Base Isolation

Seismic Vibration Control of Building using Base Isolation Technique with Friction Dampers
CHAPTER 1
INTRODUCTION
1.1 General
Earthquake in the simplest terms can be defined as Shaking and vibration at the
surface of the earth resulting from underground movement along a fault plane. The
vibrations produced by the earthquakes are due to seismic waves. Seismic waves are the
most disastrous one. However, modern high-rise buildings and tall structures cannot
conveniently be geared up with these techniques. The safety and serviceability of any
structure is thus endangered with the increasing elevation. As per the standard codes, a
structure that can resist the highest earthquake that could possibly occur in that particular
area can be called as an earthquake resistant structure.
However, the most efficient way of designing earthquake resistant structure would
be to minimize the deaths as well as minimize the destruction of functionality of the
structural element. The most disastrous thing about earthquake is its unpredictability of
time and place of occurrence. These possess a great challenge to the economy and safety
of structure. From the past and few present records, the world has experienced number of
destroying earthquakes, causing in number of increase the loss of human being due to
structural collapse and severe damages to structure. Because of such type of structural
damages, during seismic (earthquake) hazards clearly explains that the buildings /
structures like residential buildings, public life-line structures, historical structures and
industrial structures should be designed to seismic force design and very carefully to
overcome from the earthquake hazards. The approach in structural design using seismic
response control device is now widely accepted for structure and frequently used in civil
engineering field. Structural control concept into a workable technology and such devices
are installed in structures.
For controlling earthquake vibrations, Base isolation technique and Friction

dampers are being used in this study. Base isolation system decouples the superstructure
from substructure and hence reduces the effect of earthquake on the structure where as
friction dampers increase the stiffness of the structure and hence makes the structure
earthquake resistant. Till now there have been studies conducted on the behavior of the
Concrete framed structure upon the incorporation of either base isolation systems or the
friction dampers as the passive earthquake energy dissipating devices in order to mitigate
Department of Civil Engineering, UVCE Page 1

the earthquake effects on the structures. An attempt has been made in this work to check
the effectiveness of these devices as a combined control strategy for the structure.
1.2 Objectives of the study

A thorough literature study has been conducted studying journal papers related to
the use of base isolation technique and friction dampers in the reinforced concrete
structures for reducing the earthquake effects and the following objectives are set for the
study,
1. To perform Response Spectrum Analysis on an irregular “C” shaped concrete

framed structure using ETABS software.
2. To design the Lead Rubber Bearing as a base isolation system for the considered
multi-storey building and to study the seismic behaviour of the structure upon
incorporation of LRB to it.
3. To study the seismic response parameters of the considered structure with the
incorporation of just Friction Dampers to it.
4. To carry out seismic analysis by introducing both LRB and Friction Dampers as a
Dual system in the considered structure and study the Response parameters.
5. To conduct comparative study on all the four cases, reinforced concrete framed
structure, framed structure with LRB, framed structure with Friction dampers,
framed structure with LRB and Friction dampers, by considering time period, base
shear, storey displacement and storey drifts as the response parameters.
1.3 Organization of thesis

This dissertation is organized in six chapters. Chapter one gives brief introduction
about earthquake phenomenon and present objectives of the thesis. Chapter two includes
literature review of the use of Base isolation and Friction dampers in various studies, the
summary of literature and also the scope. Chapter three includes the details about the
Base isolation and Friction Dampers, classifications and their practical implementation
around the world. Chapter four includes details of methodology, analysis methods, about
the Etabs software, structural modeling sequence, designing procedures of Lead Rubber
Bearing, Friction dampers and of the analysis method used. Chapter five deals with the
results of the response parameters such as time period, base shear, storey displacement
and storey drifts. Chapter six winds up with conclusion of the thesis, inferences drawn on
the results and about the future scope of the study.

CHAPTER 2
LITERATURE REVIEW
2.1 General
There have been so many studies and researches done on these base isolation
systems and friction dampers which are used in minimising the damaging effects of
earthquake on the structures. Some of the literatures about these devices are as follows,
2.1 Literature review details on the use of Base Isolation

systems in buildings
Chandak N. R (2013), “Effect of Base Isolation on the Response of Reinforced
Concrete Building”.
In this paper, a parametric study on Reinforced Concrete building with fixed and
isolated base with rubber bearing and friction isolator are carried out using response
spectrum method. Here, the design spectra recommended by Indian Standard Code IS
1893-2002 (part -I) and Euro Code 8 are considered for comparison. The main objective
of this study is to investigate the differences caused by the use of different codes in the
dynamic analysis of multistoried RC building along with fixed and isolated base
condition. Two different floor plans that are symmetric and unsymmetric with torsional
irregularity are taken as sample building. To evaluate the seismic response of the
buildings, elastic analysis is performed using the computer program SAP2000. It is
observed from the comparative study that the building response with isolated base is very
less to that of building with fixed base in all the cases and IS code depict higher values in
all the cases with and without isolation, when compared to that of Euro code.
S.M. Dhawade(2014), “Comparative Study for Seismic Performance of Base Isolated

& Fixed Based RC Frame Structure”.
In this paper, the G+14 storied frame structure is taken to compare the seismic
effect of fixed base structure with respect to isolated structure. The (G+14) storied frame
structure is designed with base isolation by using the ETAB software. High Damping
Rubber Bearing is used as an isolator having efficient results for frame structure over the
fixed base structure than any other isolation system. The report concluded that the very
less values come for lateral loads by using High Damping Rubber Bearing. It has high
flexibility and energy absorbing capacity, so that during an earthquake, when the ground
vibrates strongly only moderate motions are induced within the structure itself.

Mohammued Irfan Faraaz and Amaresh S.Patil(2016),“Comparative Seismic
Analysis of Base Isolated and Fixed Based RC Frame Building”.
The study is performed to compare the effectiveness of base isolation over the
fixed based building and fixed based building with shear wall. For this study, 10 storied
R.C frame building is considered and Time History analysis is carried out for Bhuj
earthquake using ETABS 2015 software. The Lead Rubber Bearing is designed as per
UBC 97 code and the same was used for analysis of base isolation system. The results
obtained from the analysis were time period, deflection and base shear. The models
selected for analysis were fixed based building, fixed based building with shear wall and
base isolated building.
The installation of isolator in building at base level significantly increases the time
period of the structure, which means it reduces the possibility of resonance of the
structure giving rise to better seismic performance of the building.
Kishan Bhojani, Vishal B. Patel et al.(2017), “Seismic Vibration Control of Building

with Lead Rubber Bearing Isolator”.
This paper gives idea about base isolation system which can be used in multi-story
building to reduce seismic response of the structure. This paper represents the initialize
study of dynamic parameter like effective damping for four earthquake time history. In
this paper the optimum effective damping has been found out under the effect of Loma
Prieta earthquake time history. The parametric study has been conducted to evaluate the
effect on maximum displacement, maximum acceleration, maximum base shear in bare
frame and frame with isolator
From the results of the present study, the following conclusions are drawn:
1. It is observed that the Lead Rubber Bearing isolator is quite effective in reducing
the acceleration of building.
2. There exists the optimum value of damping of isolator.
3. The isolator is found to be effective in reducing the base shear of building.
Bhavana Balachandran and Susan Abraham (2018), “Effect of Base Isolation in

Multi-Storeyed RC Building”.
This study investigates the increase in time period and decrease in base shear due
to earthquake ground excitation, applied to superstructure of the building by installing
base isolated devices at the foundation level and then to compare the different concepts

between the fixed base condition and base isolated condition by using ETABS 2015
software.
In this study, G+3 and G+20 storey RCC building are used as test model.
Highrise, lowrise, plan irregular and vertical irregular buildings are considered for this
project. Lead rubber bearing is used as base isolation in this study. Linear time history
analysis with El-Centro time history data is considered for base isolated buildings. The
base shear and time period are compared from two time history analysis between fixed
and base isolated condition. It was observed that base isolation increases the time period
of the building and hence correspondingly reduces the base shear for all the cases
considered.
2.3 Literature review details on the use of Friction Dampers

in buildings
S.S. Sanghai(2017), “Seismic Response of Unsymmetric Building with Optimally

placed Friction dampers”.
This paper deals with the use of friction damper as a passive dissipative device in
order to seismic retrofit of existing structures and discusses the optimal placement
criteria. To fulfill this objective, six storey and ten storey L-shaped buildings have been
modelled with five different damper location formats in SAP2000 subjected to El Centro
and Uttarkashi earthquake records. Non-Linear Modal Time History Method has been
used for the analysis and base shear, joint displacement, member forces and hysteresis
energy has been compared to find out most optimal damper location format. Hence it is
cocluded that the damper placement influences significantly the structural response. Also,
the study investigates that use of larger number of dampers do not always lead to the best
benefit.
Siddhant Kishore Laddha(2018), “Effect of Friction Damper on Seismic

performance of Multistoreyed Frame Structure in High Rise Building-A Review”.
From the literature study it is concluded that they include different types of
dampers like metallic dampers, viscous dampers, viscoelastic dampers, friction dampers
etc. however there have been few investigations for the combinations of dampers, its
advantages are discussed and a detailed review is carried out. By using the mechanical
dissipating devices, it has been found effective and their application form focus of the
study.

