ETABS & STAAD Comparison
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Transcript of ETABS & STAAD Comparison
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INTRODUCTION
1.1. RCC FRAME STRUCTURES
An RCC framed structure is basically an assembly of slabs, beams, columns and
foundation inter -connected to each other as a unit. The load transfer, in such a structure
takes place from the slabs to the beams, from the beams to the columns and then to the
lower columns and finally to the foundation which in turn transfers it to the soil. The
floor area of a R.C.C framed structure building is 10 to 12 percent more than that of a
load bearing walled building. Monolithic construction is possible with R.C.C framed
structures and they can resist vibrations, earthquakes and shocks more effectively than
load bearing walled buildings. Speed of construction for RCC framed structures is more
rapid.
Fig 1.1: RCC Frame Components
1.2. REINFORCED CONCRETE
Reinforced concrete is a composite material in which concrete's relatively low tensile
strength and ductility are counteracted by the inclusion of reinforcement having higher
tensile strength and ductility. The reinforcement is usually embedded passively in the
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concrete before the concrete sets. The reinforcement needs to have the following
properties at least for the strong and durable construction:
High relative strength
High toleration of tensile strain
Good bond to the concrete, irrespective of pH, moisture, and similar factor.
Thermal compatibility, not causing unacceptable stresses in response to
changing temperatures.
1.3. OBJECTIVE
1. To check the behaviour of multi-storey regular and irregular building on
software (STAADPro. & ETABS).
2. To understand the accuracy of softwares for analysis and design for plan
and elevation Irregularity.
3. To compare the results and behaviour of structures on both the software.
1.4. DIFFERENT METHODS USED FOR DESIGN
1. Working stress method
2. Limit state method
3. Ultimate load method
1.4.1. WORKING STRESS METHOD
It is based on the elastic theory assumes reinforced concrete as elastic material. The
stress strain curve of concrete is assumed as linear from zero at neutral axis to
maximum value at extreme fibre. This method adopts permissible stresses which are
obtained by dividing ultimate stress by factor known as factor of safety. For concrete
factor of safety 3 is used and for steel it is 1.78. This factor of safety accounts for any
uncertainties in estimation of working loads and variation of material properties. In
Working stress method, the structural members are designed for working loads such that
the stresses developed are within the allowable stresses. Hence, the failure criterions are
the stresses. This method is simple and reasonably reliable. This method has been
deleted in IS 456-2000, but the concept of this method is retained for checking the
serviceability, states of deflection and cracking.
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1.4.2. LIMIT STATE METHOD
In this method, the structural elements are designed for ultimate load and checked for
serviceability (deflection, cracking etc.) at working loads so that the structure is fit for
use throughout its life period. As in working stress method this method does not assume
stress strain curve as linear. This method gives economical sections.
1.4.3. ULTIMATE LOAD METHOD
In this method structural elements are designed for ultimate loads which are obtained by
multiplying the working loads with a factor known as load factor. Hence, the designer
can able to predict the excess load the structure can carry beyond the working loads
without collapse. Hence, this method gives the true margin of safety. This method
considers the actual stress strain curve of concrete and the failure criteria is assumed as
ultimate strain. This method gives very economical sections. However it leads to
excessive deformations and cracking. This method is failed to satisfy the serviceability
and durability requirements. To overcome these drawbacks, the limit state method has
been developed to take care of both strength and serviceability requirements.
1.5. STAADPro.
One of the most famous analysis methods for analysis is “Moment Distribution
Method”, which is based on the concept of transferring the loads on the beams to the
supports at their ends. Each support will take portion of the load according to its K; K is
the stiffness factor, which equals (EI/L). E, and L is constant per span, the only variable
is I; moment of inertia. I depend on the cross section of the member. To use the moment
distribution method, you have to assume a cross section for the spans of the continuous
beam. To analyze the frame, “Stiffness Matrix Method” is used which depends upon
matrices. The main formula of this method is [P] = [K] x [Δ]. [P] is the force matrix =
Dead Load, Live Load, Wind Load, etc. [K] is the stiffness factor matrix. K= (EI/L). [Δ]
is the displacement matrix.
STAAD was the first structural software which adopted Matrix Methods for analysis.
The stiffness analysis implemented in STAAD is based on the matrix displacement
method. In the matrix analysis of structures by the displacement method, the structure is
first idealized into an assembly of discrete structural components (frame members or
finite elements). Each component has an assumed form of displacement in a manner
which satisfies the force equilibrium and displacement compatibility at the joints.
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STAAD stands for Structural Analysis and Design. STAAD.Pro is a general purpose
structural analysis and design program with applications primarily in the building
industry – commercial buildings, bridges and highways structures, and industrial
structures etc. The program hence consists of the following facilities to enable this
task:-
1. Graphical model generation utilities as well as text editor based commands for
creating the mathematical model. Beam and column members are represented
using lines. Walls, slabs and panel type entities are represented using triangular
and quadrilateral finite elements. Solid blocks are represented using brick
elements. These utilities allow the user to create the geometry, assign properties,
orient cross sections as desired, assign materials like steel, concrete, timber,
aluminium, specify supports, apply loads explicitly as well as have the program
generate loads, design parameters etc.
2. Analysis engines for performing linear elastic and p-delta analysis, finite
element analysis, frequency extraction and dynamic response.
3. Design engines for code checking and optimization of steel, aluminium and
timber members. Reinforcement calculations for concrete beams, columns, slabs
and shear walls. Design of shear and moment calculations for steel members.
4. Result viewing, result verification and report generation tools for examining
displacement diagrams, bending moment and shear force diagrams, beam, plate
and solid tress contours, etc.
5. Peripheral tools for activities like import and export of the data from and to
other widely accepted formats, links with other popular softwares for footing
design, steel connection design, etc.
1.6. ETABS
ETABS stands for Extended Three dimensional Analysis of Building Systems. ETABS
was used to create the mathematical model of the Burj Khalifa, designed by Chicago,
Illinois-based Skidmore, Owings and Merrill LLP (SOM). ETABS is commonly used to
analyze: Skyscrapers, parking garages, steel & concrete structures, low rise buildings,
portal frame structures, and high rise buildings. The input, output and numerical
solution techniques of ETABS are specifically designed to take advantage of the unique
physical and numerical characteristics associated with building type structures. A
complete suite of Windows graphical tools and utilities are included with the base
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package, including a modeller and a postprocessor for viewing all results, including
force diagrams and deflected shapes.
