JSSI 30th Anniversary Commemorative Special Issue

SEISMIC ISOLATION STRUCTURES WORLDWIDEMarch 2024

The Japan Society of Seismic Isolation

CONTENTS
PREFACEJAPANRESEARCH AND DEVELOPMENT ACTIVITIES ON SEISMICALLY ISOLATED BUILDINGS…. 1
PERFORMANCE BASED DESIGN OF SEISMICALLY ISOLATED BUILDINGS IN JAPAN…. 8
ACTIVITIES OF JSSI FOR THE PROMOTION AND DISSEMINATION OF SEISMICALLYISOLATED BUILDINGS
…. 16
CHINA
SEISMIC ISOLATION, ENERGY DISSIPATION, AND CONTROL FOR STRUCTURALRESILIENCE ENHANCEMENT IN CHINA: STATE-OF-THE-ART REVIEW ANDAPPLICATIONS…. 26
TAIWAN
CURRENT STATE AND FUTURE CHALLENGES OF SEISMIC ISOLATIONDEVELOPMENT IN TAIWAN
…. 62
INDIA
APPLICATION OF SEISMIC BASE-ISOLATION TECHNOLOGY IN INDIA…. 77
TURKEYSEISMIC ISOLATION IN TÜRKİYE…. 94
RUSSIA
EXPERIENCE OF USING SEISMIC ISOLATION SYSTEMS IN RUSSIA…. 102ITALY
CURRENT STATE AND CHALLENGES OF SEISMICALLY ISOLATED STRUCTURES IN
ITALY…. 116
U.S.
RECENT APPLICATIONS OF SEISMIC ISOLATION IN NORTH AMERICA…. 128CHILE
SEISMIC ISOLATION IN CHILE…. 136NEW ZEALAND
CURRENT STATE AND CHALLENGES OF IMPLEMENTING SEISMIC ISOLATION IN
NEW ZEALAND (2023)…. 150PREFACE
Welcome to the JSSI 30th Anniversary Commemorative Special Issue on Seismic Isolation Structures
Worldwide.
In recent decades, seismic isolation technology has emerged as a crucial tool in mitigating thedevastating effects of earthquakes on structures and infrastructure worldwide. This special issue serves
as a platform for researchers, engineers, and practitioners to share their insights, innovations, andexperiences in the field of seismic isolation.
Earthquakes remain one of the most unpredictable and destructive natural disasters, posing significant
risks to human life and infrastructure. Traditional methods of earthquake-resistant design often involve
making structures stronger and stiffer, but this approach has limitations and can be prohibitively
expensive. Seismic isolation offers a complementary strategy by decoupling structures from groundmotion, thereby reducing the forces transmitted to the building and its occupants.
The adoption of seismic isolation technology has grown steadily across the globe, with applications
ranging from critical facilities such as hospitals and nuclear power plants to cultural heritage sites andresidential buildings. As interest in seismic isolation continues to expand, so too does the need for acomprehensive understanding of its principles, design considerations, and performance characteristics.
This special issue aims to contribute to the advancement of seismic isolation technology by providing
a platform for the exchange of knowledge and ideas. Through the publication of cutting-edge research,case studies, and technical reviews, we seek to foster collaboration and innovation in this rapidly
evolving field.
We would like to express our gratitude to the authors for their contributions. We hope that this special
issue serves as a valuable resource for researchers, engineers, and practitioners working in the field ofseismic isolation, and we look forward to further advancements in this critical area of earthquake
engineering.
Taiki Saito
Editor in Chief, the 30th Anniversary of JSSI Commemorative Special Issue
Chairperson, Committee of International Affairs, Japan Society of Seismic Isolation
Professor, Toyohashi University of Technology, Toyohashi, Japan
March 2024

Research and Development Activities on Seismically Isolated Buildings
Akihiro KONDO
Chairperson of Sub Committee for Seismically Isolated Structures, Architectural Institute of Japan (AIJ）, Tokyo, Japan

ABSTRACTThis paper reviews the research and development activities on seismically isolated (SI) buildings ofArchitectural Institute of Japan (AIJ). Analysis of the number of summaries presented at AIJ annual
meetings, the number of technical papers on transactions of AIJ, and research trends in relation to thenumber of SI buildings constructed in Japan was conducted. It also describes “Design
Recommendations for Seismically Isolated buildings” published by AIJ and the current activities of
the Sub Committee for Seismically Isolated Structures of AIJ.
KEYWORDS: Architectural Institute of Japan, Sub Committee for Seismically Isolated Structures,
Trends in research
1. INTRODUCTION
In Japan, research and development of modern seismically isolated (SI) buildings has been underway
since the early 1980s. About 40 years have passed since 1983, when a modern SI building in Japanwas constructed using laminated rubber bearings. The subsequent history of seismic isolation in Japanis presented in previous technical papers1), 2).
This paper reports the number of summaries in annual meeting of AIJ and peer-reviewed technicalpapers (Transactions of AIJ).
In addition, keywords mentioned in the technical paper will be picked up and trends in research anddevelopment will be introduced. It also introduces “Design Recommendations for Seismically Isolatedbuildings” published mainly by Sub Committee for Seismically Isolated Structures of the AIJ and therecent activities of the subcommittee.
2. Dating the transition of seismic isolation in Japan
2.1 Number of seismically isolated buildings in Japan
Figure 1 shows the annual number and cumulative number of SI buildings in Japan. The number of
SI buildings increased sharply after the 1995 Southern Hyogo Prefecture Earthquake (Kobe EQ.). Also,
after the 2011 Off the Pacific Coast of Tohoku Earthquake (Tohoku EQ.), the number of SI buildings
exceeded 300 per year, but the number is gradually decreasing after the event. A total of over 5,000 SI
buildings have been constructed by 2021.
The first modern SI building in Japan was a two-story house built in 1983 using 800mm diameter1

laminated rubber bearing and friction dampers. Since then, SI buildings have been applied mainly totechnical research institutes of construction companies and to in-house buildings of seismic isolation
device manufacturers.
Although there have been cases where it has been applied to general buildings, we have heard that insome cases there were concerns from clients at the time as to whether buildings could be built on rubber
bearings.
Num.of SI Bldgs
400
1stPeriod300

2nd
Period3rd
Period4th
PeriodCumulative(4-1)

Cumulative
Num.of SI Bldgs
6000
5th 5286
Period(4-2)
TohokuEQ. ▼▲Kumamoto
EQ.

4000

200

0

2000

Kobe
EQ. ▼

0
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021

100

according to a survey by the Japan Society of Seismic Isolation (JSSI)

Figure 1 Annual number of seismically isolated buildings
The chronology of SI buildings is set up by looking back at the transition of SI buildings in Japan andcategorized as "the 1st to 4th period of SI buildings”.
The 1st to the 4th period of seismic isolation is the chronological classification used in "Structural
Response and Performance for Long Period Seismic Ground Motions" published by the Architectural
Institute of Japan (AIJ) in 20073).
The dating of the 4th period is also divided into two periods by Prof. Furuhashi : Early (4-1) and Late
(4-2) for the 4th period4).
In addition, the 5th period has been additionally established firstly in publications edited by the Japan
Society of Seismic Isolation (JSSI)5) and Kobayashi et al. also show for the 5th period by a survey of
SI building design trends based on performance sheets6).
The above chronological settings are classified mainly based on the number of SI buildings
constructed and their relationship to the earthquake damage, the Building Standard Law and otherlegislation, and social background.
Characteristics of these period categories are listed following.
1st period (～1988）Beginning stage
Application of seismic isolation by pioneering designers and researchers
Application to own facilities of construction companies, seismic isolation device manufacturers.
2nd period (1989～1994) Before Southern Hyogo Prefecture Earthquake (Kobe EQ.)
Application to housing building, Application to Mid-story SI buildings
Examination of input earthquake exceeding design level
3rd period (1995～1999) After Southern Hyogo Prefecture Earthquake (Kobe EQ.)
Rapid increase in the number of SI buildings.

2

Diversification of applications and isolation system
4th period (2000～2016) Revision of Building Standards Law
Designated seismic isolation devices as designated building materials
Application to high-rise building
5th period (2017～) Countermeasures against long-period earthquake
Mandatory countermeasures against long-period earthquake caused by Nankai TroughConsideration of characteristic changes of seismic isolation devices due to cyclic deformation
2.2 Number of technical papers of field of seismic isolation at the annual meeting of the AIJ
The annual meeting of AIJ is usually held in autumn. At the annual meeting the latest studies, findings
and information are exchanged through technical sessions, panel discussions, lectures, and exhibitions.
Figure 2 shows the number of submitted summaries in the field of seismic isolation at the annual
meeting of AIJ.
The statistical data shown in Figure 2 indicates that while the number of SI buildings was very small
between 1988 and 1991(1st and 2nd period), about 75-100 summaries were submitted.
At that time, research topics included experiments and modeling of laminated rubber bearings anddampers, vibration table tests of SI buildings, simulation analysis methods, and SI buildings design
methods. The research and development during this period may have supported the rapid increase in
SI building construction since 1995.
Although the number of summaries submissions will increase further in the 3rd period (1995-1999),
the growth in the number of SI buildings constructed in a year is slowing.
In the second half of the fourth period (4-2: 2010-2016), both the number of summaries and thenumber of SI buildings tended to be high, indicating that research and development actual applications
during this period were active.
Considering that the number of applications in the most recent 2018-2023 period was around 120140, there has been a lot of seismic isolation-related research and development in recent years. In thelast six years, about 120 summaries have been submitted per year, making it one of the most active
areas of research related to the vibration field.

Num.of
SI Bldgs
400
300

(4-1)

1st
Period2nd
Period3rd
Period(4-2)

4thPeriodNum.ofTechnical Paperof AIJ Anual Mtg.
200
5th
Period
150
100

200
100
▲Kobe
EQ.

50
▲Kumamoto
EQ.

0

1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023

0

▲Tohoku
EQ.

Figure 2 Annual number of seismically isolated buildings
and number of summaries of AIJ annual meetings

3

Figure 3 shows the classification of summaries of the recent six-year (2018-2023) AIJ annual
meetings. About 30~40% of the research topics are related to seismic isolation devices, and about
30~40% are related to response evaluation.
“Devices” include laminated rubber bearings, sliding bearings, dampers, etc.
“System” includes development of frame structures with seismic isolation, 3D seismic isolators, floor
isolation systems, displacement control systems, etc.
“Response Evaluation” includes the response evaluation of the seismic response as well as the
response evaluation considering changes in the characteristics of the seismic isolation system underlong-period earthquake, the response evaluation under strong winds, and the setting of external forces
and their response evaluation when subjected to a Tsunami.
"Observation records" show the effectiveness of SI buildings based on observation records after major
earthquakes.
In recent years, there have been studies related to large input earthquake such as research on thephenomenon of collisions with retaining walls of SI buildings, and research related to braking tocontrol large deformations of SI layers. In addition, seismic isolation effects have been verified throughseismic observation of SI buildings.
DesignExamplesObservation
Records
Devices

Response
Evaluation

Response
Evaluation

SystemSystem2018

Collision
Buffered

DesignExamplesResponse
Evaluation

2019

Response
Evaluation

Collision
Buffered2021

Devices

Collision
Buffered

System2020

Collision
BufferedAI

Experimental
systemDesignExamplesDevices

Response
Evaluation
SystemSystemResponse
Evaluation

Collision
Buffered

DesignExamplesDevices

DesignExamplesObservation
Records
Devices

DesignExamplesObservation
Records
Devices

SystemCollision

2022

2023 BufferedFigure 3 Classification of Technical paper of AIJ annual meetings
Most recently, in 2023, a series of summaries were published on the full-scale seismic isolation test
facility "E-Isolation" 7).
2.3 Trends in research published in Transactions of AIJ
Figure 4 shows a classification of technical papers in the field of seismic isolation published in theTransactions of AIJ during the recent six-years (2018-2023). The total number of papers is 43.
Transactions of AIJ is a peer-reviewed collection of technical papers. The trend of technical paper issimilar to that seen in the summaries at AIJ annual meetings, with a large proportion of papers on large
earthquakes.

4

Observation Response
Experiment
Records
Collision
Buffered

Design
MethodDevices
ExtremeGroundMotionSystemFigure 4 Classification of Transactions of AIJ

Table 1 shows the extracted keywords in the technical papers in each classified category.

Category
Response Experiment
Design Method
ExtremeGround Motion

SystemDevices
Collision,Buffered
Observation
Records

Table. 1 Keywords of Transactions of AIJ

Keywords in paper
Substructure real-time online test
Shaking Table tests
Building Mass Damper, Mid-story isolated system
Cost Minimization
Multi-Cyclic loading tests, Analysis of Heating Interaction Behavior
Fail Safe mechanism, Seismic safety evaluation,
Response Spectrum Method, Ultimate Property,Long-period ground motion
Repeated deformation
Pile Top Seismic Isolation System, Multi-story isolation
High-rise seismic isolation, Vertical seismic isolation
Displacement control system
High-Static-Low-Dynamic-Stiffness (HSLDS)Oil Damper, Steel Damper Deformation capacity
Elastic sliding bearing, Flare-like structure
Collision analysis, Retaining Wall
Strong motion record, Torsional response

Regarding large input earthquake, keywords of technical papers on multi-cyclic loading tests, analysisof heating interaction behavior, fail safe mechanism, ultimate property can be found, and it is assumed
that the research is being conducted against the background of a large earthquake in Japan.
Although the Transaction of AIJ is written in Japanese, The AIJ now publishes international academic
journals covering architectural design, planning and construction, including structural andenvironmental engineering. Japan Architectural Review (JAR).
https://onlinelibrary.wiley.com/journal/24758876
3. Design Recommendations for Seismically Isolated buildings
Design Recommendations for Seismically Isolated Buildings” was firstly published in 1989 which
was just after the 1st period of seismic isolation in Japan.
The preface in the first edition states that the design recommendations have been prepared with anemphasis on the development of objective decision-making materials to assist the designer in making

5decisions, and that they can be augmented and revised as appropriate to meet future technologicaldevelopments.
The subsequent editions of this publication follow that editorial policy, and the same editorial policy
has been followed in the subsequent editions of this publication.
Each edition of the “Design Recommendations for Seismically Isolated Buildings” includes a section
on input earthquake in Japan.
This is based on the understanding that although the estimation of input earthquake is the basis forseismic design (design of SI buildings), at present it is nearly impossible to accurately predict input
earthquakes at the construction site of a building, and that structural designers have been designingunder uncertain conditions. The reason for this is that structural designers have been designing under
uncertain conditions, and it is necessary to understand input earthquake.
For the most current English translation of the latest version is following,
Published May 25, 2016
Design Recommendations for Seismically Isolated Buildings(JPY1,650)
https://www.aij.or.jp/ppv/productId/428856/
4. Recent activities of Sub Committee for Seismically Isolated Structures of AIJ
A Sub Committee for Seismically Isolated Structures has been established within the Architectural
Institute of Japan since 1986.
In the most recent four years (2021-2024) of activity, the author has served as the chairperson of thesubcommittee, and the objectives of the subcommittee's research activities are as follows,“Conduct research and studies that contribute to the appropriate dissemination of SI buildings by
examining applied technologies and research related to SI buildings in light of time transitions.”
Based on the recent social background, the subcommittee has been studying 1. The performance
evaluation index of SI buildings, 2. The contribution of SI buildings to carbon neutrality, 3. BusinessContinuity Plan (BCP) and Life Cycle Cost (LCC) of SI buildings.
Research activities are also being undertaken in anticipation of future revisions to the latest edition of
the Design Recommendations for Seismically Isolated Buildings. We also consider it necessary todisseminate information on the guidelines in English.
5. Conclusion
Given the advanced and important nature of seismic isolation technology in Japan, it is considered
important to disseminate research activities and developed technologies globally.
Seismic isolation is one of the most important structural technologies in Japan, a country prone tolarge earthquakes. It is necessary to continue to promote research and development in cooperation with
AIJ and other related organizations such as the Japan Society of Seismic Isolation (JSSI), Japan
Structural Consultants Association (JSCA).

