assumed to have units. Instead, the units are associated
with a scale factor that multiplies the function and is specified when we define the response
spectrum case.
Figure 15- Response spectrum function graph
5.9 STATIC LOAD CASES:
Loads represent the actions upon the structure, such as force, pressure, support displacement,
thermal effects and others. A spatial distribution of loads upon the structure is called static
load case. Define as many load cases as needed. Typically separate load case definitions
would be used for dead load, live load, static earthquake load, wind load, snow load, and
Thermal load.
Figure 16- Define static load case
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5.9 DEFINE LOAD COMBINATIONS:
Define the load combinations in the appropriate form; Select the Add new combo option,
then enter the load combination name, assign the loads with suitable scale factor. When the
combination is defined, it applies to the results for every object in the model.
Figure 17- Define load combinations
12. Load combination -Table 12
COMB DEAD LOAD LIVELOAD3 WIND/ E.QLOAD
COMB01 1.5 DEADLOAD + 1.5LIVELOAD + 1.5 LIVELOAD
COMB02 1.2 DEADLOAD + 0.6LIVELOAD + 0.3 LIVELOAD +1.2 E.Q.LOADX
COMB03 1.2 DEADLOAD + 0.6 LIVELOAD + 0.3 LIVELOAD +1.2 E.Q.LOADY
COMB04 1.5 DEADLOAD + +1.5 E.Q.LOADX
COMB05 1.5 DEADLOAD + +1.5 E.Q.LOADY
COMB06 0.9 DEADLOAD + -1.5 E.Q.LOADX
COMB07 0.9 DEADLOAD + -1.5 E.Q.LOADY
COMB08 1.2 DEADLOAD + 1.2 LIVELOAD + 1.2 LIVELOAD +1.2WINDLOADX
COMB09 1.2 DEADLOAD + 1.2 LIVELOAD + 1.2 LIVELOAD -1.2WINDLOADX
COMB10 1.2 DEADLOAD + 1.2 LIVELOAD + 1.2 LIVELOAD +1.2WINDLOADY
COMB11 1.2 DEADLOAD + 1.2 LIVELOAD + 1.2 LIVELOAD -1.2WINDLOADY
COMB12 1.5 DEADLOAD + +1.5WINDLOADX
COMB13 1.5 DEADLOAD + -1.5 WINDLOADX
COMB14 1.5 DEADLOAD + +1.5WINDLOADY
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COMB15 1.5 DEADLOAD + -1.5 WINDLOADY
COMB16 0.9 DEADLOAD + +1.5WINDLOADX
COMB17 0.9 DEADLOAD + -1.5 WINDLOADX
COMB18 0.9 DEADLOAD + +1.5WINDLOADY
COMB19 0.9 DEADLOAD + -1.5 WINDLOADY
UNFACTORED COMBINATION
COMB 20 1 DEADLOAD + 1 LIVELOAD + 1 LIVELOAD
COMB 21 1 DEADLOAD + 0.5 LIVELOAD + 0.25LIVELOAD +1 E.Q.LOADX
COMB 22 1 DEADLOAD + 0.5 LIVELOAD + 0.25LIVELOAD +1 E.Q.LOADY
COMB 23 1 DEADLOAD + -1 E.Q.LOADX
COMB 24 1 DEADLOAD + -1 E.Q.LOADY
COMB 25 1 DEADLOAD + 1 LIVELOAD + 1 LIVELOAD +1 WINDLOADXCOMB 26 1 DEADLOAD + 1 LIVELOAD + 1 LIVELOAD -1 WINDLOADX
COMB 27 1 DEADLOAD + 1 LIVELOAD + 1 LIVELOAD +1 WINDLOADY
COMB 28 1 DEADLOAD + 1 LIVELOAD + 1 LIVELOAD -1 WINDLOADY
COMB 29 1 DEADLOAD + +1 WINDLOADX
COMB 30 1 DEADLOAD + -1 WINDLOADX
COMB 31 1 DEADLOAD + +1 WINDLOADY
COMB 32 1 DEADLOAD + -1 WINDLOADY
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5.11 MODEL OUTPUT
A) OUTPUT: 3D-MODEL OF A RC FRAME
Figure.18-3D model of RC frame
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B) BENDING MOMENT DIAGRAM FROM ANALYSIS
Figure 19- Bending Moment from analysis.
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C) SHEAR FORCE FROM ANALYSIS
Figure 20- Shear Force from analysis.