1. ETABS provides both static and dynamic analysis for wide range of gravity,
thermal and lateral loads. Dynamic analysis may include seismic response
spectrum or accelerogram time history.
2. ETABS can analyze any combination of 3-D frame and shear wall system, and
provides complete interaction between the two. The shear wall element is
specially formulated for ETABS and is very effective for modelling elevator
core walls, curved walls and discontinuous walls. This wall element requires no
mesh definition and the output produced is in the form of wall forces and
moments, rather than stresses.
3. A wide range of gravity, thermal and lateral loads may be applied for analysis.
Lateral loads include automated UBC, BOCA and NBCC seismic and wind load
along with ATC seismic and ASCE wind.
4. Steel Frame, Concrete Frame and Concrete/Masonry Shearwall design
capabilities based upon AISC-ASD, LFRD, UBC and ACI-89 codes.
5. Outputs- storey displacements, mode shapes and periods, lateral frame
displacements, frame member forces are obtained at each level of the frame.
6. Special features available on ETABS are design of various shapes of Columns
such as T-column, L-Column, and Poly shaped column. Design of Beams with
varying depths
7. Shear walls with and without openings according to Indian Code can be
provided in ETABS software.
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LITERATURE REVIEW
2.0. General
Most of the work for analysis of multi storey building has been done on STAADPro.
Evaluation of forces and moments for Dead load, Live load and Seismic load
considered. But there is very less work has been done using load combination.
M C Griffith and A V Pinto (2000) have investigated the specific details of a 4-story,
3-bay reinforced concrete frame test structure with unreinforced brick masonry (URM)
infill walls with attention to their weaknesses with regards to seismic loading. The
concrete frame was shown to be a “weak-column strong-beam frame” which is likely to
exhibit poor post yield hysteretic behaviour. The building was expected to have
maximum lateral deformation capacities corresponding to about 2% lateral drift. The
unreinforced masonry infill walls were likely to begin cracking at much smaller lateral
drifts, of the order of 0.3%, and completely lost their load carrying ability by drifts of
between 1% and 2%. [1]
Sanghani and Paresh (2011) studied the behaviour of beam and column at various
storey levels. It was found that the maximum axial force generated in the ground floor
columns, max reinforcement required in the second floor beams. [2]
Poonam et al. (2012) Results of the numerical analysis showed that any storey,
especially the first storey, must not be softer/weaker than the storeys above or below.
Irregularity in mass distribution also contributes to the increased response of the
buildings. The irregularities, if required to be provided, need to be provided by
appropriate and extensive analysis and design processes. [3]
Prashanth.P et al. (2012) investigated the behaviour of regular and irregular multi
storey building structure in STAADPro. and ETABS. Analysis and design was done
according to IS-456 and IS-1893(2002) code. Also manually calculations were done to
compare results. It was found that the ETABS gave the lesser steel area as that of
STAADPro. Loading combinations were not considered in the analysis and influence of
storey height on the structural behaviour was not described. [4]
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MODELLING OF RCC FRAMES
3.0. RCC FRAME STRUCTURE
An RCC framed structure is basically an assembly of slabs, beams, columns and
foundation inter-connected to each other as a unit. The load transfer, in such a structure
takes place from the slabs to the beams, from the beams to the columns and then to the
lower columns and finally to the foundation which in turn transfers it to the soil.
3.1. General
Case I Regular Building
Case II Irregular Building
3.1.1. Case I: Regular Building
A 32m x 20m 12-storey multi storey regular structure is considered for the study. Size
of the each grid portion is 4m x 4m. Height of each storey is 3m and total height of the
building is 36m. Plan of the building considered is shown in the figure 3.1.
Fig 3.1: Plan of the Building
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Table 3.1: Building Description
Length x Width 32x20m
No. of storeys 12
Storey height 3m
Beam 450x450mm
Column 1-6 storeys exterior perimeter line 800mm (diameter)
Column 1-6 storeys interior portion 600x600mm
Column 7-12 storeys 500x500mm
Slab thickness 125mm
Thickness of main wall 230mm
Height of parapet wall 0.90m
Thickness of parapet wall 115mm
Support conditions Fixed
3.1.2. Case II: Irregular Building
A 32m X 20m 12-storey multi storey irregular structure is considered for the study. Size
of each grid portion is 4m x 4m. Plan of the building considered is shown in the figure
3.2.
Fig 3.2: Plan of the Building
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Table 3.2: Building Description
Length x Width 32x20m
No. of storeys 12
Storey height 3m
Beam along length 400x450mm
Beam along width 400x400mm
Column 750x750mm
Slab thickness 125mm
Thickness of main wall 230mm
Height of parapet wall 0.90m
Thickness of parapet wall 115mm
Support conditions Fixed
3.2. Material Specifications
Table 3.3: Material
Grade of Concrete ,M25 fck= 25N/mm2
Steel fy= 415N/mm2
Density of Concrete ϒc= 25kN/m3
Density of Brick walls considered: ϒbrick= 20kN/m3
3.3. Loading
Loads acting on the structure are dead load (DL), Live load and Earthquake load (EL),
Dead load consists of Self weight of the structure, Wall load, Parapet load and floor
load.
Live load: 3kN/m2 is considered, Seismic zone: V, Soil type: II, Response reduction
factor: 5, Importance factor: 1, Damping: 5%. Members are loaded with dead load, live
load and seismic loads according to IS code 875(Part1, Part 2) and IS 1893(Part-
1):2002.
3.3.1. Selfweight
Self weight comprises of the weight of beams, columns and slab of the building.