6

REFERENCES[1] N. Kani, CURRENT STATE OF SEISMIC-ISOLATION DESIGN, The 14th World Conference on
Earthquake Engineering (14WCEE), October 2018, Beijing, China[2] Taiki Saito, Learning from the Past, The Resilient Design and Performance of Seismically Isolated Buildings
in Japan, The 18th World Conference on Seismic Isolation, Energy Dissipation, and Active Vibration Control ofStructures (18WCSI), November 2023, Antalya, Türkiye[3] Structural Response and Performance for Long Period Seismic Ground Motions, Architectural Institute ofJapan (AIJ),2007 (in Japanese)[4] Takeshi Furuhashi, Transition of Seismic Isolation in Japan, The 16th Japan Earthquake Engineering
Symposium, 2023.11 (in Japanese)[5] Seismically Isolated Structures - basic components to design and construction-, The Japan Society of Seismic
Isolation,2022 (in Japanese)[6] M. Kobayashi, N. Hirata, Design trends of seismically isolated buildings based on performance sheets:
Mainly for seismically isolated buildings planned after 1995, Summaries of Technical Papers of Annual Meeting,
AIJ, Structures II, pp. 675-676, 2023 (in Japanese)[7] Yoshikazu Takahashi, Toru Takeuchi, Shoichi Kishiki, Yozo Shinozaki, Masako Yoneda, Koichi Kajiwara,
and Akira Wada, E-Isolation: High-performance Dynamic Testing Installation for Seismic Isolation Bearings
and Damping Devices, International Journal of High-Rise Buildings March 2023, Vol 12, No 1, 93-105,
https://doi.org/10.21022/IJHRB.2023.12.1.9

7

PERFORMANCE BASED DESIGN OF SEISMICALLY ISOLATED BUILDINGSIN JAPAN

Kohei Shintani
General Manager, Nikken Sekkei Ltd

ABSTRACT
Experts often employ nonlinear time history response analysis to assess the building's andisolation layer's reaction to earthquakes in non-residential seismically isolated building design.
The analysis must accurately reflect the seismic isolators' performance variations, as theseelements affect the building's vibration behavior. Meanwhile, a 2000 Ministry of Construction
notice enabled simpler design approaches using the single mass equivalent linearization method,
streamlining the process compared to the previously obligatory nonlinear analysis. Thisevolution has simplified the engineering workload for designing seismically isolated structures
on stable ground. This article reviews Japan's seismically isolated building design progress,
highlighting nonlinear time history response analysis and single mass equivalent linearization.
It also discusses the future prospects for the surrounding situation of seismic isolation building
design.
KEYWORDS: JSCA performance design, seismic isolation, Japan, current state
1

INTRODUCTION

In Japan, seismic isolation is understood as the most effective means of upgrading buildings'
seismic performance and seismic grade. The application of seismic isolation to buildings thatwill serve as disaster prevention facilities after a large earthquake (government buildings, firestations, police stations, core hospitals, etc.) is a natural demand for improving seismic
performance since those buildings are expected to have the performance of immediate
occupancy after a large earthquake. However, in addition to the effect of reducing seismic forces
through the use of seismic isolation, from the perspective of the building owner, the value ofseismic isolation lies in the sense of secure feeling gained from the response acceleration
reduction of the superstructure, or in the prevention of damage to expensive medical equipmentin advanced medical facilities, for example. Some developers are trying to differentiate theiroffice buildings from their competitors by the high performance of seismic isolation. In addition,
seismic isolation in logistics centers, data centers, and other facilities that form the foundationof social infrastructure has become a common practice.

8

2

PERFORMANCE OF SEISMIC ISOLATION BUILDINGS

2.1 Performance Criteria
Figure 1 and Figure 2 illustrate the seismic grade and structural type that the author uses toagree with a building owner. Figure 1 illustrates the recommended structural type based on therequired seismic grade and the building height. Figure 2 is a detailed explanation of eachstructural type's seismic grade and expected performance.

Figure 1 Seismic resistance grade and recommended structural type per the height

Figure 2 Detailed performance of each seismic resistance grade and structural type9

JSCA, Japan Structural Consultants Association, also published the commentary brochure onbuilding performance design in 2018, promoting public understanding and awareness ofseismic grade. In the brochure, as part of the building performance menu, it is explained thatseismic isolation structures can achieve higher performance in reducing seismic damage thanvibration control or general aseismatic structures. (Table 1 and Figure 3)
Table 1. Target performance menu per seismic grade [1]Figure 3 The concept of relationships, the earthquake intensity vs. the building damage [1]102.2 Effectiveness of Seismic Isolation in Large Earthquake
Observation records in past large earthquakes have shown that the response acceleration of thesuperstructure of seismically isolated buildings was reduced by half to one-third compared to a
general aseismatic building.
Figure 4 shows the outline comparison of response differential regarding floor acceleration
among general aseismic, vibration-controlled, and seismically isolated buildings.

Figure 4 Comparison of response acceleration in building types
Figure 5 shows the actual acceleration
record of several seismic isolationbuildings in the past. The red lines
denote the observed acceleration at the
top of the building, and the black (orgray) line indicates the acceleration on
the ground or the base of the building.
These records show that the seismic
isolation system reduces the floor
response acceleration by around half to
one-third compared to the earthquake
input.
Because
of
the
large
displacement of the seismic isolation
layer in seismically isolated buildings,
it is important for building maintenanceto install a recording board andaccelerometers to record the response
during earthquakes.

Figure 5 Sample records of acceleration[2]113

DESIGN PROCEDURE OF SEISMIC ISOLATION BUILDINGS IN JAPAN

3.1 Time History Analysis Method
In Japan, the construction permission
process requires that for buildings
exceeding 60 m in height orseismically isolated buildings on soft
ground, the engineer in record should
execute time history analyses toprove that the response values satisfy
the design criteria.
Figure 6 shows the required analysis
type in the construction permission
process per design conditions and the
Figure 6 Building permission process
design flow based on time history
response analysis. Figure 7 shows theflow of confirming the response
results of the time history analysis
and determining the structuralmembers. In practice, a preliminary
time history response analysis isperformed initially to set a slightly
conservative design seismic force,and a confirmatory time history
analysis is executed during the
Figure 7 Flow of analysis and design
detailed design stage.
Figure 8 shows typical design criteria, and the time history analysis output will be directlycompared to the criteria. Input ground motions adopted in the time history analysis shall equal
to or more than seven (including long-period earthquake motions mentioned in section 4.1) as
extremely rare earthquakes. The maximum response values shall be compared with the design
criteria.

Figure 8 Typical performance criteria utilizing time history analysis results

123.2 Code Prescript Procedure (Single Mass Equivalent Linearization Method)
When the building height is 60 m or less, the predominant period of ground is 0.6 sec or less,and there is no risk of liquefaction, the notice provides a method to calculate the response valueof the seismic isolation layer using the equivalent linearization method.
In general, the stiffness of the superstructure is sufficiently stiff compared to the seismic
isolation layer, so it is often possible to treat the superstructure as a single mass in the evaluationof the dynamic properties of the entire building. Basically, the superstructure plan is to be
simple shape and does not exhibit complex dynamic properties.
As shown in Figure 9, the relationship between shear force and deformation of the seismic
isolation layer can be denoted by a bilinear curve, and the isolation layer displacement can bepredicted by considering various types of damping. The notice instructs us to consider
variations in product properties and other factors and take an appropriate safety factor in thecalculated values.

Figure 9 Calculation method for shear force and deformation of isolation layer [2]3.3 Feature of Isolation Layer Design
One of the critical issues in the design of seismicallyisolated buildings is how to set the ultimate state of
the entire structure. In the design of seismicallyisolated buildings, plasticity of the superstructure is
not assumed in principle. On the other hand, it is theengineer's responsibility to set the state of the entire
building in the event of a larger-than-expectedearthquake. Generally, the final state is often set toprevent failure of seismic isolation bearing in alarger-than-expected earthquake. Then, the seismic
isolation layer displacement exceeds the clearance,i.e., the building collides with a retaining wall.

13

Isolator

Figure 10 Perimeter of isolation layer

4

FUTURE PROSPECTS(Please note that the following represents my thoughts as an structural engineer and is not theconsensus of my company or organization.)
4.1 Problems induced by geological structure of metropolitan areas in JapanThe oil tank fire in the 2003 Tokachi-oki Earthquake triggered research on the effects of longperiod seismic motion on high-rise buildings and seismically isolated buildings with longnatural periods. In particular, the significant shaking observed in high-rise buildings in theTokyo metropolitan area and Osaka Bay area during the 2011 off the Pacific coast of Tohoku
Earthquake has increased momentum to incorporate long-period and long-lasting seismic
motion (so-called "long-period seismic motion") into structural design, and in 2017, the longperiod seismic motion became a mandatory seismic input for design within specified urban
areas. Because Kanto Plain, Nobi Plain, and Osaka Plain, the major metropolitan areas in Japan,
are all sedimentary basins, and their ground structures tend to amplify long-period seismic
motions due to their long excitation periods, the building law specifically mandated to consider
long-period seismic motions in those metropolitan areas.

Figure 11 Pseudo velocity response spectrum of long-period earthquake input in Osaka[3]As shown in Figure 11, the specified spectrum is much larger than the ordinary input spectrum
in the region of long period. Long-period seismic motion with a predominant long-period
component and long duration has a huge maximum velocity amplitude of 120 to 150 cm/sec
compared to the design input seismic motion used in ordinary seismic isolation design, so it isimportant to study the response characteristics of seismic isolated buildings to a ground motionthat exceeds the level specified by building law and the margin to the limit. Depending on thelevel of long-period seismic motion, the margin of energy absorption capacity in the seismic
isolation layer may be reduced or even exceed the horizontal clearance.

144.2 Reliability of seismic isolation products
The system of designated building materials for seismic isolation components, which was
institutionalized with the establishment of the public notice, contributed to the spread of
products under Japan's type approval system. However, it is still fresh in our memories that data
falsification scandals involved seismic isolation rubber products and oil damper products in2015 and 2018, respectively. These scandals undermined the confidence of "designated building
materials" system under the government notice. The society suffered doubts about the quality
assurance system based on manufacturers' in-house testing under the ministerial certification
system, and structural engineers at the time felt anger that they had nowhere to go.
As a design engineer, it is desirable to be able to employ a wide variety of seismic isolation
products to increase the means to meet the owner's requirements on the building performance.
The full-scale seismic isolator experimental device, E-isolation in Miki City, Hyogo Prefecture,
was constructed in 2023. This facility is reassuring to practitioners who can obtain proof of thereliability of the products those they adopt. Practitioners need to fulfill their accountability sothat there is a social consensus on the testing cost burden for the benefits of seismic isolation.

5 CONCLUSION
Japan is located at the complex intersection of four plates, and the frequency of earthquakes ismuch higher than in other countries and regions. 20% of the earthquakes of magnitude 6.0 or
greater between 1994 and 2003 occurred around Japan. Although seismic isolation structures
have rapidly become popular since the 1995 Southern Hyogo Prefecture Earthquake, according
to the JSSI report, the number of newly constructed seismically isolated buildings is about 200
per year, which is less than 1% of the total number of new buildings constructed in Japan eachyear.
There are several reasons why the number of seismically isolated buildings has not increasedmuch even though Japan is a highly seismic country: (1) the cost of seismic isolation layers is
close to a simple increase of 1-story cost for low-rise buildings, (2) nonlinear response analysis
is required which requires more design time and effort, (3) securing seismic isolation clearance
in urban areas reduces land use efficiency, especially in urban areas. For Owners, it is logicalto prioritize investment in comfortable facilities and beautiful design over spending money on
measures against earthquakes that may occur at any time. It is desirable that structural engineers
propose the adoption of seismic isolation to building owners more actively.
REFERENCES[1] The Guide to Safe Buildings, JSCA Performance-Based Seismic Design, JSCA, 2018[2] On courtesy of ASDO-JSCA Tokyo technical seminar[3] Countermeasures against Long-period Ground Motions caused by a large Earthquake along the
Nankai Trough in high-rise Buildings, etc., Ministry of Land, Infrastructure, Transport and Tourism,
Japan, 2016

15

ACTIVITIES OF JSSI FOR THE PROMOTION AND DISSEMINATION OF
SEISMICALLY ISOLATED BUILDINGS

Yoshihisa Kitamura
Executive Director, JSSIABSTRACTThis paper describes the activities of the Japan Society of Seismic Isolation and the status of
the spread of seismically isolated structures. In Japan, seismically isolated buildings have
rapidly become popular since the 1995 Southern Hyogo Prefecture Earthquake. In recent years,
it has been widely used in skyscrapers. It is important to design seismically isolated structures
not only against earthquakes, but also against wind. It is also necessary to take care to preventthe seismic isolation expansion joint from being damaged during an earthquake. Seismicallyisolated structures need to be properly constructed and maintained to ensure their full potential
in the event of an earthquake. The Japan Society of Seismic Isolation publishes various
standards and guidelines regarding design, construction, maintenance, and management,
contributing to the healthy spread of seismically isolated structures.
KEYWORDS: JSSI , Status of SI
1. INTRODUCTION
In Japan, the first building with a seismically isolated structure was constructed in 1983, andapproximately 40 years have passed this year.
During the 1995 Southern Hyogo Prefecture Earthquake, two seismically isolated buildings in
Kobe City were undamaged, and the effectiveness of seismic isolation was confirmed based onrecords from accelerometers installed in these buildings. This led to the rapid spread ofseismically isolated (SI) buildings in Japan.
Since the Southern Hyogo Prefecture Earthquake, Japan has frequently been struck by large
earthquakes, such as off the Pacific coast of Tohoku Earthquake and the Kumamoto Earthquake.
Through experiencing many earthquake damages, we have accumulated knowledge regarding
the design, construction, and maintenance of seismically isolated structures.

16

Sharing this kind of knowledge is essential for the development of SI structures.
The Japan Society of Seismic Isolation (JSSI) collects a variety of information regarding thesestructures and vibration controlled (VC) structures, and publishes various standards andguidelines.
This paper introduces JSSI and the current status of SI structures in Japan based on various datacollected by JSSI, also introduces various guidelines and standards published by JSSI.
2. ABOUT JSSIThe JSSI was established in 1993 with the aim of popularizing SI structures in Japan.
Since its establishment, it has conducted numerous surveys and studies on SI structures andformulated many standards regarding design, construction, materials, and maintenance.
In 2000, “The Qualification System for SI Construction Management Engineers” wasestablished to train engineers who can properly construct and maintain. Additionally, in 2003,
inspection for SI buildings, “The SI Inspection Engineer Qualification System'' was established.
In 2004, JSSI was designated as a performance evaluation organization by the Ministry of Land,
Infrastructure, Transport and Tourism (MLIT), and conducts performance evaluations ofseismic isolation materials and buildings.
Currently, JSSI consists of 87 regular members (corporations), 233 regular academic members(individuals), and 115 supporting members (corporations).
Figure 1 shows the organization of JSSI. The technical committee conducts various researchstudies on SI structures and VC structures, and publishes standards and guidelines.
The committee for foreign affairs disseminates and collects information outside of Japanthrough workshops for SI and VC, and other activities.
The dissemination committee conducts dissemination activities such as holding seminars,
publishing journals and books.

Figure 1 Organization Chart of JSSI

17

3. CURRENT STATUS OF SI BUILDINGS IN JAPANEvery year, JSSI receives information from member companies. JSSI compiles, analyzes andpublishes the data.
Based on this data, the current status of SI buildings in Japan is reported.
3.1 Number of SI Buildings
Figure 2 shows the number of SI buildings other than single-family houses constructed in Japan.
Analytical research on SI structures has been conducted in Japan since the 1960s, and in 1983
the first SI structure was constructed, a two-story reinforced concrete building using laminatedrubber bearings with a diameter of 30 cm and friction dampers.
However, the use of SI structures has mainly been limited to technical research laboratories of
construction companies and buildings owned by SI device manufacturers.
At that time, public awareness of SI was low, and its use was limited.
After the 1995 Southern Hyogo Prefecture Earthquake, the number of buildings increased
rapidly, with around 150 buildings being built each year.
In the wake of the 2011 Tohoku Pacific Coast Earthquake, the number of cases increased again
to over 300 per year, but has since gradually decreased.
A total of more than 5,000 SI buildings will be constructed by 2021.
Approximately 500,000 buildings are constructed annually in Japan, of which approximately
400,000 are single-family homes.
Of these, approximately 15,000 buildings require earthquake-resistant structural calculations,and only 1% have SI structures4).
JSSI hopes that SI structures will become more widespread in the future.

Figure 2 Number of SI buildings in Japan. by year
3.2 Usage
Figure 3 shows the usage ratio of SI buildings for the five years from 2017 to 2021.
The most common uses are condominiums and office buildings.
SI condominiums have the added value of ensuring building functionality and preserving
property in the event of major earthquakes, and are popular despite slightly expensive.

18

Furthermore, since the 2011 Tohoku Earthquake, there have been concerns about a futureearthquake directly hitting the Tokyo metropolitan area or a mega-Nankai Trough earthquakeof similar magnitude.
In addition, SI structures are increasingly being adopted in government buildings, disaster basehospitals, and other facilities as disaster prevention facilities in the event of earthquakes.
On the other hand, the adoption of SI structures in schools is limited.
In the case of public facilities such as schools, budget constraints and lack of funds are obstacles
to the adoption of SI structures.
Hospitals need to treat patients during disasters, and are required to continue functioning evenafter earthquakes.
According to a survey conducted by the Ministry of Health, Labor and Welfare in 2023, only
about 8% of the 8,160 hospitals in Japan are seismically isolated.
JSSI would like to work to increase the number of SI hospitals in Japan in the future.

