Dynamic Analysis of Irregular Structures Using ETABS Software

DEPARTMENT OF CIVIL ENGINEERING

CIV83 Project Phase II

Report on

Dynamic Analysis of Irregular Structures Using ETABS Software

Submitted in the partial fulfilment of Final Year Project Phase II Submitted by

AKASH S (1NH14CV007)

METHESH M REDDY (1NH14CV065)

NISHANTH N V (1NH14CV076)

SHALEEK AHEMED (1NH15CV116)

2018-19

VISVESVARAYA TECHNOLOGICAL UNIVERSITY

“JnanaSangama”, Belgaum: 590018

DEPARTMENT OF CIVIL ENGINEERING

Certificate

Certified that the project work entitled “DYNAMIC ANALYSIS OF IRREGULAR STRUCTURES USING ETABS SOFTWARE” is a bonafide work carried out by AKASH S with USN: lNH14CV007, METHESH M REDDY with USN: 1NH14CV065, NISHANTH NV with USN: 1NH14CV076 and SHALEEK AHEMED with USN: 1NH15CV116 in partial fulfilment for the award of Bachelor of Engineering in Civil Engineering of the Visvesvaraya Technological University, Belagavi during the year 2018-2019 to meet the academic requirement.

Signature of the guide Signature of the HOD Signature of the Principal Mr. YOGESH K S Dr. NIRANJAN P S Dr. Manjunatha

……………… ……………… ………………

Examiners:

1. …………………… 2. …………………

ACKNOWLEDGEMENT

We express our sincere thanks to Dr. MOHAN MANGHANI, Chairman of

New Horizon College of Engineering for providing necessary

infrastructure and Creating good environment.

We would express our great thanks to Dr. MANJUNATHA, Principal of

New Horizon College of Engineering, outer ring road Marathahalli,

Bengaluru -560103 for granting us permission to undertake the VTU pre

scribed project.

With a deep sense of gratitude, we would like to thank the Head of Civil E

ngineering Department, Dr. NIRANJAN P.S, for providing necessary f

acilities and encouraging us to make this project grand success.

We feel an immense pleasure to express our gratitude and profound

thanks to Mr. Yogesh K S, assistant professor, Department of Civil Engin

eering. His valuable guidance in both field and office work helped us to

carry out the project within the prescribed time.

Finally, we express our sincere thanks to lab instructors who provided he

lping hand and to all our friends for their kind co-operation for the compl

etion of the project.

Batch 5

i

ABSTRACT:

Analysis and design of buildings for static forces is a routine affair these days because of availability of

affordable computers and specialized programs which can be used for the analysis. On the other hand,

dynamic analysis is a time-consuming process and requires additional input related to mass of the

structure, and an understanding of structural dynamics for interpretation of analytical results. Reinforced

concrete (RC) frame buildings are most common type of constructions in urban India, which are

subjected to several types of forces during their lifetime, such as static forces due to dead and live loads

and dynamic forces due to the wind and earthquake.

During an earthquake, failure of structure starts off-evolved at factors of weak spot. This

weak point arises due to discontinuity in mass, stiffness and geometry of structure. The systems having

this discontinuity are termed as irregular systems. Irregular structures contribute a massive portion of

city infrastructure. Vertical irregularities are one of the essential motives of failures of systems during

earthquakes. The effect of vertically irregularities within the seismic overall performance of systems

will become definitely vital. Peak-wise changes in stiffness and mass render the dynamic traits of those

buildings exceptional from the ordinary building. The irregularity within the building structures may be

due to irregular distributions in their mass, strength and stiffness along the height of building.

The analysis can be done in Staad Pro software, ETABS software SAP 2000 software and Tekla

software. As ETABS is known widely throughout the country, it is one of the best software’s for

structural analysis. Validation of the ETABS software has been done with respect of paper [1],

comparison of Storey overturning moment, storey drift, Storey displacements, storey shear and modal

mass participation ratios has been done.

ii

TERMINOLOGIES:

Focus: The focus or hypocenter of an earthquake is where the earthquake originated from, usually underground

on the fault zone.

Epicenter: The epicenter of an earthquake is the point on the surface of Earth directly above the epicenter.

Fault Plane: A fault is a weak point within a tectonic plate where pressure from beneath the surface can break

through and causing shaking in an earthquake.

Magnitude: Magnitude is used to describe the size of the Earthquake. There are a number of different ways to

calculate the magnitude of an earthquake, including the Richter Scale. Scientists also use the moment

magnitude scale, which calculates the magnitude of an earthquake based on physical properties such as

the area of movement (slip) along the fault plane. The earthquake effects for different magnitudes are

given in the below fig a.

Fig a.

iii

Waves: Earthquake waves travel through and on top of the surface of Earth causing the shaking and vibrations

on the ground. Earthquake waves can travel hundreds of kilometers causing earthquakes to be felt a long

way away from the origin

Tectonic Plates: The outer layer (crust) of Earth is divided into sections called tectonic plates.

iv

CONTENTS

Serial number

Chapters Page numbers

1

Chapter 1: Introduction

1

2

Chapter 2: Review of literature

8

3

Chapter 3: Objective, Scope of

work and Methodology

17

4

Chapter4:Validation of Software

21

5

Chapter 5: Parametric Studies

29

6

Chapter 6:Results and discussion

47

7

Chapter 7: Conclusion

50

References

v

List of Figures

Serial number Contents Page numbers

1 Fig a: Earthquake effects v 2 Fig 1.1: Nepal Earthquake 1 3 Fig 1.2: seismic mapping zone of India 3 4 Fig 3.1: Flowchart of methodology 18 5 Fig 4.1: software rendered model of validation structure 22 6 Fig 4.2: Graph plotted for the Storey displacement 24 7 Fig 4.3: Graph plotted for the Storey displacement [1] 24

