IRJET- The State of the Art on Seismic Isolation of Shear Wall Structure using Elastomeric Isolators

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 04 | Apr-2018 www.irjet.net p-ISSN: 2395-0072
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The State of the Art on Seismic Isolation of Shear Wall Structure using
Elastomeric Isolators
N K Fasil1, Dr. P R Sreemahadevan Pillai2
1PG Student, Department of Civil Engineering, NSS College of Engineering, Palakkad
2Professor, Department of Civil Engineering, NSS College of Engineering, Palakkad
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Abstract - Base isolation refers to the principle which
introduces flexibility to the supports of the building in the
horizontal plane and ensures the period of the buildings lie
outside that of the earthquakes acting on it. In this paper, the
suitability of type of elastomeric base isolators and their
effectiveness to reduce interstorey drifts and accelerations of
the buildings is studied. The effect of shear walls on base
isolated buildings is also studied. A brief idea about base
isolation and its different types is needed beforehand. This is a
review paper prepared as a part of the thesis work.
Key Words: Base isolator, Shear wall, High Damping
Bearing, Lead Plug Bearing
1. INTRODUCTION
Seismic Isolation means basicallyisolatingthestructurewith
respect to the seismic waves produced by the earthquake. It
aims to mitigate the seismic demand on a structure by
shifting the natural period of vibration of the isolated
structure beyond the high-energy period range of
earthquake ground motions. It therefore serves as an
additional means of energy dissipation. The concept of
seismic isolation is more efficient and is adopted extensively
rather than increasing the earthquake resisting capacityofa
building.
Shear walls are structural walls that are specially designed
for resisting lateral loads. Shear walls can be composed of
different materials and concrete shear walls are most
commonly used in high rise structures. The use ofreinforced
shear wall has become more efficient as it ensures lateral
stability of the tall structures and reduces lateral sway.
Seismic performances of shear walls are guaranteed under
small earthquakes. In order to withstand large earthquakes,
shear walls with seismic isolators are provided.
The isolator device needs to be flexible in the lateral
direction while being able to carry a large vertical load. The
near incompressibility and low elastic modulus inherent in
elastomers have made elastomeric isolators the most
common type of seismic isolator in use.
2. THEORY OF SEISMIC ISOLATION
There are mainly 2 types of base isolation systems; sliding
systems and elastomeric bearing systems. Sliding systems
work by limiting the transfer of shear across the isolation
interface. Many sliding systems have been proposed and
some have been used. One commonly used sliding system is
spherical sliding bearing. In this system, the building is
supported by bearing pads that have low friction and a
curved surface. During an earth-quake the building is freeto
slide on the bearings. Since the bearings have a curved
surface, the building slides both horizontally and vertically.
Fig 1: Elastomeric Isolator
By using Elastomeric bearing systems, the building or
structure is decoupled from horizontal components of
earthquake ground motion by substituting a layer with low
horizontal stiffness between the structure and the
foundation. Conventionally, steel plates are used as
reinforcing material. Its function is to provide vertical
stiffness to the isolator to take the weight of the structure.
Bearings using steel as reinforcing material are known as
steel reinforced elastomeric bearings(SREI). Thin sheets of
steel are interspersed in between layers of rubber.
Shear walls are structural walls that are specially designed
for resisting lateral loads. They are basically vertical
elementsof horizontal force resistingsystem.Concreteshear
walls are commonly used in high rise structures. The use of
reinforced shear wall hasbecome more efficientasitensures
lateral stability of the tall structures and reduces lateral
sway.
3. LITERATURE REVIEW
The literatures that were reviewed on the various base
isolation techniques is presented in this chapter. A number
of works have been performed on base isolation using
different types of isolators and their combined action. A
review of literatures is presented in brief summarizing the
work done by different scholars and researchers on the
seismic response of multistorey structures using these
techniques.