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3.3.2. Dead load
All permanent constructions of the structure form the dead load. The dead load
comprises of the weights of walls, partition floor finishes, floors and other permanent
constructions in the building. Dead load consists of:
(a) Wall load = (unit weight of brick masonry x wall thickness x wall height)
= 20 kN/m3 x 0.230m x 3m
= 13.8 kN/m (acting on the beam)
(b) Wall load (due to Parapet wall at top floor)
= (unit weight of brick masonry x parapet wall thickness x wall
height)
= 20 kN/m3 x 0.115m x 0.90m
= 2.07 kN/m (acting on the beam)
(c) Floor load (due to floor thickness)
= (unit weight of concrete x floor thickness)
= 25 kN/m3 x 0.125m
= 3.125 kN/m2 (acting on the beam)
3.3.3. Live load
Live loads include the weight of the movable partitions, distributed and concentrated
load, load due to impact and vibration and dust loads. Live loads do not include loads
due to wind, seismic activity, snow and loads due to temperature changes to which the
structure will be subjected to etc. Live load varies acc. to type of building. Live load=
3kN/m2 on all the floors.
3.3.4. Seismic load
Seismic load can be calculated taking the view of acceleration response of the ground to
the superstructure. According to the severity of earthquake intensity they are divided
into 4 zones.
1. Zone II
2. Zone III
3. Zone IV
4. Zone V
According to the IS-code 1893(part1):2002, the horizontal Seismic Coefficient Ah for a
structure can be formulated by the following expression
Ah= (ZISa)/ (2Rg)
Where Z= Zone factor depending upon the zone the structure belongs to.
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For Zone II (Z= 0.1)
For Zone III (Z= 0.16)
For Zone IV (Z= 0.24)
For Zone V (Z= 0.36)
I= Importance factor, for Important building like hospital it is taken as 1.5 and for other
building it is taken as 1.
R= Response reduction factor
Sa/g= Average Response Acceleration Coefficient
Here Seismic load is considered along two directions- EQ LENGTH and EQ WIDTH.
3.4. Loading Combination
The structure has been analyzed for load combinations considering all the previous
loads in proper ratio. Combination of self-weight, dead load, live load and seismic load
was taken into consideration according to IS-code 875(Part 5).
Table 3.4: Load Combination
SR.
NO.
LOAD COMBINATION PRIMARY
LOAD FACTOR
ETABS STAADPro
1. DCON1 GENERATED INDIAN CODE
GENRAL_STRUCTURE 7
Self load
Dead load
1.50
1.50
2. DCON2 GENERATED INDIAN CODE
GENRAL_STRUCTURE 1
Self load
Dead load
Live load
1.50
1.50
1.50
3. DCON3 GENERATED INDIAN CODE
GENRAL_STRUCTURE 3
Self load
Dead load
Live load
EQ (along length)
1.20
1.20
1.20
1.20
4. DCON4 GENERATED INDIAN CODE
GENRAL_STRUCTURE 5
Self load
Dead load
Live load
EQ (along length)
1.20
1.20
1.20
-1.20
5. DCON5 GENERATED INDIAN CODE Self load 1.20
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GENRAL_STRUCTURE 4 Dead load
Live load
EQ (along width)
1.20
1.20
1.20
6. DCON6 GENERATED INDIAN CODE
GENRAL_STRUCTURE 6
Self load
Dead load
Live load
EQ (along width)
1.20
1.20
1.20
-1.20
7. DCON7 GENERATED INDIAN CODE
GENRAL_STRUCTURE 8
Self load
Dead load
EQ (along length)
1.50
1.50
1.50
8. DCON8 GENERATED INDIAN CODE
GENRAL_STRUCTURE 10
Self load
Dead load
EQ (along length)
1.50
1.50
-1.50
9. DCON9 GENERATED INDIAN CODE
GENRAL_STRUCTURE 9
Self load
Dead load
EQ (along width)
1.50
1.50
1.50
10. DCON10 GENERATED INDIAN CODE
GENRAL_STRUCTURE 11
Self load
Dead load
EQ (along width)
1.50
1.50
-1.50
11. DCON11 GENERATED INDIAN CODE
GENRAL_STRUCTURE 12
Self load
Dead load
EQ (along length)
0.90
0.90
1.50
12. DCON12 GENERATED INDIAN CODE
GENRAL_STRUCTURE 14
Self load
Dead load
EQ (along length)
0.90
0.90
-1.50
13. DCON13 GENERATED INDIAN CODE
GENRAL_STRUCTURE 13
Self load
Dead load
EQ (along width)
0.90
0.90
1.50
14. DCON14 GENERATED INDIAN CODE
GENRAL_STRUCTURE 15
Self load
Dead load
EQ (along width)
0.90
0.90
-1.50
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3.5. Modelling in ETABS
a) Case I: Regular Building
(a) (b)
Fig 3.3: (a) Front Elevation, (b) Side Elevation of the Building
Fig 3.4: 3-D View of the G+11 storey building in ETABS
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Loading Pattern
Dead Load
Fig 3.5: Wall and Parapet load distribution in ETABS
Live Load
Fig 3.6: Live Load distribution (Plan View)
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Seismic Load
Fig 3.7: Seismic Load (along length) on the Building
Fig 3.8: Seismic Load (along width) on the Building
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EQ along length on the First Storey
Fig 3.9: EQ along length on the First Storey
EQ along length on the Last Storey
Fig 3.10: EQ along length on the Last Storey
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b) Case II: Irregular Building
(a) (b)
Fig 3.11: (a) Front Elevation, (b) Side Elevation of the Building
Fig 3.12: 3-D View of the G+11 storey building in ETABS
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Loading Pattern
Dead Load
Fig 3.13: Wall and Parapet load distribution
Live Load
Fig 3.14: Live Load distribution
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Seismic Load
Fig 3.15: Seismic Load (along length) on the Building
Fig 3.16: Seismic Load (along width) on the Building
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EQ along length on the First Storey
Fig 3.17: EQ along length on the First Storey
EQ along length on the Last Storey
Fig 3.18: EQ along length on the Last Storey
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3.6. Modelling in STAADPro.
a) Case I: Regular Building
(a) (b)
Fig 3.19: (a) Front Elevation, (b) Side Elevation of the Building
Fig 3.20: 3-D View of the G+11 storey building in STAADPro.