8 Fig 4.4: Graph plotted for the Storey drift 25

9 Fig 4.5: Graph plotted for the Storey drift [1] 25

10 Fig 4.6: Graph plotted for the Storey overturning moment 26

11 Fig 4.7: Graph plotted for the Storey overturning moment [1]

26

12 Fig 4.8: Graph plotted for the Storey Shear 27

13 Fig 4.9: Graph plotted for the Storey Shear [1] 27

14 Fig 5.1: Software rendered model of regular structure 30 15 Fig 5.2: Software rendered model of regular structure

under sloping ground 1:25 32

16 Fig 5.3: Software rendered model of regular structure under sloping ground 1:50

33


34


35

19 Fig 5.6: Bar graph for storey shear results 36 20 Fig 5.7: Bar graph for storey displacement results 36 21 Fig 5.8: Bar graph for storey stiffness results 37 22 Fig 5.9: Software rendered model of irregular structure

under plane ground 38

23 Fig 5.10: Software rendered model of irregular structure under sloping ground 1:25

40


41


42


43

27 Fig 5.14: Bar graph for storey shear results 44 28 Fig 5.15: Bar graph for storey displacement results 44 29 Fig 5.16: Bar graph for storey stiffness results 45 30 Fig 5.17: graph showing the comparison of centre of load

vi

List of tables

1 Table 2.1: Anthology of Dynamic Analysis of Building with

Plan Irregularity. 17

2 Table 2.2: Anthology of Dynamic analysis of structures subjected to earthquake load.

18

3 Table 2.3: Anthology of Dynamic analysis of multi storey structure for different shapes

19

4 Table 2.4: Anthology of Seismic Analysis of a Multi- Storeyed Building with Irregular Plan

20

5 Table 2.5: Anthology of Dynamics analysis of RC regular and irregular structures using Time History Method

21

6 Table 4.1: The material properties and geometry of the model

21

7 Table 4.2: Load details for the model 22 8 Table 4.3: Data from dynamic analysis performed 23 9 Table 4.4: Data from dynamic analysis from [1] 23 10 Table 4.5: The results for storey displacement 24 11 Table 4.6: The results for storey drift 25 12 Table 4.7: The results for storey overturning moments 26 13 Table 4.8: The results for storey Shear 27 14 Table 5.1: Plan details of the regular structure 29 15 Table 5.2: Details of the seismic loads 29 16 Table 5.3: Plan details of the regular structure under

sloping ground 31

17 Table 5.4: Details of the seismic loads 31 18 Table 5.5: Plan details of the irregular structure under

sloping ground 39

19 Table 5.6: Details of the seismic loads 39 20 Table 5.7: The results of centre of load 46

Dynamic analysis of irregular structures using ETABS software

Department of Civil Engineering, NHCE, Bangalore, 2018-19 Page 1

CHAPTER 1

Introduction:

Earthquakes are caused by tectonic movements in the Earth's crust. The main cause is that

when tectonic plates collide, one rides over the other, causing earthquakes and volcanoes.

The earthquakes are caused by the vibrations set up in the earth's crust which spread

outwards in all directions from the source of disturbance. Some of the earthquakes are

artificial, while others are natural. But it is undoubtedly true that all the earthquakes are

caused due to the disequilibrium in the earth's crust.

One of the latest earthquakes happened was in Nepal, it sits on the boundary of the two

massive tectonic plates that collided to build the Himalayas. Their ongoing convergence

also means earthquakes. The April 25, 2015 earthquake in Nepal destroyed housing in

Kathmandu, damaged World Heritage sites, and triggered deadly avalanches around Mount

Everest as shown in fig 1.1. The earthquake magnitude was around 7.8.

Fig:1.1: Nepal Earthquake



1.1 Seismic zones

Seismic zone is an area of seismicity potentially sharing a common cause. It may also be

a region on a map for which a common areal rate of seismicity is assumed for the purpose

of calculating probabilistic ground motions.

The seismic zone is another factor on which destruction of the structure depends. The

Geological Survey of India (G. S. I.) first published the seismic zoning map of the country

in the year 1935. With numerous modifications made afterwards, this map was initially

based on the amount of damage suffered by the different regions of India because of

earthquakes. Colour coded in different shades of the colour red, this map shows the four

distinct seismic zones of India. Following are the varied seismic zones of the nation,

Which are prominently shown in the map:

Zone - II: This is said to be the least active seismic zone.

Zone - III: It is included in the moderate seismic zone.

Zone - IV: This is considered to be the high seismic zone.

Zone - V: It is the highest seismic zone.

This map helps them in planning for a natural disaster like earthquake. An Indian seismic

zoning map assists one in identifying the lowest, moderate as well as highest hazardous or

earthquake prone areas in India. Even such maps are looked into before constructing any

high rise building so as to check the level of seismology in any particular area. This in turn

results in saving life in the long run. The figure 1.2 shows the seismic mapping zone.



Fig:1.2: seismic mapping zone of India



1.3 Irregularities Nowadays, most buildings are marked by irregularity in both plan and vertical

configurations. Irregularity in structures means lack of symmetry which implies vital

eccentricity between the building mass and stiffness centres, give rise to damaging coupled

lateral response. Moreover, to design and analyse an irregular building effectively, high

levels of engineering and designer efforts are needed, whereas a poor designer will design

and analyze a structure by leaving many parameters not under consideration resulting in

unsafe design. , to design and analyze an irregular building effectively, high levels of

engineering and designer efforts are needed Therefore, irregular structures would require

an additional, careful structural analysis so as to improve their dynamic response in case of

an earthquake.