Figure 3 Usage ratio of SI buildings(from 2017 to 2021)

Figure 4 Usage ratio for isolation divices(from 2017 to 2021)

3.3 SI Devices
As shown in Figure 4, most seismic isolation members in Japan are laminated rubber bearings
such as NRB (natural rubber bearing), LRB (lead rubber bearing), and HDR (high damping
rubber bearing).
Sliding bearings with elastomer are also often used to extend the natural period of SI buildings.
In recent years, spherical sliding bearings have also come into widespread use.
Laminated rubber bearings have very low tensile resistance, and sliding bearings have no tensile
resistance.
For these reasons, when tensile force during an earthquake acts on the bearings of high-risebuildings, linear rotating ball bearings, which have tensile resistance and a very small
coefficient of friction, are sometimes used.
Furthermore, in the case of laminated natural rubber bearings that do not have damping
performance, steel dampers, oil dampers, or viscous dampers are used as dampers.

19In a SI structure, the isolator supports the weight of the superstructure while deforming
significantly in the horizontal direction.
Since the performance of a SI structure depends on the quality of each isolator, it is importantto verify and confirm the dynamic characteristics of the isolators and ensure their quality.
In order to verify and understand the performance of large-scale SI devices, it is necessary to
conduct full-scale dynamic tests that reproduce the conditions in which a full-scale SI device is
exposed to earthquakes.
Until now, there was no large-scale dynamic test equipment in Japan that could verify the
dynamic characteristics of actual large-scale SI devices.
In 2023, a “full-scale SI experimental device E-Isolation” was completed in Miki City, Hyogo
Prefecture, which allows experiments on full-scale SI and VC devices under velocity anddisplacement conditions during major earthquakes.
It is expected that the active use of this facility will further increase the reliability of Japan's SI
and VC technology.
3.4 SI Retrofit
Figure 5 shows the annual number of existing buildings that have been retrofitted with SI
structures.
Renovations to SI structures not only have high earthquake resistance, but can also be done
while the building is still in use, so the usability of the building will not be compromised either
during or after the renovation.
Transferring the weight of buildings to SI bearings is extremely difficult and expensive, but todate approximately 200 buildings have been retrofitted to be earthquake resistant, more thanhalf of which are government facilities.
SI retrofits are also often used in historic buildings with high architectural evaluation and low
earthquake resistance.

Figure 5 Number of buildings retrofitted for seismic isolation. by year
3.5 Application to High-rise Buildings
According to Japan's Building Standards Law, buildings with a height of 60m or more areclassified as super high-rise buildings.

20

For super high-rise buildings, it is mandatory to confirm seismic performance through time
history response analysis method, and the seismic design must be reviewed by a performance
evaluation facility designated by the MLIT.
Additionally, there are no height restrictions for SI buildings.
In other countries, it is common for SI buildings to have height restrictions, so these regulations
are unique to Japan.
Figure 6 shows the annual number of SI super high-rise buildings in Japan.
Initially, SI technology was not applied to high-rise buildings because their natural period was
already long.
However, the benefits of using SI structures in improving safety have been recognized, andsince 2000, the use of SI structures in super high-rise buildings has increased.
To date, more than 700 SI super high-rise buildings have been constructed, of which more than
500 are condominiums.
Japan's tallest SI building seismically isolated at mid-story is 228m high.
The tallest SI building, with a seismic isolation layer in the foundation, is 192 meters high.
Super high-rise buildings have long natural periods, so in order to exhibit sufficient SI effects,
it is necessary to lengthen the SI period.
In addition, structural measures must be taken to prevent the generation of tensile forces in the
bearing during earthquakes.
In addition, as the building is high-rise, it is greatly affected by wind, so countermeasures must
be considered to the case of strong winds.

Figure 6 Number of SI super high rise buildings. by year
4. STANDARDS ISSUED BY JSSI
4.1 Wind Resistant Design Guidelines
In Japan, tropical cyclones called typhoons come several times a year from summer to autumn.
Typhoons hit buildings over a long period of time with strong winds with a maximum
instantaneous wind speed of 30 to 60 m/s.
The higher SI building becomes, the greater the impact will be.
When designing high-rise buildings, it is necessary to confirm that the horizontal displacement21

of SI buildings does not become excessive during strong winds.
Wind load has an average component and a fluctuating component, but laminated rubber
bearing with lead plug and laminated high-damped rubber bearing, creep deformation occurs
due to the average wind component, so countermeasure must be taken.
Sometimes a mechanism is used that includes a rod (shear pin) that cannot be broken by wind,
but can be broken by a slightly larger earthquake.
Additionally, some systems have a mechanism to stop the oil damper from moving duringstrong winds based on information from anemometers.
JSSI publishes wind resistant design guidelines.
As shown in Figure 7, JSSI's seismic design guidelines classify the response state of SI layer
due to wind loads into three levels (ranks A, B, and C), and consider the creep and fatigue
characteristics of SI devices.
Horizontal force
of seismic isolation layer
Rank B
Yield of damper
Elastic in fluctuation range

Wind force
Average

Fluctuation

Rank C
Yielding of damper
Nonlinear in fluctuation range

Steel damper
LRB

Fluctuation
Creep
Rank A
Elastic

Hysteresis energy
Average

Average

Seismic isolation structurewith hysteresis dampers

Horizontal displacementof seismic isolation layer

Figure 7 Design of seismically isolated buildings2)4)4.2 SI Expansion Joint Guidelines
During the 2011 Tohoku Earthquake, SI buildings were fully effective, and there was no damage
to the building's main structure or finishing materials such as ceiling materials.
However, many SI expansion joints (Exp) were damaged. According to a survey conducted by
JSSI after the earthquake, some of the SI expansion joints were damaged in 30% of thebuildings surveyed.
Even if the building itself can continue to function, damage around the SI expansion joints makeit difficult for people and vehicles to enter and exit, affecting the continued functioning of thebuilding.
Damage to SI expansion joints can occur even in small to medium earthquakes and is costly torepair.
This is a serious problem for the widespread use of SI structures, as it gives the impression thatbuildings with SI structures have inferior performance in small to medium earthquakes thannormal buildings.
JSSI has created guidelines that summarize points to keep in mind when designing,
manufacturing, constructing, and maintaining SI expansion joints.

22

Table 1 shows the design target performance of SI expansion joints, and there are three grades:Type A, Type B, and Type C.
Type A, which has the highest performance, maintains its functionality even after a major
earthquake and can continue to be used without repair, whereas Type B and Type C are subject
to "damage level 1" when shaken by a major earthquake, or become "damage level 2".
Damage level 1 means that there are no major deformations, inclinations, or gaps, and it ispossible to continue using the expansion joints after an earthquake by adjusting and repairingthem.
Damage level 2 is a more serious condition, where there is no falling off, but there are steps in
the floor and protrusions in the wall, and large-scale repairs and parts replacement are required
before the SI expansion joint can be used again.
Building designers are required to set target performance in agreement with the building ownerand clearly state the performance indicators in the design documents.
Table 1. Performance Classification of Seismic Isolation Expansion Joints1)4)
performance
index

Under moderate
earthquake

Under large
earthquake

Confirmation
methodLocation of use

A

Functional

Functional

Shaking table test

Areas with heavy
pedestrian traffic

B

Functional

Damage Level 1

Shaking table test
or static test

Areas with moderate pedestrian
traffic

C

Damage Level 1

Damage Level 2

Confirm by drawing

Areas with little orNo pedestrian traffic

4.3 Maintenance and Management Standards for SI Buildings
In order to properly perform SI buildings, it is necessary to properly maintain and manage them.
JSSI has published “Maintenance and Management Standards for Seismically Isolated
Buildings”, so that what maintenance and management should be carried out at the time ofdesign should be described in the design documents.
Many buildings have maintenance plans based on these standards.
As shown in Table 2, the maintenance management standards specify the timing, types, anditems of inspections.
Additionally, JSSI has established a “Seismic Isolation Inspection Engineer Qualification
System” to certify inspection engineers.
Approximately 2,700 engineers have this qualification, 2023.
Inspections of SI buildings are to be carried out by engineers who have this qualification.

23

Table 2 Classification of inspection 3)
Classification of
inspections

When

How

Items

Control values

Contents
SI devices, piping for equipment, electricalequipment, SI layer, outer periphery of building,seismic gap, fireproofing, expansion joints,
marks for maintenance, others (structures inwhich SI devices are set, signboard
indicating SI building, scratch plate to record
displacement, separately-placed isolator fortests)

Inspection atcompletion

Upon building
completion

Visualinspections andmeasurements

All items

To be decided
by the designer:inconsistencies
are corrected

Inspection
afterrenovation

After work
related to SI
functions

Visualinspections andmeasurements

All items related
to SI functions

To be decided
by the designer

Area of renovation construction and affected
peripheral area

Inspection

Annually

Visualinspections

All items

To be decided
by the designer

Those listed in inspection upon completion

Periodic
inspection

5 and 10years after
completion,then every 10
years

Visualinspections andmeasurements

All items (visualinspection),
Some items(measurement)

To be decided by
the designer

The number of items is fewer than that ininspection at completion.
(This is based on the premise that inspection atcompletion was carried out by IE)

Emergency
inspection

After a major
earthquake,strong winds,
flood, fire

Visualinspections

All items

To be decided
by the designer

The purposes of this insppection is to identify
damaged parts and to quickly notify thebuilding manager and the designer of saiddamage:contents are the same as the annual check.

Detailed
inspection

When unusual
conditions to
be dealt withare recognized
during otherinspection

Visualinspections andmeasurements

Damaged items
decided by thedesigner

To be decided
by the designer

Damaged portions are selected for inspection

4.4 Construction Standards
There are many elements in the construction of SI buildings that are different from those of
conventional buildings. In the construction of SI layers, the installation accuracy (horizontal,
vertical, slope) of the base plate on which the SI devices are installed and the filling rate ofconcrete under the base plate are important.
In addition, in preparation for earthquakes that may occur during construction, it is important
to install restraints to prevent the SI devices from horizontally displacing, and to install external
scaffolding that can follow the displacement of the SI layer during an earthquake.
JSSI has published “Seismic Isolation Structure Construction Standard”, which indicates points
to keep in mind when constructing SI buildings.
Additionally, JSSI has established a “Seismic Isolation Section Construction Management
Engineer Qualification System” to certify SI building construction engineers.
Approximately 6,500 engineers have this qualification, 2023.

24

5. CONCLUSION
Although SI structures are becoming more popular in Japan, the proportion of SI buildings
among all buildings is extremely small.
The SI structure is undamaged even in large earthquakes, furniture inside the building will not
fall, and equipment will not be damaged, making it an excellent building that can continue tobe used even after an earthquake.
The Japan Society of Seismic Isolation is conducting various promotional activities with thegoal of making all buildings seismically isolated.
REFERENCES
1) Guidelines for Seismic Isolation Expansion Joints, JSSI, 2013 (written in Japanese)
2) Guidelines for the Wind-resistant Design of Seismically Base-isolated Buildings, JSSI, 20183) Maintenance Standards for Seismically Isolated Buildings, JSSI, 2020
4) Taiki Saito, Learning from the Past, The Resilient Design and Performance of Seismically Isolated
Buildings in Japan, The 18th World Conference on Seismic Isolation, Energy Dissipation, andActive Vibration Control of Structures (18WCSI), November 2023, Antalya, Türkiye

25

SEISMIC ISOLATION, ENERGY DISSIPATION, AND CONTROL FOR STRUCTURALRESILIENCE ENHANCEMENT IN CHINA: STATE-OF-THE-ART REVIEW ANDAPPLICATIONS

Ping Tan1,*, Fulin Zhou2, Wenzhi Zheng3, Yangyang Chen4
1 Professor, School of Civil Engineering, Guangzhou University, Guangzhou, China
2 Professor, Earthquake Engineering Research & Test Center (EERTC), Guangzhou University, Guangzhou, China
3 Associate Professor, School of Civil Engineering, Guangzhou University, Guangzhou, China
4 Professor, Earthquake Engineering Research & Test Center (EERTC), Guangzhou University, Guangzhou, China

ABSTRACT
Currently, there are nearly 16,000 seismically isolated structures and about 14,000 structures with
passive energy dissipation or hybrid control in China. This study presents a state-of-the-art review on
design rules and innovative devices of seismic isolation, energy dissipation, and hybrid control for
civil engineering structures. The basic concepts of seismic isolation and energy dissipation arebriefly introduced, and the technical rules, testing and design, important design codes, andapplications to new strategic and public structures are shown, pointing out the excellent seismic
behavior of the seismic isolation and energy dissipation systems during real seismic events. The
most interesting applications on existing building structures, rural buildings, bridges, undergroundstructures, tank structures, and transmission tower structures point out the specific challenges foreach case. Finally, recordings obtained during the seismic events in China are presented anddiscussed. The findings are useful for analyzing the seismic behavior of isolation and energy
dissipation systems and their effectiveness during earthquakes. This study also discusses thedevelopment trends for future energy dissipation and hybrid control techniques in China.
KEYWORDS: seismic isolation, energy dissipation, hybrid control, structural application, seismic
retrofitting, seismic monitoring

1. INTRODUCTION
The civil infrastructure in China, located around Euro-Asia and Pacific seismic zones, has sufferedserious damage and failure due to being frequently subjected to earthquakes in past decades (Zhou2023; Ou 2023). To overcome these challenges, the vibration control system for civil infrastructure
in China has been widely developed (Zhou and Tan 2017; Zhang et al. 2017), specifically passive
control systems, such as seismic isolation, damping system, and shock absorption (tuned massdamper). Seismic isolation means the isolator is designed between the bottom of the superstructure26

and the top of the substructure to mitigate the seismic energy transferred to the superstructure andreduce the seismic responses of the superstructure. Seismic isolation is generally suitable forstructures with middle and low height and structures with large stiffness. The seismic responses ofthe structures can be effectively mitigated when the isolation system is appropriately designed (Tanget al. 2015; Zhang et al. 2016). Seismic isolation is an effective measure to enhance the seismic
resilience and mitigate structural damage (China Journal of Highway and Transport, 2021; Zhu et al.
2020, 2022).
Compared with the passive control system, the active control system, which needs an external power
supply, can effectively mitigate structural dynamic responses by actively adding the external
instantaneous force or instantaneously changing structural dynamic characteristics when subjected toexternal excitations. In view of the fact that the added control force is adaptive based on the
structural dynamic responses, the active control system is much better than the passive control
system in terms of continuously and automatically adjusting structural dynamic properties,
especially for wind-induced structural vibration control. Semi-active control systems, which require
only low external energy, achieve the mitigation targets by adjusting the working state of the control
system based on the input or responses and providing the control force to change structural stiffnessand damping. The semi-active control system combines the advantages of the passive and active
control systems. It mainly includes the active variable stiffness system, active variable damping
system, magnetorheological damper, piezoelectric friction damper, and eddy-current damper.
Hybrid control systems, which generally comprise two or more control systems working in parallelin a structure, can utilize the advantages of the passive control system to dissipate the vibrationenergy and that of the active control system to achieve better response mitigation effectiveness (Xuet al. 2014), e.g., the hybrid mass-damping system with AMD, hybrid isolation system with active
system, and hybrid mass-damping with liquid mass control system. The hybrid isolation systemshows the advantages of achieving performance requirements in terms of displacement response,
acceleration responses, and force responses for engineering structures. Several studies have been
conducted to investigate and validate the hybrid isolation system incorporating TMDs and inerter
damper, optimal design methods, and response control effectiveness (Zhu et al. 2019; Ye et al. 2019;
Wang H et al. 2021; Zhao et al. 2019).
Since the construction of the first isolation building in China in 1990, the modern structural isolation
technology marked by the application of laminated rubber bearings has been developed for over 30
years in China. As of September 2022, there are more than 16000 isolation buildings, including
houses, schools, hospitals, offices, and museums, and 1950 bridges have been constructed in China(Zhou 2023), making China one of the countries having the largest number of seismically isolatedbuildings in the world. In particular, after the Regulations for Management of Seismic Protection of
Building Constructions was issued in 2021, the number of isolation buildings increased remarkably.
The total number of newly constructed isolation buildings reached at least 2000 or more during halfa year in 2022. Isolation technology has experienced rapid developments from systematic
experimental investigations to real structural applications, and from natural rubber bearings, leadrubber bearings, high-damping rubber bearings, friction pendulum bearings to SMA-rubber bearings,
adaptive variable frequency and friction pendulum bearings, and hybrid 3D isolation bearings.

27

Seismic isolation has been developed as a relatively reliable technology accepted by the engineeringcommunity and the public.
However, seismic isolation has experienced severe challenges during its development. During the Ms
7.0 Lushan earthquake in 2013, two non-isolated buildings in Lushan County Hospital weresignificantly damaged, as shown in Figures 1 and 2. However, the isolated outpatient buildings in
Lushan County Hospital successfully withstood the destructive earthquake effects, playing a criticalrole in the rapid promotion of the seismic isolation technology, as shown in Figures 1 and 3.

