seismic analysis of multistory building using etabs with

© 2020 JETIR May 2020, Volume 7, Issue 5 www.jetir.org (ISSN-2349-5162)

JETIR2005412 Journal of Emerging Technologies and Innovative Research (JETIR) www.jetir.org 711

SEISMIC ANALYSIS OF MULTISTORY

BUILDING USING ETABS WITH

COMPARISON OF RESPONSE SPECTRUM

METHOD AND TIME HISTORY METHOD Kusuma.S Dr. E. Ramesh Babu

PG Student, M Tech Associate Professor

Dept of Civil Engineering Dept of Civil Engineering

Ghousia College of Engineering Ghousia College of Engineering

Ramanagaram Ramanagaram

Abstract: - Most of the buildings were damaged

and collapse during in strong earthquake hence we

will have to confirm safety against the earthquake

force that are affecting the structure, and determine

seismic responses of such building.

The present work deals with the analysis of

multistorey building subjected to seismic condition.

In addition to the dead load and live load, the

seismic loads are applied and analysis is carried

out. In the present scenario, a structure of situated

in Bangalore is considered for analysis which

consists of a ground floor upto tenth floor. The

analysis is carried out for seismic zone -2. The

building model are analyzed using IS1893-2002

recommended Response spectrum method and Time

history method. Time history analysis is significant

technique for structural seismic analysis

particularly when evaluated structural response is

nonlinear. In Time history analysis, earthquake

data from previous earthquake (EL Centro 1940) is

taken. Study focuses to evaluate two important

parameters which are (a) Base shear and (b)

maximum deflection. Analysis has been carried out

using E-Tabs software. The E-Tabs software has

been adopted as with its new features surpassed its

predecessors with its data sharing for analysis and

design. Based on result it is found that the base

shear obtain from RSM is slightly higher compared

to THM, and also storey deflection is more in

Response spectrum method than Time history

method.

Keywords: Seismic analysis, Response spectrum

method and Time history method.

1. INTRODUCTION

As our country is the fastest growing country

across the globe so the need of shelter for highly

populated cities where the cost of land is high and

further horizontal expansion is not possible due to

unavailability of space, so the only solution is

vertical expansion. After an earthquake occurs it

causes great damage due to unpredictable seismic

motion striking & when the height of building is

increased the wind load effect also acts on building.

This causes major loss of life with a more casualties

therefore such structures need to be analyzed and

designed properly before constructing.

Different earthquake have different intensities,

different magnitude at different place and in this

place the destruction causes are also different.

Therefore it is very important to study the seismic

behavior of RC structure for different function in

terms of responses such as Base shear, storey

displacement etc. Seismic analysis is needed to

calculate the seismic response of the building,

seismic analysis is part of the process of structural

design where earthquakes are prevalent.

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Fig. 1. Example of sesismic force affected on

building.

1.1 Response Spectrum Analysis:

This method is derived from time history

analysis. A designer is not often bothered about the

structure’s response at every instance of time,

maximum response is enough information to design

adequately strong structure. In this method graph

between maximum spectral acceleration and various

time period of structure is prepared for some ground

acceleration and structures response at every

instance of time is not calculated. Response

spectrum method, it is the linear dynamic analysis

method. This method involves the calculation of

only the maximum values of displacements and

member forces in each mode of vibration. This

method uses smooth design spectra that are the

average of several earthquake motions. Different

earthquake will have different response spectra but

for ease of structural engineer IS 1893:2002 has

given a generalpurpose response spectra which is

derived by considering few big earthquakes from

past.

1.2 Time History Analysis:

Time history analysis provides for linear or

non linear evalution of dynamic structural response

under loading which may vary according to the

specified time function. Intial conditions may be set

by continuing the structural state from the end of

the previous analysis. This method calculates

response of structure subjected to earthquake

excitation at every instant of time, various seismic

data are necessary to carry out the seismic analysis

i.e. acceleration, velocity, displacement data etc.,

which can be easily procured from seismograph

data analysis for any particular earthquake. It is an

important technique for structural seismic analysis

especially when the evaluated structural response is

nonlinear.

1.3 About E-TABS Software:

E-Tabs is an engineering software product that

caters to multi-storey building analysis and design.