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Loading Pattern
Selfweight of the building
Fig 3.21: Self Weight of the Building
Dead Load
Fig 3.22: Wall load distribution
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(a) (b)
Fig 3.23: (a) Parapet load on the last floor (b) Floor load (Plan View)
Live Load
Fig 3.24: Live Load distribution on the Building
Seismic Load
(a) (b)
Fig 3.25: (a) Seismic Load (along length) (b) Seismic load (along width) on building
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b) Case II: Irregular Building
(a) (b)
Fig 3.26: (a) Front Elevation, (b) Side Elevation of the Building
Fig 3.27: 3-D View of the G+11 storey building in STAADPro.
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Loading Pattern
Selfweight of the building
Fig 3.28: Self Weight of the Building
Dead Load
Fig 3.29: Wall load distribution
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(a) (b)
Fig 3.30: (a) Wall and Parapet load on the 6th floor (b) Floor Load
Fig 3.31: Live Load distribution
(a) (b)
Fig 3.32: (a) Seismic Load (along length) (b) Seismic Load (along width)
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RESULTS AND OBSERVATIONS
Some of the sample analysis and design results have been shown below for beams and
columns of various floor of the building.
4.1. ETABS software
a) Case I: Regular Building
(a) (b)
Fig 4.1: (a) B.M. Diagram for Selfweight (b) Shear Force diagram for Selfweight
Fig 4.1(a): shows that the beams undergo sagging in middle portion and hogging in end
portion due to Selfweight. Beams behave like continuous beam.
Fig 4.2: Max Stress Diagram for load (0.9Self +0.9Dead +1.5EQlength)
Figure shows that the max stress in the range 60-70kN/m2 is produced at the
bottommost storey and decreases with the increase in storey height.
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4.1.1. BEAM NO. B53 of top floor
Fig 4.3: Beam B53
Fig 4.4: B.M. Diagram for load combination 1.5(Selfweight + Dead + EQlength)
Above figure shows that the reaction of 11.59kN and 52.38kN is produced at left and
right end of the beam respectively due to load combination 1.5(Selfweight + Dead +
EQlength). Maximum shear force of 52.38kN is obtained at right end of the beam.
Maximum axial force, shear force, B.M. of the beam B53
Table 4.1: Analysis Data
Forces
Axial Force (P) 1.51 kN
Shear Force (V2) 74.57 kN
Shear Force (V3) 0.051 kN
Bending Moment (M2) 0.09 kN-m
Bending Moment (M3) 35.62 kN-m
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ETABS CONCRETE DESIGN
Fig 4.5: Concrete Design of Beam 53 of Regular building
Fig 4.6: Concrete Design of Beam B53 (Envelope) of Regular building
Fig 4.5 shows that moment is 13250.97kN-m for designing beam and steel provided is
586mm2. Fig 4.6 shows that controlling load combination for flexural and shear is
DCON13 (0.9 Self +0.9Dead +1.5EQwidth) and DCON14 (0.9Self +0.9Dead -
1.5EQwidth).
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4.1.2. COLUMN NO. C30 of storey 11
Fig 4.7: Column C30
(a) (b)
Fig 4.8: (a) Axial Force (b) B.M. Diagram for load 1.5(Self +Dead load +EQlength)
Above fig. 4.8(a) shows that axial force is maximum at the bottom storey columns and
minimum at top storey columns. Fig 4.8(b) shows that bending moment decreases with
increase in the storey height.
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Maximum axial force, shear force, B.M. of the column C30 of storey11
Table 4.2: Analysis Data
Column forces/ B.M.
Axial Force (P) 10.61 kN
Shear Force (V2) 33.42 kN
Shear Force (V3) 63.45 kN
Torsion (T) 0.008 kN -m
Bending Moment (M2) 85.29 kN -m
Bending Moment (M3) 73.84 kN -m
ETABS CONCRETE DESIGN
Fig 4.9: Concrete Design of Column C30 (Flexural Details) of Regular building
As column is designed according to sway analysis and design load is 208.041kN and
design moment is 712.01kN-m. Steel obtained acc. to design load is 2000mm2.
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Fig 4.10: Concrete Design of Column C30 of Regular building
4.1.3. Area of Steel obtained from ETABS for beams of 1st floor
Table 4.3: Area of Steel for beams of 1st floor
Beam No.
(450 X 450 mm)
Area of steel (mm2)
( Bottom Reinforcement)
Area of steel (mm2)
( Top Reinforcement)
B1 685 967
B2 680 936
B3 680 935
B4 680 935
B5 680 935
B6 680 935
B7 680 936
B8 685 967
B9 652 1015
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B10 655 1021
B11 655 1021
B12 652 1015
B13 685 967
B14 604 980
B15 604 980
B16 604 980
B17 604 980
B18 602 980
B19 602 979
B20 602 979
B21 602 980
B22 604 980
B23 652 1015
B24 601 979
B25 601 978
B26 601 978
B27 601 979
B28 655 1021
B29 604 980
B30 601 979
B31 601 978
B32 601 978
B33 601 979
B34 604 980
B35 655 1021
B36 602 980
B37 602 978
B38 602 978
B39 602 980
B40 604 980
B41 652 1015
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B42 680 936
B43 680 935
B44 680 935
B45 680 935
B46 680 935
B47 680 936
B48 685 967
B49 698 981
B50 665 1029
B51 668 1035
B52 669 1036
B53 669 1036
B54 669 1036
B55 668 1035
B56 616 994
B57 665 1029
B58 698 981
B59 693 950
B60 617 994
B61 618 995
B62 618 996
B63 618 995
B64 617 994
B65 616 994
B66 693 950
B67 692 948
B68 614 992
B69 615 992
B70 614 992
B71 615 993
B72 615 992