According to the previous studies and researches, the application of different
kinds of dissipation devices especially friction dampers have been discussed and
presented.
1. Building with dampers well reduced seismic quantities more as compared to
building with bracing.
2. It was found that the presence of dampers tremendously influences the stiffness of
structures. At high stiffness of dampers, the building behaved as rigidly connected
and at low or zero stiffness the building returned to unconnected condition. As the
number of story decreased the overall stiffness of building increased, to counter
act this damping stiffness was reduced relative to the higher number of story.
Whereas continuous decrease in effective stiffness of dampers showed increase in
story drift and base shear. The controlling devices reduce damages and also
increase the structural safety, serviceability and prevent the building from collapse
during the earthquake.
3. The damping devices reduced the story drifts, base shear, absolute acceleration
and the roof accelerations considerably when installed in a tall building.
4. The optimization of the damping system leads to significant savings in the cost of
the supplemental damping system.
Aparna Bhoyar and Bhupesh Nandurkar(2019), “Seismic Evaluation of Reinforced

Concrete Building with Friction Dampers”.
The paper mainly emphasized use of one such device friction damper for response
control of structures. In this paper the comparison of reinforced concrete building
connected with and without damper for G+5,G+10,G+15 storied building for seismic
zone IV is considered. Analysis is done using equivalent static method, response
spectrum method and time history method in finite element software package, ETABS
version 16.2.For seismic load combination IS 1893:2016 is used. The model analysis is
carried out by all four methods of analysis and results are discussed in terms of storey
displacement, storey drift, base shear, bending moment and axial forces. From result
obtained it is concluded that storey drift and displacement in friction damper building is
reduced where as base shear is less in building without damper.
S. Lakshmi Shireen Banu and Kothakonda Ramesh(2019), “Seismic Response Study

and Evaluation of Vibration Control of Elevated RCC Structure using Friction
Damper”.

This work deals with a 10 storey RCC building with square and rectangular
columns with the square and rectangular shape of the structure was analyzed with and
without friction damper in ETABS 2016. Four different cases of buildings with and
without friction damper have been analyzed in ETABS 2016. The study performs
response spectrum analysis and nonlinear time history analysis on these buildings. The
time history data of Bhuj earthquake is used in the analysis. In the present study the
effectiveness of friction damper in reducing the responses of a structure is evaluated. The
responses of the structure in terms of pseudo spectral acceleration, pseudo spectral
velocity and spectral displacement have been compared with and without friction damper.
2.4 Summary of literature review

The above literature gives a brief idea about effects of using Base isolation
systems and Friction dampers as seismic controlling measures and the summary of the
literature review is as follows,
1. The use of base isolation systems have well reduced the response parameters of
the structure, such as time period, base shear and storey drifts.
2. Lead rubber bearing (LRB) is the most commonly used and is the best isolation
system in order to make the structure more earthquake resistant.
3. Building with dampers well reduced seismic quantities more as compared to
building with bracing.
4. Structures with friction dampers increase the stiffness and hence reduce the
response parameters such a as storey displacement, storey drift and there is
increase in base shear in buildings with friction dampers.
5. The damper placement influences significantly the structural response and also,
the above study investigates that use of larger number of dampers do not always
lead to the best benefit.
2.5 Scope of the study

Here in this work, the study has been conducted to check the effectiveness of the
use of both lead rubber bearing and friction dampers as a dual system in order to mitigate
the earthquake effects of an eight storey RC structure.
The results of response parameters are compared for four different models,
conventional model, model with base isolation, model with friction damper and at last the
model with both base isolation system and friction dampers

CHAPTER 3
BASE ISOLATION AND FRICTION DAMPERS
3.1 BASE ISOLATION
Base isolation, also known as seismic base isolation or base isolation system is
one of the most popular means of protecting a structure against earthquake forces. It is a
collection of structural elements which should substantially decouple a superstructure
from its substructure resting on a shaking ground thus protecting a building or non-
building structure's integrity.
Base isolation system is the frequently adopted earthquake resistance system. It
reduces the effect of ground motion and thus leads to nullify the effect of earthquake to
on the structure.
Base isolation has become popular in last couple of decades in its implementations
in buildings and bridges. Base isolation has become a traditional concept for structural
design of buildings and bridges in high risk areas. The isolation system decouples the
structure from the horizontal components of the ground motion and reduces the
possibility of resonance as shown in Figure 3.1. This decoupling is achieved by
increasing the flexibility of the system, together with appropriate damping by providing
isolator at the basement level of the structure.
Figure 3.1: Typical explanation of base isolation system.

The principle in base isolation is,

1. To provide horizontal flexibility as well as vertical stiffness to the
building.
2. To lengthen the natural period of the building.
3. Damping in the Isolation system reduces the displacement.
4. It also reduces in the acceleration of the story.
Base isolation system should contain following:
1. An elastic mount to add enough vibration periods to the structure to lower
down the forces in the structure over.
2. An energy dissipater or damper to ease the deflection taking place between
the structure and the ground introducing the stiffness against the seismic
actions and wind loads.
Base isolation is required if any circumstances arise of the following:
1. Need to increase the safety of the structure.
2. Low lateral seismic forces needed.
3. Any existing building is not capable to withstand any earthquake.
4. Withstand small earthquakes without any damage.
5. Structure will not collapse in high level earthquake but some structural and
non-structural damage will occur.
In the category of structural control, base isolation system is
classified as passive control. Isolators are the major devices that are implemented
in a structural system for the purpose of isolation. The typical isolators and are classified
in below Figure 3.2.
Figure 3.2: Classification of isolators.

3.1.1 Lead-plug Rubber Bearings-(LRB)
Lead-plug rubber bearings were invented in New Zealand in 1975. The

mechanism of lead-plug rubber bearings is very similar to that of low-damping natural
rubber bearings. As show in Figure 3.3, there are three main pieces of equipment,
layers of steel plates, rubber layers and lead core, respectively. Same as the steel
shims in natural rubber bearings, the layers of steel provide vertical stiffness and the
layers of rubber supply the device with high lateral flexibility. Lead core is the
device that will supply extra stiffness to the isolators and appropriate damping to the
system.
Owing to current well-developed technologies, it is possible to manufacture lead-
plug rubber bearings with high stiffness and enormous shear deformation. Innovations in
materials and design related technologies such as analysis software and construction
methods have enabled the concept of isolation become a reality.
Figure 3.3: Typical lead rubber bearing.

3.2 Friction Dampers

Earthquake cause ground vibration due to the sudden release of energy. This
energy can be absorbed by using the vibration control device called friction damper. The
friction dampers are designed to have moving parts that will slide over each other during
a strong earthquake. When the parts slide over each other, they create a friction which
uses some of the energy from earthquake that goes into the building. This Friction damper
increases the stiffness of the building as a result vibration of the building is reduced. The
structural response to the seismic excitation has reduced by applying friction dampers
based on different construction techniques. Friction dampers come under passive seismic
control system does not require any external energy source to operate and is activated by
the earthquake input motion only. The friction surfaces of these systems are clamped with
pre-stressing bolts. Since the amount of energy dissipated is proportional to displacement
these systems are referred as displacement dependent systems. Contact surfaces of these
systems used are lead–bronze against stainless steel or Teflon against stainless steel.
Below Figure 3.4 depicts various types of Friction damper images.
Figure 3.4: Friction Damper.
3.3 Practical implementation

3.3.1 Base Isolation
Japan, the most seismically active country, employs it most extensively, with 4100
base- isolated commercial and institutional buildings as of Dec 2015.
Turkey, another very seismically active country, is also firmly committed to base
isolation methodology. One notable project there is an integrated Health Campus in
Istambul which contains almost 2000 isolators.
Other countries pushing base isolation include China, New Zealand, Chile, Peru,
Columbia and Ecuador.
In India, the first building incorporated with Base Isolation system is Bhuj
hospital building, Figure 3.5, in the state of Gujarat having 300 bed facilities. This base
isolated building sits on 280 lead-rubber bearings constructed in the year 2001. The
following figure shows that building.
Figure 3.5: Bhuj Hospital Building incorporated with Lead Rubber Bearing
isolators.
3.3.2. Friction Damper