Vertical irregularities are one of the major reasons of failures of structures during

earthquakes. For example, structures with soft storeys were the most notable structures

which collapsed. So, the effect of vertically irregularities in the seismic performance of

structures becomes really important. Height-wise changes in stiffness and mass render the

dynamic characteristics of these buildings different from the regular building. IS 1893

definition of vertically irregular structures states that the irregularity in the building

structures is due to irregular distributions in their mass, strength and stiffness along the

height of building. When such buildings are constructed in high seismic zones, the analysis

and design become more complicated.

During an earthquake, failure of structure starts off-evolved at factors of weak spot. This

weak point arises due to discontinuity in mass, stiffness and geometry of structure. The

systems having this discontinuity are termed as irregular systems. Irregular structures

contribute a massive portion of city infrastructure. Irregularities are one of the essential

motives of failures of systems during earthquakes. The effect of irregularities within the

seismic overall performance of systems will become definitely vital. Peak-wise changes in

stiffness and mass render the dynamic traits of those buildings exceptional from the

ordinary building. The irregularity within the building structures may be due to irregular

distributions in their mass, strength and stiffness along the height of building. Whilst such

buildings are built in high seismic zones, the analysis and design turns into more complexes.



Vertical irregularities are one of the major reasons of failures of structures during

earthquakes. For example, structures with soft storeys were the most notable structures

which collapsed. So, the effect of vertically irregularities in the seismic performance of

structures becomes really important. Height-wise changes in stiffness and mass render the

dynamic characteristics of these buildings different from the regular building. IS 1893

definition of vertically irregular structuresstates that the irregularity in the building

structures is due to irregular distributions in their mass, strength and stiffness along the

height of building. When such buildings are constructed in high seismic zones, the analysis

and design becomes more complicated. There are two types of irregularities-

1. Vertical Irregularities

2. Plan Irregularities

1.3.1 VERTICAL IRREGULARITIES ARE MAINLY OF FIVE TYPES-

i.a) Stiffness Irregularity — Soft Storey-A soft storey is one in which the lateral stiffness

isless than 70 percent of the storey above or less than 80 percent of the average lateral

stiffness of the three storeys above.

i.b) Stiffness Irregularity — Extreme Soft Storey-An extreme soft storey is one in which

the lateralstiffness is less than 60 percent of that in the storey above or less than 70 percent

of the average stiffness of the three storeys above.

ii) Mass Irregularity-Mass irregularity shall be considered to exist where the seismic

weight of anystorey is more than 200 percent of that of its adjacent storeys. In case of roofs

irregularity need not be considered.

iii) Vertical Geometric Irregularity- A structure is considered to be Vertical geometric

irregularwhen the horizontal dimension of the lateral force resisting system in any storey is

more than 150 percent of that in its adjacent storey.

iv) In-Plane Discontinuity in Vertical Elements Resisting Lateral Force-An in-plane

offset of thelateral force resisting elements greater than the length of those elements.

v) Discontinuity in Capacity — Weak Storey-A weak storey is one in which the storey

lateralstrength is less than 80 percent of that in the storey above.



As per IS 1893, Part 1 Linear static analysis of structures can be used for regular structures

of limited height as in this process lateral forces are calculated as per code based

fundamental time period of the structure. Linear dynamic analysis is an improvement over

linear static analysis, as this analysis produces the effect of the higher modes of vibration

and the actual distribution of forces in the elastic range in a better way.

Buildings are designed as per Design based earthquake, but the actual forces acting on the

structure is far more than that of DBE. So, in higher seismic zones Ductility based design

approach is preferred as ductility of the structure narrows the gap. The primary objective

in designing an earthquake resistant structure is to ensure that the building has enough

ductility to withstand the earthquake forces, which it will be subjected to during an

earthquake.

In essence all the loads are dynamic including the self-weight of the structure because at

some point in time these loads were not there. The distinction is made between the dynamic

and the static analysis on the basis of whether the applied action has enough acceleration

in comparison to the structure's natural frequency. Structural dynamics, therefore, is a type

of structural analysis which covers the behaviour of structures subjected to dynamic

(actions having high acceleration) loading. Dynamic loads include people, wind, waves,

traffic, earthquakes, and blasts. Any structure can be subjected to dynamic loading.

Dynamic analysis can be used to find dynamic displacements, time history, and modal

analysis by using the software’s like STAAD PRO & ETABS.

1.4 Method of analysis:

1.4.1 seismic analysis:

Seismic analysis is a major tool in earthquake engineering which is used to understand the

response of buildings due Response Spectrum Analysis to seismic excitations in a simpler

manner. In the past the buildings were designed just for gravity loads and seismic analysis

is a recent development. It is a part of structural analysis and a part of structural design

where earthquake is prevalent.

There are different types of earthquake analysis methods. Some of them used in the

project are

Response Spectrum Analysis



Time History Analysis

Response spectrum method: In this concept the multiple modes of vibration of a structure can be used. This analysis can

be used in many building codes for all except for simple or complex structures. The

vibration of a building is defined as the combination of many special modes that are in a

vibrating string corresponding to the “harmonics”. Computer aided structural analysis is

used to determine these mode shapes for the structure. For every mode shape, from design

spectrum responses are studied, with the help of parameters such as modal participation

mass and modal frequency, and then they are combined to provide an evaluation of the total

responses of the structure.