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D) DIAPHRAGM
Figure 21-Diaphram output from analysis.
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E) PLAN SHOWING SLAB ID
Figure 22- Plan showing slab ID
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E) PLAN SHOWING BEAM ID
Figure 23- Plan showing Beam ID
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6.0 DESIGN OF FOUNDATION
6.1GENERAL
In a typical structure built on a ground, that part of structure which is located above the
ground is generally referred to as the superstructure and the part which lies below ground is
referred to as substructure or foundation. The purpose of the foundation is to effectively
support the superstructure by
Transmitting the applied load effects to the soil below without exceeding the safe
bearing capacity of soil.
Ensuring that the settlement of the structure is within the tolerable limits, and as
uniform as possible.
Further the foundation should provide adequate safety against possible instability due to
overturning or sliding and possible pullout.
Footings belong to the category of shallow foundation, types of footings are Isolated footing,
Combined footing and Wall footing.
In some cases it may be inconvenient to provide separate isolated footings for columns (or
walls) on account of inadequate areas available in plan. This may occur when two or more
columns are located close to each other or if they are relatively heavily loaded and rest on soil
with low safe bearing capacity resulting in an overlap of areas if isolated footings are
attempted. In such cases it is advantageous to provide a single footing for the column.
Isolated footing
Figure 24-Types of footing
6.2 DESIGN OF ISOLATED FOOTING
For ordinary structures located on reasonably firm soil, it usually suffices to provide a
separate footing is also called an isolated column. It is generally square or rectangular in plan
other shapes are resorted to under special circumstances. The footing basically comprises a
thick slab which may be flat, stepped or sloped.
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6.3 DESIGN OF TYPICAL ISOLATED FOOTING
6.3.1 DESIGN PARAMETERS:
Grade of concrete using (f ck ) = 30N/mm2
Grade of steel using (fy) = 500 N/mm
2
Load combination considered (COMBO 5) = 1.5D.L+1.5E.L
Axial load = 1584.89 kN
Moment in X direction (Mux) = 18.26 kNm
Moment in X direction (Muy) = 16.13 kNm
Safe bearing capacity of soil = 100 kN/ m2
Unit weight of concrete = 25kN/m3
Shape of the footing = Square footing
Type of the footing = Flat
Assume self-weight of footing as 15% = 1.15×1584.89 kN
Total weight = 1822.62 kN(unfactored)
[P/A] ± [Mx /Z] ± [My] ≤ q (SBC of soil)
[1822.62/B.L] + [18.26×6/B.L2
] + [18.26×6/B.L2
] = 100 kN/ m2
Assume L/B ratio =1 (L=B)
Solve the above equation, Size of the footing = 4.4m×4.4 m
[P/A] + [Mx /Z] + [My] P1 = 96.01 kN/ m2
[P/A] +[Mx /Z] - [My] P2 = 93.73 kN/ m2
[P/A] - [Mx /Z] + [My] P3 = 94.55 kN/ m2
[P/A] - [Mx /Z] - [My] P4 = 92.27 kN/ m2
Assume depth of footing = 700 mm
Downward pressure due to base slab (0.7×25) = 17.5 kN/ m2
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Figure 25-Pressure diagram
6.3.2 BENDING MOMENT IN X DIRECTION
Cantilever projection along X = 1.825 m
Mx [94.22×0.5×1.8252]+[.5×1.825×1.945×.67×1.825]-[17.5×0.5×1.825
2] =129.91kNm
Steel required along X direction
Mu lim = 0.138×f ck ×b×d2
Depth required = 178mm
Depth provided [700-50-(25/2)] = 637mm
Mu/b.d2 = [1.5×129.91×10
6] / [1000×637
2] = 0.48
Percentage of steel = 0.117
Provide percentage of steel = 0.75
Provide 25mm diameter bars and spacing [.785×252×1000]/4400 =111.50
Provide 25mm diameter bars at spacing of 100mm c/c.
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6.3.3 BENDING MOMENT IN Y DIRECTION:
Cantilever projection along Y = 1.825 m
My[94.22×0.5×1.8252]+[.5×1.825×1.945×.67×1.825]-[17.5×0.5×1.825
2]=129.91kNm
Steel required along Y direction
Mu lim = 0.138×f ck ×b×d2
Depth required = 178mm
Depth provided [700-50-(25/2)] = 637mm
Mu/b.d2 = [1.5×129.91×10
6] / [1000×637
2] = 0.48
Percentage of steel = 0.117
Provide percentage of steel = 0.75
Provide 25mm diameter bars and spacing [0.785×252×1000]/4400 =111.50
Provide 25mm diameter bars at spacing of 100mm c/c.