The first building with seismic dampers, was built with Pall Friction dampers
[PFD] in 1987. It was Concordia University Library in Montreal, Figure 3.6. Since then,
PFDs are finding increasing application worldwide for new construction and retrofit of
existing buildings. These have been used in more than 300 buildings around the globe. In
1998, the Boeing engineers were in search for the best technology for seismic retrofit of
the Boeing Commercial Airplane Factory at Everett, WA, Figure 3.7. Since then, Boeing
is a repeat client and has retrofitted six more buildings with PFD‟s, saving more than $50
million.
The City of San Francisco chose PFDs for Moscone Convention Center, Figure
3.9, and saved tens of million dollars. PFDs have been used in Wilshire Grand in Los
Angeles as “Load-Limiting Device” and to control floor vibrations in Dancing Hall.
Canadian Embassies in Beijing, China; Tehran, Iran; and Islamabad, Pakistan, are
retrofitted with PFDs. In Montreal more than 30 buildings are with PFDs, Casino de
Montreal, Figure 3.10, Canadian Space Agency HQ, Figure 3.13; a dozen hospitals, and

University buildings; Palace de Congress. In Ottawa, about a dozen buildings including
St. Vincent Hospital and Justice Headquarters on Parliament Hill in Figure 3.11 and 3.14.
In India, PFDs are used for mitigating earthquake effects on LA GARDENIA Towers
South City, Gurgaon, which is an eighteen-storey apartment building, Figure 3.15.
Figure 3.6 Concordia University Library, Montreal.
Figure 3.7: Boeing Airplane Factory¸Everret, WA. Figure 3.8: 3M Gallon

Water Tower, Sacramento
Figure: 3.9: Moscone Convention Center, Figure 3.10: Casino de Montreal.

San Fransisco.

Figure 3.11: Saint Joseph Hospital, Patient Towers, Seattle, 40’ Soft Story,
Retrofitted with X-Brace PFDs.
Figure 3.12: Boeing Development Center near Figure 3.13: Canadian Space
Seattle,WA. Agency Headquarters.
Figure 3.14: Justice Headquarters Building, Ottawa.
Figure 3.15: La Gardenia Complex, Gurgaon, India.

CHAPTER 4
METHODOLOGY
4.1 Introduction
This chapter explains the methodology used in the study. It describes the software
package used in the modelling and describes some of the important area in the modelling
and analysis using ETABS in brief.
4.2 Methods of seismic analysis of structure

There are various methods of seismic analysis procedures available, out of which
choosing the correct method for the study is a crucial issue which can be done according
to the guidelines of the code of practice for earthquake resistant design of structures, that
is IS 1893(Part-1)-2016.
4.2.1 Static analysis

In the static analysis, the lateral loads that is seismic loads applied does not vary
with time, hence the name static analysis. Static analysis is again classified as Linear
Static analysis and Non-linear static analysis, which is Push over analysis.
4.2.2 Dynamic analysis

The illustration of maximum response of idealized SDOF system have some
period and damping, during earthquake. The max response plotted against undamped
natural period and for different damping values can be expressed as maximum absolute
acceleration, maximum relative displacement or maximum relative velocity. Here also
there are two types one is linear dynamic, Response spectrum analysis and the other is
non-linear dynamic analysis, Time history analysis.
Dynamic method includes response spectrum method and time history method. Response
spectrum is a plot of steady state response (displacement, velocity) with natural
frequency. This analysis method is used in assessing the response of linear systems with
multiple modes of vibration, although they are only accurate for low levels of damping.
Modal analysis is carried out to identify the modes, and the response in that mode can be
picked from the response spectrum. These peak responses are combined to estimate the
total response. Combination methods include Complete Quadratic Combination (CQC)
and Square Root of Sum of Squares (SRSS).
As per IS 1893 (Part 1): 2016 clause 7.7.1 dynamic analysis to be performed to all
buildings other than buildings of height less than 15 m located in Zone II. Dynamic
analysis may be performed by Response Spectrum Method. The base shear from dynamic
analysis shall not be less than the base shear calculated as per clause 7.6.2 of IS 1893:
2016.
In this study, equivalent static analysis and response spectrum analysis are done and
base shear is matched as mentioned in code by providing suitable scale factor. Results of
dynamic and static analysis are compared in terms of Storey drift, maximum Storey
displacement. Limits of the Storey displacement and Storey drift are checked as per IS
1893: 2016. Top Storey displacement should not exceed H/250 and Storey drift should
not exceed more than 0.004 h for earthquake load cases.
Base shear is the estimation of maximum expected lateral force coming on to

structure due to seismic ground motion at the base of the structure. Base shear is
calculated on the basis of structure mass and fundamental period of the structure.
Procedure for calculation of base shear as per IS 1893(Part 1): 2016 is explained below.
The design base shear,

Ah = Design Horizontal Acceleration Coefficient
W = Seismic Weight of Building
( )( )
( )
Where,
Z = Zone factor as per Table 3 of IS 1893(Part 1): 2016.
R = Response reduction factor as per Table 9 of IS 1893(Part 1): 2016.
I = Importance factor as per clause 6.4.2 of IS 1893(Part 1): 2016.
Sa/g depends on the fundamental time period (T) of structure and soil type.
- RC frame building with brick infill panels

√
0.75
- RC frame building without brick infill panels
h = Height of the building in m

d = Base dimension of the building in direction of earthquake shaking in m

4.2.3 Assumptions in Earthquake Resistant Design

 Earthquake causes impulsive ground motions, which are complex and irregular in
character, changing in period and amplitude each lasting for a small duration.
Therefore, resonance of the type as visualized under steady-state sinusoidal
excitations will not occur, as it would need time to build up such amplitudes.
 Earthquake is not likely to occur simultaneously with wind or maximum flood or
maximum sea waves.
 The value of elastic modules of materials, wherever required, may be taken as for
static analysis unless a more definite value is available for use in such condition.
4.2.4 Generation of Response Spectra

According to the code “IS 1893-2016”, India is classified into four seismic zones
i.e. The magnitude of earthquake that may occur in zone II is 5-6, in zone III is 6-6.5, in
zone IV is 6.5-7 and in zone V is more than 7. For analytical design of structures and
spectrum for seismic testing for the structures standing on rocks or soil for above four
zones and for different value of damping of the structure.
. Figure 4.1: Seismic Zones of India (as per IS 1893 – 2016).

The design horizontal seismic coefficient Ah for a structure is determined by the
following expression:
( )( )
( )
Provided that for any structure with T ≤ 0.1 s, the value of Ah will not be taken less than
Z/2 whatever be the value of I/R.
Where,
Z = Zone factor is for the Maximum Considered Earthquake (MCE) and service life of
structure in a zone. The factor 2 in the denominator of Z is used so as to reduce the
Maximum Considered Earthquake (MCE) zone factor to the factor for Design Basis
Earthquake (DBE).
I = Importance factor, depending upon the functional use of the structures, characterized
by hazardous consequences of its failure, post- earthquake functional needs, historical
value, or economic importance.
R = Response reduction factor, depending on the perceived seismic damage performance

of the structure, characterized by ductile or brittle deformations. Response factor given in
IS 1893-2016 (part 1 to 5) for corresponding structure
Sa/g = Average response acceleration coefficient, in case design spectrum is specifically

prepared for a structure at a particular project site; the same may be used for design at the
discretion of the project authorities. For rock and soil sites and based on appropriate
natural periods and damping of the structure. These curves represent free field ground
motion.
a) Equivalent Static Method
For Rocky or Hard soil sites (Soil type I)
Sa/g 2.50 0.00T0.10

1/T 0.40T4.00
0.25 T > 4.00 s

For Medium soil sites (Soil Type II)
Sa/g 2.50 0.00T0.10

1.36/T 0.55T4.00
0.34 T > 4.00 s
For Soft soil sites (Soil Type III)
Sa/g 2.50 0T0.67

1.67/T 0.67T4.00
0.42 T> 4.0
b) Response Spectrum Method
For Rocky or Hard soil sites (Soil type I)
1+15T; 0.00T0.10
Sa/g 2.50 0.10T0.40
1.00/T 0.40T4.00
0.25 T > 4.00 s
For Medium soil sites ( Soil Type II)
1+15T; 0.00T0.10
Sa/g 2.50 0.10T0.55
1.36/T 0.55T4.00
0.34 T > 4.00 s
For Soft soil sites (Soil Type III)
1+15T < 0.10 s

Sa/g 2.50 0.10T0.67
1.67/T 0.67T4.00
0.42 T> 4.0

Figure 4.2: Spectra curve for different soil strata (as per IS 1893 – 2016)
Zone factor: For Zone II = 0.10

For Zone III = 0.16
For Zone IV = 0.24
For Zone V = 0.36
Importance factor I = 1.50
Response reduction factor R = 5.00
4.3 Modelling using a finite element package ETABS

In the present work, an 8 Storey building is modelled with fixed base, with LRB
as base isolator, with Friction damper and fourth model consists of both LRB and
Friction damper. For this purpose the software used is ETABS-2017 version.
4.3.1 ETABS (Extended Three Dimensional Analysis of Building

System)
The modelling and analysis is carried using ETAB software. ETABS is a powerful
system developed by computers and structure Inc. Berkeley, California USA, which
improves the engineers analysis and design capabilities for structure.
ETAB is advanced, easy to handle specially developed for design and analysis of
building system. It has inbuilt graphical interface with ultimate modelling and design
procedures integrated using common database. The method for using program is very
easy. The user one should establish the gridlines, defines the material properties, place the
objects to the grid.
4.4 Description of analytical model
Figure 4.3: Plan of the building.
The above Figure 4.3 shows the plan of the building having 40m*20m as the
dimension, 5 and 5 bays along X and Y respectively. Figure 4.4 is about sequence of
methodology steps.