Figure 1 Lushan County Hospital, including three buildings

Figure 2 Two damaged non-isolated inpatient buildings in Lushan County Hospital

Figure 3 One isolated outpatient building in Lushan County Hospital
In contrast to the completely undamaged isolator of the isolated buildings during the Wenchuan andLushan earthquakes, during the Ms 6.8 Luding earthquake on September 5, 2022, seismic damage
and failure were observed in the isolation bearings and auxiliary dampers in two different isolatedbuildings (Dai et al. 2022; Pan et al. 2023; Qu et al. 2023), as shown in Figures 4 and 5. The main28difference is that there was no seismic damage in the isolated residential buildings of the Beishan
Post Office during the Wenchuan earthquake since the distance to the epicenter was approximately
300 km. In contrast, the distance of the isolated outpatient building of the Lushan Hospital from theepicenter was approximately 20 km; only the isolation configurations were damaged, and the main
structure remained intact during the Lushan earthquake, as shown in Figure 3. During the Ms 6.8
Luding earthquake, one of the isolated buildings showing damaged isolators was located in Moxi
town, and the distance to the epicenter was 6.9 km. The other isolated buildings showing failed
dampers were located at the junction between Yanzigou Town and Moxi Town, and the distance tothe epicenter was 8.9 km, i.e., the two isolated buildings were closer to the epicenter.

Figure 4 Damage of the rubber bearings in the #1 building(a) Buckling failure of the viscous damper(b) End connection failure of the damper
Figure 5 Damage of the rubber bearings in the #2 building during the Luding earthquake
In this paper, a state-of-the-art review of seismic isolation, energy, and hybrid control for engineering
structures in China is presented. The evolution of seismic technical specifications and design codes istraced, and an overview of the typical investigations and applications of seismic isolation, mitigation,and retrofitting are subsequently provided. The importance of seismic monitoring to improveknowledge under different loading conditions is emphasized. Finally, the urgent engineering
demands of structural seismic isolation, energy dissipation, and hybrid control technologies aresuggested.

29

2. TECHNICAL RULES FOR SEISMIC ISOLATION AND ENERGY DISSIPATIONSYSTEMS IN CHINA

There are several sets of technical rules for seismic isolation and energy dissipation systems in
China.
2.1 Technical SpecificationsTechnical specification for seismic isolation with laminated rubber bearing isolators(CECS 2001). This is a recommended association technical specification for the design andconstruction of buildings and bridges with seismic isolation, issued in 2001 in China.

Technical specification for seismic energy dissipation of buildings (JGJ 297-2013). This is
the industry standard for the design and construction of buildings and bridges with energy
dissipation, issued in 2013 in China.

Seismic isolation design code for bridges (Chapter 10 in the national code for seismic designof bridges, JTG/T 2231-01-2020). This is part of the Specifications for the Seismic Design ofHighway Bridges updated and issued in 2020 in China.

Standard for structural design of urban over-track buildings (T/CECS 1035- 2022). To
provide a reliable basis for the design of urban railway systems in China, the standard clarifies
the design requirements of laminated rubber bearings with thick rubber layers andthree-dimensional combination isolators for isolated and non-isolated structural design andcomfortability evaluation methods (CECS. 2022).

Technical standard for dual control of engineering vibration and seismic vibration ofbuilding engineering (T/CECS 1234-2023). This is also association technical specificationthat guides the effect analysis and response check, design method, and auxiliary measures forthe dual control of engineering vibration and seismic vibration, which is based on the technicalprogress and practical experience in China (CECS. 2023).



Guideline for seismic technology to maintain functionality of buildings in earthquakes(RISN-TG046-2023). This is the national technical guideline that outlines the basic regulations,seismic effects, seismic checks, nonstructural components, attached mechanical and electricalequipment, and functional facilities (MHURD. 2023).

2.2 Design Codes

Seismic design code of buildings with isolation and energy dissipation (Chapter 12 in the
National Code for Seismic Design of Buildings, GB50011-2001 and 2010). This is part of thenational code for the seismic design of buildings issued in 2001 and 2010 in China.

30Standard for seismic isolation design of buildings (GB/T 51408-2021). This is the national
code for the seismic isolation design of building structures, issued in 2021 in China.

2.3 Standards for Isolators and Energy Dissipation Dampers
Standard of laminated rubber bearing isolators (GB 20688-2006). This is the national
standard for laminated rubber bearing isolators, issued in 2006 in China.

Standard of energy dissipation dampers (JG/T 209-2011). This is the industry standard forenergy dissipation dampers issued in 2011 in China.

Friction pendulum isolation bearings for buildings (GB/T 37358-2019). This is the national
standard for friction pendulum isolation bearings for buildings issued in 2019 in China

3. TESTING AND DESIGN OF SEISMIC ISOLATION SYSTEMS
Several types of seismic isolators have been employed in real engineering structures in China.
Rubber isolator and sliding friction isolator are the most widely used for structural seismic protection.
Hence, based on the structural application requirements, testing devices for large-scale isolators,
dampers, and seismic isolation and mitigation of structural systems have been developed in recent
decades.
3.1 Testing System for Seismic Isolators and Dampers(1) Worldwide advanced seismic isolation and mitigation device test system, which wasconstructed by the Earthquake Engineering Research & Test Center at Guangzhou University, China,
as shown in Figure 6. The test system can be used to test seismic isolators and dampers, etc., provide
reliable testing results for the optimal design and quality inspection of seismic isolation andmitigation devices, and directly serve the development of national seismic isolation and mitigation
technologies. The overall testing indices reach the international leading level. In particular, thevertical capacity is 100000kN in compression and 30000kN in tension, and the maximum horizontal
loading forces reaches 10000kN in longitudinal direction and 5000kN in transverse direction, whichmeet the testing requirements of most large-scale isolators such as friction pendulums. The
maximum vertical loading velocity reaches 254mm/s, and the maximum horizontal loading velocity
reaches 1000m/s, which meets the real velocity simulation of earthquakes. Simultaneous
tension-compression and bidirectional horizontal shear testing for isolators and performance testingfor high-speed dampers can also be conducted.

31

Figure 6 10000-ton tri-axial testing system for seismic isolator and damper
Multi-functional testing machine for seismic isolator, which was constructed by the Wuhan Hirun
Laboratory. The main objective of the testing machine is to test sliding pendulum isolators, which
require dynamic control of one horizontal axis and the vertical axis simultaneously. The maximum
vertical and horizontal loads are 75000kN and 6000kN, respectively. The maximum vertical andhorizontal displacements are 120mm and 1200mm, respectively. The maximum horizontal peakvelocity is greater than 1000 mm/s.
(2) Most advanced shake table test system, which features three directions and six degrees of
freedom for comprehensive performance testing of large-scale seismic isolators, was constructed by
the Earthquake Engineering Research & Test Center at Guangzhou University, China, as shown in
Figure 7. The shake table consists of three subtables, sized 8m×10m, 4m×4m, and 4m×4m,
respectively. The shake table tests of the large-scale bridge, building structural model, prototype
seismic simulation, and vibration test of the industrial equipment and product can all be conducted.
The advanced laser displacement sensor, acceleration transducer, dynamic strain measurement
system, spectrum analysis and advanced data acquisition system, and matched software arearranged.

Figure 7 Advanced shake table test system
3.2 Three Types of Experimental Testings
Several experimental tests have been conducted, and an extensive analysis theory of seismic
isolation systems has been widely developed in China, including three types of isolator testing as

32

follows.
(1) Mechanical characteristics tests of isolators, which include compression tests to quantify thevertical stiffness and cyclic compression-shear tests to quantify the horizontal stiffness, damping
ratio, and maximum horizontal displacement. The test results show that the maximum compression
stress of the isolators can reach 90 MPa when the horizontal strain is zero or 35 MPa when thehorizontal strain is 400%. Therefore, it is safer to use a maximum compressive stress of less than 15MPa.
(2) Durability tests of isolators, which include low-cycle fatigue failure, creep, and ozone aging
tests. It can be observed from the rubber aging tests that the maximum thickness of rubber ozone
was 5 mm when exposed to sunlight and air for 105 years. Hence, the working life of the rubber
isolator could reach over 100 years for a 10 mm coverer layer to protect it from air and sunlight.
(3) Shake table tests on large-scale structural models, including isolation structures with different
isolator locations shown in Figure 8, long-span bridges. The results revealed that the effectivenesswas dependent on the mass ratio of the superstructure to the substructure, and base isolation showed
the best effectiveness, in which the accelerations of an isolated structure could be reduced to 1/12–
1/4 compared with a fixed-base structure.

Figure 8 Shaking table test for different configurations of isolation bearing layers
3.3 Integrated Design Method for Isolation System
To fully consider the non-proportional damping characteristics of the isolated structure, an integrated
design method (Tan et al. 2022), as shown in Figure 9, which converts a nonlinear seismic isolation
structure into a linear seismic isolation structure using the equivalent linearization method, wasproposed and issued in the Standard for seismic isolation design of buildings (GB/T 51408-2021).
The convergence principle was based on the maximum displacement error of the isolation layer. The
equivalent parameters of the bearings were determined through repeated iterative calculations. The
principle of complex modal decoupling was applied to linear seismic isolation structures. The peak
response caused by the magnitude of a specific seismic excitation was calculated using the CCQC
rule. Finally, a nonlinear response history analysis was conducted, including the maximum
considered earthquake (MCE), to verify the design requirements.

33

Figure 9 Integrated design method for seismically isolated structures
4. OVERVIEW OF RESEARCH PROGRESS AND TYPICAL APPLICATIONSAs of July 2023, there were more than 16000 isolation buildings of different heights (3 and 31
stories), including houses, schools, hospitals, libraries, and museums, and 1950 isolation bridges had
been constructed in China, which is one of the most seismically isolated structures in the world.
Sand or graphite lime mortar isolation layers for rural buildings, laminated rubber bearings,
high-damping rubber bearings, lead rubber bearings, sliding friction isolators, friction pendulum
isolators, roller isolators, and SMA high-damping rubber bearings have mainly been employed inreal structures. The use of seismic isolation systems has become widespread in China (Zhou 2016;
Dai et al. 2022).
4.1 Seismic Isolation for Residential Buildings
Several studies have investigated the performance of different types of isolators in residentialbuildings. In particular, the temperature dependencies of the yield force, stiffness, damping ratio,loading cycles, shear frequency, and aging properties of laminated rubber bearings, lead rubber
bearings, and high-damping rubber bearings have been investigated for rubber isolators (Zhuang etal. 2009; Li et al. 2009; Li et al. 2021; Ge et al. 2022). The high temperature accelerated aging
testing of rubber bearings (Shen et al. (2020), isolator thermal displacement and dynamic
characteristics variations of isolation buildings and temperature dependency models for performance
evaluation (Du et al. 2015,2017), hysteretic strength degradation effect of lead rubber bearing and its
effects on seismic performance (Qin et al. 2017; Zheng 2022; Liu 2022), fatigue performance testingof the lead rubber bearing (He et al. 2019), constitute model for rubber bearing (Yuan et al. 2020),
aging-seawater corrosion on the performance of rubber bearings (Ma et al. 2020,2021), have been

34

widely investigated. Seismic isolation and energy dissipation technologies have been widely
investigated for mid- to high-rise modular steel constructions (Deng et al. 2020). The modules canbe preserved for reuse after earthquake excitations to establish a damage-controllable system, which
is preferred for incorporating modules or inter-module connections and should be replaceable.
In addition, reasonable tectonics of isolated buildings is particularly important to ensure that thedesign requirements of isolated buildings are met. The main tectonics of the isolated buildings is thegap between the isolation layer and the ground. According to the requirements of the Code for
Seismic Design of Buildings (GB 50011-2010), the gap in the vertical direction should be no lessthan 20 mm, and the gap in the horizontal direction should be no less than 1.2 times of the peak
displacement when subjected to a rare earthquake, which is less than 200 mm. The Code forConstruction and Acceptance of Building Isolation Engineering (JGJ 360-2015) was issued in 2015.
Corresponding local regulations related to the design and construction of seismically isolatedbuildings have been prepared for issuance in the Yunnan, Gansu, and Fujian provinces. The Codefor Construction and Acceptance of Rubber Seismic Isolation Bearing and Device for Building
Isolation Engineering in Fujian (DBJ/T 13-252-2016) was issued (Wu et al. 2018).
In recent decades, several novel friction pendulum bearings have been developed and investigated.
The friction coefficient, curvature radius of the sliding surface, re-centering and seismic isolation
performance, and response control effectiveness of friction sliding isolators, for example, single,
double, and quadruple friction pendulums, vertical tensile resistant friction pendulums (Liu et al.
2016; Zhang et al. 2021), variable friction pendulum isolators (Zhang et al. 2020; Shang et al.
2021a,b,2022), variable frequency friction pendulum isolators (Tsai et al. 2003; Lu et al. 2011; Hanet al. 2012; Hong et al. 2018; Tan et al. 2023).
Several studies have been conducted to incorporate traditional isolators with superelastic shapememory alloy (SMA) dampers, such as cables and U-type dampers, which are arranged around theisolators and connected to the upper and lower steel plates (Xue et al. 2004; Ren et al. 2010; Fang
2022; Fang et al. 2023; Wang et al. 2018). The seismic isolation performance of
SMA-cable-controlled sliding isolators (Liang et al. 2020) and SMA-lead rubber bearings (Wang etal. 2020, 2023; Chen et al. 2022) for building structures such as residential buildings, has been
widely investigated.
Typical structural applications of the seismic isolation in residential buildings are introduced asfollows:
Example 1: Reinforced concrete (RC) seismically isolated apartment building, which is a
residential apartment building group constructed in Beijing, China, and includes 24 high-risebuildings (31 stories). The total floor area is 980,000 m2 and is the largest area of an isolated
apartment building in the world, as shown in Figure 10. Several similar isolated residential buildings
were constructed in Xinjiang Province, Yunnan Province, and other areas in China.

35

Figure 10 Seismically isolated residential apartment buildings
Example 2: RC frame seismically isolated buildings. In an isolated school building constructed in
2008, during the Lushan Earthquake Ms 7.0 on April 20, 2013, the peak structural acceleration of theisolated school building was reduced to 1/6 of that of the fixed-base buildings. Teachers were able to
instruct the young students as quoted: ‘When an earthquake happens, keep inside of the room, don’t
run out! This is a base isolated building; inside this building is safer than outside!’ No damage wasobserved, and no students were injured after the earthquake, as shown in Figure 11.

Figure 11 Seismically isolated building school in Wenchuan County and recorded acceleration
response
Example 3: RC inter-story isolated frame with 2-story platform and 9-story residential
structure. The large platform (2 stories, RC frame), with a width of 1500 m and a length of 2000m,
is the largest area with 3D isolation worldwide, as shown in Figure 12. It covers a railway area in
Beijing City. 48 isolated residential buildings with a total floor area of 240,000 m2 were constructed
on top of the 2nd story platform. These residential buildings are 7 to 9-story RC frames and feature
3-dimensional isolations for seismic motion and railway vibration.

Figure 12 48 inter-story isolated buildings with 3D isolation on RC Platform

36

4.2 Seismic Isolation for Large-span Space Structure
Several studies have investigated the seismic performances of different types of isolators inlarge-span space structures (Shu et al. 2019; Deng et al. 2019; Han et al. 2020; Pan et al. 2022). In
particular, the seismic performance and effectiveness of different types of isolators for large-span
space structures have been investigated and demonstrated, for example, SMA rubber bearings (Xueet al. 2004), vertical tensile-resistant friction pendulum bearings (Liu et al. 2016), laminated rubber
bearings (Nie et al. 2020), and double friction pendulums with SMA cables (Zhuang et al. 2021) for
space reticulated shell structures.
The typical structural applications of seismic isolation in residential buildings with large-span spacestructures are as follows:
Example 4: Seismic isolation of new Kunming airport terminal (2007-2012). The new Kunming
airport terminal, which is one of the largest isolated structures (10 km) near seismic faults globally, isisolated using 1,892 rubber bearings (ϕ1200 mm) and 108 oil dampers to protect the column withcurved shapes, large glass facades, large ceiling, and critical facilities during an earthquake, as
shown in Figure 13. The total floor area was 500,000 m2. The dynamic responses of the airport
terminal under Ms 4.5 Chonmin Earthquake on March 9, 2015, were recorded. The response of theterminal floor F3 was 1/4 that of the base.

Figure 13 Seismic isolation of new Kunming airport terminal (2007-2012)
Example 5: Seismic isolation of new Daxing airport terminal (2015-2019). The new Beijing
airport terminal has a super long irregular structure, and its length is larger than 300m. The total
isolated floor area is 700,000 m2. A high-speed railway or subway crossing under an airport terminal
may induce significant vibrations. The isolation system, which consists of lead rubber bearings,
laminated rubber bearings, elastic sliding bearings, and velocity-type dampers, uses 1,118 rubber
bearings (ϕ1200mm, 1500 mm), sliding bearings, and 160 velocity-type dampers aimed atenhancing seismic resilience, as shown in Figure 14.

