IRJET- A Study on Seismic Performance of Reinforced Concrete Frame with Lead Rubber Bearing Base Isolation System

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 04 | Apr 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 1370
A Study on Seismic Performance of Reinforced Concrete Frame with
Lead Rubber Bearing Base Isolation System
R. Santhoshkumr1, J. Premalatha2
1P.G Scholar, Kumaraguru College of Technology, Coimbatore.
2Professor in Civil Engineering Department, Kumaraguru College of Technology, Coimbatore, Tamilnadu, India
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Abstract - In the present work, an analytical study on
seismic performance of G+10 storeyed Reinforced Concrete
(RC) frame with various lateral force resistant systems like
base isolation system and X-bracings was carried out using
ETBS software. The Lead Rubber bearing (LRB) system was
designed for the frame and their properties were used in the
modelling of LRB for the RC frame. Static analysis, Linear
Time History analysis (El-centro)andpushoveranalysis were
carried out for the frame. Maximum storey displacement,
storey drift and maximum base shear were found out to find
the effect of LRB used for the base isolation system. From the
Time history analysis, the maximum drift for the RC frame
with fixed base, X bracing and base isolation are found out
26.62mm, 1.914 mm and 0.415mm respectively. From the
Time history analysis, the maximum displacement for the RC
frame with fixed base, X bracing and base isolation are found
out 163.03mm, . 13.344 mm and 2.504mm respectively. The
base shear for the RC frame with fixed base, X bracing and
base isolation are found out as 2294.3kN, 2606.7kN, 32.935
kN respectively. From the analytical study it is observed that,
provision of base isolation has enhanced the seismic
performance of the RC frame to a great extent. The results of
Static and push over analysis also exhibit the similar trend in
the performance of the frame.
Key Words: Lead Rubber Bearing, Time History analysis,
Pushover analysis, X-bracing, storey displacement
1. INTRODUCTION
Earth quake is a shaking of the ground caused by
movement of the tectonic plates relative to each other, both
in direction and magnitude. A large part of the world people
lives in area of seismic hazard at risk from earthquake of
varying harshness and varying frequency of existence.
Earthquake cause significant loss of life and destruction to
property every year. During past earthquake most of the
irregular buildings collapsed due to the non-uniform
distribution of the load compared to regular buildings. The
earthquakes in the recent past have provided enough
evidence of performance of different type of structures
under different earthquake conditions and at different
foundation conditions as a food for thought to the engineers
and scientists. This has given birth to different type of
techniques to save the structures from the earthquakes
effects. Conventional seismic design attempts to make
buildings that do not collapse under strong earthquake
shaking, but may sustain damage to non-structural elements
(like glass facades) and to some structural members in the
building. This may render the building non-functional after
the earthquake, which may be problematic in some
structures, like hospitals, which need to remainfunctional in
the aftermath of the earthquake. Two basic technologies are
used to protect buildings from damaging earthquakeeffects.
These are Base Isolation Devices and SeismicDampers.Base
isolation is also known as ‘seismic base isolation’ or ‘base
isolation system’. Seismic isolation separates the structure
from the harmful motions of the ground by providing
flexibility and energy dissipation capability through the
insertion of the isolated device so called isolators between
the foundation and the building structure.
Figure1: Behaviour of Fixed base & isolated base
buildings.
Donato Cancellara, et al. (2016) have studied the
dynamic nonlinear analysis of different base isolation
systems for a multi-storey RC building irregular in plan.
Athanasios et al. (2016) have conducted a study
onresponse simulation of hybrid base isolation systems
under earthquake excitation .Investigated the response of a
hybrid base isolation system under earthquake excitation. J.
C. Ramallo1, et al. (2008) have presented an
innovativebase isolation strategy and showed how it can
effectively protect the structures against extreme
earthquakes without sacrificing performance during the
more frequent, moderate seismic events. Minal Ashok
Somwanshi et al. (2015) carried out a studyon Seismic
Analysis of Fixed Based and Base Isolated Building
Structures. The work deals with modelling and analysis of
13-storey rigid jointed plane frame for two cases. First case
is fixed base and second case is base isolated. Modelling and
analysis is done using E-TABS software for Bhuj earthquake
ground motion records. Tremblay et al. (2003) performed
an experimental study on the seismic performance of
concentrically braced X bracing and single diagonal bracing