Modelling and Analysis of conventional building (RRC Model)

For gravity and seismic load
Find Support Reactions and Time period of the structure
Design the LRB for the corresponding input values

extracted from the above model
Model the building incorporating designed LRB(RCC

Model+LRB) and get the results
Model the building with Friction Dampers(RCC

Model+FD) at appropriate locations and get the results
Model the building with LRB and Friction(RCC

Model+LRB+FD) Dampers and get the results
The Responce parameters in terms of Time period ,Base

shear, Max Storey displacement and Storey Drift are plotted
and hence a comparison is carried out for all the models.
Figure 4.4: Flow chart of methodology.

Table 4.1: Storey Details.
Sl.
Storey Ht. of Storey(m)
No.
1 Base 0
2 Plinth 2
3 Storey1 3.2
4 Storey2 3.2
5 Storey3 3.2
6 Storey4 3.2
7 Storey5 3.2
8 Storey6 3.2
9 Storey7 3.2
10 Storey8 3.2
Total Height of building 27.6
4.4.1 Defining material Properties

 M30 Grade of concrete.
 HYSD rebar of Fe500 are considered.
4.4.2 Defining the Structural elements
 Column size of 350X450mm of M30 grade concrete utilizing Fe500 rebars.
 Beam size of 300X450mm of M30 grade concrete utilizing Fe500 rebars.
 The slab of 150 mm thickness of M30 grade concrete utilizing Fe500 rebars. are
considered for modelling of a structure.
Figure 4.5: 3D Model of the conventional building.

The above Figure 4.5 is about the 3D model done in Etabs software.

4.4.3 Load, Defining Load Pattern and Load cases

Table 4.2: Loads assigned on building.
Live Load As Per IS-875 Part 2 4 kN/m² and 1.5kN/m² at terrace

Wall Thickness 230 mm
Wall Load 14 kN/m²
Floor Finish 1 kN/m²
Terrace Finish (WPC) 1.75 kN/m²
Parappet wall load 4 kN/m²
Table 4.3: Seismic data.
Sl.
Particulars Codes Values
No
1 Zone Factor Z IS 1893:2016( part 1) 0.24
2 Importance Factor I IS 1893:2016( part 1) 1.5
3 Soil Type II Sa/g IS 1893:2016 (part 1) 2.5
4 Reduction Factor R IS 1893:2016 (part 1) 5
Figure 4.6: ETABS load pattern.
Figure 4.7: ETABS load cases.

The above Figures 4.6 and 4.7 are about the load pattern and load case definitions in the
Etabs software.
4.4.4 Assigning the support condition

The base of the structure in the arrangement the XY plane view is chosen and fixed
condition was allocated and depicted in Figure 4.8
Figure 4.8: ETABS joint restraints.
4.4.5 Load Combination in ETABS
Table 4.4: Load combination.
Following load combinations are used for the analysis

1.5DL+1.5LL
1.5DL+1.5EQX 1.5DL+1.5RSX
1.5DL+1.5EQY 1.5DL+1.5RSY
1.5DL-1.5EQX 1.5DL-1.5RSX
1.5DL-1.5EQY 1.5DL-1.5RSY
1.2DL+1.2LL+1.2EQX 1.2DL+1.2LL+1.2RSX
1.2DL+1.2LL+1.2EQY 1.2DL+1.2LL+1.2RSY
1.2DL+1.2LL-1.2EQX 1.2DL+1.2LL-1.5RSX
1.2DL+1.2LL-1.2EQY 1.2DL+1.2LL-1.2RSY
0.9DL+1.5EQX 0.9DL+1.5RSX
0.9DL+1.5EQY 0.9DL+1.5RSY
0.9DL-1.5EQX 0.9DL-1.5RSX
0.9DL-1.5EQY 0.9DL-1.5RSY

4.5 DESIGN OF LRB FOR THE STRUCTURE

Design Procedure for Lead Rubber Bearings
1. Specify the soil condition for the isolated structure.

2. Select the design shear strain γmax and effective damping ratio ξeff for the bearing,
and the target design period TD for the isolated structure.
3. Use code formulas, or static or dynamic analysis to determine the effective
horizontal stiffness Keff and maximum horizontal (design) displacement D of the
bearing.
4. Select the material properties, including Young‟s modulus E and shear modulus
G, from the manufacturer‟s test report.
5. Calculate the total height of rubber layers, tr, in the bearing according to the
design displacement D and design shear strain γmax:
𝐭𝐫=𝐃/𝛄𝐦𝐚𝐱………………………. (1)
6. Lead core design: Determine the cross-sectional area Ap and diameter dp of the
lead core based on the short-term yield force Qd and yield strength fpy:
𝐀𝐩=𝐐𝐝/𝐟𝐩𝐲………………………... (2)
7. Determine the area A and thickness t of individual rubber layers.
a. Select the shape factor S under no rocking condition:
𝐊𝐯/𝐊𝐡=((𝐄𝐜.𝐀)/(𝐭𝐫)/(𝐆.𝐀/𝐭𝐫))=𝐄𝐜/𝐆=𝐄.(𝟏+𝟐𝐤𝐒𝟐)/𝐆≥𝟒𝟎𝟎………(3)
b. Compute the effective cross-sectional area A0 of the bearing based on the

allowable axial stress σc under the vertical load case P (DL+LL):
𝛔𝐜=𝐏𝐃𝐋+𝐋𝐋/𝐀0≤𝟖𝟎𝐤𝐠𝐟/𝐜𝐦𝟐=𝟕.𝟖𝟒𝐌𝐍/𝐦𝟐……………………... (4)
c. Determine the effective cross-sectional area A1 of the bearing from the shear
strain due to the vertical load P (DL+LL):
𝛄𝐜(𝐃𝐋+𝐋𝐋)=𝟔𝐒 𝐏𝐃𝐋+𝐋𝐋/𝐄𝐜.𝐀𝐭≤𝛆𝐛/𝟑………………………….. (5)
d. Determine the elastic modulus Kr of the bearing:
𝐊𝐝=(𝟏+𝟏𝟐𝐀𝐩/𝐀0)……………………………….. (6)
Where Kd = post-yield stiffness of the LRB in horizontal direction

𝐊𝐝=𝐊𝐞𝐟𝐟−𝐐𝐝/𝐃............................................................ (7)
e. Obtain the minimum cross-sectional area Asf for shear failure of the bearing:
𝐀𝐬𝐟=𝐊𝐫.𝐭𝐫/𝐆………………………………………….... (8)
Use Asf to determine the dimensions of the bearing. Then compute the effective
cross-sectional area A2 as the reduced area is given below:
Are=L.(B−Δs) For a rectangular bearing
Are=d2/4(β−sinβ) For a circular bearing
f. The design cross-sectional area A of the bearing is the maximum among the
three values
Computed: A0, A1, and A2.
g. Select proper dimensions for the rubber layer based on the design area A.
8. Thickness of individual rubber layer, t and the number of rubber layers, N:
a. Determine the thickness of individual rubber layer, t, from the shape factor S
and dimensions of the rubber layer:
𝐒=𝐋.𝐁/(𝐋+𝐁).𝐭 For a rectangular bearing…………….. (9a)
𝐒=𝐝/𝟒𝐭 For a circular bearing………………... (9b)
Use tr = N × t to determine the required number of rubber layers, N.
9. Steel plate thickness, ts:
𝐭𝐬≥𝟐(𝐭𝐢+𝐭𝐢+𝟏)𝐏𝐃𝐋+𝐋𝐋/𝐀𝐫𝐞.𝐅𝐬≥𝟐𝐦𝐦……………………… (10)
Where, each parameter has been defined previously.
10. The shear strain and stability conditions are given in the section to follow. If the
dimensions determined for the bearing cannot satisfy the shear strain and stability
requirements, then repeat steps 2 to 9 for an improved design.

