ETABS & STAAD Comparison

1

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.

6

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


GENRAL_STRUCTURE 1

Self load

Dead load

Live load

1.50

1.50

1.50


GENRAL_STRUCTURE 3

Self load

Dead load

Live load

EQ (along length)

1.20

1.20

1.20

1.20


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


GENRAL_STRUCTURE 6

Self load

Dead load

Live load

EQ (along width)

1.20

1.20

1.20

-1.20


GENRAL_STRUCTURE 8

Self load

Dead load

EQ (along length)

1.50

1.50

1.50


GENRAL_STRUCTURE 10

Self load

Dead load

EQ (along length)

1.50

1.50

-1.50


GENRAL_STRUCTURE 9

Self load

Dead load

EQ (along width)

1.50

1.50

1.50


GENRAL_STRUCTURE 11

Self load

Dead load

EQ (along width)

1.50

1.50

-1.50


GENRAL_STRUCTURE 12

Self load

Dead load

EQ (along length)

0.90

0.90

1.50


GENRAL_STRUCTURE 14

Self load

Dead load

EQ (along length)

0.90

0.90

-1.50


GENRAL_STRUCTURE 13

Self load

Dead load

EQ (along width)

0.90

0.90

1.50


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 3.12: 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) (b)


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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(a) (b)


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) (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


Bending Moment (M2) 0.09 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


Column forces/ B.M.

Axial Force (P) 10.61 kN



Torsion (T) 0.008 kN -m

Bending Moment (M2) 85.29 kN -m

Bending Moment (M3) 73.84 kN -m


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

33

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

34

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

35

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





36





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

37

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

38

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


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


(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


Forces

Axial Force (P) -0.347 kN



Torsion (T) 0.066 kN-m




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


Forces

Axial Force (P) -118.49 kN



Torsion (T) 0.48 kN-m

Bending Moment (M2) 88.69kN-m


43

(a) (b)

Fig 4.20: (a) B.M. (b) Axial Force diagram for load combination 1.2(Self +Dead

+Live +EQwidth)


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)


Area of steel (mm2)


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



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


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


Fig 4.25: Graph of Storey Vs Max Storey Displacement due to EQ length


with increase in storey height along x-direction for EQlength load and varies constantly

(app.) along y-direction for EQlength.


Fig 4.26: Graph of Storey Vs Max Storey Displacement due to EQ width


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


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


X - Direction

Y - Direction

49

4.2. STAADPro.


(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


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


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


Forces







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)


Area of steel (mm2)


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


(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


Forces







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 4.43: 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


Forces







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)


Area of steel (mm2)


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


EQwidth) 173.98kN

B.M. MX

1.5(Self +Dead

+EQwidth)

397.17

kN-m


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


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


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


Mode I


Mode IV

69


Mode VIII


Mode XI


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.

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