steel frames with cold-formed rectangular tubular bracing
system. The loading sequences used were a displacement
history obtained from nonlinear dynamic analysis of typical
braced steel frames. Results were obtained for different
cyclic loading and were used to characterize the hysteretic
response, which includes the energy dissipation capabilities
of the frame.
1.2 Seismic Resistant Systems
The types of lateral resistant Systems Such as base isolation
systems, seismic damper systems were reviewed andfinally
bracing systems and base isolation systemwerefixedforthe
study purpose.
1.2.1 1BASE ISOLATION
In base isolation technology during earthquake, separating
the superstructure or reducing the lateral movements of
building superstructure from the movement of ground or
foundation. The bearings of base isolation are designed in
such a way that they are stiff vertically and flexible
horizontally to allow for the difference in lateral movement
while still supporting the superstructure. The base isolated
structures are different than that of fixed base structure, in
which the connection between the superstructure and the
foundation are rigid and the superstructuretranslationin all
direction is constrained.
Figure 2: Effect of Seismic Isolation on Spectral
Acceleration
The main aim of base isolation is to reduce the
earthquake force produced on building superstructure. To
some extent by reducing the superstructure’s spectral
acceleration, the reductioninseismic forceatsuperstructure
is achieved. By increasing the base isolated structure
fundamental period and through damping caused by
dissipation energy within bearing the accelerations are
reduced.
1.2.2 Bracing Systems
A Bracing is a system that is provided to reduce the lateral
deflection of the structure. The use of braced frames has
become more effective in high rise structure and also in
seismic design of structure. A Braced Frame is designed
primarily to resist wind and earthquake forces in and a
structural system. These braced frames are made of steel
members. Similar to a truss a braced frame is designed to
work in tension and compression.
2. OBJECTIVES OF THE RESEARCH
A G+10 storey reinforced concrete building was
designed in accordance with IS 1893:2002 provisions;
Three types of frames with lateral resistant systems were
considered in the study. One with fixed base, other is base
isolated and the third one was a braced frame. By analysing
the fixed base buildings, we get maximum reactions under
each column. For these maximum values Lead Rubber
Bearings (LRBs) were designed manually in order to isolate
the superstructurefromsubstructure.Andforbracedsystem
the X bracings are provided along the periphery walls.
Response Spectrum Analysis, Push over Analysis are done
and the Time History Analysis (THA) is carried out bytaking
El-Centro earthquake ground motion records.
The objectives of the present work are as follows:
1. To carry out modelling and analysis of fixed base,
braced and base isolated buildings byusingE-TABS
software and study the effects of earthquake
ground motions on these models.
2. To design and study the effectivenessofleadrubber
bearing used as base isolation system.
3. To compare the fixed base, bracedandbaseisolated
building on the basis of their vital dynamic
properties such as base shear and drift etc.
2.0MODELLINGANDANALYSISOFTHESTRUCTURE
The current study involves the actual modelling of
the G+10 RC Building using ETAB software and performing
the analyses such as RSA, THA and POA. The building is
modelled and designed as per IS 456:2000 in ETABS
software version 2016. Structural responses are compared
using Response Spectrum, Time History Analysis and Push
Over Analysis.
Materials properties and section properties are
defined and assigned. Reinforced concrete frame elements
are modelled as beam and column element. Slab is modelled
as area element. The design of isolators is done as per UBC
97 and suitable values are incorporated in ETABS software
for modelling of base isolated structure.
Models considered for analysis:
The G+10 Storied RC building is taken for analysis and
various models are created.
Model A : Fixed Base Model
Model B : Braced Structure Model