Shear Strain and Stability Checks
1. In the design of rubber layers, the following shear strain condition for the normal
load case should be satisfied:
𝛄𝐜,𝐃𝐋+𝐋𝐋=𝟔.𝐒.𝛆𝐜=𝟔.𝐒 𝐏𝐃𝐋+𝐋𝐋/ 𝐄𝐂.𝐀≤𝛆𝐛/𝟑………………... (11)
Where, all the parameters have been defined following
2. Stability condition: To prevent the bearing from becoming unstable, the average
compression stress ζc of the bearing should fulfill the following condition:
𝛔𝐜=𝐏/𝐀<𝛔𝐜𝐫=𝐆.𝐒.𝐋/𝟐.𝟓𝐭𝐫………………………………… (12)
3. Lead core size: The lead core provides the initial stiffness and energy dissipation
capability to the bearing, whose dimensions should meet the following condition
1.25≤𝑯𝒑/𝒅𝒑≤𝟓.𝟎………………………………….… (13)
4. Load combination including the earthquake
𝛄𝐬𝐜+𝛄𝐞𝐪+𝛄𝐬𝐫≤𝟎.𝟕𝟓𝛆𝐛…………………………. (14)
5. To protect the bearing from the occurrence of rollout, the displacement D of the
bearing under the earthquake load should fulfill the following condition:
𝐃≤𝛅𝐫𝐨𝐥𝐥−𝐨𝐮𝐭=𝐏𝐃𝐋+𝐋𝐋+𝐄𝐐.𝐋/𝐏𝐃𝐋+𝐋𝐋+𝐄𝐐+𝐊𝐝.𝐡………………………... (15)
Formulas for calculating the link property are given in design Example 1
where
Kv = vertical stiffness of the bearing
Kh = horizontal stiffness of the bearing
G = shear modulus, in the range of 0.4 to 1.0 MPa
E = Young‟s modulus, in the range of 1.5 to 5.0 MPa
Ec = compression modulus of the rubber-steel composite, Ec = E(1 + 2kS2)
A = full cross-sectional area (loaded area) of the bearing
tr = total height of rubber layers

k = modified factor, in the range of 1 to 0.5
S = shape factor = A/Af [Kelly, 1993]
A regular G+7 building with fixed support is analysed and max column load at
base is considered for a load combination of (DL+LL+FF).
4.5.1 Design Example
With the following parameters considered the design of LRB is as follows.
Data required for the calculation of dimensions of bearing are as follows:
1. The target period TD = 1.93 sec

2. Maximum shear strain of rubber bearing γmax = 50%
3. Effective damping ratio ξeff = 20%
4. Damping coefficient BD = 1.5
5. Seismic coefficient SD = 0.4
6. Maximum sustained load PDL+LL = 2990.84 kN
7. Breadth of building b = 20 m
8. Length of building l = 40 m
9. Accidental eccentricity e = 5%
10. Acceleration due to gravity g = 9.81m/s2
Analysis:
The effective horizontal stiffness Keff of the isolator is
𝐾𝑒𝑓𝑓 = (𝑊/𝑔)/(2𝜋/𝑇𝐷)2 |𝑊=𝑃𝐷𝐿+𝐿𝐿 Keff = 3231.24kN/m
Keff = 3.231 MN/m
Based on Equation 16-79 of IBC 2000, the design displacement DD is
𝐷𝐷=(𝑔/4𝜋2)/(𝑆𝐷×𝑇𝐷/𝐵𝐷) DD = 0.2m
The short term yield force Qd is
𝑄𝑑=𝑊𝐷/4𝐷𝐷=(𝜋/2)𝐾𝑒𝑓𝑓𝜉𝑒𝑓𝑓𝐷𝐷 Qd = 203.02kN
The post-yield horizontal stiffness Kd is
𝐾𝑑 = 𝐾𝑒𝑓𝑓−(𝑄𝑑/𝐷𝐷) Kd = 2216.12kN/m

Design:
Design lead core
Assume the yield strength of the lead core to be fpy = 8.82MN/m2
The required lead area is
𝐴𝑝=𝑄𝑑/𝑓𝑝𝑦 Ap = 0.02301869m2
Use diameter dp = 0.125m
Ap = 0.01431388 m2
Design the area and dimensions of rubber layers
The total rubber height
𝑡 𝑟= 𝐷𝐷/𝛾𝑚𝑎𝑥 tr = 0.4m
Use tr = 0.35m
Select the rubber properties
Use the following Material constant for the Rubber hardness
Rubber hardness IRDH = 60
Elongation at break εb = 400%
Young‟s Modulus E = 4.45MN/m2
Shear Modulus G = 1.06MN/m2
Modified Factor k = 0.57
Calculate the area A and thickness t of individual rubber layers
a. Select the shape factor S
E.(1+kS2)/G≥400
Therefore S > 9.09
Use, S = 20
Ec = E.(1+2kS^2) = 2033.65 MN/m2

b. Determine the effective area A0 for the bearing based on the allowable axial stress ζc
for the vertical load case PDL+LL:
𝜎𝑐 = PDL+LL/A0 𝜎𝑐 ≤ 7.84MN/m2
A0 > 0.38148469m2
c. Determine the effective area A1 for the bearing from the shear strain condition under
the vertical load case PDL+LL:
6S.P DL+LL /EC.A1 ≤ εb/3 >>>> A1 > 0.132m2
Elastic stiffness Kr of the bearing
𝐾𝑑=(1+12(𝐴𝑝/𝐴0)) Kr = 1528.084kN/m
d. Determine the effective area A of individual rubber layers based on shear failure
condition
𝐺=𝐾𝑟.𝑡𝑟/𝐴𝑠𝑓 𝐴𝑠𝑓=𝐾𝑟.𝑡𝑟/𝐺 = 0.50455608m2
For a circular bearing, the diameter corresponding to the area Asf is
𝐴2=((𝑑^2)/4)(β−sinβ) d = 0.62m
β = 2.48468342
A2 = 0.18009247m2
e. The design cross-sectional area for the bearing is
𝐴 = (𝐴0,1,𝐴2) A = 0.381m2
f. Determine the size of rubber layers
Use the following equations for a circular bearing
𝐴𝑟𝑒≤((𝑑^2)/4)(β−sinβ) β=2cos−1(𝐷𝐷/𝑑)
Diameter d = 0.7m
Area A = 0.385m2
β = 2.56208925
Reduced Area Are = 0.24677389m2

g. Single layer thickness, t, and number of layers, N:
For a circular bearing:
𝑆=𝑑/4𝑡 t = 0.009m
Use t = 0.02m
tr = N.t Therefore N = 17.5
Use N = 18
Determine the steel plate thickness, ts:
ts≥(2(ti+t1+i).PDL+LL)/ Are.Fs≥2mm
F s= 0.6Fy Fs = 0.65fy
where, for A36 steel: Fy = 274.4MN/m2
ts ≥ 0.0058891m
5.88909548mm
Use ts = 6mm
Total height h of the bearing:
Assume both the top and bottom cover plates are 2.5 mm thick.
h = tr +17x ts+ 2 x 2.5 = 50.2cm
Shear strain and stability conditions:
Shear strain due to Vertical load PDL+LL
γc = 6S 𝑃𝐷𝐿+𝐿𝐿 /𝐸𝐶.𝐴≤εb/ 3 γc = 0.45839248
≤ 𝜀𝑏/3 = 1.333
O.K
Stability check: ζc = 𝑃/𝐴 ζc = 7768.41558kN/m2
≤ζc=𝐺.𝑆.𝐿/2.5𝑡𝑟 = 16960kN/m2
O.K

Check on diameter of the lead core:
1.25≤𝐻𝑝/𝑑𝑝≤5 Hp/dp = 2.59259259
Lies In lmit O.K
Design result: dimensions of the LRB:
Diameter of the bearing d = 700mm
Total height of the bearing h = 502mm
Number of rubber layers N = 18
Thickness of individual layers t = 20mm
Diameter of the lead core dp = 125mm
Number of steel plates Ns = 17
Thickness of individual plates ts = 6mm
Thickness of top and bottom cover plates = 25mm
Checks on stability and rollout under the earthquake load
Shear strain condition including the earthquake effect
P(DL+LL+EQ) = 2.9MN
γsc = 6SPDL+L+EQ/ AreEc γsc = 0.6934
γe q= D/tr γeq = 0.57142857
𝜃 = (12𝐷𝐷×𝑒)/𝑏2+𝑙2 θ = 0.002
γsr = B2.θ/2.t.tr γsr = 0.070
(Here B is interpreted as the diameter d for circular bearings):
𝛾𝑠𝑐+𝛾𝑒𝑞+𝛾𝑠𝑟 = 1.33486048
<0.75𝜀𝑏 = 3
O.K