6.3.4 CHECK FOR ONE WAY SHEAR:
Critical section located a distance of ‘d’ from the face of the column.
Average pressure (95.187+94.215)/2 = 94.70 kN/ m2
Shear force at critical section (94.70-15)×(1.825-.637) = 94.60
Nominal shear stress τv = (Vu×1.5)/b.d = 0.22N/ mm2
From IS: 456-2000, table 19 Percentage of reinforcement = 0.59N/ mm2
Safe in one way shear. τv < τc
6.3.5 CHECK FOR TWO WAY SHEAR:
Average pressure (94.345+94.14)/2 = 94.24 kN/ m2
Vu = 94.24× [(4.4×4.4)-(0.75+0.637)(0.75+0.637)] =1563.06kN
Nominal shear stress τv = (Vu×1.5)/b.d = 0.66 N/ mm2
τc = 0.25×√(f ck ) = 1.37 N/ mm2
τv < τc Hence safe in two way shear.
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6.3.6 TRANSFER OF FORCES AT COLUMN BASE:
As some bars are in tension, no transfer of forces is possible through bearing at the column
footing interface. So, these bars may be extended into the footing.
Development length required for 32mm diameter bars (In tension)
Ld = (φ×fy×0.87)/ (4×1.6×1.8) = 38φ
Ld = 38 ×32 = 1216mm
Length available = 750-50-25-16+(8×32) = 915mm
The balance length = 301mm adopt = 350mm
Need to be provided beyond the bend point.
6.4 DETAILING OF FOOTING
Figure 26-RC detailing of footing detailing
Y 25 AT 100 mm C/C = 25mm dia bars at 100mm c/c
Y 25 AT 100 mm C/C = 25mm dia bars at 100mm c/c
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7.0 COLUMN DESIGN
7.1 GENERAL
The column is a compression member which is subjected (predominantly) to axial forces. The
IS 456:2000 code (clause 25.1.1) defines the column as a ‘compression member’ the effective
length of which exceeds three times the least lateral dimension. The term ‘pedestal’ is used to
describe a vertical compression member whose effective length is less than three times to
least lateral dimension.
Classification of columns
Based on type of Reinforcement:
1) Tied columns
2) Spiral columns
3) Composite columns
Figure 27-Types of column
Based on type of loading
1) Axially loaded column
2) Columns with uniaxial eccentric loading
3) Columns with biaxial eccentric loading
Based on Slenderness Ratio
1) Short columns
2)
Slender or long columns
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7.2 COLUMN DESIGN
7.2.1 DEIGN PARAMETERS:
Terrace level: C-1
Grade of concrete using (f ck ) = 30N/mm2
Grade of steel using (fy) = 500 N/mm2
Load combination considered (COMBO 5) = 1.5D.L+1.5E.L
Axial load = 316.44kN
Moment in X direction (Mux) = 235.84kNm
Moment in X direction (Muy) = 128.0 kNm
Size of the column = 750×750mm
d' = 60mm
Ratio of d’/D = 60/750= 0.08
Pt / f ck = 1.0/ 30= 0.03
Pu / f ck bd =(316×103)/(30×750×750) = 0.018
Mu / f ck bd2[From the code IS 456- 1978 chart 48] = 0.08
Mux1 =0.08×30×750×7502
=1012.50kNm
Ratio of d’/D =60/750= 0.08
Pt / f ck = 1.0/ 30 =0.03
Pu / f ck bd =(1586×103)/(30×750×750) = 0.018
Mu / f ck bd2[From the code IS 456- 1978 chart 48] = 0.08
Muy1 =0.08×30×750×7502
=1012.50kNm
Percentage of reinforcement = 1.0
Puz / Ag [From the code IS 456- 1978 chart 63] = 17
= 17×750×750
= 9562 kN/m2
7.2.2 BENDING MOMENT CALCULATION:
[Mux / Mux1] αn
+ [Muy / Muy1] αn≤ 1
[Pu /Puz] = (316.44/ 9562)
= 0.03
[Pu /Puz]≤0.2 so αn =1
[235.84/ 1012.50] +[128/1012.50] = 0.36
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0.36 ≤ 1
[Muy / Muy1] αn
[From the code IS 456- 1978 chart 64] = 0.80 > 0.0.13
7.2.3 REINFORCEMENT PROVIDED:Pt = 1.0
Ast = (1.0×750× 750)/ 100
Ast =5625mm2
Provide 20 numbers of 20 mm diameter bars. (Ast=6280mm2)
Transverse reinforcement
Tie diameter φt = φ long/4
25/4 = 6.25mmProvide 8 mm diameter tie bars
Tie spacing St < or = 16 φ
=16×25= 517mm
Spacing of ties should not greater than 300mm.