Time history analysis:

It is known as Time history analysis. It is an important technique for structural seismic

analysis especially when the evaluated structural response is nonlinear. To perform such an

analysis, a representative earthquake time history is required for a structure being

evaluated. Time history analysis is a step-by-step analysis of the dynamic response of a

structure to a specified loading that may vary with time. Time history analysis is used to

determine the seismic response of a structure under dynamic loading of representative

earthquake.



CHAPTER 2

Literature review:

2.1 A Study on design of vertically irregular RC building frames by Ankesh and

Biswobhanu, NIT Odisha.

Seismic analysis and design of vertically irregular rc building frames proposed by Ankesh

Sharma and BiswobhanuBhadra of National Institute of Technology Rourkela Odisha,

India According to results of RSA, the storey shear force was found to be maximum for the

first storey and it decreased to a minimum in the top storey in all cases and mass irregular

building frames experience larger base shear than similar regular building frames and the

stiffness irregular building experienced lesser base shear and has larger inter storey drifts

2.2 A Study on Dynamic analysis of multi-storey building for different shapes by

Rizwan and Peera, P.G student, JNTUA, Anantapura.

Dynamic analysis of multi-storey building for different shapes proposed by Mohammed

Rizwan Sultan*and D. GousePeera Department of civil engineering P.G student, JNTUA,

Anantapura . The aim of this study is to grasp the behaviour of the structure in high seismic

zone and also to evaluate Storey overturning moment, Storey Drift, Displacement in a 15

storey-high building on four totally different shapes like Rectangular, L-shape, H-shape,

and C-shape. Result has been proved that Irregular shapes are severely affected during

earthquakes especially in high seismic zones and C shaped building is more vulnerable

compare to all other different shapes.

2.3 A Study on Response of multi-storey regular and irregular buildings by

‘Md.Mashfiqulislam’ a senior lecture, AUST, Dhaka, Bangladesh.

‘Response of multi-storey regular and irregular buildings weight under static and dynamic

loading in context of Bangladesh’ proposed by ‘Md. Mashfiqulislam’ a senior lecturer,

department in civil engineering, ahsanullah university technology (AUST), Dhaka,

Bangladesh. The aim of this paper is to assess the seismic vulnerability and response of

regular and irregular shaped multi-storey building of identical weight in context of

Bangladesh (zone-2) which is seismically active region including north eastern part of India

by using response spectrum analysis method.



2.4 A Study on dynamic effect on unsymmetrical building (RCC & Steel) by

‘PralobhS.Gaikwad’, ‘Prof.Kamhaiya K. Talani.

‘Study of dynamic effect on unsymmetrical building (RCC & Steel) by ‘Pralobh S.

Gaikwad’, ‘Prof.Kamhaiya K. Talani’ there main objective of earthquake engineer is to

design and build a structure in such a way that damage to the structure during the earthquake

is minimize. The analysis carried by using ETABS software. Permissible limit of storey

drift 12 mm as per IS1893 By analysis of G+9 storey structure it is found that maximum

storey drift of RCC structure is 0.679.

2.5 A Study on dynamic equations for system of irregularly shaped plane bodies by

Oleg Vinogradov.

Study on Dynamic equations for system of irregularly shaped plane bodies by Oleg there

mainobjective is the computer simulation of dynamic behavior of irregularly shaped

granular-type materials by the system of differential and algebraic equations. Also use of

Lagrange’s equations for the simplicity. As a result, an explicit form of the governing

equations and analytical cancellation of the terms in Lagrange’s equations, lead to more

efficient and accurate (in term of accumulated error) computer simulations.

2.6 A study on Seismic Response of R.C.C Building with Soft Storey Dr.SaraswatiSetia

and Vineet Sharma, NIT, Kurukshetra, India.

Study on Seismic Response of R.C.C Building with Soft Storey by

Dr.SaraswatiSetiaandVineet Sharma, Associate Professor, NIT Kurukshetra, India and

lecturer, Civil Engineering Department. G.P. Nilokheri Haryana, India. Their main aim to

study behavior of R.C.C Building under seismic loading in +x direction, +z direction, -x

direction, -z direction. Result are Lateral displacement is largest in bare frame with soft

storey defect both for earthquake force in X-direction as well as in z-direction for corner

columns as well as for intermediate columns. Displacement of intermediate column is more

by 0.02% and 0.04% in X and Z-direction respectively w.r.t. corner column. Minimum

displacement for corner column is observed in the building in which a shear wall is

introduced in X-direction as well as in Z-direction. Building having masonry infill in upper

floors and with increased column stiffness of bottom story and building with shear wall in

core has a small first storey displacement of about 18% and 16% respectively of that of

building having masonry in fill in upper floors only.



2.7 A study on Earthquake Analysis of High Rise Building with and Without Infilled

Walls ByWakchaure M.R, Ped S. P Amrutvahini College of Engineering,

Sangamner.

A study on Earthquake Analysis of High-Rise Building with and Without In filled

WallsByWakchaure M.R, Ped S. P H.O.D of Civil Engineering Department at Amrutvahini

College of Engineering, Sangamner, and Maharashtra. The result of the present study show

that structural infill wall have very important effect on structural behaviour under

earthquake effect. On structural capacity under earthquake effect displacement and relative

story displacement are affected by the structural irregularities. Regarding with the result,

infill walls are very important effect on structural behaviour. 1) Base Shear: From the

results it is shown that due to infill walls in building the base shear is increased from 2.49

to 7.81%. and the difference is 4.86%. 2) Displacement: The displacements at top story of

the building with infill’s wall for single strut reduce 0.77% to 0.39%. 3. Storey Drift: Storey

drift for infilled wall model is within permissible limit. Storey drift is reduced 0.0034% to

0.018%. Due to infill walls in the High Rise Building top storey displacement is reduces.