Rollout condition:
δroll−out =(1/2)×((P DL+LL+EQ .L−Qd.h )/(PDL+LL+EQ +Keff.h) )
δroll-out = 0.21318512 m
δroll-out > DD
0.33 > 0.20m
O.K
(Here L is interpreted as the diameter d for circular bearings)
All of the conditions are within the limit, therefore, it is satisfied.
Required formulae for the calculation of the analysis properties of a base isolator for
ETABS input data are as follow.
Vertical stiffness of the bearing, Kv
KV = Ec.A/tr Kv = 2237015kN/m
Effective horizontal stiffness of the bearing, Keff
𝐾𝑒𝑓𝑓=(𝑊/𝑔)(2𝜋𝑇𝐷)2 Keff = 3231.24kN/m
The post-yield horizontal stiffness, Kd
Kd = Keff−(Qd/DD) Kd = 2216.12 kN/m
Post yield stiffness of the bearing, Kp
KP = G.A/tr Kp = 1166kN/m
Elastic stiffness of the bearing, Ke
Ke = (6.5 to 10)Kp Ke = 11660kN/m
The short term yield force Qd is:
Qd = WD/4DD = (π/2)KeffξeffDD Qd = 203.02kN
Yield displacement of the bearing, Dy
Dy = Qd/9KD Dy = 0.01017921m

The yield force, Fy(QR)
FY=(π/2)(Keffξeff(DD)2/(DD−Dy) ) Fy = 213.912114kN
Effective horizontal stiffness of the bearing, Keff
Keff(R)=Keff−(QR/DD ) Keff(R) = 2161.68kN/m
Final input values for ETABS
U1
1 Vertical stiffness of bearing, Kv = 2237015 kN/m
2 Effective damping of bearing, ξeff = 20%
U2 & U3 Linear Property
3 Effective horizontal stiffness, Keff = 2161.68 kN/m
4 Effective damping of bearing, ξeff = 20%
Non-Linear Property
5 Initial Stiffness of Bearing, Ke = 11660 kN/m
6 Yeild Force of Bearing, Fy = 213.912114 kN
7 Post yield stiffness ratio = 0.1
Figure 4 .9: Typical Hysterisis curve for LRB isolator.

4.6 Modelling of the LRB using ETABS
After the designing process is completed, the values from the design are use to
model LRB in ETABS by the following steps,
1. Go to Define>Section>Link/Support Properties>Define the Support

2. Go to Define>Point Springs>Define Point Springs using above mentioned link
supports. (Axial Direction Z+ for Etabs)
3. Assign LRB at base for all the Columns.
Figure 4 .10: LRB definition in ETABS.
The Figure 4.10 is about the LRB definition in Etabs modeled as the Rubber
isolator in the link property option. Figure 4.11 is of the picture of the structure after the
incorporation LRB to it. At the support reactions region we can see those LRBs installed
instead of fixed supports.

Figure 4 .11: Building after the incorporation of LRBs at the base of it.
4.7 Modeling of the Friction Dampers using ETABS
For the purpose of modelling Friction Dampers, have referred Quaketek

company‟s guidelines, which is a Canada based company known for its manufacturing of
Friction dampers. The damper has been modelled as according to their guidelines.
Following link property has been assigned for modelling damper,
Mass of damper = 80 kg
Weight = 0.784 kN
Effective Stiffness = 108855.218 kN m-1
Yield strength or slip load = 250 kN
Figure 4.12 represent the definition of friction damper in the modeling software
Etabs as the damper link property. Figure 4.13 shows the actual model after the
incorporation of damper.

Figure 4 .12: Friction damper definition in ETABS.
Figure 4 .13: Building after the incorporation of Friction Dampers.

4. 8 Modelling of the Building with both LRB and Friction Dampers
There is no extra work required for modelling the building with the inclusion of
both LRB and Friction damper. It is just applying the above mentioned steps in the
individual cases here as a dual system. The same design values are used here also. After
modelling the building looks as in Figure 4.14 below,
Figure 4.14: Building with the inclusion of LRB and Friction Dampers.
4.9 Analysis
The analysis procedure chosen for the study is linear dynamic analysis which is
Response Spectrum Analysis.
After the analysis, the response parameters such as Time period, Base shear,
Storey displacements and Storey drift values are looked for, tabulated, plotted and
compared.

CHAPTER 5
RESULTS AND DISCUSSION

This chapter gives the tabulation of results from 3-Dimensional analysis. The
parameters discussed in this analysis includes Base shear, Time period, Storey
displacement and storey drift values for Response spectrum analysis. The results obtained
are given below under various topics.
1. Conventional 8 storey building.

2. Conventional model with LRB.
3. Conventional model with Friction Damper.
4. Conventional model with LRB and Friction Damper.
5.1 Time Period

The time taken by the wave to complete one cycle is called its time period.
After modelling on ETABS following results are obtained as shown in table 5.1.
Table 5. 1: Time Period results of all the models.
RCC Model
Mode RCC Model RCC Model+FD RCC Model+LRB
+LRB+FD
(sec) (sec) (sec)
(sec)
1 1.93 1.252 2.798 2.398
2 1.777 1.201 2.622 2.33
3 1.695 1.029 2.608 2.168
4 0.634 0.407 0.82 0.588
5 0.583 0.393 0.76 0.564
6 0.553 0.336 0.735 0.499
7 0.37 0.234 0.441 0.285
8 0.34 0.225 0.408 0.275
9 0.319 0.192 0.388 0.238
10 0.258 0.181 0.297 0.228
11 0.237 0.168 0.275 0.205
12 0.219 0.16 0.257 0.199

Time Period for different Models

3 2.798
2.398
Time Period (sec) 2.5
1.93
2
1.5 1.252
0.5
0
M1 M2 M3 M4
Models
Figure 5. 1: Time periods of all the models considering only the first mode.
Table 5.2: Percentage variation in Time Periods calculated with respect to the
Time period of conventional model considering 1st Mode results only.
Model type Percentage variation

RCC + FD 35.12%
RCC + LRB 44.50%
RCC +LRB+ FD 24.24%
The Figure 5.1 shows the comparison of time period of different models in
seconds. With the incorporation of LRB at base of the building, has increased time period
to an extent of 44% that is from 1.93 seconds to 2.798 seconds, with only FDs reduced
time period to 35% that is from 1.93 seconds to 1.252 seconds and upon the inclusion of
both LRB and FDs, have resulted in increase of time period to 24% that is from 1.93
seconds to 2.398 seconds, on comparing with time period of first mode of conventional
model which is fixed base and without dampers.
5.2 Base Shear
Base shear is the total estimate of the lateral force that would act at the base of the
building.The base shear values have been taken for the Load combinations 1.5DL+1.5
RSX and 1.5DL +1.5 RSY and the results are plotted for the same.

Table 5. 3: Base Shear results of all the models.
Models Base Shear in X direction, Base Shear in Y direction,

kN kN
3234.417 2839.98
RCC Model
4571.989 4386.222
RCC+FD Model
2088.447 1956.878
RCC+LRB Model
2352.887 2285.644
RCC+FD+LRB
Base Shear for all models in X and Y

direction in KN
5000
Base Shear (KN)
4000
3000
2000 Base shear X
1000
Base shear Y
0
M1 M2 M3 M4
Models
Figure 5. 2: Base Shear of all the models in both X and Y direction.
Table 5.4: Percentage variation in Base Shear calculated with respect to the Base
Shear of conventional model.
Model type Percentage variation in Percentage variation in

X Y
RCC + FD 41.35% 54.44%

RCC + LRB 35.43% 31.09%
RCC +LRB+ FD 27.25% 19.51%
When LRBs are introduced at the base of building, it has reduced the base shear
values to 35% in X and 31% in Y directions. With the inclusion of only FDs in the model,
base shear values have increased to an extent of 41% in X and 54% in Y direction. But in
the combined control strategy , that is LRB with FD, the base shear values decrease to
27.25% in X and 19.51% in Y direction as compared with conventional model which is
clearly depicted in the Figure 5.2.