As per IS13920:1993
Spacing of hoops should not greater than = (1/4 of least lateral dimension)
(1/4)×750=187.5mmProvide 8 mm bars at spacing 190mm c/c as a transverse reinforcement
7.2.4 DESIGN PARAMETERS:
Fifth floor level
Grade of concrete using (f ck ) =30N/mm2
Grade of steel using (fy) = 500 N/mm2
Load combination considered (COMBO 5) = 1.5D.L+1.5E.L
Axial load = 659.88kN/mm2
Mux = 122.65kNm
Muy = 59.10kNm
Size of the column = 750×750mm
d' = 60mm
Ratio of d’/D = 60/750= 0.08
Pt / f ck = 1.0/ 30= 0.03
Pu / f ck bd (659.88×103)/(30×750×750) = 0.04
Mu / f ck bd2 [From the code IS 456- 1978 chart 48] = 0.08
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Mux1 =0.08×30×750×7502
=1012.50kNm
Ratio of d’/D =60/75= 0.08
Pt / f ck = 1.0/ 30=0.03
Pu / f ck bd (659.88×103)/(30×750×750) = 0.04
Mu / f ck bd2 [From the code IS 456- 1978 chart 48] = 0.08
Muy1 =0.08×30×750×7502
=1012.50kNm
Percentage of reinforcement = 1.0
Puz / Ag [From the code IS 456- 1978 chart 63] = 17
= 17×750×750
= 9562 kN/m2
7.2.5 BENDING MOMENT CALCULATION:
[Mux / Mux1] αn
+ [Muy / Muy1] αn≤ 1
[Pu /Puz] = (659.88 / 9562.5) = 0.07
[Pu /Puz]≤0.2 so αn =1
[122.16/ 1012.5] + [59.10/1012.5] = 0.18
0.18 ≤ 1
[Muy / Muy1] αn
[From the code IS 456- 1978 chart 64] =0.80> 0.05(calculated).
7.2.6 REINFORCEMENT DETAILS:
Pt = 1.0
Ast = (1.0×750× 750)/ 100
Ast =5625mm2
Provide 20 numbers of 20 mm diameter bars 4 on each face (6280 mm2)
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7.3 COLUMN DETAILING:
Figure 28.a-Longitudinal section
Figure 28.b-Cross section
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8.0 BEAM DESIGN
8.1 GENERAL:
A reinforced concrete flexure member should be able to resist tensile, compressive
and shear stresses induced in it by loads acting on the member.
Concrete is fairly strong in compression but week in tension.
Thus the tensile weakness of concrete is overcome by the provision of reinforcing
steel in the tension zone.
A flexure member may be Beam, slab, Wall or Component of foundation.
There are three types of reinforced concrete beams:
1. Singly reinforced beams
2. Doubly reinforced beams
3. Singly or doubly reinforced flanged beams
Singly Reinforced Beams.
In Singly reinforced simply supported beams or slabs reinforcing steel bars are placed
near the bottom of beam or slabs where they are most effective in resisting the tensile
stresses.
In the case of cantilever beams or slabs reinforcing steel bars are placed near the top
of the beam or slabs for the same reason.
Doubly Reinforced Beams.
A doubly reinforced concrete section is reinforced in both compression and tension regions.
The section of the beam or slab may be rectangle, T and L section. The necessity of usingsteel in compression region arises due to two main reasons:
When depth of the section is restricted, the strength available from singly reinforced
section is in adequate.
At a support of a continuous beam or slab where bending moment changes sign. Such
a situation may also arise in the design of a beam circular in plan.
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Flanged beams:
When a reinforced concrete slab is cast monolithically with the beam as in the case of
beam supported floor slab system, the beams can be considered as flanged beams with
slab acting as an effective flange on compression side.
Minimum reinforcement – The minimum area of tension reinforcement shall not be
less than that given by the following:
Ast min=0.85bd/ fy
The maximum area of compression reinforcement shall not exceed 0.04 bD.