37

Figure 14 Seismic isolation of new Daxing airport terminal (2015-2019)
Example 6: Seismic isolation of new Meilan airport terminal (2016-2019). The new Hainan
airport terminal with an isolated floor area of 300,000 m2 was constructed. The isolation bearings
effectively accommodated the thermal deformation caused by the structural concrete shrinkage ofthe floor slab. The structural plane of the airport terminal is irregular, with a structural length of
300m. The rubber isolation bearing, lead-core rubber isolation bearing, and elastic slide bearing werecombined, as shown in Figure 15. Many new airports with base isolation are being planned ordesigned in China.

Figure 15 Seismic isolation of new Meilan airport terminal (2016-2019)
Example 7: Seismic isolation of new Sanyi airport terminal. The new Sanyi airport terminal, oneof the largest isolated buildings, was isolated using friction pendulum bearings. The single span of
the airport terminal reached 69m. The total floor area is 100,000 m2, as shown in Figure 16.

Figure 16 Seismically isolation of new Sanyi airport terminal
4.3 Seismic Isolation for Low-rise Rural Buildings
Several structural damages and failures have occurred in large rural regions; for example, several
rural buildings have collapsed, and heavy casualties have occurred. On May 12, 2008, the Ms 8.0
Wenchuan earthquake caused serious damage and failure of buildings, most of which were village

38houses. On April 14, 2010, the 7.1 Yushu earthquake caused the failure and collapse of a number ofrural buildings. Under the same earthquake, rural buildings showed much more serious damage thancity structures. Hence, seismic isolation and mitigation technologies used in rural buildings should
be considered (Shang et al. 2016; Yin et al. 2018; Huang et al. 2019; Li et al. 2021).
Hence, a novel isolation technology was employed in rural buildings. In particular, reinforced
asphalt composite isolation systems (Shang et al. 2009, 2013), slide-limited friction base isolation(Ma et al. 2011), spring asphalt three-dimensional isolation bearings for low-rise buildings (Shang etal. 2012; ), glass-bead graphite rolling isolation systems (Cao wanlin et al. 2010), and sand cushion
sliding isolation (Li et al. 2010; Han. 2013; Qian et al. 2013; Shi et al. 2014; Li et al. 2017),
laminated rubber isolation systems for rural masonry structures (Wang et al. 2014), and novel
fiber-reinforced plastic plate rubber isolation bearings (SFRPB) (Tan et al. 2012,2013,2017), havewere experimentally and theoretically investigated. The seismic isolation performance of the novel
isolation strategies for real rural structural applications, considering cold regions, frequent and rareearthquakes, and frost-heaving resistance, was demonstrated and validated through experimental
tests. Further field tests showed that the seismic responses of the superstructures of rural buildings
can be effectively mitigated. The ‘Technical Specification for Steel Bar-asphalt Base Isolation
Technology in Multi-story Building (DBJ43 /T304-2014)’ has been issued for the design of steel
bar-asphalt isolated rural buildings. Low-cost isolation strategies for rural buildings show promise
for structural applications. Rural structural isolation systems should be further investigated toenhance the seismic performance.
Typical applications of seismic isolation in low-rise rural buildings are introduced as follows:
Example 8: Low-rise rural buildings with “elastic isolation brick.” To enhance the seismic
performance of low-rise rural buildings, which are always low-cost, simple designs constructedsimply, a new isolation system called “elastic isolation brick” has been developed and employed inlarge countryside areas in China (Tan et al. 2014, 2017) as shown in Figure 17. Compared with theisolation rubber bearing, the cost of this elastic isolation brick was reduced by 75%. The elastic
isolation bricks have a simple design and construction. The seismic performance of the low-rise ruralbuildings isolated by elastic isolation bricks has been demonstrated using shake table tests. The
results revealed that the elastic isolation brick system could withstand very strong earthquakes, andno damage was observed when the peak ground accelerations reached 0.80 g. The rural buildings
with elastic isolation bricks could become the ‘safety island’ in a very strong earthquake.

Figure 17 Low-rise residential building with “elastic isolation brick”

39

4.4 Seismic Isolation for Bridges
Seismic isolators and dampers, which dissipate seismic energy by deformation and lengthen theisolation period by reducing the horizontal stiffness or enhancing the damping capacity, have been
widely used in bridges (Tan et al. 2009; Jia et al. 2021). Lead rubber bearings have been used in theBuguzi railway bridge (Zhang et al. 2002) in Xinjiang Province and the Shijin Canal bridge in
Heibei Province, China.
The seismic performance, e.g., lead rubber bearing (Wu et al. 2016; Wang et al. 2019; Zheng et al.
2020), high damping rubber bearing, sliding bearing (Peng et al. 2019;), friction pendulum (Xia et al.
2014; Li et al. 2015; Zhang et al. 2018; Wang et al. 2019; Shi et al. 2018; Huang et al. 2016; Liu et al.
2019; Jiang et al. 2019; Wei et al. 2019; Zeng et al. 2020; Chen et al. 2020), novel function
separation isolation system (Wen et al. 2017; Yang et al. 2020), polyurethane elastomeric bearings(Yuan et al. 2020; Wang et al. 2023) for bridges have been investigated and proposed different
design strategies to promote the applications of seismic isolation in real bridge applications (Zhao et
al. 2020,2021).
Several studies have been conducted to incorporate superelastic SMA devices with isolators toenhance seismic resilience. The seismic performance, energy dissipation mechanism, dynamic
behavior, and design methods of the different novel isolators for bridges were systematicallyinvestigated by numerical experiments or shake table tests (Li et al. 2007; Han et al. 2008; Yuan et al.
2008; Guo et al. 2009; Yi et al. 2019; ), including the SMA rubber bearing (Li et al. 2002; Miao et al.
2012; Wang et al. 2019; Zheng et al. 2020,2021; Cao et al. 2020,2022; Deng et al. 2022), SMA-highdamping rubber bearing (Fang et al. 2023), damping enhanced re-centering seismic isolator (Zheng
et al. 2022); SMA friction pendulum (Zheng et al. 2019, 2021,2022; ); 3D seismic isolator (Jia et al.
2017), SMA-cable-controlled sliding bearings (Fang et al. 2020), superelastic variable stiffness
friction pendulum (Han et al. 2020; Zheng et al. 2022,2023), SMA cable-based negative stiffness
seismic isolator (Cao et al. 2022,2023), and superelastic conical friction pendulum (Zheng et al.
2023a,b).
Typical applications of the seismic isolation in bridges are introduced as follows:
Example 9: HK-MACAO-ZHUHAI seismically isolated bridge. A high-damping rubber bearing
with cable restrainers was employed in the HK-MACAO-ZHUHAI bridge to enhance the seismic
performance, which crosses the South China Sea with a length of 26 km, as shown in Figure 18. The
piers of bridges in seawater are effectively protected from cracking and are elastic during
earthquakes. The seismic isolation system protects the bridge against strong earthquakes and windand reduces the seismic response to 1/4 of the response of the traditional bridge.

40Figure 18 Seismically isolated HK-MACAO-ZHUHAI bridge
Example 10: Seismically isolated highway bridge. The developed SMA cable-restrained
high-damping rubber bearings were employed in the Datianba #2 highway curved bridge (curve
radius of 500m) located in Yunnan Province, China, as shown in Figure 19 (Fang et al. 2022). This
was the first study to adopt the proposed SMA-cable-restrained high-damping rubber bearings in theworld. The bridge is 368.76 m in length, and the nine-span prefabricated T-section RC girders were
simply supported by either column-type or wall-type piers and abutments.

Figure 19 Datianba #2 highway bridge with SMA-HDRs in Yunnan Province, China
4.5 Seismic Isolation for Underground Structures
Several studies have revealed that urban underground structures experienced serious damage during
the Chi Chi earthquake (Wang et al. 2000) and Wenchuan earthquake (Wang et al. 2009). The
seismic safety of urban underground structures has attracted considerable attention. In 2014, theCode for Seismic Design of Urban Underground Structures (GB 50909-2014) in China was issued(MHURD, 2014).
Seismic isolation has been widely employed to enhance the seismic resilience of urban undergroundstructures and is an effective measure for transferring the shear deformation of the main components.
The effectiveness of different types of seismic isolators, such as friction pendulum isolators (Du et al.
2019; Xu et al. 2020), roller friction pendulum bearings (Tao et al. 2016; Ma et al. 2018), laminatedrubber bearings (Zheng et al. 2020; Liu et al. 2020), and lead rubber bearings (Huang et al. 2011;
Chen et al. 2016) has been investigated and demonstrated through numerical, experimental, andshake table tests.
Most seismic technologies focus on reducing the earthquake-induced damage to improve the seismic
resilience of underground structures. Research on the restoration of the function of undergroundstructures after earthquakes is generally insufficient. Future studies should focus on restoring the41

function of underground structures after earthquakes, particularly the degree and speed of restoration.
Moreover, new structural systems and large-scale model tests, which form the basis of seismic
behavior assessments, should be further developed. Seismic design standards and codes forearthquake-resilient underground structures should be established to promote further applications.
Example 11: Seismically isolated urban over-track buildings. To effectively utilize the space ofurban over-track buildings and enhance their serviceability and seismic performance, friction
pendulum three-dimensional isolation bearings were utilized in over-track buildings at the Beianhe
station of Beijing metro Line 16. The urban overtrack building consisted of reinforced concrete andsteel frames, as shown in Figure 20.

Figure 20 Seismically isolated urban over-track buildings
4.6 Seismic Isolation for Tank Structures
Owing to the high requirements of liquefied natural gas (LNG) tanks, several studies have focusedon the search for an appropriate isolation system for tank structures. In particular, the seismic
performance of the plate-shell integrated concrete tank structures with different isolation systems,
including lead rubber bearings, sliding bearings, friction pendulum bearings, and SMA devices, hasbeen investigated (Sun et al. 2013; Qu et al. 2014; Shan et al. 2018; Jing et al. 2019; Tang et al. 2021;
Qi et aet al. 2022; Zhu H. et al. 2023; Zhang et al. 2023) through theoretical and experimental
studies.
Example 12: Seismically isolated LNG tank structure. To effectively enhance the seismic
performance, base isolation was employed in an LNG tank structure with a capacity of two million
tons and 200,000 tons in Caofeidian, Tangshan City, Hebei Province. Lead-rubber bearings wereused, as shown in Figure 21. Seismic isolation can also effectively enhance the load-carrying
capacity of large tank structures.

42

Figure 21 Seismically isolated LNG tank structure
4.7 Seismic Isolation for Cultural Relic

Example 13: Seismically isolated historic statue and stone tablet (1200 years history). Historicalrelics, thousands of years old in China, play an important role in providing public cultural services
and meeting the needs of spiritual and cultural life. Base isolation is employed in historical relics
such as statues, tablets, or pictures to protect cultural relics from earthquake damage. Base isolation
can reduce the horizontal response of the relics to 1/12 of the ground motion and ensure safety
during earthquakes, as shown in Figure 22.

Figure 22 Seismically isolated history statues and stone tablets
4.8 Seismic Isolation for Structural Retrofitting

Example 14: Seismic isolation retrofits for old structures. Several old structures, including
buildings and bridges such as schools, office buildings, hospitals, girder bridges, and other criticalfacilities, lack seismic resistance in China. Therefore, it is necessary to employ seismic isolation for
retrofitting and enhancing the performance during strong earthquakes. Seismic isolation retrofittingof school buildings was successfully conducted in the Shanxi Province. The government extended
this demonstration activity through a national meeting, as shown in Figure 23.

43

Figure 23 Base Isolation and 1st story isolation retrofit in Shaanxi Province
Example 15: Seismic isolation retrofits for historical buildings. A historical building located in
Nanjing City was uplifted by 3m in 2013 and then retrofitted using seismic isolation, as shown in
Figure 24 (Du and Wang et al. 2022). Lead and laminated rubber bearings are used. Historicalbuildings are culturally protected. A real-time monitoring system was built to record the static anddynamic behaviors of the isolation bearings and provide real-time warnings. This was the firstmonitoring system in China for seismically isolated historical buildings.

Figure 24 Panorama of the historical building and sensor layout
5. ENERGY DISSIPATION DEVICES
By the end of 2022, different types of energy-dissipation devices were employed in over 14,000
actual buildings. An energy-dissipation system consisting of several energy-dissipation devices isparticularly effective in enhancing damping capacity, thereby mitigating seismic energy andprotecting the structure from damage and failure under earthquakes. Different types of energy
dissipation devices, such as braces, walls, joints, connections, restrainers, nonstructural elements, andsuitable spaces (Qian et al. 2016; Qiu and Zhu. 2017; Zhang et al. 2020; Qiu et al. 2020; Ke et al.
2023; Dong et al. 2023), also contribute to the stiffness against wind loads for safety requirements.
The structural responses can be mitigated by 50%-70% using energy dissipation devices, which arereliable, simple, and suitable measures for aseismic structures, including six typical types of energy
dissipation devices used in China: (1) Steel yielding dampers, (2) Lead yielding dampers, (3) Oil
dampers, (4) BRB bracing, (5) SMA dampers, and (6) Eddy-current dampers (ECD).
Example 16: Eddy-current damper developed by Chen Zhengqing in China. The eddy-current
damper, a new generation of noncontact energy dissipation devices, can provide large damping for44

response mitigation and exhibit better durability. To effectively mitigate the wind-induced response,an eddy-current damper was employed in the Shanghai Center building with a height of 606m, as
shown in Figure 25, which reduced the wind-induced response by 30%-50% during strong wind
events. The eddy-current damper is more effective, durable, and economical than other types ofdampers and has also been used in bridges.

Figure 25 Eddy-current damper in Shanghai Center Building
Example 17: Shear wall with SMA damper. A novel Fe-SMA shear damper was developed andemployed in actual shear wall structures (Fang et al. 2021), as shown in Figure 26. Seismic
performance was investigated both numerically and experimentally. The Fe-SMA shear damper
exhibits superior performance in low cycle fatigue, and its low-cycle fatigue life is 10 times that of a
traditional mild steel damper.

Figure 26 New Fe-SMA shear damper for shear wall structures
Example 18: Tunnel with SMA soft connection. Tunnels always cross rivers or seas, and thetunnel joints may open during an earthquake, which means that water may enter the tunnel andinduce serious disasters. To address this problem, soft joints incorporating SMA devices weredeveloped and employed in a 6 km-long tunnel below sea located in a seismic area with a seismic
intensity of 0.40 g in Southern China, as shown in Figure 27. SMA devices aim to close tunnel joints
after an earthquake and ensure that tunnel joints are watertight. The effectiveness of the SMA softconnection system has been demonstrated theoretically and by test results for being waterproof
during very strong earthquakes, and the tunnel response can be reduced by approximately 30%-50%.

45

Figure 27 New SMA soft connection for tunnel joints
6. HYBRID CONTROL DEVICES FOR STRUCTURES
Structural hybrid control has been employed in approximately 30 buildings and bridges (Lu et al.
2001; Fan et al. 2007; Tan et al. 2011). TMD devices with favorable stability and low cost hardly
satisfy the requirements for earthquakes or winds. Compared with TMD devices, AMD are more
effective, require external energy input, and increase costs. Hence, a low-cost hybrid control system,
which consists of a TMD and AMD, was developed and can satisfy the requirements for responsecontrol under earthquakes or strong winds. Hybrid control systems are among the best options forcontrolling structural vibrations in China.
Example 19: Hybrid control system of Canton Tower with a height of 600 m. The advantages of
the hybrid control system for the Guangzhou Tower are as follows.
(1) The Guangzhou tower, with a height of 600 m, is sensitive to long-period ground motion andstrong winds; hence, the earthquake- and wind-induced vibration responses are significant in termsof the requirements of comfort and safety.
(2) The torsion effects under an earthquake or wind are significant because the structural plan is anellipse.
(3) The slender conformation was not achieved under strong winds (Figure 28).
(4) The TMD is low-cost, but it hardly satisfies the safety and comfortability requirements. AMD iseffective for earthquake- and wind-induced response mitigation, but its cost is excessively high. As aresult, the hybrid control system consisting of two water tanks, as TMD and two AMDs, may
provide the best balance, as shown in Figure 28, effectively enhancing the control performance andreducing costs.

46

Figure 28 Hybrid control system consisting of two water tanks as TMD and two AMDs for Canton
Tower
7. MONITORING OF SEISMICALLY ISOLATED STRUCTURES

Example 20: Monitoring of isolated hospitals. The hospital, located in the west of China, consistsof three sub-towers with plane sizes 32.7m×18.6m, 64.0m×18.6m, and 32.4m×18.6m and a large
podium. Each sub-tower had six stories. The seasonal climate changed significantly. Ambient
temperature, initial displacement of isolation bearings, and dynamic characteristics were monitoredfrom construction to the service period (Du et al. 2015, 2017). The overall layout of the hospitalbuilding sensors is illustrated in Figure 29. The variations in ambient temperature and frequency
during the operation period are shown in Figure 30.