B73 614 992
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B74 614 992
B75 692 948
B76 698 981
B77 693 950
B78 616 994
B79 665 1029
B80 617 994
B81 668 1035
B82 618 994
B83 669 1036
B84 618 996
B85 669 1036
B86 618 996
B87 669 1036
B88 617 994
B89 668 1035
B90 616 994
B91 665 1029
B92 693 950
B93 698 981
4.1.4. Area of Steel obtained from ETABS for columns of 1st storey
Table 4.4: Area of Steel for column of 1st storey
Column Section (mm) Area of steel (mm2)
C1 800 (diameter) 4021
C2 800 (diameter) 4021
C3 800 (diameter) 4021
C4 800 (diameter) 4021
C5 800 (diameter) 4021
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C6 800 (diameter) 4021
C7 800 (diameter) 4021
C8 800 (diameter) 4021
C9 800 (diameter) 4021
C10 800 (diameter) 4021
C11 800 (diameter) 4021
C12 800 (diameter) 4021
C13 800 (diameter) 4021
C14 800 (diameter) 4021
C15 800 (diameter) 4021
C16 800 (diameter) 4021
C17 800 (diameter) 4021
C18 800 (diameter) 4021
C19 800 (diameter) 4021
C20 800 (diameter) 4021
C21 800 (diameter) 4021
C22 800 (diameter) 4021
C23 800 (diameter) 4021
C24 800 (diameter) 4021
C25 800 (diameter) 4021
C26 800 (diameter) 4021
C27 600 X 600 2880
C28 600 X 600 3709
C29 600 X 600 3709
C30 600 X 600 2880
C31 600 X 600 3737
C32 600 X 600 4801
C33 600 X 600 4801
C34 600 X 600 3737
C35 600 X 600 3845
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C36 600 X 600 4918
C37 600 X 600 4918
C38 600 X 600 3845
C39 600 X 600 3857
C40 600 X 600 4931
C41 600 X 600 4931
C42 600 X 600 3857
C43 600 X 600 3845
C44 600 X 600 4918
C45 600 X 600 4918
C46 600 X 600 3845
C47 600 X 600 3737
C48 600 X 600 4801
C49 600 X 600 4801
C50 600 X 600 3737
C51 600 X 600 2880
C52 600 X 600 3709
C53 600 X 600 3709
C54 600 X 600 2880
4.1.5. Area of Steel obtained from ETABS for columns of 3rd storey to 12th storey
Table 4.5: Area of Steel for columns of 3rd storey to 12th storey
Storey Column Area of Steel (mm2)
3rd 800 mm (dia) 4021
3rd 600 X 600 mm 2880
4th 800 mm (dia) 4021
4th 600 X 600 mm 2880
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5th 800 mm (dia) 4021
5th 600 X 600 mm 2880
6th 800 mm (dia) 4021
6th 600 X 600 mm 2880
7th 500 X 500 mm 2000
8th 500 X 500 mm 2000
9th 500 X 500 mm 2000
10th 500 X 500 mm 2000
11th 500 X 500 mm 2000
12th 500 X 500 mm 2000
Table 4.5 shows that the steel area decreases with increase in storey height and become
constant after 6th storey level.
4.1.6. Storey Overturning Moment for structure
Fig 4.11: Graph of Storey Vs Overturning Moment
As per above graph it has been concluded that the storey overturning moment decreases
with increase in storey height in both x and y-directions for EQlength and EQwidth
respectively
0
20000
40000
60000
80000
100000
120000
Sto
rey O
vert
urn
ing
Mom
ents
(kN
-m)
Storey
STOREY OVERTURNING MOMENTS
EQ length (X-Direction)
EQ width (Y-Direction)
39
4.1.7. Storey Shear for structure
Fig 4.12: Graph of Storey Vs Storey Shear
As per above graph it has been concluded that the storey shear decreases with increase
in storey height in both x and y-directions for EQlength and EQwidth respectively.
4.1.8. Max Storey Displacement for structure
Fig 4.13: Graph of Storey Vs Max Storey Displacement
As per above graph it has been concluded that the max storey displacement increases
with increase in storey height in both x and y-directions for EQlength and EQwidth
respectively.
0
500
1000
1500
2000
2500
3000
3500
4000
4500
1 2 3 4 5 6 7 8 9 10 11 12
Sto
rey S
hear
(kN
)
Storey
STOREY SHEAR
EQ length (X-Direction)
EQ width (Y- Direction)
0
5
10
15
20
25
30
35
40
Ba
se 1 2 3 4 5 6 7 8 9
10
11
12
Max
Sto
rey
Dis
pla
cem
ent
(m
m)
Storey
MAX STOREY DISPLACEMENT
EQ length( in X-Direction)
EQ width(in Y-Direction)
40
b) Case II: Irregular Building
(a) (b)
Fig 4.14: (a) B.M. (b) Shear Force diagram for Dead load
Fig 4.15: Max Stress Diagram for load combination 1.5(Self +dead +Live)
Figure shows that the max stress in the range 14-21kN/m2 is produced at the
bottommost storey and decreases with the increase in storey height, from storey 2nd to
11th storey a stress of (-7 to +7kN/m2) is acting .
41
4.1.9. BEAM NO. B26 of top floor 12
Fig 4.16: Beam B26 of Irregular building
Maximum Axial force, Shear force, B.M. of the beam B26
Table 4.6: Analysis Data
Forces
Axial Force (P) -0.347 kN
Shear Force (V2) 56.23 kN
Shear Force (V3) 0.024 kN
Torsion (T) 0.066 kN-m
Bending Moment (M2) 0.047 kN-m
Bending Moment (M3) 26.94 kN-m
ETABS CONCRETE DESIGN
Fig 4.17: Concrete Design of Beam 26 of Irregular building
42
Fig 4.18: Concrete Design of Beam 26 (Envelope)
4.1.10. COLUMN NO. C18 of storey 11
Fig 4.19: Column C18
Maximum axial force, shear force, B.M. of the column C18 of storey11
Table 4.7: Analysis Data
Forces
Axial Force (P) -118.49 kN
Shear Force (V2) 9.18 kN
Shear Force (V3) 4.02 kN
Torsion (T) 0.48 kN-m
Bending Moment (M2) 88.69kN-m
Bending Moment (M3) 92.96 kN-m
43
(a) (b)
Fig 4.20: (a) B.M. (b) Axial Force diagram for load combination 1.2(Self +Dead
+Live +EQwidth)
ETABS CONCRETE DESIGN
Fig 4.21: Concrete Design of Column C18
44
Fig 4.22: Concrete Design of Column C18 (Flexural Details)
4.1.11. Area of Steel obtained from ETABS for beams of 1st floor
Table 4.8: Area of Steel for beams of 1st floor
Beam No.