Compression reinforcement shall be enclosed by stirrups for effective restraint. The
anchorage length of straight bars in compression shall be equal to the development
length of bars in compression.
Where the depth of the web in a beam exceeds 750 mm side face reinforcement shall
be provided along the two faces. The total area of such reinforcement shall be not less
than 0.1 percent of the web area and shall be distributed equally on two faces at a
spacing not exceeding 300 mm or web thickness whichever is less.
8.2 DESIGN OF TYPICAL BEAM
8.2.1 DESIGN PARAMETERS
Grade of concrete using (f ck ) = 30N/mm2
Grade of steel using (fy) = 500 N/mm2
Length of the beam = 8.20m
Size of the beam = 300×750mm
Load combination considered Envelope of factored loads.
8.2.2 BENDING MOMENT CALCULATION:
Maximum positive moment [Mmax] = 124.61kNm
Mu / b.d2 = (124.61×10
6)/ 300×690
2 = 0.87
Mulim = 3.99 > 0.87, Beam section is designed as singly reinforced.
[From table 4 of SP:16] Pt = 0.215
Ast = (Pt×bd)/100 = 438.84mm2
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Minimum Ast = (0.85/f y)= Ast/bd = 360.16 mm2
Provide 3 numbers of 16mm dia bars
Maximum negative moment [Mmax] = 300.20kNm
Mu / b.d2= (300.20×10
6)/ 300×690
2 = 2.10
[From table 4 of SP:16] Pt = 1097.10mm2
Ast = (Pt×bd)/100 = 1097.10mm2
3 numbers of 16mm dia bars, 2 numbers of 12mm dia bars.
8.2.3 SHEAR REINFORCEMENT AT SUPPORT:τv = Vu/ b.d =134×10
3 /300×690 = 0.64
Pt (100×1097.10/690×300) = 0.50
τc = 0.50
τc < τv
Hence the beam is unsafe against shear so shear reinforcement is required.
Vs = Vu- (τc × b×d)
(134-(0.5×300×690×10-3
) = 30.5kN
Sv = (0.87×500×2×113×690)/ (30.5×103) = 222mm
As per ductile detailing should be greater than (d/4) = (690/4) =172.50mm
Adopt stirrup spacing 200mm c/c for a distance 2d = 2×690 =1.5m from the face of the
support.
8.2.4 SHEAR REINFORCEMENT AT MID SPAN:
τv = Vu/ b.d = 70.5×103 /300×690 = 0.34
Pt (100×1097.10/750×300) = 0.5
τc = 0.5
τc > τv
Minimum shear reinforcement is to be provided.
Asv / b.Sv = 0.4/ 0.87× f y
0.785×82 / 300×Sv = 0.4/ 300×500
Sv = 182mm
< 0.75×d = 517.5mm
< Least lateral dimension = 300 mm
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< 300mm
So provide 8mm dia 2 legged stirrups at 100 mm c/c for a distance of L-4d = 8.20- 2.76 =
5.44m
8.2.5 DESIGN OF HANGER BARS:
Maximum shear due to secondary beam Vu = 61.19kN
For single bar or single group of parallel bars all bent up to the same cross section.
Vus = 0.87×f y×Asv ×Sin α×2
0.87×500×.785×122×Sin60 ×2 = 170.34kN
So provide 2 numbers of bars 12 mm diameters at an angle of 60’
8.2.6 DEVELOPMENT LENGTH
Ld = (φ×fy×0.87)/ (4×1.6×1.8) = 1.2
For ductile detailing
Development length = Ld + 10d- allowance for 90’ bent.
1.2+(10×.032×)-(8×.032) = 1.7m
8.2.7 CHECK FOR DEFLECTION:
Deflection actual = 8250 / 690 = 11.96 mm
Deflection allowable for continuous beam = 26 mm
Stress in steel f s = 0.58×fy×[Ast required/ Ast provided] =0.58(438.82/452.16)500
f s (Permissible stress in steel) = 281 N/mm2
Find k1 (From IS 456-2000figure 4 modification factor chart)
Pt =(100×452.16)/ bd = 0.22
k1 = 0.95
Find k2
Pt =(100×1205.86)/ bd = 0.58
K2 = 0.9
Deflection allowable = k1×k2×26
Deflection allowable = 0.95×0.9×26
= 22.23mm
11.26 < 22.23 Safe in deflection
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8.3 BEAM DETAILING
Figure 29-Longitudinal section of beam
3a -Y16 = 3 numbers of 16mm dia bars (top layer-1)
2b -Y12 = 2 numbers of 12mm dia bars (top layer-2)
3c- Y16 = 3 numbers of 16mm dia bars (bottom layer-1)
Shear reinforcement =2×d = 1500mm stirrup spacing 200mm c/c for a distance 2d = 2×750
=1.5m from the face of the support.