Gomase O.P, Bakre S.V (2011) studied the effect of base
isolation on a four storied reinforced concretebuildingusing
El Centro, Kobe and Northridge earthquakes. High damping
rubber bearings are designed according to UBC-97 for near
fault earthquake. The force deformation behaviour of
isolator is modelled as a Bi-linear hysteretic type. The
analysis results and results from the design calculation was
found to be same. The Floor accelerations and Storey drifts
were reduced for base isolated building when compared to
fixed type building.
Dia Eddin Nassani, Mustafa Wassef Abdulmajeed(2015)
studied the effects of base isolation systems using high
damping rubber isolation system installed at the foundation
level of regular and irregular buildings. The time history
analysis is performed on three earthquakes, El Centro,Loma
and Coyote using finite element software SAP2000. A five
storey reinforced school building with fixed and base
isolated conditions are modelled forstudyingthevariationof
seismic responses. Based on the results it is found that base
isolation system reduces the base shear and storey drifts
with respect to fixed base structures. However, the
displacement values were increased for the base isolated
buildings.
Zaheer and Ravichandra.R (2015)didacomparativestudy
on performance of Multi-Storey StructureusingLeadRubber
Bearing and Friction Pendulum Base IsolationSystemsonan
irregular RC building of G+10 storeysand analysed withand
without base isolators using SAP 2000 software. Both
Equivalent Static Analysis and Time History Analysis were
carried out using El-Centro earth-quake. Storey
displacements and drifts at earth-quake zone V using 15%
damping in both isolators and found that Lead Rubber
Bearings has lesser displacements and variations with
respect to Friction Pendulum System. The base shear was
found same of the vertically irregular L shapedbuildingwith
both isolators.
Darshale S.D and Shelke N.L (2016) studied the seismic
behaviour of a G+14 regular RCC building by time history
analysis and response spectrum analysis using Lead Rubber
Bearings. Here mass irregularity, stiffness irregularity and
vertical geometric irregularity were studied. For El centro
earthquake excitation was taken for time history analysis.
The parameters like shear force, maxi-mum bending
moment, base shear, storey acceleration and storey drifts
were reduced for base isolated building.Hencebaseisolation
effectively reduces the seismic responses. The fundamental
time period increasesfor base isolation asthe stiffnessofthe
buildings reduces using base isolation.
Donato Cancellara et al (2016) adopted a combination of
two different types of passive base isolation systems along
with a friction slider. Two base isolation systems which are
considered are High Damping Rubber Bearing (HDRB) is
used along a Friction Slider (FS) and the Lead Rubber
Bearing (LRB) with a Friction Slider (FS). The fast nonlinear
dynamic analysis algorithm (FNA) is used for the numerical
solution of the dynamic response of the structure. A
comparative analysis is done to find the effectiveness of the
considered base isolation systems when the RC building is
subjected to bi-directional ground motions. Thetimehistory
analysis of the base shear, the peak values of the base shear,
the base acceleration, the base displacements of the
superstructure and Storey drift is done so that a complete
assessment can be performed of the seismicbehaviourofthe
base isolated structure. The results show that the LRB
isolators show a greater dissipative capacity com-pared to
HDRB isolators but this needs to be con-trolled as it creates
higher Storey drifts. The studiesalso showthatLRBisolators
are more robust and stable in their hysteretic cycles when
com-pared to the hysteretic cycles of the HDRB isolators.
Nitya M and Arathi S (2016) performed non-linear time
history of a base isolated building of G+6 storey using El
Centro Earthquake. Analysis was done by finite element
software SAP2000. An irregular RC building of plus shape
located in the seismic zone V was selected. Here Rubber
bearings and friction pendulum bearings were used as the
isolation systems. The base shear, time period and storey
displacement were compared for each model. It was found
that time period was in-creased for base isolated buildings,
reducing the induced forces due to earthquakes. The
displacement variation between stories were reduced using
base isolation technique.
Venkatesh, Arunkumar H.R (2016) comparedthe seismic
responses of fixed and isolated buildings using response
spectrum analysis. An Eleven storey RC building frame was
isolated using Lead Rubber Bearing. The design of isolators
wascarried out according to UBC 1997. The parameterslike
storey shear, base shear, storey drift were reduced for base
isolated buildings. The time periods were increased for
isolated models.
Agim Seranaj et al (2015) analysed the effect of isolation
location a ten storey reinforce concrete Box structure is
considered. The structure is analysed in three different
conditions: the first model is fixed base, the second model
with isolators on the base and third model with isolators on
the middle story. Elastomeric rubber bearing isolators are
used. The analysis shows the influence of isolators location
on the dynamic properties of building structure and its
influence on the dis-placement and internal forces of
structural elements. Based on the analysis results, it has
been concluded that the location of isolatorscan be selected
in every story of the building based on the interested
parameters to be modified.
Anusha R Reddy and V Ramesh ﴾2015﴿carriedoutdetailed
seismic analysis on RC framed base isolated building. Two
buildings are considered first structure is G+13 storey
building and second is G+5 storey building whichisanalysed
in E TABS 13.2.1 software. Lead rubber isolatorareprovided
to both the structures and then time history analysis and
linear response spectrum are carried out for both fixed base
and base isolated buildings under zone v and soil type II i.e.

medium soil (according to IS 1893(part 1):2002). The mode
period, acceleration, base shear, and dis-placement are
compared for response spectrum and time history analysis
for fixed base and base isolated buildings. It is found thatthe
mode period is increased after providing rubberisolatordue
to the flexible property of the isolator.Whencom-paredwith
fixed base structure, the base shear is reduced in base
isolated structures, thus the response of building is good in
base isolated structures than fixed base structures.
P. P. Chandurkar et al (2013) performed a study to
determine the solution for shear wall location in multi-
storey building. Effectivenessof shear wall hasbeen studied
with the help of four different models. Model one is bare
frame structural system and other three models are dual
type structural system. Seismic loads are applied to a
buildingof ten storieslocated in zone II, zone III, zoneIVand
zone V. Based on the analysis results, it was observed that
changing the position of shear wall will affect the attraction
of forces, so that walls must be in proper position. Also
providing shear walls at adequate locations substantially
reduces the displacements due to earthquake.
Many other literatures are referred and reviewed and an
idea of the state of the art is obtained.
8. CONCLUSION
The concept of base isolation is not a recent topic and recent
developments in full-scale shake table testing and
advancement in accurate software oriented analysis has
made this technique more acceptable. This technique
ensures a simultaneous reduction acceleration and drift
responses of the building even under a large and
unpredictable seismic event. However, there are still gapsin
the research to be filled like seismic isolation cannot ensure
a complete protection of buildings, challenges are still there
like how to protect components of buildings subjected to
vertical excitation, mitigation of overturning forces in
slender structures which causes local uplifts and
superstructure yielding in extreme events. This paper
attempts to summarize the effectiveness of base isolators
and also determines the efficiency of shear walls used in a
building.
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IRJET- The State of the Art on Seismic Isolation of Shear Wall Structure using Elastomeric Isolators

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IRJET- The State of the Art on Seismic Isolation of Shear Wall Structure using Elastomeric Isolators