Area of steel (mm2)
( Bottom Reinforcement)
Area of steel (mm2)
( Top Reinforcement)
B1 644 520
B2 645 520
B3 669 520
B4 669 520
B5 655 520
B6 655 520
B7 636 520
B8 641 520
B9 626 520
B10 620 520
B11 566 520
B12 571 520
B13 566 520
B14 571 520
45
B15 620 520
B16 626 520
B17 641 520
B18 636 520
B19 655 520
B20 655 520
B21 669 520
B22 669 520
B23 645 520
B24 644 520
B25 604 463
B26 643 463
B27 640 463
B28 640 463
B29 643 463
B30 604 463
B31 591 463
B32 631 463
B33 628 463
B34 594 463
B35 630 463
B36 599 463
B37 593 463
B38 630 463
B39 594 463
B40 604 463
B41 642 463
B42 602 463
B43 602 463
B44 593 463
46
B45 599 463
B46 628 463
B47 631 463
B48 595 463
B49 594 463
B50 630 463
B51 594 463
B52 569 463
B53 642 463
B54 630 463
B55 606 520
B56 565 520
B57 565 520
B58 606 520
B59 670 520
B60 618 520
B61 618 520
B62 670 520
B63 661 520
B64 599 520
B65 599 520
B66 661 520
B67 634 463
B68 633 463
B69 634 463
B70 633 463
B71 632 463
B72 633 463
4.1.12. Area of Steel obtained from ETABS for columns
All columns of 1st to 12th Storey have steel area = 4500 mm2
47
4.1.13. Storey Overturning Moment for structure
Fig 4.23: Graph of Storey Vs Overturning Moment
As per above graph it has been concluded that the storey overturning moment decreases
with increase in storey height in both x and y-directions for EQlength and EQwidth
respectively.
4.1.14. Storey Shear for structure
Fig 4.24: Graph of Storey Vs Storey Shear
As per above graph it has been concluded that the storey shear decreases with increase
in storey height in both x and y-directions for EQlength and EQwidth respectively.
0
10000
20000
30000
40000
50000
60000
Sto
rey
Ov
ert
urn
ing
Mo
men
ts(k
N-m
)
Storey
STOREY OVERTURNING MOMENTS
EQ length (X- direction)
EQ width (Y- direction)
0
500
1000
1500
2000
2500
1 2 3 4 5 6 7 8 9 10 11 12
Sto
rey S
hear
(kN
)
Storey
STOREY SHEAR
EQ length (X- direction)
EQ width (Y- direction)
48
4.1.15. Max Storey Displacement for structure
Fig 4.25: Graph of Storey Vs Max Storey Displacement due to EQ length
As per above graph it has been concluded that the max storey displacement increases
with increase in storey height along x-direction for EQlength load and varies constantly
(app.) along y-direction for EQlength.
4.1.16. Max Storey Displacement for structure
Fig 4.26: Graph of Storey Vs Max Storey Displacement due to EQ width
As per above graph it has been concluded that the max storey displacement increases
with increase in storey height along x-direction for EQwidth load and varies constantly
(app.) along y-direction for EQwidth load.
0
5
10
15
20
25
30
35
Ba
se 1 2 3 4 5 6 7 8 9
10
11
12
Max S
tore
y D
ispla
cem
ent
(mm
)
Storey
MAX STOREY DISPLACEMENT
X - Direction
Y - Direction
0
5
10
15
20
25
30
Ba
se 1 2 3 4 5 6 7 8 9
10
11
12
Max
Sto
rey
Dis
pla
cem
en
t (m
m)
Storey
MAX STOREY DISPLACEMENT
X - Direction
Y - Direction
49
4.2. STAADPro.
a) Case I: Regular Building
(a) (b)
Fig 4.27: (a) B.M. (b) Shear Force diagram for load 1.5(Self +Dead – EQlength)
4.2.1. Beam No. 1835 of top floor
Fig 4.28: Beam 1853
(a) (b)
Fig 4.29: (a) B.M. (b) S.F. diagram for load 1.2(Self +Dead +Live +EQlength)
40
40
40
40
80
80
80
80
1 2 3 4
653 684
70.7
-12.8
-28.6
2.67
Mz(kNm)
40
40
40
40
80
80
80
80
1 2 3 4
653 684
61.7
-20
Fy(kN)
50
Maximum axial force, shear force, B.M. of the beam 1853
Table 4.9: Analysis Data
Forces
Axial Force (Fx) 52.71 kN
Shear Force (Fy) 77.17 kN
Shear Force (Fz) 4.82 kN
Torsion (Mx) 0.14 kN-m
Bending Moment (My) 9.97 kN-m
Bending Moment (Mz) 88.35 kN-m
STAADPro. CONCRETE DESIGN
Fig 4.30: Concrete Design of Beam 1835 (Hogging) of Regular building
51
Fig 4.31: Concrete Design of Beam 1835 (Sagging) of Regular building
4.2.2. COLUMN NO. 1602 of storey 11
Fig 4.32: Column C1602
52
Fig 4.33: B.M. diagram for load combination 1.5(Self +Dead –EQlength)
Maximum axial force, shear force, B.M. of the column 1602
Table 4.10: Analysis Data
Forces
Axial Force (Fx) 522.99 kN
Shear Force (Fy) 37.37 kN
Shear Force (Fz) 71.26 kN
Torsion (Mx) 0.05 kN-m
Bending Moment (My) 122.130 kN-m
Bending Moment (Mz) 114.40 kN-m
STAADPro. CONCRETE DESIGN of column 1602/member 873
Fig 4.34: Main Reinforcement Cross-Section
53
Fig 4.35: Main Reinforcement
4.2.3. Area of Steel obtained from STAADPro. for beams of 1st floor
Table 4.11: Area of steel for beams of 1st floor
Member
(450 X 450 mm)
Area of steel (mm2)
( Bottom Reinforcement)
Area of steel (mm2)
( Top Reinforcement)
M1 1257 1885
M2 1257 1963