Base shear is increased.

2.8 Comparative Static and Dynamic Study on Seismic Analysis of Uniform and Non

Uniform Column Sections in a Building Adhikari1 , Dr K. Rajasekhar Andhra

University Visakhapatnam.

This study is related to column analysis of uniform and non-uniform multi-storey building

under earthquake loading and to determine the critical behaviour of column using ETABS

software with the response spectrum method. The result of analysis areETABS gives less

value for dynamic shearby response spectrum method. Those values should be scaled

appropriately according to IS code 1893 - 2000 clause 7.8.2. Static approach gives higher

values of forces and moments which makes building uneconomical hence consideration of

dynamic approach is also needed. Lateral force at floor level due to static shear is almost

same for both building but due to dynamic shear it is less in storey 4 & 5 in case1 and more

in storey 8.



2.9 A Study on review paper on seismic responses of multi-stored RCC building with

mass irregularity by Sagar R Padol, Rajashekhar S. Talikoti.

In this project work seismic analysis of RCC buildings with mass irregularity at different

floor level are carried out. Here for analysis different time histories have been used. This

paper highlights the effect of mass irregularity on different floor in RCC buildings with

time history and analysis is done by using ETABS software many of the studies have shown

seismic analysis of the RCC structures with different irregularities such as mass

irregularity, stiffness and vertical geometry irregularity. Whenever a structure having

different irregularity, it is necessary to analyze the building in various earthquake zones.

From many past studies it is clear that effect of earthquake on structure can be minimize by

providing shear wall, base isolation etc.

2.10A study on Review Paper on Dynamic Analysis of Building by Pralobh S. and

Kanhaiya K.

A study on Review Paper on Dynamic Analysis of Building by Pralobh S. Gaikwad

andKanhaiya K. Tolani, Late G. N. Sapkal College of Engineering, Nasik, Maharashtra,

the dynamic effect on the building with symmetrical configuration for the analysis purpose

basic parameter taken are lateral force, base shear, storey drift , storey shear and results are

interpreted on the bases of this parameter. Lack of research have observed on the building

with unsymmetrical configuration thus in the further work i will compared the building

with unsymmetrical configuration. Due to the unsymmetrical the important factor to be

considered is torsion.

2.11 summary of the literature review

From all the above literature paper we come to know that the review on the irregular

structures has less papers comparatively to other topics. From the above papers the problem

was learnt, analysed and solved. The topic which we are doing has very less journal papers

published.



Anthology

Table 2.1: Anthology of Dynamic Analysis of Building with Plan Irregularity.



Table 2.2: Anthology of Dynamic analysis of structures subjected to earthquake load.



Table 2.3: Anthology of Dynamic analysis of multi storey structure for different shapes



Table 2.4: Anthology of Seismic Analysis of a Multi- Storeyed Building with Irregular Plan



Table 2.5: Anthology of Dynamics analysis of RC regular and irregular structures using Time History Method



CHAPTER 3

3.1 OBJECTIVES:

1. Understand the dynamic behaviour of structural frames.

2. Understand the behaviour of regular and irregular structures under dyanamic loading

conditions.

3. Analyse the dynamic behaviour of regular structure using responce spectrum method.

4. Analyse the behaviour of regular structure on sloping terrain conditions.

5. Analyse the vertically irregular structure under sloping terrain conditions.

6. To recommend a proper awareness for the construction of structures under sloping terr

ain conditions



3.2 Methodology:

The problem has been identified through the review of literature. the identified problem an

d suitability of proper methodology for the solution was found out through software simul

ation and analysis. In this research analysis of irregular structure has done through ETAB

S software. For the proper working of software validation was done for one of the journal

article. Parametric study includes analysis of regular structure, structure on sloping ground

and vertical irregular structure under sloping ground has been done through response spec

trum analysis. Comparison of result like base shear, overturning moment, storey displace

ment, storey shear, centre of stiffness, centre of load, centre of gravity has been done for t

he above mentioned structure. A sample flowchart is indicated below fig 3.1.

Fig 3.1 flowchart of methodology

Software Validation

Software Learning

Results Discussion and Conclusion

Parametric Studies



3.3 ETABS software:

ETABS is an engineering software product that caters to multi-story building analysis and

design. Modelling 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 ETABS. For a sophisticated assessment of seismic performance, modal and direct-

integration time-history analyses may couple with P-Delta and Large Displacement effects.

Nonlinear links and concentrated PMM or fibre hinges may capture material nonlinearity

under monotonic or hysteretic behaviour. Intuitive and integrated features make

applications of any complexity practical to implement. Interoperability with a series of

design and documentation platforms makes ETABS a coordinated and productive tool for

designs which range from simple 2D frames to elaborate modern high-rises.

3.3.1 Modelling of Structural Systems

Fundamental to ETABS modelling is the generalization that multi-story buildings typically

consist of identical or similar floor plans that repeat in the vertical direction. Modelling

features that streamline analytical-model generation, and simulate advanced seismic

systems, are listed as follows:

Templates for global-system and local-element modelling

Customized section geometry and constitutive behaviour

Grouping of frame and shell objects

Link assignment for modelling isolators, dampers, and other advanced seismic systems

Nonlinear hinge specification

Automatic meshing with manual options

Editing and assignment features for plan, elevation, and 3D views



3.3.2 Loading, Analysis and Design

Once modelling is complete, ETABS automatically generates and assigns code-based

loading conditions for gravity, seismic, wind, and thermal forces. Users may specify an

unlimited number of load cases and combinations.