Model C : Base Isolated Model
Figure 3: Plan – Model A, B, C
Figure 4:Elevation and 3D View – Model A
Following are the elevation and 3dviewof bracedmodel and
base isolated model of the G+10 RC building.
Figure 5: Elevation and 3D View – Model B

Figure 6: Elevation and 3D View – Model C
2.1 Details of The RC model frame
Following are the data given for modelling of the structure :
Table 2: Building Specifications
Grade of Concrete for Beam M25
Grade of Concrete for Column M30
Grade of Steel Fe415
Story Height 4 m
Beam Size 310 x 610 mm
Column Size 310 x 460 mm
Slab Thickness 150 mm
Wall Thickness 230 mm
Live load on floor 3 kN/m2
Live load on roof 1.5 kN/m2
2.2 Seismic Properties
Table 3: Seismic Properties
Zone III
Importance Factor 1
Type of Soil Medium
OMRF R = 3
Earthquake loads are taken as per IS 1893(part
1):2002
2.3 Modelling of LRB Isolator
A variety of isolation devices including elastomeric
bearings (with and without lead core), frictional/sliding
bearings and roller bearings have been developed and used
practically for a seismic design of buildings during the last
25 years. Among the various base isolation system, the lead
rubber bearing had been used extensively. It consists of
alternate layers of rubber and steel plates with one or more
lead plugs that are inserted into the holes. Due to lateral
forces the lead core deforms, yields at low level of shear
stresses approximately 8 to10 Mpa at normal (200c)
temperature, so the lead bearing lateral stiffness is
significantly reduced. Due to this period of structure
increases. One of the features of lead core is that it can
recrystallize at normal temperature and will not encounter
the problems of fatigue failure under cyclic loadings.
Figure 7: Lead Rubber Bearing with Layers of Rubber
and Steel and Lead Core
3.0 RESULTS AND DISCUSSIONS
Both fixed base and isolated bearing models were
analysed and designed in ETABS 2016 software. Themodels
were designed as per IS456:2000andfoundthattheselected
sections are safe under given loading and seismic condition
and thus the study was further proceeded. The main seismic
parameters selected for the comparison of models are story
drift, story displacement, shear and acceleration. These
analysis results are compared separately with each other.

3.1 Time History Analysis (THA) results
3.1.1 Story Drift
Table 4: Drift Comparison THA
Story Max Drift
in mm
MODEL A MODEL B MODEL C
Story10 3.485 0.899 0.09
Story9 6.362 1.003 0.132
Story8 9.352 1.024 0.152
Story7 12.372 1.243 0.187
Story6 15.16 1.365 0.243
Story5 18.125 1.419 0.332
Story4 20.981 1.537 0.415
Story3 23.7 1.67 0.407
Story2 26.622 1.672 0.299
Story1 26.114 1.914 0.171
P Story 3.537 0.7 0.061
The variation of drift with respect to various models is
shown. It is observed that the Model C ie,. Base Isolated
model exhibits very small value compared to Model A ie,.
Fixed Base model.
3.1.2 Story Displacement
Table 5: Displacement Comparison THA
Story Max Displacement
in mm
Story10 140.448 13.344 2.504
Story9 159.892 12.445 2.416
Story8 153.895 11.443 2.285
Story7 144.808 10.419 2.146
Story6 132.725 9.39 1.989
Story5 117.897 8.275 1.766
Story4 100.396 3.383 1.438
Story3 79.955 5.427 1.027
Story2 56.255 3.81 0.622
Story1 29.634 2.215 0.323
P Story 3.537 0.7 0.17
Similar to drift values here also the base isolated
Model C showed minimum displacement rather than other
models.
3.1.3 Story Shear
Table 6: Shear Comparison THA
Story Max Shear
in kN
MODEL A MODEL B
MODEL
C
Story10 420.6981 239.4552 6.5402
Story9 745.3428 460.4168 9.7818
Story8 935.3044 680.4854 10.9434
Story7 998.7036 910.1322 13.4481
Story6 1306.2672 1117.8037 17.6732
Story5 1597.8748 1343.3374 24.756
Story4 1822.2565 1561.0872 31.8546
Story3 1929.8354 1766.6139 31.4968
Story2 2214.194 2010.9969 22.6512
Story1 2592.4333 2169.5289 10.749
P Story 2606.7375 2172.7263 9.512
Here it is observed that the shear values donotvary
much between Model A and Model B, while the Model C
showed major variation.
3.1.4 Story Acceleration
Table 7: Acceleration Comparison THA
Story Acceleration
in mm/sec²
MODEL
A
MODEL B
MODEL
C
Story10 498.19 325.27 6.03
Story9 319.08 292.72 4.71
Story8 446.58 313.88 5.52
Story7 509.23 298.31 5.38
Story6 369.14 314.09 4.94
Story5 455.69 328.2 5.36
Story4 540.87 297.1 5.18