M3 1257 1885
M4 1257 1963
M5 1257 2413
M6 1257 1885
M7 1257 2413
M8 1257 1963
M9 1257 2413
54
M10 1257 2413
M11 1257 2413
M12 1257 2413
M13 1257 2413
M14 1257 2413
M15 1257 2413
M16 1257 2413
M17 1257 2413
M18 1257 2413
M19 1257 2413
M20 1257 2413
4.2.4. Area of Steel obtained from STAADPro. for columns
Table 4.12: Area of steel for columns
Storey Column Area of Steel (mm2) Main Reinforcement
1st 600 X 600 mm 3927 8- T25
1st 800 mm (dia) 3436 7- T25
3rd 800 mm (dia) 2827 9- T20
3rd 600 X 600 mm 3768 12- T20
4th 800 mm (dia) 2827 9- T20
4th 600 X 600 mm 3768 12- T20
5th 800 mm (dia) 2199 7- T20
5th 600 X 600 mm 1885 6- T20
6th 800 mm (dia) 2199 7- T20
6th 600 X 600 mm 1885 6- T20
7th 500 X 500 mm 1885 6- T20
8th 500 X 500 mm 1885 6- T20
9th 500 X 500 mm 1885 6- T20
10th 500 X 500 mm 1885 6- T20
11th 500 X 500 mm 1885 6- T20
12th 500 X 500 mm 1885 6- T20
55
b) Case II: Irregular Building
(a) (b)
Fig 4.36: (a) B.M. (b) S.F. diagram for load 1.5(Self +Dead +EQlength)
4.2.5. Beam No. 1313 of 6th floor
Fig 4.37: Beam 1313
(a) (b)
Fig 4.38: (a) B.M. (b) S.F. diagram for load 1.5(Self + Dead –EQ width)
56
Maximum axial force, shear force, B.M. of the beam 1313
Table 4.13: Analysis Data
Forces
Axial Force (Fx) 35.34 kN
Shear Force (Fy) 92.08 kN
Shear Force (Fz) 35.44 kN
Torsion (Mx) 1.43 kN-m
Bending Moment (My) 75.01 kN-m
Bending Moment (Mz) 148.62 kN-m
Fig 4.39: Stress diagram for load combination 1.5(Self + Dead –EQ width)
57
STAADPro. CONCRETE DESIGN of beam 1313 (Member 222)
Fig 4.40: Concrete Design of Beam 1313 (Hogging) of Irregular building
Fig 4.41: Concrete Design of Beam 1313 (Sagging) of Irregular building
58
4.2.6. COLUMN C99 of 1st storey
Fig 4.42: Column C99
Fig 4.43: B.M. diagram for load combination (0.9Self +0.9Dead +1.5EQlength)
Fig 4.44: Stress diagram for load combination (0.9Self +0.9Dead +1.5EQlength)
59
Maximum axial force, shear force, B.M. of the column 99
Table 4.14: Analysis Data
Forces
Axial Force (Fx) 4056.02 kN
Shear Force (Fy) 101.16 kN
Shear Force (Fz) 145.56 kN
Torsion (Mx) 10.46 kN-m
Bending Moment (My) 576.62 kN-m
Bending Moment (Mz) 476.52 kN-m
STAADPro. CONCRETE DESIGN of column 99(member 249)
Fig 4.45: Main Reinforcement Cross-Section
Fig 4.46: Main Reinforcement
60
4.2.7. Area of Steel obtained from STAADPro. for beams of 1st floor
Table 4.15: Area of steel for beams of 1st floor
Member
Beam Section
(mm)
Area of steel (mm2)
( Bottom Reinforcement)
Area of steel (mm2)
( Top Reinforcement)
M1 400 x 450 1257 1885
M2 400 x 400 942 1885
M3 400 x 450 942 1473
M4 400 x 400 942 1571
M5 400 x 450 942 1473
M6 400 x 400 942 1571
M7 400 x 450 1257 1885
M8 400 x 400 942 1885
M9 400 x 400 942 1885
M10 400 x 400 942 1885
M11 400 x 450 942 1885
M12 400 x 450 1257 1885
M13 400 x 450 942 1885
M14 400 x 450 942 1885
M15 400 x 450 942 1885
M16 400 x 450 1257 1885
4.2.8. Area of Steel obtained from STAADPro. for columns of 1st storey
Table 4.16: Area of steel for column (750 x 750mm)
Member
(750 x 750mm) Area of Steel (mm2) Main Reinforcement
223 5891 12 – T25
224 3770 12 – T20
225 5027 16 – T20
226 3770 12 – T20
61
227 3770 12 – T20
228 3770 12 – T20
229 3770 12 – T20
230 5027 16 – T20
231 3770 12 – T20
232 5027 16 – T20
233 3770 12 – T20
234 5027 16 – T20
235 5027 16 – T20
236 5891 12 – T25
237 5027 16 – T20
238 3770 12 – T20
239 5027 16 – T20
240 3770 12 – T20
241 3770 12 – T20
242 3770 12 – T20
243 3770 12 – T20
244 5027 16 – T20
245 3770 12 – T20
246 5891 12 – T25
247 5891 12 – T25
248 5891 12 – T25
249 3770 12 – T20
250 5027 16 – T20
251 3770 12 – T20
252 3770 12 – T20
253 3770 12 – T20
254 3770 12 – T20
255 3770 12 – T20
256 3770 12 – T20
257 3770 12 – T20
258 3770 12 – T20
62
4.2.9. Area of Steel obtained from STAADPro. for columns from 3rd to 12th storey
Table 4.17: Area of steel for column (750 x 750mm)
Storey Area of Steel (mm2) Main Reinforcement
3rd 3770 12 - T20
4th 3770 12 - T20
5th 3770 12 - T20
6th 3770 12 - T20
7th 3770 12 - T20
8th 3770 12 - T20
9th 3770 12 - T20
10th 3770 12 - T20
11th 3770 12 - T20
12th 3770 12 - T20
63
CONCLUSIONS
General
After Discussion of results and observation some of results are summarized. Based on
the behaviour of RCC frames on STAADPro. and ETABS some important conclusions
are drawn:-
1. Results of max vertical reactions of a 12-storey regular building. As per table 5.1 it has
been concluded that the max reaction produced is 4572.12kN in ETABS and
4624.92kN in STAADPro. due to load 1.5(Self +Dead +Live).