Analysis capabilities then offer advanced nonlinear methods for characterization of static-

pushover and dynamic response. Dynamic considerations may include modal, response-

spectrum, or time-history analysis. P-delta effect account for geometric nonlinearity.

Given enveloping specification, design features will automatically size elements and

systems, design reinforcing schemes, and otherwise optimize the structure according to

desired performance measures.

3.3.3 Output

Output and display formats are also practical and intuitive. Moment, shear, and axial force

diagrams, presented in 2D and 3D views with corresponding data sets, may be organized

into customizable reports are also available in detailed section cuts depicting various local

response measures. Global perspectives depicting static displaced configurations or video

animations of time-history response are available as well.

3.4 Response-spectrum analysis

Response spectrum analysis is a linear-dynamic statistical analysis method which measures

the contribution from each natural mode of vibration to indicate the likely maximum

seismic response of an essentially elastic structure. Response-spectrum analysis provides

insight into dynamic behaviour by measuring pseudo-spectral acceleration, velocity, or

displacement as a function of structural period for a given time history and level of

damping. It is practical to envelope response spectra such that a smooth curve represents

the peak response for each realization of structural period.

Response-spectrum analysis is useful for design decision-making because it relates

structural type-selection to dynamic performance. Structures of shorter period experience

greater acceleration, whereas those of longer period experience greater displacement.

Structural performance objectives should be taken into account during preliminary design

and response-spectrum analysis.



CHAPTER 4

4.1 Validation of ETABS software:

Validation is done with data respect to the regular G+12 storey structure, from the

research paper [1]. Response spectrum analysis is done by applying seismic loads.

PLAN DETAILS:

The structure is 32m in x-direction & 24m in y-direction with columns spaced at 4m from

centre to centre. The storey height is kept as 3m. Basically model consists of multiple bay

fifteen storey building, each bay having width of 4m. The storey height between two floors

is 3.0m with beam and column sizes of 0.45x0.45m respectively and also the slab thickness

is taken as 0. 125m.Shape of the building for all the cases is shown in figure. The material

properties and geometry of the model are described below in table 4.1.

TABLE 4.1: The material properties and geometry of the model

Dimensions Values

Length X width 32m X 24m

Number of stories 15

Support conditions Fixed

Storey height 3 m

Grade of concrete 30 Mpa

Grade of steel Fe415

Size of columns from 1-5 storey 650mm x 650mm


Size of beams 450mm x 450mm

Height of parapet wall 0.9m

Thickness of main wall 230mm

Thickness of parapet wall 115mm



Load details for the model is given in the below table 4.2

TABLE 4.2: Load details of the model

Loads Values

Wall load 13.8 KN/m

Wall load (of Parapet wall at top floor): 2.07 KN/m

Live load:

Floor load 4KN/m2

Roof load 2KN/m2

Seismic Load:

Seismic zone V (Z=0.36)

Soil type II

Importance factor 1

Response reduction factor 5

Damping 5%

All the results are given below. We have selected rectangular section from the paper [1].

And the comparison of results is also given below.

Fig 4.1 software rendered model of validation structure



Data from dynamic analysis performed is given in the table 4.3 and the data from

dynamic analysis from [1] is given in the table 4.4.

TABLE 4.3: Data from dynamic analysis performed

TABLE 4.4: Data from dynamic analysis from [1]

modes time period Frequency modal mass participation ratios

X trans Y trans

1 1.332729 0.75034 0 77.0963

2 1.303713 0.767039 77.3483 0

3 1.200129 0.833243 0 0

sum of 12 modes 94.6027 94.5829

Modes time period Frequency modal mass participation

ratios

X trans Y trans

1 1.57 0.637 0 75.5

2 1.524 0.656 75.82 0

3 1.372 0.729 0 0

sum of 12 modes 93.32 93.28



The below Fig 4.2 and Fig 4.3 is the graph plotted for the Storey displacement. The graph is plotted for displacement vs Storey. The results for storey displacement are given in the table 4.5.

Fig 4.2: Graph plotted for the Storey displacement

Fig 4.3: Graph plotted for the Storey displacement [1]

TABLE 4.5: The results for storey displacement

Result obtained Result of the paper

43 mm 38mm

0 0.2352.744

6.229.871

13.43816.85

20.80624.49

27.931.03

33.86336.376

38.5340.27741.56842.389

0

5

10

15

20

25

30

35

40

45

base plinth GF 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th 12th 13th 14th

DIS

PLA

MEN

T (M

M)

STOREY

STOREY DISPLACEMENT

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

storey



The below Fig 4.4 and Fig 4.5 is the graph plotted for the Storey drift. The graph is plotted for storey drift vs Storey. The results for storey drift are given in the table 4.6.

Fig 4.4: Graph plotted for the Storey drift

Fig 4.5: Graph plotted for the Storey drift [1]

TABLE 4.6: The results for storey drift


4.3 mm 9mm

0.8

2.94

4.1074.344 4.359 4.299 4.152 4.182 4.011 3.834 3.651

3.1652.817

1.8

1.14

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 2 4 6 8 10 12 14 16

STO

REY

DR

IFT

(MM

)

STOREY

storey drift (mm)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

STOREY



The below Fig 4.6 and Fig 4.7 is the graph plotted for the Storey Overturning moment. The graph is plotted for storey moment vs Storey. The results for storey Overturning moment are given in the table 4.7.