Story3 421.34 333.3 4.83
Story2 476.05 317.72 5.07
Story1 500.43 436.94 4.8
P Story 731.14 724.07 7.43
Base 769.64 769.64 8.75
Here again it is observed that the acceleration values do not
vary much between Model A and Model B, while the Model C
showed major variation. Hence based on the THAresultsthe
base isolated model – Model C is effective in seismic
performance criteria.
3.2 Response Spectrum Analysis (RSA) Results
3.2.1 Story Drift
Figure 8: Drift Comparison RSA
The variation of drift with respect to various models is
shown. It is observed that theModel Cdriftslessercompared
to Model A and B.
Figure 9: Displacement Comparison RSA
Here both Model B and C showed great reduction in
displacement.
3.2.3 Story Shear
Figure 10: Shear Comparison RSA
showed major variation.
3.2.4 Story Acceleration
Figure 11: Acceleration Comparison THA
Here again it is observed that the acceleration
values do not vary much between Model A and Model B,
while the Model C showed major variation. Hence based on
the RSA results the base isolated model – Model C shows
high seismic performance.
3.3 Push Over Analysis (Poa) Results
3.3.1 Story Drift
Figure 12: Drift Comparison POA

The variation of drift with respect to various
models is shown. It is observed that the Model C drifts
lesser compared to Model A and B.
Table 13: Displacement Comparison POA
Story Max Displacement
in mm
Story10 226.421 124.656 9.09
Story9 223.484 122.174 8.56
Story8 218.471 117.972 7.955
Story7 211.26 111.951 7.26
Story6 201.845 104.107 6.475
Story5 190.219 94.447 5.604
Story4 176.287 82.979 4.658
Story3 159.247 69.687 3.65
Story2 132.948 54.367 2.601
Story1 86.719 35.622 1.513
Here C showed greater reduction in displacement with
respect to A and B.
3.3.3 Story Shear
Table 14: Shear Comparison POA
Story Max Shear
in kN
Story10 400.2501 198.5654 24.1258
Story9 658.2547 410.7158 45.1474
Story8 814.5987 687.7694 63.5548
Story7 950.2248 841.0248 75.0017
Story6 1072.7711 998.5641 87.7779
Story5 1178.5853 1024.2563 98.0334
Story4 1281.5471 1125.23 107.5778
Story3 1364.439 1247.326 116.16
Story2 1459.0221 1341.231 123.8953
Story1 1555.1459 1410.265 131.7208
P Story 1556.2547 1435.528 132.547
showed major variation. HencebasedonthePOAresultsthe
base isolated model again showedmaximumperformancein
withstanding seismic forces.
4.0 COMPARISON OF SEISMIC PARAMETERS
The following table shows the result comparison of all the
three analysis methods.
Table 15: Drift Comparison
Type Max Drift
in mm
THA RS POA
Fixed Base 26.622 18.13 83.234
Braced 1.914 3.963 24.809
Base Isolated 0.415 1.815 2.344
Table 16: Displacement Comparison
Type Max Displacement
in mm
THA RS POA
Fixed Base 163.03 123.36 226.42
Braced 13.344 32.689 124.66
Base Isolated 2.504 13.165 9.09
Table 17: Shear Comparison
Type Max Shear
in kN
THA RS POA
Fixed Base 2294.3 1557.7 2310.5
Braced 2606.7 1883.9 2209.5
Base Isolated 32.935 132.67 1912.3
From this comparisonitisclearlyconcludedthatthe
base isolated model shows high seismic performance when
compared to fixed base model and braced model. And the