Table 5.1: Comparison of vertical reaction of Regular building
Forces
ETABS STAADPro
Loading Value Loading Value
Axial
Force FX
1.5(Self +Dead –
EQlength) 140.23kN
1.2(Self +Dead +Live –
EQlength) 171.48kN
Shear
Force FY
1.5(Self +Dead
+Live) 4572.12kN 1.5(Self +Dead +Live) 4624.92kN
Shear
Force FZ
1.5(Self +Dead –
EQwidth) 138.11kN
1.2(Self +Dead +Live –
EQwidth) 173.98kN
B.M. MX
1.5(Self +Dead
+EQwidth)
397.17
kN-m
1.2(Self +Dead +Live –
EQwidth)
535.81
kN-m
MY
1.5(Self +Dead –
EQwidth) 0.35kN-m
1.2(Self +Dead +Live
+EQlength) 3.04kN-m
MZ
1.5(Self +Dead –
EQlength)
397.74
kN-m
1.2(Self +Dead +Live +
EQlength)
518.89
kN-m
64
2. Max Deformation of members of 12-storey regular and irregular building
Table 5.2: Max Node Displacement
Displacement Direction
Max Node Displacement (mm)
Regular building Irregular building
STAADPro. ETABS STAADPro. ETABS
X 75.48 51.36 106.25 44.9
Y 1.11 0.77 1.062 0.48
Z 81.57 53.47 93.40 42.38
As per above table it has been concluded that the maximum displacement is along x-
direction and its value is 106.25mm (in STAADPro.) for irregular building and
53.47mm (in ETABS) along z-direction for regular building. So, more precise results
are generated by ETABS which leads to economical design of the building.
3. Design Results of sample beam and column
Column C13 of storey 6 from ETABS and Column 851 of storey 6 from STAADPro. of
12 storey – regular building are taken for comparison.
Table 5.3: Steel Reinforcement
Section
Total Reinforcement ( mm2)
STAADPro. ETABS
Beam (450 x 450mm) 1257 1172
Column (dia-800 mm) 4021 4021
As per above table it has been concluded that the ETABS gave lesser area of steel
required as compared to STAADPro. in case of beam whereas in case of column steel
calculated is same by both softwares.
65
4. Comparison of Storey Overturning Moments
Fig 5.1: Storey Vs Storey Overturning Moments due to EQ length in X-direction
As per above graph it has been concluded that the storey overturning moment decreases
with increase in storey height along x-direction for EQlength load and they are more in
regular building than the irregular building.
5. Maximum Steel Reinforcement of beam and column of regular and irregular building
in ETABS.
Table 5.4: Steel Reinforcement
Section Total Reinforcement ( mm2)
Regular Building Irregular Building
Beam 1595 1293
Column 4931 4500
As per above table it has been concluded that the ETABS gave lesser area of steel
reinforcement for irregular building as compared to regular building in case of beams
and columns.
0
20000
40000
60000
80000
100000
120000
Ba
se 1 2 3 4 5 6 7 8 9
10
11
12
Sto
rey O
vert
urn
ing
mom
ents
(k
N-m
)
Storey
STOREY OVERTURNING MOMENTS
Regular Building
Irregular Building
66
REFERENCES
[1] Griffith M. C., Pinto A. V. (2000), “Seismic Retrofit of RC Buildings - A
Review and Case Study”, University of Adelaide, Adelaide, Australia and
European Commission, Joint Research Centre, Ispra Italy.
[2] Sanghani bharat k. and Paresh Girishbhai Patel, 2011, “Behaviour of Building
Component in Various Zones,” International Journal of Advances in
Engineering Sciences, Vol. 1, Issue 1(Jan. 2011)
[3] Poonam, Kumar Anil and Gupta Ashok K, 2012, “Study of Response of
Structural Irregular Building Frames to Seismic Excitations,” International
Journal of Civil, Structural, Environmental and Infrastructure Engineering
Research and Development (IJCSEIERD), ISSN 2249-6866 Vol.2, Issue 2
(2012) 25-31
[4] Prashanth.P, Anshuman. S, Pandey. R.K, Arpan Herbert (2012), “Comparison of
design results of a Structure designed using STAAD and ETABS Software,”
INTERNATIONAL JOURNAL OF CIVIL AND STRUCTURAL
ENGINEERING, ISSN 0976 – 4399, Volume 2, No 3, 2012
[5] Bureau of Indian Standards: IS-875, part 1 (1987), Dead Loads on Buildings and
Structures, New Delhi, India.
67
[6] Bureau of Indian Standards: IS-875, part 2 (1987), Live Loads on Buildings and
Structures, New Delhi, India.
[7] Bureau of Indian Standards: IS-1893, part 1 (2002), Criteria for Earthquake
Resistant Design of Structures: Part 1 General provisions and Buildings, New
Delhi, India.
[8] Hammad Salahuddin, Saqib Habib, Talha Rehman (2010), “Comparison of
design of a building using ETABS V 9.5 & STAAD PRO 2005,” University of
Engineering and Technology, Taxila, Pakistan.
68
APPENDIX A
A.1) Comparison of Mode Shapes for regular and irregular building
Regular Building Irregular Building
Mode I
Regular Building Irregular Building
Mode IV
69
Regular Building Irregular Building
Mode VIII
Regular Building Irregular Building
Mode XI
Regular Building Irregular Building
Mode XII
70
A.2) Shear Force and B.M. of Column
Column C13 of storey 6 from ETABS and Column 851 of storey 6 from STAADPro.
of 12 storey - regular building are taken for comparison of bending moment and shear
force.
Table 5.2: B.M. and S.F. of Column
Forces STAADPro. ETABS
Axial Force FX 450.05 kN 220.06 kN
Shear Force FY 46.29 kN 32.56 kN
Shear Force FZ 159.36 kN 121.57 kN
Bending Moment MX 0.38 kN-m 1.796 kN-m
MY 167.81 kN-m 172.593 kN-m
MZ 103.10 kN-m 257.25N-m
The S.F. FX, FY, FZ which are obtained in STAADPro. higher side as compare to
ETABS whereas value of B.M. are higher side in ETABS as compared to STAADPro.