Fig 4.6: Graph plotted for the Storey overturning moment

Fig 4.7: Graph plotted for the Storey overturning moment [1]

TABLE 4.7 The results for storey overturning moments


119000 KN 112000 KN

0

20000

40000

60000

80000

100000

120000

140000

MO

MEN

T

STOREY

STOREY OVERTURNING MOMENT

1 2 3 4 5 6 7 8 9 101112 13 141516

storey



The below Fig 4.8 and Fig 4.9 is the bar graph plotted for the Storey Shear. The graph is plotted for storey Shear vs Storey. The results for storey Shear are given in the table 4.8.

Fig 4.8: Graph plotted for the Storey Shear

Fig 4.9: Graph plotted for the Storey Shear [1]

TABLE4.8: The results for storey Shear

4166.3

3294.6

2351.61

633.19

0

500

1000

1500

2000

2500

3000

3500

4000

4500

1st storey 5th storey 10th storey 15th storey

STO

REY

SH

EAR

(K

N)

storey shear KN

storey Storey shear obtained storey shear [1]

1st storey 4166.3 3000

5th storey 3294.6 2800 10th storey 2351.61 2000

15th storey 633.19 500

Storey shear (KN)

3500

3000

2500

2000

1500



4.2 Conclusion of validation

Validation of the software has been done by selecting a suitable journal paper [1]

Comparison of modal mass participation ratios was done using ETABS software.

A very less variation of 1.3 % was found.

Comparison of storey displacement values resulted in 18% variation.

The comparison of storey drift value resulted in the difference of 3.76 mm.

The comparison of storey overturning moment obtained was 13.8% greater than the

value in paper.

The Storey shear results we obtained were nearly 1000 KN difference

Seeing all the results we obtained and validation of software is also done, it is

expected to proceed with the parametric studies.



CHAPTER 5

Parametric studies

5.1 Analysis of regular structure under plane ground

Table 5.1: Plan details of the regular structure

Dimensions Values




Storey height 3 m






Table 5.2: Details of the seismic loads

Loads Values

Live load: 5KN/m2

Floor finish 1KN/m2

Seismic Load:


Soil type II

Importance factor 1


Damping 5%



Fig 5.1 software rendered model of regular structure



5.2 Analysis of structure under sloping ground

Table 5.3: Plan details of the structure under sloping ground

Dimensions Values




Storey height 3 m






Slopes Deducted height

1:25 200 mm

1:50 100 mm

1:100 50 mm

1:200 25 mm


Loads Values

Live load: 5KN/m2

Floor finish 1KN/m2

Seismic Load:


Soil type II

Importance factor 1


Damping 5%



5.2.1 Structure under sloping ground 1:25

Fig 5.2 software rendered model of structure under sloping ground 1:25















Results of parametric studies 5.2

REGULAR 1 in 25 1 in 50 1 in 100 1 in 200

Fig 5.6 Bar graph for Storey Shear results


Fig 5.7 Bar graph for Storey Displacement results

8187.04 8230.0504

9440.84

9681.71

8183.83 8148.56 8187.71 8188.97 8189.6 8211.18

7000

7500

8000

8500

9000

9500

10000

EQX- EQY- EQX- EQY- EQX- EQY- EQX- EQY- EQX- EQY-

STOREY SHEAR (KN)

60.72

59.785

54.78 54.6

59.8559.46

60.3159.64

60.5259.72

51

52

53

54

55

56

57

58

59

60

61

62


STOREY DISPLACEMENT (mm)




Fig 5.8 Bar graph for Storey Stiffness results

9592254 9761572

5419863

24759971816378 1817984 1754401 1771623 1730347 1753660

0

2000000

4000000

6000000

8000000

10000000

12000000


STOREY STIFFNESSS (KN/m)



5.3 Analysis of Irregular structure under plane ground

Fig 5.9 software rendered model of irregular structure under plane ground



5.3 Analysis of Irregular structure under sloping ground

Table 5.5: Plan details of the structure under sloping ground

Dimensions Values




Storey height 3 m






Slopes Deducted height

1:25 200 mm

1:50 100 mm

1:100 50 mm

1:200 25 mm


Loads Values

Live load: 5KN/m2

Floor finish 1KN/m2

Seismic Load:


Soil type II

Importance factor 1


Damping 5%




Fig 5.10 software rendered model of irregular structure under sloping ground 1:25















Results of parametric studies 5.4


5.14 Bar graph for Storey Shear


5.15 Bar graph for Storey Displacement

8019.76

6586.48

9540.25

7837.17 8034.52

6568.03

8029.63

6578.33

8026.95

6584.31

0

2000

4000

6000

8000

10000

12000


STOREY SHEAR (KN)

51.98

54.02

47.33

49.17

51.47

53.75

51.74

53.9

51.87

53.96

42

44

46

48

50

52

54

56


STOREY DISPLACMENT (mm)




5.16 Bar graph for Storey Stiffness

98500768518682

6034806

2592627 18649091586036 18020011547478 1777733

1532448

0

2000000

4000000

6000000

8000000

10000000

12000000


STOREY STIFFNESS (KN/m)



The results of coordinates of centre of load

Table 5.7: The results of centre of load

Fig 5.16: Graph showing the comparison of centre of load

15.3614.23 14.31

15 15.8116.45

13.88 14.79 14.06

17.29

0

2

4

6

8

10

12

14

16

18

20

NORMAL 1 in 25 1 in 50 1 in 100 1 in 200

COORDINATES OF CENTER OF LOAD REGULAR

IRREGULAR

Regular (m) Irregular (m) Eccentricity (m)

Normal 15.36 16.45 1.09

1 in 25 14.23 13.88 0.35

1 in 50 14.31 14.79 0.48

1 in 100 15 14.06 0.94

1 in 200 15.81 17.29 1.48



Chapter 6

Results and discussion

6.1 Comparison of point of action of centre of load:

The centre of area for remain constant for all the structures.