Modeling tools and templates, code-based load

prescriptions, analysis methods and solution

techniques, all coordinate with the grid-like

geometry unique to this class of structure. Basic or

advanced systems under static or dynamic

conditions may be evaluated using E-Tabs. it

provides an unequaled suite of tools for structural

engineers designing buildings, whether they are

working on one-storey industrial structures or the

tallest commercial high-rises. Immensely capable,

yet easy-to-use, has been the hallmark of E-Tabs

since its introduction decades ago, and this latest

release continues that tradition by providing

engineers with the technologically-advanced, yet

intuitive, software they require to be their most

productive

Advantages of E-tabs Software:

1. E-Tabs allows user for graphic input and

modification for the sake of easy and quick model

creation for any type of structure.

2. Creation of 3D model with the utilization of plan

views and elevations,3D model of any kind of

complex structure can be created easily.

3. With the help of similar storey concept creation

of 3D model is very easy and quicker. If the storeys

are similar then the model generation time can be

reduced multiple time through similar storey

concept.

4. Editing of model is very easy. Moving any object

from one position to other, combining two or more

objects using merge commond, making the similar

object using mirror command and make copy of any

object in the same level of different storey level.

5. To analyse and design slab with any shape and

mat foundations E-Tabs is integrated with safe

allowing you to complete analysis and design of

any type of slab.




Procedure for Analysis and Design Building by

Etabs:

The procedure carried out for Modeling and

analyzing the structure involves the followings

Step1: Create the Grid points and Generation of

structure After getting opened the program, select a

new model and a window appears where we had

entered the details of grid dimensions and storey

dimensions of our building. Here the program had

generated 2D and 3D structure by specifying the

building details in the following two windows

Step 2: Define property

After created the grids, start to define the material

property by selecting define menu material

properties (define concrete and steel

reinforcements). After that define section properties

(beams, columns, slabs, and wall) by giving the

specified details in defining. After that we define

section size by selecting frame sections as shown

below and added the required section for beams,

columns etc.

Step 3: Assigning of Property

After defining the property for materials and

section properties, now draw the structural

components using command menu → Draw line for

beam and create columns in region for columns by

which property assigning is completed for beams

and columns sections.

Step 4: Assigning of Supports

After drawing the details of building (beams,

columns, slabs, wall), now assigned the supports by

going to assign menu →joint\frame →Restraints

(supports) →fixed.

Step 5: Defining of loads

The loads in ETABS program are defined as using

static load cases command in define menu.

Step 6: Assigning of Dead loads

After defining all the loads, dead loads are assigned

for external walls and internal walls.

Step 7: Assigning of Live loads Live loads are

assigned for the entire structure including floor

finishing.

Step 8: Assigning of wind loads

Wind loads are defined and assigned as per IS 875

1987 PART 3 (Indian code) by giving the value of

wind speed and wind angle in X, X1, Z & Z1

directions as 0, 180, 90, 270 respectively.

Step 9: Assigning of Seismic loads

Seismic loads are defined and assigned as per IS

1893: 2002(Indian code) by giving the details of

zone, soil type, and response reduction factor in X

and Y directions.

Step 10: Assigning of load combinations

Load combinations are given based on IS 875 1987

PART 5 (Indian code) using load combinations

command in define menu

Step 11: Analysis After the completed all the above

steps, now performed the analysis and check all the

errors.

2. AIM AND OBJECTIVES

1.To make the building earthquake resistant against

seismic effect.

2.To study the behavior of multi storey building in

various seismic zone 2.

3.Analysis of multi-storey building subjected to all

possible loading conditions including seismic load

and to see that structure is safe against those loading

conditions.

4.To analysis storey drift, displacement, shear,

storey stiffness,model period & frequency on

different storeys.

3. MODELLING

Generally, a building consist of slabs,

beams, columns and foundation and the load

transfer in the structures is in the same order finally

structure resisting on soil (depends on S.B.C). In

this building consisting of basement, a ground floor

and upper floors. It also has 3 staircases and 3 open

well for lift. The height of each storey is considered

as 3 meters. The building description is briefly

shown in Table 1 and the materials used are

depicted in Table 2.

Table 1. Design Data

No. of storey 10

Height of each storey 3 meters

Slab thickness 175 mm

Beam dimension 200 x 450mm

Column dimensions, C1 200 x 450 mm

Column dimensions, C2 230 mm




Thickness of wall 200 mm

Support conditions Fixed

Table 2. Material properties

Grade of concrete M30, fck = 30 N/mm2

Grade of steel Fe415, fy = 415 N/mm2

Density of concrete 25 KN/m3

Modulus of elasticity of

concrete

5000 Sqr(fck) N/mm2

Density of steel 78.5 KN/m3

Modulus of elasticity of

steel

2 x 105 N/mm2

4. ANALYSIS

4.1 Loading Calculations and its Details

The following loads were considered while

analysing the building model in the Etab Software.