DIS(A1)
DIS(A2)

北M1

Right Tower

N

DIS(1)DIS(2)
TEM(1)

yMiddle Towerx

M5

DIS(9)
DIS(10)
TEM(5)Left Tower

DIS(B1)
DIS(B2)

M3

M4
DIS : displacement sensor

DIS(3)
DIS(4)
TEM(2)M2

DIS(5)DIS(6)

TEM(3)DIS(7)DIS(8)
TEM(4)

TEM : temperature meterM : measuring location

Figure 29 Sensor layout of a hospital building (Du et al. 2015, 2017)47

Magnitude (10-5 m/s)

2.0

January, 2013
January, 2014
August, 2014

1.5
1.0
0.5
0

1

2

3
Frequency (Hz)

4

5

6

Figure 30 Variations of ambient temperature and frequency in operation period
Example 21: Monitoring of isolated school buildings. Teaching Building #1 of the school was
based on isolation using rubber bearings and was located in western China. The height of the schoolbuilding was 27.3m with five stories, as shown in Figure 31. To achieve service conditions andinvestigate the performance of the isolation system, the dynamic characteristics of an isolated schoolbuilding were monitored using acceleration sensors (Du et al. 2018). Two earthquakes, the Qilian
earthquake in 2016 and the Menyuan earthquake in 2017, and their corresponding seismic responses
were recorded. The time–frequency distribution of the seismic response of an isolated schoolbuilding under the two earthquakes is shown in Figure 32.

Figure 31 Acceleration sensor layout of a school building (Du et al. 2018)(a) Qilian earthquake in 2016(b) Menyuan earthquake in 2017
Figure 32 Time-frequency analysis of seismic response of isolated school
Example 22: Monitoring of large-span complex buildings. A huge seismically isolated steel
framework is shown in Figure 33. Base isolation is employed in this steel framework, and theseismic isolators were installed at the foot of the steel column. The steel columns provided reliable
stiffness to ensure the cooperation of the rubber isolation bearings. The sensor arrangement of thehuge steel framework is shown in Figure 33. The isolator displacement, ambient temperature,
structural acceleration, and wind speed were mainly monitored (Zhu et al. 2014).

48

Figure 33 Sensor arrangement of huge steel framework
8. URGENT ENGINEERING DEMANDS FOR SEISMIC ISOLATIONIn recent decades, the isolation technology in China has experienced strong earthquakes thrice, i.e.,the Ms 8.0 Wenchuan earthquake in 2008, Ms 7.0 Lushan earthquake in 2013, and Ms 6.8 Luding
earthquake in 2022. Some shortcomings have also been observed after the earthquake, for example,
the energy dissipation components also behaved serious damage and failure and the connection of
the isolation configurations was failed. Possible reasons include the quality of the isolator products,
management, and supervision. From a technological perspective, related standards and specifications
are required to ensure reasonable products, design, and construction quality indices.
The severe damage and failure of the laminated rubber bearing and viscous dampers revealed thereliability of the isolator under earthquake excitation with a large-velocity pulse. The ground motions
vary from short-time micro-vibrations to large-velocity pulses, in which the structural components,for example, the dampers for energy dissipation, rapidly work directly with high velocity without acertain response time to normal activation. Notably, no specific targeted measures are adaptable tothe sampling inspection tests and construction site installation of the current isolation products,
which is particularly important in terms of whether the seismic performance of the isolators anddampers can be achieved under pulse-type near-fault earthquakes.
According to the standard Rubber bearing 1st part: Testing method of rubber isolation bearing(GB/T 20688.1-2007), the requirement, ‘minimum loading frequency is 0.001 Hz’, is hardly apply
to the rapid response demand of the isolator corresponding to the structural behavior underearthquake. On the other hand, the requirement, ‘reference loading frequency should be 0.5 Hz’, isrelatively higher for most isolation bearings in structures. This is because besides a few early
constructed brick-concrete or masonry structural isolation buildings, the basic isolation period of theisolation structures, e.g., isolated multi-story reinforced concrete frame, frame-shear, and shear wall
structure, mainly ranges from 2.5s to 4.5s, i.e., from 0.2 Hz to 0.4 Hz. The requirement, ‘Reference
testing values should be the values of the third cycle,’ which is selected as the measured performanceparameters, the adaptability of the reference testing values to the near-fault earthquake with large
velocity pulses should be open to discussion.
According to Dampers for vibration energy dissipation of buildings (JG/T 209-2012), theexperimental method for viscous dampers clarifies that the basic structural frequency, defined as the49reference testing frequency, is reasonable. However, the experimental loading procedure involves
step-by-step loading from small to large displacements. The method, by which the measured
damping coefficient and damping index corresponding to the third cycle are selected as the design
values, is limited. It is still a challenge to meet the demand for near-fault pulse-type earthquakes
remains challenging.
To overcome these challenges, the following suggestions are provided.
(1) When designing a seismic isolation system, the maximum velocity response of the isolation
system corresponding to the acceleration levels of different fortification intensities should be
provided for isolator development, production, and inspection.
(2) It is more reasonable and feasible to add the testing method of benchmark detection indices for
related guidelines, including the base frequency of the targeted building and the maximum velocity.
(3) To adapt to the rapid response requirements of the isolator and viscous dampers under near-fault
ground motions with large velocity pulses, particularly for near-fault isolation structures, it isnecessary to investigate the feasibility of using the test value of the third cycle as the measured
performance parameters of the isolators and dampers.
(4) According to the damage and failure reasons, it is also necessary to add the test method of thetorsion-tension-shear coupling of isolation bearings into relevant product inspection standards.
Furthermore, to address the challenges of on-servicing isolation buildings, e.g., the compatibility of
the real performance of existing isolators and matched viscous dampers, unreasonable isolator
configurations degrade the service function. To avoid the unreasonable design and construction of
the isolator configurations, the relevant isolation equipment production, design, construction, andacceptance standards need to be improved, and a reliable basis for developing the isolation
technology should be provided.
To enhance the structural seismic resilience, post-earthquake function recoverability, repairability, It
is an effective measure to develop the resilience-based structural system and design method. For
many near fault or crossing fault building and bridge structures, such as the bridges along the
Sichuan-Tibet railway, the impulse effect, slip effect, and strong vertical earthquake effect pose asevere challenge to the existing seismic isolation and mitigation theory, technology and design
method.
It is needed to accurately predict the dynamic behavior of the structures under near-fault earthquakes
by using advanced technologies such as real-time dynamic substructure test. Urgent demands fordeveloping more adaptable resilient systems and protecting the bridge structural safety, traffic safety,
and even post-earthquake function recoverability under near or crossing fault earthquakes, should tobe addressed for the engineering structure construction.

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9. CONCLUSIONS
Seismic isolation, energy dissipation, and hybrid control are the most effective and reliable measuresto achieve the resilience goals of engineering structures. This study conducts a state-of-the-art review
of seismic isolation, energy dissipation, and hybrid control in China, and the typical structural
applications have been presented, demonstrating that seismic isolation and mitigation technologies
are now advancing as the most effective measures to enhance the structural seismic resilience against
strong earthquakes all over the world. The technical rules, experimental testing system, and design
method of seismic isolation and mitigation devices have been widely developed, and the structural
applications in residential buildings, low-rise rural buildings, bridges, underground structures, tankstructures, cultural relics, and structural retrofitting have increased remarkably in recent years.
Different types of isolators, e.g., laminated rubber bearing, lead rubber bearing, high damping rubber
bearing, friction pendulum isolator, variable stiffness and friction isolator, SMA-rubber bearing,
SMA cable-restrained sliding bearing and high damping rubber bearing, SMA lead rubber bearing,superelastic variable stiffness and friction pendulum isolators, and dampers, e.g., Steel damper,
TMD, AMD, SMA damper, eddy-current damper.
The laminated rubber bearing, high-damping rubber bearing, and lead rubber bearing are the mostwidely used for building applications in China. They are incorporated with steel and viscousdampers to optimize the structural seismic performance. The number of existing structures withseismic isolation retrofitting has increased significantly owing to its increased service life advantage.
The most interesting applications on reinforced concrete, wood, concrete girder bridges, and historic
structures have been conducted. Some applications are in areas that recently experienced seismic
events, in which seismically isolated structures showed better performance in protecting structuralsafety. Meanwhile, some damage cases have also been observed in seismic isolation and mitigation
structures.
Several applications have focused on the monitoring of seismic isolated structures with dampers
under service and seismic events to reveal the structural static and dynamic behavior. The recordings
obtained during the Luding earthquake on September 5, 2022, have been presented and discussed,
pointing out that the behavior of isolation and mitigation devices can be quite different underearthquakes with large velocity pulses, which should be further experimentally and numericallyanalyzed in detail for future developments and seismic monitoring of seismically isolated structures.
ACKNOWLEDGEMENT
The research was financially supported by the National Key R&D Program of China (No.
2021YFC3100700), National Natural Science Foundation of China (No. 51978185, 52108278), andProgram for Changjiang Scholars and Innovative Research Team in University (No. IRT13057). The
authors also would like to thank Prof. Yongfeng Du, and Prof. Cheng Fang for providing the typicalengineering photos. The authors also would like to thank the Safetyinside Technology Co. LTD, andLiuzhou Dongfang Engineering Rubber Product Co., LTD for providing the available data.

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REFERENCES[1] Zhou Fulin. Development of earthquake prevention and disaster mitigation strategies and seismic
isolation and mitigation technologies in China. The 12th National Conference on Earthquake Disaster
Prevention and Mitigation, Lanzhou, 2023.
[2] Ou Jinping. Seismic isolation performance and vertical isolation strategy of structure withlarge-displacement friction pendulum under vary rare earthquakes-A discussion on dual control onseismic and vibration. The 12th National Conference on Earthquake Disaster Prevention and Mitigation,
Lanzhou, 2023.
[3] Zhou F, Tan P. Recent progress and application on seismic isolation energy dissipation and control for
structures in China. Earthquake Engineering and Engineering Vibration. 2018; 17: 19-27.
[4] China Association for Engineering Construction Standardization. Standard for structural design of urban
over-track buildings (T/CECS 1035-2022), 2022.
[5] China Association for Engineering Construction Standardization. Technical standard for dual control ofengineering vibration and seismic vibration of building engineering (T/CECS 1234-2023), 2023.
[6] Ministry of Housing and Urban-Rural Development of the PRC. Guideline for seismic technology tomaintain functionality of buildings in earthquakes (RISN-TG046-2023), 2023.
[7] China Association for Engineering Construction Standardization. Friction pendulum isolation bearingsfor buildings (GB/T 37358-2019), 2019.
[8] Zhang Guojun, Zhang Yuxin, Billie F.Spencer. Research and development tendency of the seismic
response control of tuned mass damper. Journal of Shanghai Normal University(Natural Sciences), 2017,46(2): 269-277.
[9] Tang Chengzhi，Zhang Yongshan，Wang Dayang，He Chaobo. State-of-the-art of base-isolated structuresin near-fault excitations(I)-influence of seismic characteristics and parameter optimization analysis.
Earthquake Resistant Engineering and Retrofitting, 2015, 37(4): 74-82.
[10] Zhang Yongshan, Tang Cheng-zhi, Wang Da-yang, Zhuang Chu-li. State of the art of base-isolated
structures in near-fault excitations (II)-horizontal＆three-dimensional isolations and displacement-limit
technology. Earthquake Resistant Engineering and Retrofitting, 2016,38(1):42-51.
[11] Editorial Department of China Journal of Highway and Transport. Review on China’s bridge engineeringresearch: 2021. China Journal of Highway and Transport, 2021, 34(2): 1-97.
[12] Zhu Hongping, Fan Jian, Yuan Yong, Long Xiaohong, Ye Kun, Zhou Fangyuan, Shen Wenai,
Performance evaluation and promotion of base isolation systems：state of the art. Journal of Huazhong
University of Science and Technology (Natural Science Edition), 2022, 50(8): 40-49.
[13] Zhu Hongping, Shen Wenai, Lei Ying, Yuan Yong, Hu Yuhang, Zhang Ying. Performance monitoring,evaluation, and improvement of structural vibration mitigation or isolation systems. Engineering
Mechanics, 2020, 37(1): 1-16.
[14] Xu HB, Ou JP, Zhang CW, Li H, Tan P, Zhou FL. Active mass driver control system for suppressing
wind-induced vibration of the Canton Tower. Smart Structures and Systems, An International Journal.
2014;13(2):281-303.
[15] Zhu H, Li Y, Shen W, Zhu S. Mechanical and energy-harvesting model for electromagnetic inertial massdampers. Mechanical Systems and Signal Processing. 2019; 120: 203-20.
[16] Ye K, Shu S, Hu L, Zhu H. Analytical solution of seismic response of base‐isolated structure with
supplemental inerter. Earthquake Engineering & Structural Dynamics. 2019, 48(9): 1083-90.
[17] Wang H, Shen W, Li Y, Zhu H, Zhu S. Dynamic behavior and seismic performance of base-isolated52

structures with electromagnetic inertial mass dampers: analytical solutions and simulations. Engineering
Structures. 2021, 246: 113072.
[18] Zhao Z, Zhang R, Jiang Y, Pan C. Seismic response mitigation of structures with a friction pendulum
inerter system. Engineering Structures. 2019, 193: 110-20.
[19] Dai Junwu, Bai Wen, Zhou Baofeng, Liu Rongheng. Urgent problems need to be solved in thedevelopment of seismic base isolation for buildings from the Luding Ms6.8 earthquake. Earthquake
Engineering and Engineering Dynamics, 2022, 42(6): 1-11.
[20] Pan Yi, Gao Haiwang, Xiong Yaoqing, Wu Xiaobin. Seismic damage investigation and analysis ofenergy-dissipated and seismically isolated buildings in Ms 6.8 Luding earthquake. Journal of Building
Structures, 2023, 1-19.
[21] Qu Zhe, Fu Haoran, Wang Xiaoyue. Seismic Response Analysis of the Isolation Layer andSuperstructure of a Base-Isolated Building in the 2022 Luding Earthquake, China. Progress in Steel
Building Structures, 2022, 1-11.
[22] Zhou FL. Discussion on compiling Chinese design code of seismic isolation and energy dissipation.
Guangzhou, China. 2014.
[23] Tan P, Yang K, Tan J, Zheng W. Complex Modal Shapes Superposition Response Spectrum Based
Design Method for Seismically Isolated Structures in China. In World Conference on Seismic Isolation,
Cham: Springer International Publishing, 2022, pp. 361-376.
[24] Zhou Fulin. Seismic Isolation, Energy Dissipation and Structural Control System. City and Disaster
Reduction, Beijing, No.5, 2016.
[25] Chen B, Dai J, Song T, Guan Q. Research and development of high-performance high-damping rubber
Materials for high-damping rubber isolation bearings: A review. Polymers. 2022, 14(12): 2427.
[26] Zhuang Xuezhen, Zhou Fulin, Xu Li, et al. Research on temperature dependence and aging rigidity
steel-plate-aminated-rubber-bearing of lead isolation bearings for building. Journal of Xi’an University ofArchitecture & Technology (Natural Science Edition), 2009, 41(6): 791-798.
[27] Li Li, Ye Kun, Jiang Yicheng. Thermal effect on the mechanical behavior of lead-rubber Bearing.
Journal of Huazhong University of Science and Technology(Urban Science Edition), 2009, 26(3): 1-3.
[28] Li Aiqun, Zhang Ruijun, Xu Gang. Research progress on temperature dependence of rubber isolation
bearings. Journal of Building Structures, 2021, 42(7): 1-11.
[29] Ge Qingzi, Yang Yijian, Dai Kaoshan, Xiong Feng, Wu Ti, Zhang Shaming. Review of mechanicalproperties for high damping rubber bearing. Building Structure, 2022, 52(12): 70-79, 85.
[30] Shen Chaoyong, Huang Xiangyun, Chen Yangyang, et al. Analysis of the factors on temperaturedependence of behavior of SHDR. Journal of Seismological Research, 2020, 43(3): 471-477, 601.
[31] Du Yongfeng, Zhao Lijie, Zhang Tao, et al. Study on construction mechanics of long complicatedisolated structures and life-cycle monitoring. Engineering Mechanics, 2015, 32 (7): 1-10.
[32] Du Yongfeng, Zheng Wenzhi, Li Wanrun, et al. Study on the dependency static and dynamic
characteristics with environmental temperature for long irregular base-isolated structures. Engineering
Mechanics, 2017, 34(7): 69-78.
[33] Qin Chuan, Liu Wenguang, He Wenfu, et al. Comparative analysis of lead heating effects on lead rubber
bearing behaviours. Journal of Vibration and Shock, 2017, 36(10) :182-89.
[34] Zheng W, Wang H, Tan P, Li J, Liu Y. Numerical modeling and experimental validation of
Sliding-LRBs considering hysteretic strength degradation. Engineering Structures. 2022, 262: 114374.
[35] Liu Yanhui, Jiang Tingting, Zhong Weijian, Zhou Fulin, Tan Ping. Study on seismic action of baseisolation structure considering mechanical performance degradation of lead rubber bearings. China Civil