The centre of mass and centre of stiffness varies with the sloping ground and vertical

irregularity creating enormous eccentricity in the structure.

The centre of load for the regular structure without any irregularity was found to be

15.36 m where as for the vertically irregular structure in a flat ground was 16.45 m for

which the eccentricity is 1.09, Similarly, the eccentricity of the structure on the sloping

terrain condition without vertical irregularities for the slope 1:25, 1:50, 1:100, 1:200 are

1.13 m, 1.05 m, 0.36 m and 0.45 m respectively.

The centre of load for the vertical irregular in flat ground was 16.45 m. the eccentricity

of the structure on the sloping terrain condition without vertical irregularities for the

slope 1:25, 1:50, 1:100, 1:200 are 2.57 m, 1.66 m, 2.39 m and 0.82 m respectively.

Comparing the above results we come to know that for the terrain slope of 1:100 the

structure without any irregularity can be constructed.

6.2 Comparison of results of Storey shear

The results of storey shear of the regular structure on flat ground are compared with

the other structures of sloping terrain condition of slope 1:25, 1:50, 1:100, 1:200. The

storey shear results have been tabulated for the earthquake load in both X and Y

direction.

The results obtained for the regular structure are 8187.04 KN in X direction and

8230.0504 KN in Y direction. Whereas for the slopes, the results are tabulate which

can be seen in table 5.6.

The storey shear results are found out for the vertical irregular structure under sloping

terrain and also for the vertical irregular structure on flat ground. The results have

been tabulated in the below table5.14.

From the results we notice that the regular structure under sloping terrain slope 1:100

gives us the similar result as that of the regular structure on the flat ground.



6.3 Comparison of Centre of stiffness

The centre of stiffness for a regular structure at flat ground and structure with sloping

terrain acts at 15.14 m in X direction and 15.114 m in Y direction.

The centre of stiffness for vertical irregularity structure at flat ground and structure with

sloping terrain acts at 15.14 m in X direction and 15.114 m in Y direction upto 6th storey

and centre of stiffness for 7th and 8th storey is 15.75 m in X direction and 10.53 m in Y

direction. Similarly, for 9th and 10th storey, Centre of stiffness is 15.29 m at X direction

and 5.22 m in Y direction.

The sloping terrain does not influence in the centre of stiffness of the structure.

6.4 Comparison of results of storey stiffness

The results of storey stiffness of the regular structure on flat ground are compared

with the other structures of sloping terrain condition of slope 1:25, 1:50, 1:100, 1:200.

The storey stiffness results have been tabulated for the earthquake load in both X and

Y direction.

The results obtained for the regular structure are 9592254 KN/m in X direction and

9761572 KN/m in Y direction. Whereas for the slopes, the results are tabulate which

can be seen in table 5.8.








6.5 Comparison of results of storey displacement

The results of storey displacement of the regular structure on flat ground are

compared with the other structures of sloping terrain condition of slope 1:25, 1:50,

1:100, 1:200. The storey shear results have been tabulated for the earthquake load in

both X and Y direction.

The results obtained for the regular structure are 60.72 mm in X direction and 59.785

mm in Y direction. Whereas for the slopes, the results are tabulate which can be seen

in table 5.7.








Chapter 7

CONCLUSION

The dynamic behaviour of the structure has been understood from the validation of

journal [1].

From the analysis for both vertically regular and vertically irregular structure the

behaviour of the structure has been studied under dynamic loading.

The dynamic analysis of the vertically regular and vertically irregular structure has been

done using response spectrum method.

The behaviour of the vertically regular and vertically irregular structure under sloping

terrain conditions has been analyse through the response spectrum method.

We conclude that the vertically regular structure under sloping terrain condition 1:100

can be constructed even in earthquake prone areas.



REFERENCES:

1 Mohammed Rizwansultan and Gousepeera on Dynamic Analysis of multi-storey building for different shapes international journal of innovative research in advanced engineering (ijirae) issn: 2349-2163issue 8, volume 2 (august 2015).

2 MalavikaManilal and S.V.Rajeeva on Dynamic Analysis of RC Regular and

Irregular Structures using Time History Method of international journal of research in Engineering and technology.

3 Komal R Bele and S B Borghate on Dynamic analysis of building with Plan Irregularity of journal of civil Engineering and Environmental Technology, print issn 2349-8404, volume 2 (April June2015).

4 Dr. S K Dubey, Prakash Sangamnerkar and Ankit Agarwal on Dynamic Analysis of Structures subjected to Earthquake Load of International Journal of Advance Engineering and Research Development volume 2 issue 9 (sept 2015).

5 K Upendra Reddy and Dr. E Arunakanthi on Dynamic Analysis of Multistorey Structures for different shapes of IJTIMES Volume 3, Issue 12 (Dec 2017).

6 N Mohan Reddy and Dr. E Arunakanthi on Seismic analysis of Multistoreyed Building with Irregular plan configuration using ETABS of IJSRD volume 3, issue 9, 2015.

7 IS code book 1893 (part 1) 2002, Indian standard criteria for Earthquake resistant design of structures.

8 Some Concepts in Earthquake behaviour of buildings by C.V.R Murty, RupenGoswami, A.R. Vijaya Narayana and Vipul V Mehta. 9

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Dynamic Analysis of Irregular Structures Using ETABS Software

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