5.3 Storey Displacement
According to IS 1893-2016, allowable displacement is calculated as h/250. Where

„h‟ is the total height of building in millimetres(mm). Adopting this practice, the
displacement in X and Y direction must lie within 110.4 mm (27600/250) where 27600 is
the height of model building. The table 5.5 and 5.6 helps us to compare the displacement
of the different models along X and Y direction respectively.
The storey displacement values have been taken for the 1.5DL+1.5RSX and
1.5DL+1.5RSY Load combinations and plotted for the same.
Table 5. 5: Storey Displacement results of all the models in X direction.
RCC RCC RCC RCC

Story Elevation Model Model +FD Model+LRB Model+LRB+FD
m mm mm mm mm
Story8 27.6 46.679 38.891 57.638 50.857
Story7 24.4 45.188 37.011 56.726 50.065
Story6 21.2 42.298 34.138 55.11 48.938
Story5 18 38.079 30.333 52.813 47.432
Story4 14.8 32.717 25.753 49.787 45.567
Story3 11.6 26.32 20.536 46.068 43.375
Story2 8.4 18.943 14.809 41.691 40.871
Story1 5.2 10.727 8.694 36.677 38.01
Plinth 2 2.383 2.529 30.59 34.677
Base 0 0 0 25.972 33.8

30 Storey Displacement
M1
25
M2
Building Height(m) 20
M3
15
M4
10
0
0 20 40 60 80
Storey Displacement (mm)
Figure 5. 3: Storey Displacement of all the models in X direction.
M1: RCC Model;
M2: RCC Model +FD;
M3: RCC Model+LRB;
M4: RCC Model+LRB+FD.
Table 5.6: Storey Displacement results of all the models in Y direction.
RCC RCC RCC RCC

m mm mm mm mm
Story8 27.6 52.58 39.139 63.321 53.777
Story7 24.4 50.843 36.781 62.252 52.375
Story6 21.2 47.494 33.483 60.244 50.617
Story5 18 42.7 29.399 57.288 48.515
Story4 14.8 36.681 24.712 53.448 46.112
Story3 11.6 29.56 19.581 48.801 43.453
Story2 8.4 21.389 14.107 43.405 40.613
Story1 5.2 12.266 8.419 37.272 37.637
Plinth 2 2.726 2.887 29.934 34.891
Base 0 0 0 24.303 34.005

Storey Displacement
30
M1
25
M2
20
Building Height(m)
M3
15
M4
10
0
0 10 20 30 40 50 60 70
Storey Displacement(mm)
Figure 5.4: Storey Displacement of all the models in Y direction.
Table 5.7: Percentage variation in Storey Displacement calculated with respect to

the Top Storey Displacement of conventional model.

X Y
RCC + FD 16.68% 25.56%
RCC + LRB 23.47% 20.42%
RCC +LRB+ FD 8.95% 2.27%
Figure from 5.3 and 5.4 shows the variation of lateral displacement of the building
at each story in both X and Y direction. For all models the lateral displacement is
maximum at top and minimum at the bottom.
The maximum storey displacement values decrease to an extent of 16.68% in X

and 25.56% in Y direction that is from 46.679 mm to 38.891mm in X and52.58 mm to
39.139 mm in Y for the model with FDs. For the model with LRB, the maximum storey
displacements increase to an extent of 23.47% in X and 20.42% in Y directions that is
from 46.679 mm to 57.638 mm in X and 52.58 mm to 63.321 mm in Y. For the model
with both LRB and FDs there is increase of 8.95% in X and 2.27% in Y directions that is
from 46.679 mm to 50.857 mm in X and 52.58 mm to 53.777 mm in Y as compared with
conventional case.

5.4 Storey Drift
Story drift can be defined as the lateral displacement of one level relative to the
level above or below it. As per clause no 7.11.1 of IS 1893 (Part 1): 2016, the storey drift
in any storey due to specified lateral force with partial load factor of 1.0, shall not exceed
0.004 times the storey height. The storey drift values have been taken for the
1.5DL+1.5RSX and 1.5DL+1.5RSY Load combinations and plotted for the same.
Table 5.8: Storey Drift results of all the models in X direction.
RCC RCC RCC RCC

m
Story8 27.6 0.000643 0.000657 0.000325 0.000271
Story7 24.4 0.001151 0.001012 0.000577 0.000385
Story6 21.2 0.001586 0.001315 0.00084 0.000509
Story5 18 0.0019 0.001541 0.00107 0.000622
Story4 14.8 0.002144 0.00171 0.00127 0.00072
Story3 11.6 0.002374 0.001838 0.001448 0.000812
Story2 8.4 0.00259 0.001937 0.001659 0.000916
Story1 5.2 0.002621 0.002 0.002204 0.001664
Plinth 2 0.001191 0.001264 0.003418 0.003277
Base 0 0 0 0 0

30
Storey Drift
M1
25
M2
M3
15
M4
10
0
0 0.001 0.002 0.003 0.004
Storey Drift
Figure 5.5: Storey Drift of all the models in X direction.
Table 5.9: Storey Drift results of all the models in Y direction.
RCC RCC RCC RCC

Story Elevation
Model Model +FD Model+LRB Model+LRB+FD
m
Story8 27.6 0.000712 0.000827 0.000389 0.000467
Story7 24.4 0.001343 0.001141 0.000724 0.000583
Story6 21.2 0.001819 0.001392 0.00104 0.000696

Story5 18 0.002152 0.001569 0.00131 0.000789
Story4 14.8 0.002408 0.001684 0.001541 0.000863
Story3 11.6 0.002646 0.001758 0.001745 0.000921
Story2 8.4 0.002881 0.001815 0.001945 0.001016
Story1 5.2 0.002991 0.002011 0.002478 0.002315
Plinth 2 0.001363 0.001444 0.004128 0.004144

Base 0 0 0 0 0

30 Storey Drift
M1
25
M2
M3
15
M4
10
0
0 0.001 0.002 0.003 0.004 0.005
Storey Drift
Figure 5.6: Storey Drift of all the models in Y direction.
Table 5.10: Percentage variation in Storey Drifts calculated with respect to the
Maximum Storey Drift of conventional model.

X Y
RCC + FD 25.21% 37.00%
RCC + LRB 35.94% 32.48%
RCC +LRB+ FD 64.63% 64.73%
It is very clear from the results and Figures 5.5 and 5.6 that for both the individual
models equipped with LRB singally, with Friction Dampers alone and with both of them
as a dual system has reduced the storey drift values which is a major parameter to look for
in seismic analysis. The following points depict the actual decrease in storey drift values
in percentages,
1. The storey drift values gets reduced almost to a range of 25.21% in X

direction and to 37% reduction in Y direction after the incorporation of
friction dampers.
2. When LRB is introduced in the place of fixed base condition, has effectively
reduced storey drift values to 35.94% at the storey 2 in X direction and to
32.48% reduction in Y direction. In the other stories, LRBs effect is seen in
the reduction of drift values to almost 30% on an average.

3. To an extent, the dual effect of LRB and Friction dampers has worked on the
same way as above in reducing the drift values effctively, reduced almost to a
range of 64% in both X and Y direction.

CHAPTER 6
CONCLUSIONS AND FUTURE SCOPE
6.1 CONCLUSIONS
From this study, the following conclusions are drawn,
 The seismic control methods that are used, base isolation (LRB) and Friction Dampers
(FD) have effectively reduced the response parameters caused due to earthquake.
 With the incorporation of LRB at base of the building, has increased time period to an
extent of 44.50%, with only FDs reduced time period to 35.12% and upon the inclusion
of both LRB and FDs, have resulted in increase of time period to 24.24% on comparing
with time period of first mode of conventional model which is fixed base and without
dampers.
 When LRBs are introduced at the base of building, it has reduced the base shear values
of 35.43% in X and 31.09% in Y directions. With the inclusion of only FDs in the
model, base shear values have increased to an extent of 41.35% in X and 54.44% in Y
direction. But in the combined control strategy, that is LRB with FD, the base shear
values decrease to 27.25% in X and 19.51% in Y direction as compared with
conventional model.
 The maximum storey displacement values decrease to an extent of 16.68% in X and
25.56% in Y direction for the model with FDs. For the model with LRB, the maximum
storey displacements increase to an extent of 23.47% in X and 20.42% in Y directions.
For the model with both LRB and FDs there is increase of 8.95% in X and 2.27% in Y
directions as compared with conventional case.
 In the model with LRB and in the model with both LRB and FDs, shows some little
displacement at base level to an extent of 25 mm in X and 34 mm in Y, which is
zero in case of fixed base building.
 The storey drift values significantly decrease in all the models with LRB, with FDs and
even in the dual system that is with both LRB and FDs as compared with conventional
building.
 The storey drift values have reduced to an extent of 25% in X and 37% in Y directions
for model with FDs. Those drift values have decreased to 35% and 32% in both X and
Y directions for model with LRB and to 64% in the case of model with both LRB and
FDs in both X and Y directions as compared with conventional case.