53

Engineering Journal, 2022, 55(8): 46-54.
[36] He Wenfu, Zhou Libei, Xu Hao, et al. Static and structural response analysis for LRB fatigue effect.
Journal of Vibration Engineering, 2019, 32(2): 314-323.
[37] Wei Wei, Yuan Yong, Tan Ping, et al. Experimental and analytical investigation influence of thecompressive load on rate-dependent high-damping rubber bearings. China Civil Engineering Journal,
2020, 53( 2): 23-32.
[38] Liu Rong, Ma Yuhong, Zhao Guifeng, et al. Experimental study on dependence of shear property of highdamper rubber bearing under aging-marine erosion cycle. Journal of Building Structures, 2020, 41(S1):349-354.
[39] Ma Yuhong, Qiu Jiepeng, Liu Yongqi, et al. Seismic response analysis of offshore isolated bridge basedon performance degradation of high damping rubber bearing and pier. Journal of Chang’an University(Natural Science Edition), 2021, 412: 23-33.
[40] Deng EF, Zong L, Ding Y, Zhang Z, Zhang JF, Shi FW, Cai LM, Gao SC. Seismic performance of
mid-to-high rise modular steel construction-A critical review. Thin-Walled Structures. 2020; 155:106924.
[41] Wu Yingxiong, Huang Jing, Lin Shuzhi, Qi Ai. Design and application status of seismic isolation
constitution of building. China Civil Engineering Journal, 2018, 51(2): 62-73, 94.
[42] Zhang C, Ali A. The advancement of seismic isolation and energy dissipation mechanisms based on
friction. Soil Dynamics and Earthquake Engineering. 2021, 146: 106746.
[43] Tsai CS, Chiang TC, Chen BJ. Finite element formulations and theoretical study for variable curvature
friction pendulum system. Eng Struct. 2003; 25(14): 1719-30.
[44] Lu LY, Lee TY, Yeh SW. Theory and experimental study for sliding isolators with variable curvature.
Earthq Eng Struct Dyn. 2011, 40(14): 1609-1627.
[45] Han Qiang, Liu Weigang, Du Xiuli, Qi Lukuan. Computational model and experimental validation ofmulti-spherical sliding friction isolation bearing, China Journal of Highway and Transport, 2012, 25(5):82-88.
[46] Hong Yue, Tang Zhenyun, Lin Shuchao, Li Zhenbao. Experimental study on mechanical properties of a
new type of VCFPB. Engineering Mechanics, 2018, 35(S1): 113-119.
[47] Han Qiang, De Xiuli, Liu Wenguang, et al. Shaking table test of isolated continuous girder bridge model
under different earthquake intensity excitations. China Journal of Highway and Transport, 2008, 21(6):50-56.
[48] Zhang Yafei, Tan Ping, Shang Jiying, Jin Jianmin. Study on mechanical properties of rail variable friction
pendulum system. Journal of Vibration Engineering, 2020, 33(2): 314-321.
[49] Shang J, Tan P, Zhang Y, Han J, Mi P. Seismic isolation design of structure using variable friction
pendulum bearings. Soil Dynamics and Earthquake Engineering. 2021, 148: 106855.
[50] Shang J, Tan P, Zhang Y, Han J, Qin J. Experimental and analytical investigation of variable friction
pendulum isolator. Engineering Structures. 2021, 243: 112575.
[51] Shang J, Tan P, Han J, Zhang Y, Li Y. Performance of seismically isolated buildings with variablefriction pendulum bearings under near-fault ground motions. Journal of Building Engineering. 2022 Jan
1;45:103584.
[52] Fang C. SMAs for infrastructures in seismic zones: A critical review of latest trends and future needs.
Journal of Building Engineering. 2022, 57: 104918.
[53] Fang C, Qiu C, Wang W, Alam MS. Self-Centering Structures Against Earthquakes: A Critical Review.
Journal of Earthquake Engineering. 2023, 1-36.
[54] Xue Suduo, Zhou Qian. Seismic isolation of SMA-rubber bearings in spatial lattice shells. Journal of54

Beijing University of Technology, 2004, 30(2): 176-179.
[55] Ren Wenjie, Qian Hui, Yi Tinghua, Song Wali, Dai Chen. A new superelastic SMA-aminated rubber
base-solation bearings. Journal of Disaster Prevention and Mitigation Engineering. 200, 30 (S1): 238-242.
[56] Liang D, Zheng Y, Fang C, Yam MC, Zhang C. Shape memory alloy (SMA)-cable-controlled sliding
bearings: development, testing, and system behavior. Smart Materials and Structures. 2020 Jun
24;29(8):085006.
[57] Fang C, Liu X, Wang W, Zheng Y. Full‐scale shaking table test and numerical analysis of structural
frames with SMA cable‐restrained base isolation. Earthquake Engineering & Structural Dynamics. 2023.
[58] Wang B, Zhu S. Superelastic SMA U-shaped dampers with self-centering functions. Smart Mater Struct.
2018; 27: 055003.
[59] Wang B, Zhu S, Casciati F. Experimental study of novel self-centering seismic base isolators
incorporating superelastic shape memory alloys. ASCE J Struct Eng. 2020; 146: 04020129.
[60] Wang B, Chen P, Zhu S, Dai K. Seismic performance of buildings with novel self‐centering baseisolation system for earthquake resilience. Earthquake Engineering & Structural Dynamics. 2023; 52(5):1360-80.
[61] Chen ZP, Wang B, Zhu S, Wu G. Two-level performance-based seismic design approach for steel frameswith novel self-centring seismic base isolators. Journal of Constructional Steel Research. 2022, 195:107352.
[62] Shu Weinong, Zhu Zhongyi, Bu Longgui, Zhang Lin. Research and application of seismic isolation
design of airport terminal structure. Building Structures, 2019, 49(18): 5-12.
[63] Deng Changgen, Zeng Miao, Xu Zhonggen. Progress of research on vertical isolation technology instructural engineering. Journal of Architecture and Civil Engineering, 2019, 36(4): 1-11.
[64] Han Qinghua, Jing Ming, Lu Yan. Seismic isolation and vibration reduction system of large-span spatial
structures-a review, Steel Construction, 2020, 35(7): 17-28.
[65] Pan Yi, Song Jiayu Yang Long, Chen Peng, Shen Yun. Review on seismic isolation technology
application and research status in railway station buildings. China Railway Science, 2022, 43(4):186-197.
[66] Liu Yi, Xue Suduo, Pan Kejun, Li Xiongyan. Effect of a new friction pendulum bearing on seismic
response of single-layer cylindrical reticulated shell considering pile-soil-structure interaction, Journal ofCentral South University(Science and Technology), 2016, 47(3): 967-976.
[67] Nie Guibo, Wang Wei, Du Ke, Wang Duozhi, Ma Jialu. A review and prospect of the seismic design
theory for large span spatial structures. World Earthquake Engineering, 2020, 36(2): 21-34.
[68] Zhuang P, Wang W, Li Y, Han M. Cyclic behavior of an adaptive seismic isolation system combining adouble friction pendulum bearing and shape memory alloy cables. Smart Mater Struct. 2021; 30(7):075003.
[69] Shang Shouping, Cui Xianglong. New progress and problems in research and application of baseisolation. Journal of Guangxi University (Natural Science Edition), 2016, 41(1): 21-28.
[70] Yin Zhiyong, Sun Haifeng, Jing Liping, Du Qiunan. Research status of isolation technology of rural
residential structure. World Earthquake Engineering, 2018, 34(2): 157-165.
[71] Huang Yan. Review of research on seismic safety of rural residences in Hunan province, China. Journalof Natural Disasters, 2019, 28(2): 37-48.
[72] Li Yajing, Wang Hao, Wang Zhenyuan, Luo Chao. A review of research on base isolation technology inrural buildings. Earthquake Resistant Engineering and Retrofitting, 2021, 43(2): 88-95, 136.
[73] Shang Shouping, Zhou Zhiji, Liu Ke, Yao Fei. The research on the steel-asphalt isolation lay. Journal of55Railway Science and Engineering, 2009, 6(3): 13-16.
[74] Shang Shouping, Zhu Bowen, Wu Jianren, Lu Huawei. Research on steel asphalt isolation layer inpractical engineering, Journal of Hunan University (Natural Sciences), 2013, 40(7): 1-8.
[75] Qian Guozhen, Xu Zhe, Xiong Shishu, Shi Shuzhong, Liu Nonger. Introduction of a trail seismic
isolation project using constrained sand mats, Zhejiang Construction, 30(10): 13-16.
[76] Zhao Guifeng, Ma Yuhong. Parameters study of rural buildings structures supported on slide-limited
friction base isolation system. Journal of Vibration and Shock, 2011, (11): 148-152.
[77] Shang Shouping, Huang Quntang, Shen Rong, Zhu Bowen. Full-scale experimental research on steelasphalt isolation pier, Journal of Building Structures, 2012, 33(3): 132-139.
[78] Zhou Zhongyi, Cao Wanlin, Wang Qing, Dong Hongying, Zhang Jianwei. Experimental study on basevibration isolation in rural areas by shaking table test, Journal of Civil. Architectural & Environmental
Engineering, 2010, 32(2), 521-523.
[79] Cao Wanlin, Zhou Zhongyi, Wang Qing, Dong Hongying, Zhang Jianwei. Experimental study on basevibration isolation and anti-seismic masonry structure in rural areas by shaking table test. Journal of
Vibration and Shock, 2011, 30(11): 209-2013.
[80] Liu Kaikang. Research on friction sliding isolation technology for adobe structure in rural regions. Dalian:
Dalian University of Technology, 2010.
[81] Wang Haigang. Experimental research on frictional sliding properties of rural isolated structure of sandcushion. Xi’an: Xian University of Architecture and Technology, 2013.
[82] Shi Qingxuan, Rong Yuzhong, Wang Qiuwei, et al. Study on sliding isolation performance of masonry.
Technology for buildings structure of rural Earthquake Disaster Prevention, 2014, (04): 891-897.
[83] Li Yingming, Liu Liu. The seismic fortification criterion sliding and technical measures of simple seismic
isolation technique for rural buildings. Industrial Architecture, 2015, 45(11): 24-29.
[84] Wang Yihong, Zhang You-chao, Fan Kun, et al. Isolation performance test of laminated rubber isolator
for rural masonry structure. Earthquake Resistant Engineering and Retrofitting. 2014, 36(2): 15-20.
[85] Tan P, Xu K, Wang B, Chang C, Liu H, Zhou F. Development and performance evaluation of an
innovative low-cost seismic isolator. Science China Technological Sciences. 2014, 57: 2050-61.
[86] Tan Ping, Xu Kai, Liu Han, et al. Study of new seismic isolation technology for rural buildings.
Engineering Mechanics, 2017, 34( S1) : 233-238.
[87] Wang Bin, Tan Ping, Xu Kai, Zhou Fulin, Ning Xiangliang. Mechanical performance tests of a novel
fiber-reinforced-plastic plate isolation bearing, China Civil Engineering Journal, 2012, 45(S1): 187-191.
[88] Tan Ping, Wang Bin, Jin Jianmin, Zhou Fulin. Finite element analysis for a fiber-reinforced-plastic plate
isolation bearing, Journal of Vibration and Shock, 2013, 33(24): 95-100.
[89] Tan P, Agrawal AK. Benchmark structural control problem for a seismically excited highway bridge-part
II: phase I sample control designs. Struct Control Health Monit. 2009; 16(5): 530-48.
[90] Jia Hongyu, Yang Jian, Zheng Shixiong, Zhao Canhui, Du Xiuli. A review on aseismic bridges crossing
fault rupture regions. Journal of Southwest JiaoTong University, 2021, 56(5): 1075-1093.
[91] Zhang Junping, Zhou Fulin, Liao Shuqiao. Shaking table test study of bridge isolation system (I)-ananalysis of measured results. Earthquake Engineering and Engineering Vibration. 2002, 22(2): 136-142.
[92] Li Jianzhong, Guan Zhongguo. Research progress on bridge seismic design: target from seismic
alleviation to post-earthquake structural resilience. China Journal of Highway and Transport, 2017,30(12): 1-9, 59.
[93] Wu Guobin, Tan Ping, Wang Bing, Ma Ancai. Study on isolated high-speed railway girder bridge. South
China Journal of Seismology, 2016, 36(02): 32-40.

56

[94] Wang H, Zheng WZ, Li J, Gao YQ. Effects of temperature and lead core heating on response of
seismically isolated bridges under near-fault excitations. Advances in Structural Engineering. 2019
Oct;22(14):2966-81.
[95] Zheng WZ, Wang H, Hao H, Bi KM, Shen HJ. Performance of bridges isolated with sliding-lead rubber
bearings subjected to near-fault earthquakes. Int J Struct Stab Dynam. 2020; 20: 2050023.
[96] Peng YB, Ding LC, Chen JB. Performance evaluation of base-isolated structures with slidinghydromagnetic bearings. Struct Control Health Monit. 2019, 26(1): e2278.
[97] Xia Xiushen, Zhao Huidong, OuYang Huilai. Study on seismic isolation of high speed railway bridgewith friction pendulum bearings. Earthquake Resistant Engineering and Retrofitting, 2014, 36(03): 21-26.
[98] Li Bing, Wang Shaohua, Deng Bin. Research on isolation properties of friction pendulum bearing forhigh-speed railway bridges. Mechanical Science and Technology for Aerospace Engineering, 2015,
34(03): 339-343.
[99] Zhang Lei. Research on the seismic response for isolated bridge of friction pendulum bearing in
high-speed railwa. Cheng Du: Southwest Jiaotong University, 2018.
[100] Wang Chuankun, Yang Menggang. Research on seismic isolation of high-speed railway continuous
beam bridge with friction pendulum bearing. Journal of Railway Science and Engineering, 2019, 16(03):564-572.
[101] Shi Yan. Seismic fragility analysis of FPS isolated high-speed railway bridge based on response surface
method. Guang Zhou: GuangZhou University, 2018.
[102] Huang Yuchen, Wang Junwen, Wang Shaojun. Parametric study of mechanical performances ofballastless track on high-speed railway bridge isolated with FPS during earthquake. Railway Standard
Design, 2016, 60(01): 27-33.
[103] Liu Zhengnan, Chen Xingchong, Zhang Yongliang, et al. Research on seismic mitigation and isolationof continuous beam bridge for high speed railway based on friction pendulum bearing under near-and-far
field ground motions. China Railway Science, 2019, 40(1): 47-54.
[104] Jiang L Z, He W K, Wei B, et al. The shear pin strength of friction pendulum bearings (FPB) in simply
supported railway bridges. Bulletin of Earthquake Engineering. 2019, 17(11): 6109-6139.
[105] Wei B, Li C B, Jia X L, et al. Effects of shear keys on seismic performance of an isolation system. Smart
Structures and Systems, 2019, 24 (3): 345-360.
[106] Chen Kejian, Li Jilin, Wei Biao, et al. Research on applicable pier height range of friction pendulum
bearing of simply supported bridges in a double line railway. Journal of Railway Science andEngineering, 2020, 17(2): 364-371.
[107] Wenliuhan·Heisha, Zou Shuang, Zhou Fulin, Yang Bin, Chen Shu, Zhao Haichao, Zhu Dejun. Researchon the seismic isolation of high-speed railway bridges. Journal of Railway Engineering Society, 2017,34(07): 47-52.
[108] Zeng Yongping, Dong Jun, Chen Kejian, et al. Adaptability analysis of the seismic isolation system forhigh-speed railway simply supported beam bridge in nine-degree seismic regions. Journal of Railway
Engineering Society, 2020, 37(2): 46-52.
[109] Yang Menggang, Meng Dongliang, Wei kanghua, et al. Transverse seismic pounding effect andpounding reduction of simply-supported girder bridge for high-speed railway. Journal of Southwest
Jiaotong University, 2020, 55(1): 100-108.
[110] Wang S, Tan P, Yuan Y, Zheng W, Jin S, Xu X. Efficacy of 3M-PTGL on low-temperature seismic
performance of polyurethane elastomeric bearings for bridges. Engineering Structures. 2023 Nov
1;294:116703.