result is validated by doing three different types of analysis
that yields same kind of observation.
5. CONCLUSIONS
In this project the fixed base model, braced model
and base isolated model base isolated model by providing
lead rubber bearing were analyzed by time history analysis
(El-centro), response spectrum analysis and push over
analysis. From these Analysis results following conclusions
can be made.
 Story shear reduced greatly after the lead rubber
bearing (LRB) is provided as base isolation system
when compared to braced system and hence LRB
isolators reduces the seismic effect on building
more effectively.
 Also the max storey shear is also reduced after base
isolation is introduced,whichmakesstructuremore
stable than braced system during earthquake .
 Story drift are also minimized especially in higher
stories which makes structure safe against
earthquake.
 And overviewing all comparison the base isolation
technique is found to improve the performance of
the building by about 98%.
Therefore, it is concluded that the base isolation
technique is superior in reducing the seismic response
of the structure thus enhancing the performance of the
building subjected to earthquake loads.
REFERENCES
[1] Athanasios A. Markou (2016) Response simulation of
hybrid base isolation systems under earthquake
excitation Soil Dynamics and Earthquake Engineering
84(2016) 120– 133.
[2] Donato Cancellara et al., A novel seismic base isolation
system consisting of a lead rubber bearingin serieswith
a friction slider. Part I: nonlinear modeling of the
system, Applied Mechanics and Materials Online: 2012,
Vols. 256-259, pp 2185-2192.
[3] ETABS Three Dimensional Analysis and Design of
Building Systems Tutorial Computers and Structures,
Inc. Berkeley, California, USA First Edition July 2000.
[4] Juan C Ramallo (2008) “Smart’’ Base Isolation Systems
Journal of Engineering Mechanics, Vol. 128, No. 10,
October 1, 2002. ©ASCE.
[5] Indian Standard Criteria for Earthquake Resistant
Design Structure 1839-2002.and IS 875 (Part 2):1987.
[6] Minal Ashok Somwanshi (2015), Seismic Analysis of
Fixed Based and Base Isolated Building Structures,
International Journal of Multidisciplinary and Current
Research,Vol 3.
[7] Pankaj Agarwal and Manish Shirkhande (2010)
Textbook on “Earthquake Resistant Design of
Structures”, PHI Learning Private Limited, New Delhi .
[8] Tremblay, R. Archambault, M.H., and Filiatrault, A.
(2003). Seismic Performance of Concentrically Braced
Steel Frames made with Rectangular Hollow Bracing
Members. ASCE J. of Struct. Eng., 129:12, 1626-1636.
[9] Trevor E Kelly, S.E (2001) “Design Guidelines on Base
Isolation of Structures”, Holmes consulting group, New
Zealand.
[10] Wang, Y., “Fundamental of seismic base isolation”,
international training programs for seismic design of
building structures hosted by NCREE, 139-149.

IRJET- A Study on Seismic Performance of Reinforced Concrete Frame with Lead Rubber Bearing Base Isolation System

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IRJET- A Study on Seismic Performance of Reinforced Concrete Frame with Lead Rubber Bearing Base Isolation System