 The decrease in storey drifts in the case of combined strategy, that is with LRB and
FDs, is because of the seismic energy dissipation and increased stiffness of the
structure due to both LRB and FDs. Hence this combined control strategy can be
adopted to mitigate the effects of earthquake.
6.2 Future Scope of the work
 This combined control strategy, the use of both seismic isolators and seismic
dampers in a structure as seismic resistant method, can be extended to study its
effect by changing the type of isolators and dampers and researched for a
better combination of both.
 This can be extended to study its effect in mass asymmetric buildings.
 This analytical study can be extended to test its efficacy in practical
application by subjecting it to Quake table tests.

REFERENCE
1. Aparna Bhoyar and Bhupesh Nandurkar, “Seismic Evaluation of Reinforced

Concrete Building with Friction Dampers”- International Research Journal of
Engineering and Technology (IRJET), e-ISSN: 2395-0056,p-ISSN: 2395-0072,
Volume: 06 Issue: 03 , Mar 2019.
2. Base Isolated and Fixed Based RC Frame Building”- International Journal for
Scientific Research & Development -IJSRD ,Vol. 4, ISSN (online): 2321-0613,
Vol. 4, Issue 06, 2016.
3. Bhavana Balachandran and Susan Abraham, “Effect of Base Isolation in Multi-
Storeyed RC Building”-2018. IOSR Journal of Engineering (IOSRJEN), ISSN(e):
2250-3021,ISSN (p): 2278-8719, Vol. 08, Issue 6, June,2018.
4. Chandak N.R , “ Effect of Base Isolation on the Response of Reinforced Concrete

Building ” - Journal of Civil Engineering Research , 3(4): 135-142, 2013.
5. IS 1893-2002(Part-1): Criteria for Earthquake Resistant Design of Structures.
6. IS 456-2000, “Plain and Reinf0rced c0ncrete-Code 0f Practice”, Bureau 0f Indian
Standards, New Delhi
7. IS 875(Part 1) : 1987, code of practice for Design Loads(other than earthquake),
Dead L0ads-Unit Weights 0f Building Materials and St0red Materials For
Buildings and Structures.
8. IS 875(Part 2) : 1987, code of practice for Design Loads(other than Earthquake),
Imp0sed L0ads For Buildings and Structures.
9. Kishan Bhojani, Vishal B. Patel and Snehal V. Mevada, “Seismic Vibration
Control of Building with Lead Rubber Bearing Isolator”- 2017
10. Mohammed Irfan Faraaz and Amaresh S.Patil,“Comparative Seismic Analysis of
11. S. Lakshmi Shireen Banu and Kothakonda Ramesh, “Seismic Response Study and
Evaluation of Vibration Control of ElevatedRCC Structure using Friction
Damper”- International Journal of Innovative Technology and Exploring
Engineering (IJITEE) ISSN: 2278-3075, Volume-8 Issue-7, May, 2019.
12. S.M. Dhawade , “Comparative Study for Seismic Performance of Base Isolated &
Fixed Based RC Frame Structure”- International Journal of Civil Engineering
Research, ISSN 2278-3652 Volume 5, Number 2 (2014), pp. 183-190
13. S.S. Sanghai, “Seismic Response of Unsymmetric Building with Optimally
placed Friction dampers”- International Journal of Civil Engineering and

Technology (IJCIET) Volume 8, Issue 2, February 2017, pp. 72–88 Article ID:
IJCIET_08_02_008
14. Siddhant Kishore Laddha, “ Effect of Friction Damper on Seismic performance of
Multistoreyed Frame Structure in High Rise Building-A Review”- International
Engineering Journal For Research & Development (IEJRD), E-ISSN NO:-2349-
0721, Impact factor : 6.03,Vol-4, Issue-4,2018

APPENDIX A
Sl. N0 Design data for all the buildings

1 Details of Building
i) Number of stories G+7

ii) Type of building Institutional
iii) Story height 3.2 m
2 Material Properties
i) Grade of concrete M30
ii) Grade of steel Fe 500
3 Member Properties
a Slab
i) Grade M30
ii) Thickness 150 mm
b Beam
i) Grade M30
ii) Size 300 x 450 mm
c Column
i) Grade M30
ii) Size 350 x 450 mm
4 Types of Loads and Intensities
i) Live Load on all the floors 4 kN/m2
ii) Live Load on terrace 1.5 kN/m2
iii) Floor Finish 1 kN/m2
iv) Terrace Finish 1.75 kN/m2
v) Wall load 14 kN/m²
vi) Parapet Wall load 4 kN/m²
5 Seismic Properties from IS : 1893 (part 1) - 2016
i) Zone factor 0.24
ii) Importance factor 1.5
iii) Response reduction Factor 5.0
iv) Soil Type Medium

6 LRB link properties

For U1
i) Vertical stiffness of bearing, Kv 2237015 kN/m
ii) Effective damping of bearing, ξeff 20%
For U2 & U3 Linear Property
iii) Effective horizontal stiffness, Keff 2161.68 kN/m
iv) Effective damping of bearing, ξeff 20%
For U2 & U3 Non-Linear Property
v) Initial Stiffness of Bearing, Ke 11660 kN/m
vi) Yeild Force of Bearing, Fy 213.912114 kN
vii) Post yield stiffness ratio 0.1
7 Link (Friction damper) Properties
i) Mass 80 kg
ii) Weight 0.784 kN
iii) Effective Stiffness 108855.218 kN/m
iv) Yield strength or Slip load 250 kN

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Seismic Vibration Control of Building using Base Isolation Technique with Friction Dampers

For controlling earthquake vibrations, Base isolation technique and Friction

Department of Civil Engineering, UVCE Page 1

1.2 Objectives of the study

1. To perform Response Spectrum Analysis on an irregular “C” shaped concrete

1.3 Organization of thesis

Department of Civil Engineering, UVCE Page 2

2.1 Literature review details on the use of Base Isolation

S.M. Dhawade(2014), “Comparative Study for Seismic Performance of Base Isolated

Department of Civil Engineering, UVCE Page 3

Kishan Bhojani, Vishal B. Patel et al.(2017), “Seismic Vibration Control of Building

Bhavana Balachandran and Susan Abraham (2018), “Effect of Base Isolation in

Department of Civil Engineering, UVCE Page 4

2.3 Literature review details on the use of Friction Dampers

S.S. Sanghai(2017), “Seismic Response of Unsymmetric Building with Optimally

Siddhant Kishore Laddha(2018), “Effect of Friction Damper on Seismic

Department of Civil Engineering, UVCE Page 5

Aparna Bhoyar and Bhupesh Nandurkar(2019), “Seismic Evaluation of Reinforced

S. Lakshmi Shireen Banu and Kothakonda Ramesh(2019), “Seismic Response Study

Department of Civil Engineering, UVCE Page 6

2.4 Summary of literature review

2.5 Scope of the study

Department of Civil Engineering, UVCE Page 7

BASE ISOLATION AND FRICTION DAMPERS

3.1 BASE ISOLATION

Figure 3.1: Typical explanation of base isolation system.

Department of Civil Engineering, UVCE Page 8

The principle in base isolation is,

Figure 3.2: Classification of isolators.

Department of Civil Engineering, UVCE Page 9

3.1.1 Lead-plug Rubber Bearings-(LRB)

Lead-plug rubber bearings were invented in New Zealand in 1975. The

Figure 3.3: Typical lead rubber bearing.

Department of Civil Engineering, UVCE Page 10

3.2 Friction Dampers

Figure 3.4: Friction Damper.

3.3 Practical implementation

3.3.2. Friction Damper

Department of Civil Engineering, UVCE Page 12

Figure 3.6 Concordia University Library, Montreal.

Figure 3.7: Boeing Airplane Factory¸Everret, WA. Figure 3.8: 3M Gallon

Figure: 3.9: Moscone Convention Center, Figure 3.10: Casino de Montreal.

Department of Civil Engineering, UVCE Page 13

Figure 3.14: Justice Headquarters Building, Ottawa.

Figure 3.15: La Gardenia Complex, Gurgaon, India.

Department of Civil Engineering, UVCE Page 14

4.2 Methods of seismic analysis of structure

4.2.1 Static analysis

4.2.2 Dynamic analysis

Base shear is the estimation of maximum expected lateral force coming on to

The design base shear,

- RC frame building with brick infill panels

h = Height of the building in m

Department of Civil Engineering, UVCE Page 16

4.2.3 Assumptions in Earthquake Resistant Design

4.2.4 Generation of Response Spectra

. Figure 4.1: Seismic Zones of India (as per IS 1893 – 2016).

Department of Civil Engineering, UVCE Page 17