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9.0 DESIGN OF SLAB
9.1 ONE WAY AND TWO WAY SLAB
The most common type of structural element used to cover floors and roofs of buildings are
reinforced concrete slabs of different types. One way slabs are those supported on the two
opposite sides so that the loads are carried along one direction only. A common example of
one way slab is the verandah slab spanning in the shorter direction with main reinforcements
and distribution reinforcements in the transverse direction.
ONE -WAY SLAB
Reinforced concrete slabs supported on two opposite sides with their longer dimension
exceeding two times the shorter dimension are referred to as one- way slabs.[ Ly /Lx >2 ]
TWO WAY SLAB
Reinforced concrete slabs supported on all the four sides with their effective span in the
longer direction not exceeding two times the effective span in the shorter direction are
designed as two way slabs. Two- way slabs bending moments are maximum at the centre of
the slab and the larger moment invariably develops along the short span. [Ly /Lx ≤2]
Figure 30-Types of slab
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Shorter of the two spans should be used for calculating the span to effective
depth ratios.
For two way slab of shorter span- up to 3.5m with fy=250, the span to overall
depth ratios given below & vertical deflection limits up to 3 kN per squaremeter.
1. f y = 500, values given below should be multiplied to 0.8.
2. Simply Supported slabs = 35
3. Continuous slabs =40
Span to effective depth ratios for spans up to 10m
i. Cantilever =7
ii. Simply supported =20
iii. Continuous = 26
Spans above 10m- value may be multiplied by 10/span in m.
Effective span
Simply Supported slab & Continuous slab(width of the support is less than
1/12 of clear span)
the least of,
1. Clear span + effective Depth
2. Centre to Centre of supports
3. Continuous slab-(width of the support are wider than 1/12 of clear
span or 600mm whichever is less)
One end fixed and other continuous- clear span bet’ support.
One end free and other continuous- the least one,
1. clear span+1/2x eff. Depth of slab
2. Clear span+1/2x width of the discontinuous support.
Roller or rocket bearing- distance bet’ the Centre of bearing.
i. Cantilever-Face of the support +1/2 eff. Depth.
ii. Frame : (continuous frame )c/c distance
Slabs spanning in two directions at right angles
1. The most commonly used limit state of collapse method is based on
yield-line theory.
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Figure 31- load distribution in two way slab
9.2 DESIGN OF TYPICAL TWOWAY SLAB
9.2.1 DESIGN PARAMETERS:
Length of slab in X-direction (L×) = 3.60m
Length of slab in Y direction (Ly) =4.55m
Grade of concrete using (f ck ) =30N/mm2
Grade of steel using (fy) = 500 N/mm2
Ly /L× = 4.55/3.60
= 1.2 < 2 (two way slab)
Basic value of L/D ratio = 3600/28
Effective depth = 130mmOverall depth = 150mm
Effective span =clearspan+eff.depth
= 3.6+0.130
= 3.73m
Self-weight of the slab = 1× 25× 0.150
= 3.75kN/m2
Live load = 4kN/m2
Floor Finish = 24×1×0.06 = 1.5kN/m2
Total Load =9.25kN/m2
Ultimate load = 9.25×1.5
=13.875kN/m2
9.2.2 DESIGN OF BENDING MOMENT:
Two adjacent edges discontinuous (from code IS456:2000 table 26)
Ly /L× = 1.2
Mxe = α×e× W × L×2
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13. Moment calculation Table-13
Moment coefficients Ultimate load(W) in
kN
Length (Lx) in m M= α×e×W× L× (kNm)
α×e
=0.065 (Edge) 13.875 3.73 12.54
α×m=0.049 (Span) 13.875 3.73 9.45
αye =0.047 (Edge) 13.875 3.73 9.07
αym=0.035 (Span) 13.875 3.73 6.75
9.2.3 REINFORCEMENT CALCULATION: TABLE-14
Moment
(kN-m)
Ast calculation Ast No .of bars with
diameter.