Dead loads – 11.8 kN/m for outer wall and

inner walls and 1kN/m on slabs.

Live loads – 3 kN/m on slabs.

Seismic loads- Seismic zone: II (Z=0.24),

Soil type: II, Importance factor: 1, Response

reduction factor: 5, Damping: 5%.

4.2 Load combinations

The structure is analysed considering proper

ratios of the applied dead loads, live loads and

seismic loads. The Load combinations are given in

IS 1893 (part-1):2002 which has been presented in

Table 3. As the seismic loads are assigned in both X

and Y direction so ELX and ELY should be

considered.

Table 3. Load Combinations

SL. No Loads Factors

1 Dead Load 1.5

Live Load 1.5

2 Dead Load 1.2

Live Load 1.2

Seismic Load (X-Dir) ±1.2

3 Dead Load 1.2

Live Load 1.2

Seismic Load (Y- Dir) ±1.2

4 Dead Load 1.5

Seismic Load (X- Dir) ±1.5




5 Dead Load 1.5


6 Dead Load 0.9

Seismic Load (X- Dir) ±1.5

7 Dead Load 0.9





5. Experimental Results of Response Spectrum

Analysis







6. Experimental Results of Time History Analysis




7. Discussion

Top displacement values of time history

analysis are lesser than the displacement

value of response spectrum analysis.




For important structure time history method

should be used over response analysis as it

predicts structure behavior more accurately.

Difference in structure displacement is very

small in lower stories in both the methods

results predicts almost same for lower

stories.

Difference in structural displacement by

both methods become large for higher

stories only.

Time history method is accurate but very

resource consuming, on the other hand

response spectrum is quick but marginally

uneconomical.

8. Conclusion

By use of Response spectrum method will

get higher base shear value 2% and higher

displacement value 15 to 25% when

compare to Time history.

Time history methods results depends

heavily on earthquake excitation so a

number of various earthquakes of varying

intensities should be taken and maximum of

these should be considered.

Based on this study it can be concluded that

use of time history method will give

reasonable value when compare to response

spectrum method. Time history method

should be prefered whenever detailed

analysis is required but response spectrum is

not a bad approximation. Response

spectrum method gives fairly accurate

results.

9.References

[1]. N R Shwetha, Naveen, Pampanna Moolimani,

S Naveen kumar, Mahesh Sajjan “Analysis and

design of multi storey building subjected to

seismic load using E-tabs” (Department of Civil

Engineering, RYMEC Ballari), published-6 June

2019, (IRJET).

[2]. Ali Kadhim Sallal “Design and analysis ten

storied building using ETABS software-2016” Department of Hydraulic Structures, College of

Water Resource Engineering, Iraq, published- 2

May 2018, (IJRAET).

[3]. Sayyed A. Ahad, Hashmi S Afzal, Pathan

Tabrej, Shaikh Ammar, Shaikh Vikhar, Shivaji

Bidve “Analysis and design of multistorey

apartment building using ETABS” India

(Department of Civil Engineering, Sandipani

Technical Campus Faculty of Engineering,

SRTMUN University, Latur, Maharashtra),

published-5 May 2017, International Journal of

Engineering and Computer Science.

[4]. Yash Kumar K. Jain, V. Naga Sri Nikhil

“Analysis of a commercial building using

ETABS” Department of Civil Engineering K L

University, Andhra Pradesh, India, published- 4

April 2017, International Journal of Civil

Engineering and Technology (IJCIET).

[5]. Prakriti Chandrakar, Dr. P. S. Bokare

“Earthquake Analysis of G+10 Building using

Response Spectrum Method and Time History

Method - A Comparison” Department of Civil

Engineering RSR Rungta Collage of Engineering

and Technology, Bhilai (C.G), India, published- 8,

August 2017, International Journal of Science and

Research (IJSR).

Author Profile:

Kusuma.S

PG student MTec

Dept of Civil Engineering

Ghousia College of Engineering

Ramanagaram

Author Profile:

Dr. E. Ramesh Babu

Associate Professor

Dept of Civil Engineering

Ghousia College of Engineering

Ramanagaram


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seismic analysis of multistory building using etabs with