Spacing
12.54 87×500 × Ast ×130(1 –
500×Ast /30×1000 ×130)
230 mm Provide 10mm dia bars 300mm
9.45 87×500 × Ast ×130(1 –
500×Ast /30×1000 ×130)
171mm Provide 10mm dia bars 300mm
9.07 87×500 × Ast ×130(1 –
500×Ast /30×1000 ×130)
164mm Provide 10mm dia bars 300mm
6.75 87×500 × Ast ×130(1 –
500×Ast /30×1000 ×130)
122mm Provide 10mm dia bars 300mm
9.2.4 CHECK FOR DEPTH:
Max. B.M in the slab = 12.68 kN/m2
M.R = 0.138 × f ck × b × d2
12.68 kNm = 0.138 ×30×1000× d2
Depth = 55.34 < 130 mm
9.2.5 CHECK FOR SHEAR:
V ux = 0.5×13.875×3.73
= 25.88kN
Max. S.F. of support, Vu =(25.88×103)/(1000×150)
Nominal shear stress τv = 0.17 N/mm2
100Ast / bd = 0.15
Critical shear τc = 0.29 N/mm2
Hence the slab is safe against shear. τc > τv
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9.2.6 CHECK FOR DEFLECTION:
Deflection actual = 3730/ 130 = 28mm
Stress in steel f s = 0.58 × (230/304) × 500
f s(From IS 456-2000 figure 4 ) modification factor) = 220 N/mm2
Modification factor (k 1) = 1.8
Deflection allowable = 1.8×20×1×1 = 36mm
[28mm < 36mm] The slab having the sufficient stiffness and the deflection will be within the
permissible value.
9.3 REINFORCEMENT DETAILS
Figure 32- R.C.Slab details
Tension reinforcement;(lower part of the slab)
1. 0.25L-continuous edge
2. 0.15L-discontinuous edge
Continuous edges of middle strip, the tension reinforcement. Shall extend in the upper part of
the slab a distance 0.15L from the support and at least 50 % shall extend a distance of 0.3L.
1. Negative moments at discontinuous edge- 0.1L
2. Torsion reinforcement shall be provided at any corner
Minimum distance- 1/5 x shorter span
Area of reinforcement-3/4 x area required for the max. Mid-span
meters in the slab.
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Spacing
1. main steel- ≠ > 3d or 300mm whichever is smaller
2. Distribution steel- ≠> 5d or 450mm whichever is smaller
Minimum reinforcement: ≠< 0.15 % of the total cross sectional
area for f y=250 and 0.12% when f y=415 bars are used
Maximum diameter of bars : ≠> 1/8 x D
Cover: should not be less then15mm nor < dia. of bar whichever is higher
Figure 33-Slab detailing
1- 10mm dia bars at 300mm spacing 3,4-10mm dia bars at 300mm spacing
2,3-10mm dia bars at 300mm spacing 5,6-10mm dia bars at 300mm spacing
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10.0 DESIGN OF STAIRCASE
10.1 GENERAL:
Functionally the staircase is an important component of building, and often the only means of
access between the various floors in the building. It consists of a flight of steps, usually with
one or more intermediate landings provided between floor levels. Following are the structural
components of staircase.
A) Thread: The horizontal portion of a step where the foot rests is referred to as tread.
The typical dimension of a tread is 250mm to 300mm.
B) Riser: Riser is the vertical distance between the adjacent treads or the vertical
projection of one step with value of the step 150 to 190mm depending upon the type of
building. The width of stairs is generally 1 to 1.5m and in case not less than 850mm. Public
buildings should be provided with larger widths to facilitate free passage to users and prevent
overcrowding.
C) Going: Going is the horizontal projection (plan) of an inclined flight of steps
between the first and last riser. A typical flight comprises two landings and one going. To
break the monotony of climbing, the number of steps in a flight should not exceed 10 to12.
The tread riser combination can be provided in conjunction with
1) Waist slab type
2) Tread riser type
3) Isolated cantilever type
4)
Double cantilever precast tread slab with a central inclined beam.
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Figure 34-Types of staircases
Types of staircases
The various types of staircases adopted in different types of buildings can be grouped under
geometrical and structural classifications depending upon their shape and plan pattern and
their structural behavior under loads. Types of staircases based on geometrical classification.
1) Straight stairs (with or without landing)
2) Quarter-turn stairs
3)
Dog-legged stairs
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4) Open well stairs
5) Spiral stairs
6) Helical stairs
10.2 DESIGN PARAMTERS
Type of staircase = Waist slab type
Number of steps in flight = 12
Tread (T) =300mm
Riser (R) =150mm
Width of landing beams =600mm
Grade of concrete using (f ck ) =30N/mm2
Grade of steel using (fy) = 500 N/mm2
Effective span (L) = [(12×300) +600] = 4200mm
Thickness of waist slab = [4200/20]
= 210mm
10.3 LOAD ACTING ON STAIRS
Dead load of slab (on slope) (Ws) = (0.21×1×25) = 5.25kN/m
Dead load of slab on horizontal span [Ws√R
2
+T
2
/ T] = 5.59kN/mDead of one step (0.5×0.15×0.3×25) = 0.56kN/m
Load of steps/m length = [0.56×(1000/300)] =1.86kN/m
Floor finishes = 1.5kN/m
Total dead = 8.95kN/m
Live load (overcrowding) per meter = 5kN/m
Total service load =13.95kN/m
Total ultimate load = (1.5×13.95)
=20.93kN/m
10.4 DESIGN OF WAIST SLAB TYPE STAIRCASE
Maximum bending moment (0.125×20.93×4.22) = 46.15kNm
Check for depth of waist slab(d)=√46.15×106 /(0.138×30×1000) = 106mm
Assume a cover of 20mm and using 12mm dia bars [210-20-6] = 184mm
Effective depth provided is greater than the required depth (184 >106)
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10.5 REINFORCEMENT PROVIDED
Using table 2 from SP: 16
[Mu/ b×d2] = [46.15×106 /1000×184
2] = 1.35
Pt = [Ast×100/b×d] =0.329
Ast =606mm2
Provide 12mm diameter bars at 200mm spacing (Ast=678mm2) as main reinforcement.
Distribution reinforcement (0.0012×1000×210)=252mm2
Provide 8mm diameter bars at 200mm spacing (Ast=252mm2) as distribution reinforcement.
10.6 STAIRCASE DETAILING
Figure 35-Detailing of staircases
Longitudinal reinforcement: Y 12 AT 200 c/c
Distribution reinforcement: Y 8 at 200 c/c
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11.0 DESIGN OF SHEAR WALL
11.1 GENERAL
Lateral force resisting system in the building is a dual system consisting of SMRF and shear
walls. In general, the shear walls will resist all the lateral force being a relatively stiff
element.
The design of shear wall is based on the assumption that it will be the part of the lateral force
resisting system of the structure.
The shear wall is provided in between the middle two columns of the exterior frames. These
columns will act as a flange element or boundary elements for the shear wall. Therefore,
there is no need for further thickening of shear wall at the end or boundary regions.
Calculated reinforcement in horizontal and vertical direction is greater than the minimum
prescribed reinforcement provided reinforcement is uniformly distributed in both the
directions.
Figure 36-Shear Wall
11.2 WALL DIMENSIONS:
Length of the wall = 7.2m
Thickness of wall = 230mm
Height of the wall = 4.0m
Load combinations considered = 1.5DL + 1.5 EQL
= 0.9DL + 1.5 EQL
P1 Axial load (1.5DL + 1.5 EQL) = 3349 kN
Shear force = 7532.98 kN
Bending moment = 33781.95
P2 Axial load = 2197 kN
Shear force = 7529.02 kN
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Bending moment = 33756 kNm
Grade of concrete using (f ck ) =30N/mm2
Grade of steel using (fy) = 500 N/mm2
11.3 CHECK FOR BOUNDARY ELEMENT:
Moment of inertia I= (t ×L3)/ 12 = (230 ×7.2
3)/ 12
= 7.15 ×1012
mm4
Area= t×L = 230×7200
=1656×103 mm
2
f c= (P/A)±( Mt ×L/ I) =2.02 ± 17.03
= 19.05 and -15.01kN/ m2
11.4 FIXING BOUNDARY ELEMENT:
Assume width of flange (Wf) = 230 mm
Length of flange (Lf) = (0.1×L) = 0.1×7200
= 720mm
Provide 750×250mm boundary element.
Lw = 7200-(2×750) = 5700
c/c = 7200-750 = 6450
Wall thickness is 230mm so provide two layers of steel.
11.5 DETERMINATION OF MINIMUM STEEL:
1) VERTICAL REINFORCEMENT = 0.0025×Ag
0.0025×1000×230 = 575 mm2
Provide area of steel is 1% of gross area. That is 0.5% in each layer.
Area of steel in each layer (Ast) = (0.575×1000×230)/100
= 1322.5mm2
Diameter of b