57

[111] Yuan Y, Wang S, Tan P, Zhu H. Mechanical performance and shear constitutive model study of a new
high-capacity polyurethane elastomeric bearing. Construction and Building Materials. 2020 Jan
30;232:117227.
[112] Zhao Canhui, Zeng Xianzhi, Deng Kailai. State-of-the-art review of seismic design of bridges in 2019.
Journal of Civil and Environmental Engineering, 2020, 42(5): 139-146.
[113] Zhao Canhui, Jia Hongyu, Yue Weiqin, You Gang, Jia Kang, Zheng Shixiong. State-of-the-art review ofseismic design of bridges in 2020. Journal of Civil and Environmental Engineering, 2021, 43(S): 91-99.
[114] Li Zhongxian, Zhang Yong, Yue Fuqing. Shaking table test on pounding isolated bridges underresponses of simply supported earthquake excitation. Earthquake Engineering and Engineering
Vibration. 2007, 27(2): 152-157.
[115] Yuan Yong, Xiong Shishu, Zhu Hongping. Real-time substructure hybrid test system for earthquake
response of isolated bridge using velocity control. Journal of Huazhong University of Science andTechnology (Natural Science Edition), 2008, 36(8): 117-120.
[116] Guo A X, Li Z J, Li H, et al Experimental and analytical study on pounding reduction of base-isolated
highway bridges using MR dampers. Earthquake Engineering &Structural Dynamics, 2009, 38(11):1307-1333.
[117] Yi J，Yang HY，Li JZ. Experimental and numerical study on isolated simply supported bridges subjected
to a fault rupture. Soil Dynamics and Earthquake Engineering, 2019, 127: 105819.
[118] Li Zhongxian, Chen Haiqun, Liu Jiantao. Bridge isolation with SMA-composite rubber bearing,
Earthquake Engineering and Engineering Vibration, 2002, 22(2): 144-149.
[119] Miao Xiaoyu, Wang Sheliang, Tang Xian, Weng Guangyuan. Mechanical property and applied study of
SMA-rubber bearing for bridge structures, Journal of Xi’an University of Architecture &Technology(Natural Science Edition), 2012, 44(1): 28-32.
[120] Wang J Q, Li S, Dezfuli F H, et al. Sensitivity analysis and multi-criteria optimization of SMA cable
restrainers for longitudinal seismic protection of isolated simply supported highway bridges. Engineering
Structures, 2019, 189: 509-522.
[121] Zheng, W., Wang, H., Li, J., & Shen, H. (2020). Parametric study of superelastic-sliding LRB system forseismic response control of continuous bridges. Journal of Bridge Engineering, 25(9), 04020062.
[122] Zheng, W., Wang, H., Hao, H., & Bi, K. (2021). Superelastic CuAlBe wire-based sliding lead rubber
bearings for seismic isolation of bridges in cold regions. Engineering Structures, 247, 113102.
[123] Cao S, Ozbulut OE, Wu S, Sun Z, Deng J. Multi-level SMA/lead rubber bearing isolation system forseismic protection of bridges. Smart Materials and Structures. 2020 Apr 20;29(5):055045.
[124] Cao S, Ozbulut OE, Shi F, Deng J. Experimental and numerical investigations on hysteretic response ofa multi-level SMA/lead rubber bearing seismic isolation system. Smart Materials and Structures. 2022
Feb 9;31(3):035024.
[125] Deng J, Hu F, Ozbulut OE, Cao S. Verification of multi-level SMA/lead rubber bearing isolation system
for seismic protection of bridges. Soil Dynamics and Earthquake Engineering. 2022 Oct 1;161:107380.
[126] Fang C, Liang D, Zheng Y, Lu S. Seismic performance of bridges with novel SMA cable‐restrained highdamping rubber bearings against near‐fault ground motions. Earthquake Engineering & Structural
Dynamics. 2022, 51(1): 44-65.
[127] Zheng, W., Tan, P., Zhang, Z., Wang, H., & Sun, Z. (2022). Damping enhanced novel re-centering
seismic isolator incorporating superelastic SMA for response control of bridges under near-fault
earthquakes. Smart Materials and Structures, 31(6), 065015.
[128] Jia Junfeng, Zhao Jianyu, Guo Yang, et al. Shaking table tests on seismic simulation of58

three-dimensional isolated continuous girder bridges. China J. Highw. Transp, 2017, 30(12): 290-298.
[129] Zheng W. Z., Wang, H., Li, J., & Shen, H. J. (2021). Parametric study of SMA-based friction pendulum
system for response control of bridges under near-fault ground motions. Journal of Earthquake
Engineering, 25(8), 1494-1512.
[130] Zheng W Z，Wang H，Li J, et al. Performance evaluation of bridges isolated with SMA-based friction
pendulum system at low temperatures. Soil Dynamics and Earthquake Engineering, 2019, 125: 105734.
[131] Zheng W, Tan P, Li J, Wang H, Tan J, Sun Z. Sliding-LRB incorporating superelastic SMA for seismic
protection of bridges under near-fault earthquakes: A comparative study. Soil Dynamics and Earthquake
Engineering. 2022, 155:107161.
[132] Han Q, Liang X, Wen J, Zhang J, Du X, Wang Z. Multiple-variable frequency pendulum isolator withhigh-performance materials. Smart Mater Struct. 2020, 29(7): 075002.
[133] Zheng W, Tan P, Liu Y, Wang H, Chen H. Multi‐stage superelastic variable stiffness pendulum isolation
system for seismic response control of bridges under near‐fault earthquakes. Structural Control and
Health Monitoring. 2022 Dec;29(12):e3114.
[134] Zheng W, Tan P, Li J, Wang H, Liu Y, Yang K. Seismic performance upgrading of bridges using
superelastic pendulum isolators with variable stiffness considering temperature effects. Engineering
Structures. 2023 Jan 15;275:115244.
[135] Cao S, Ozbulut OE, Shi F, Deng J. An SMA cable-based negative stiffness seismic isolator:
Development, experimental characterization, and numerical modeling. J Intell Mater Sys Struct. 2022;
1045389X211072211.
[136] Zhang F, Deng J, Cao S, Dang X. Experimental and simulation studies of adaptive stiffness double
friction pendulum bearing. Structures, 2023, 57: 105026.
[137] Zheng W, Tan P, Li J, Wang H, Liu Y, Xian Z. Superelastic Conical Friction Pendulum Isolator for
Seismic Isolation of Bridges under Near-Fault Ground Motions. Structural Control and Health
Monitoring. 2023 Apr 4;2023.
[138] Zheng W, Tan P, Li J, Wang H, Liu Y, Xian Z. Superelastic pendulum isolator with multi-stage variablecurvature for seismic resilience enhancement of cold-regional bridges. Engineering Structures. 2023 Jun
1;284:115960.
[139] Wang W L, Wang T T, Su J J, et al. Assessment of damage in mountain tunnels due to the Taiwan
Chi-Chi earthquake. Tunn Undergr Space Tech, 2000, 16: 133–150.
[140] Wang Z Z, Gao B, Jiang Y J, et al. Investigation and assessment on mountain tunnels and geotechnicaldamage after the Wenchuan earthquake. Sci China Ser E-Tech Sci, 2009, 52: 546–558.
[141] Ministry of Housing and Urban-Rural Development of the PRC. Code for seismic design of urban railtransit structures (GB 50909-2014). 2014.
[142] Du Xiu-Li , Xu Zi-Gang , Xu Cheng-Shun , Jiang Jia-Wei . Seismic mitigation effect analysis on friction
pendulum bearing applied in the underground subway station. Engineering Mechanics, 2019, 36(9):60-67+88.
[143] Xu Z, Du X, Xu C, et al. Numerical analyses of seismic performance of underground and abovegroundstructures with friction pendulum bearings. Soil Dyn Earthq Eng, 2020, 130: 105967.
[144] Tao L J, An J H, Ge N. Isolation effect analysis on bidirectional RFPS bearing applied in the metro
stations engineering. Earthq Eng Eng Dyn, 2016, 36: 52-58.
[145] Ma C, Lu D C, Du X L. Seismic performance upgrading for underground structures by introducing
sliding isolation bearings. Tunn Undergr Space Tech, 2018, 74: 1–9.
[146] Zheng Y, Yue C. Shaking table test study on the functionality of rubber isolation bearing used in59underground structure subjected to earthquakes. Tunn Undergr Space Tech, 2020, 98: 103153.
[147] Liu Z, Chen Z, Liang S, et al. Isolation mechanism of a subway station structure with flexible devices atcolumn ends obtained in shaking-table tests. Tunn Undergr Space Tech, 2020, 98: 103328.
[148] Huan Y, Fang Q, Chen L, et al. 3D nonlinear damage analysis of metro station structures under strong
seismic loading (in Chinese). J Beijing Univ Technol, 2011, 37: 852–862.
[149] Chen Z Y, Zhao H, Lou M L. Seismic performance and optimal design of framed undergroundstructures with lead-rubber bearings. Struct Eng Mech, 2016, 58: 259–276.
[150] Sun J, Zheng J, Cui L, Li J, Xu L. Base isolation response spectrum design of LNG storage tank. Harbin
Gongye Daxue Xuebao (Journal of Harbin Institute of Technology). 2013, 45(4): 105-9.
[151] Qu Changlong, Zhang Chao, Chen Tuanhai. Analysis of measures for seismic isolation and shock
absorption for LNG storage tank. Chemical Industry and Engineering Pro-gress,2014,33(7): 1713-1717.
[152] Shan Tongwen. New advances and future development trends of LNG tank research. China Offshore Oil
and Gas, 2018, 30(2): 145-151.
[153] Jing W, Cheng X. Dynamic responses of sliding isolation concrete liquid storage tank under far-fieldlong-period earthquake. Journal of Applied Fluid Mechanics. 2019 May 1;12(3):907-19.
[154] Tang Z, Hong Y, He L, Li Z. Seismic performance of storage tank isolated by different isolators throughreal-time hybrid simulation. International Journal of Structural Stability and Dynamics. 2021 Dec
9;21(13):2150190.
[155] Qi L, Cheng X, Zhang S, Wang F, Xia P. Shaking table test of combination isolation plate-shell
integrated concrete liquid-storage structure. Canadian Journal of Civil Engineering. 2022; 49(6):1014-25.
[156] Zhang L, Guo M, Zhu L, Meng Y. Optimal design and seismic performance of base-isolated storage
tanks using friction pendulum inerter systems. Structures, 43: 234-248.
[157] Zhu H, Tang Z, Luo H. Seismic performance of a base-isolated flexible liquid storage tank equippedwith a novel rate-independent damping device. Structures, 2023, 51: 215-225.
[158] Zhuang Haiyang, Tang Baizan, Yu Bingyan1, Xu Zigang, Zhang Ji, Zhou Zhenwei. Review andprospect of earthquake resistance and seismic isolation of underground structures. Technology for
Earthquake Disaster Prevention, 2023, 18(1): 1-12.
[159] Shi Sheng, Du Dongsheng, Xu Jinghai, et al. Multi-level early-warning system for base-isolated
structures based on real-time monitoring data and its application on the Old Hall of Nanjing Museum.
Journal of Building Structures, 2022, 43(04): 47-57.
[160] Qian H, Li H, Song G. Experimental investigations of building structure with a superelastic shapememory alloy friction damper subject to seismic loads. Smart Mater Struct. 2016; 25: 125026.
[161] Qiu C, Zhu S. Shake table test and numerical study of self‐centering steel frame with SMA braces.
Earthquake Engineering & Structural Dynamics. 2017; 46(1): 117-37.
[162] Zhang ZH, Bi KM, Hao H, Sheng P, Feng L, Xiao D. Development of a novel deformation-amplified
shape memory alloy-friction damper for mitigating seismic responses of RC frame buildings. Eng Struct.
2020; 216: 110751.
[163] Qiu C, Fang C, Liang D, Du X, Yam MC. Behavior and application of self-centering dampers equippedwith buckling-restrained SMA bars. Smart Mater Struct. 2020; 29(3):035009.
[164] Ke K, Zhou X, Zhu M, Yam MC, Zhang H. Seismic demand amplification of steel frames with SMAs
induced by earthquake sequences. Journal of Constructional Steel Research. 2023, 207: 107929.
[165] Dong Y, Xu Z, Li Q, He Z, Yan X, Cheng Y. Tests and Micro–Macro Cross-Scale Model ofHigh-Performance Acrylate Viscoelastic Dampers Used in Structural Resistance. Journal of Structural

60

Engineering. 2023, 149(7): 04023088.
[166] Fang C, Wang W, Ji Y, Yam MC. Superior low-cycle fatigue performance of iron-based SMA forseismic damping application. Journal of Constructional Steel Research. 2021, 184:106817.
[167] Lu Xilin, Zhu Yuhua, Shi Weixing. Shaking table test on building models with comined isolation system.
China Civil Engineering Journal, 2001, 34(2): 43-49.
[168] Wei Junjie, Fan Jian, Wang Zhitong. Seismic analysis of hybrid damping base-isolated system against
near-fault ground motions, Earthquake Resistant Engineering and Retrofitting, 2007, 29(5): 21-24.
[169] Guo Hongfeng, Ning Xiangliang, Tan Ping, Yu Guangzhong, Tang Lu, Liu Jun. Hybrid isolation
analysis of bridge structure excited by near-fault ground motion. Earthquake Engineering andEngineering Dynamics, 2011, 31(5): 172-177.
[170] Du Yongfeng, Zhu Qingxin, Li Wanrun, et al. Analysis of the abnormal change of isolated structure
modal parameters under healthy condition based on long-term monitoring data. Journal of Vibration,
Measurement &. Diagnosis, 2018, 38(03): 517-525.
[171] Zhu Wenzheng, Zhang Jichao. Real time monitoring of isolation system of Guangdong science center
based on intelligent sensor technology. China Civil Engineering Journal, 2014, 47(05): 40-45.

61CURRENT STATE AND FUTURE CHALLENGES OF SEISMIC ISOLATIONDEVELOPMENT IN TAIWAN

S.J. Wang1, W.C. Lin2, C.H. Yu2, C.Y. Yang2, K.C. Chang3, and J.S. Hwang1
1 Professor, Dept. of Civil and Construction Engineering, National Taiwan University of Science and Technology, Taipei,
Taiwan2 Associate Researcher, Structural Monitoring and Control Division, National Center for Research on Earthquake
Engineering, Taipei, Taiwan
3 Professor, Dept. of Civil Engineering, National Taiwan University, Taipei, Taiwan

ABSTRACT
Since the 1999 Chi-Chi Earthquake, passive control technology has been widely used in both new
construction and retrofitting of buildings and infrastructure to mitigate against seismic attacks in
Taiwan. In 2005, the Taiwan Seismic Design Specifications and Commentary of Buildings was
upgraded and expanded to include the design for seismically isolated buildings and buildings with
damping systems. The specifications promote and facilitate the proper application of passive control
technology for buildings. Initially, passive control technology was applied primarily to criticalstructures, such as hospitals and emergency response facilities, which must maintain full functionality
during and after earthquakes. However, since 2009, the use of such technology has been greatly
expanded to residential buildings for better seismic protection and quality of life. According to thespecific design provisions, there have been more than 200 seismically isolated structures constructedin Taiwan. In this paper, several modern applications of seismic isolation technology for building
structures and bridges in Taiwan are presented. Moreover, seismic isolation technology has beendeveloped to protect non-structural components and equipment, including communication andindustrial processing equipment. Among the many techniques of seismic isolation for equipment, thesloped rolling-type isolation devices, which feature constant horizontal transmitted acceleration
regardless of the intensity and frequency content of input excitations, have been widely applied in thetelecommunications industry and high-technique facilities in Taiwan.
Taiwan has established a committee dedicated to regular revisions of the specifications for the designof seismically isolated buildings. Recently, the committee announced two significant provisions forseismically isolated buildings. The first provision involves considering the variability of seismic
isolation units in the design stage. The second provision entails implementing a more exhaustive andpractical testing and verification process. In this paper, additionally, the latest seismic design code forbuildings with isolation systems in Taiwan is briefly introduced. To meet the increasing requirementsof domestic and international research and tests for full-scale seismic isolation and velocity-dependent
damping devices with long stroke and high velocity, the bi-axial dynamic testing system (BATS),
which possesses high-performance lateral and vertical dynamic control capacities, has been established62

in National Center for Research on Earthquake Engineering (NCREE) in Taiwan. The friction
performance of BATS and the feasibility of the direct force measurement strategy is examined in thispaper. To practically demonstrate the efficacy of seismic isolation design, the strong motion monitoringof a seismically isolated building in Hualien is examined and compared with numerical analysis in thispaper. Some effects induced by near-fault ground motions are raised and discussed accordingly. Lastly,some future challenges, in terms of design and promotion, to the application of seismic isolation
technology in Taiwan are addressed in this paper.
KEYWORDS: Seismic Isolation, Practical Application, Taiwan Seismic Design Code,
Large-Scale Multiaxial Testing Facility, Strong Motion Monitoring, Future Challenge.

1. RECENT PRACTICAL APPLICATION OF SEISMIC ISOLATION TECHNOLOGY IN
TAIWAN
Since the 1999 Chi-Chi Earthquake, passive control technology has been widely adopted in both new
construction and retrofitting of buildings and infrastructure against seismic attacks in Taiwan. To date,there have been more than 200 seismically isolated structures constructed in Taiwan. Initially, theseapplications primarily focused on critical structures, including medical facilities and emergency
response centers, which must maintain full functionality during and after earthquakes. For instance,
several hospitals in Taiwan, including the Taipei Tzu Chi Hospital, the He Xin Building at Hualien Tzu
Chi Hospital, and the Taichung Tzu Chi Hospital, have implemented isolation technology to enhancetheir seismic resistant capacities and seismic performances. The Taipei Tzu Chi Hospital, which began
operation in 2005, is a 15-story steel-reinforced concrete (SRC) structure with a 3-story basement, asshown in Fig. 1(a). The installed isolation system beneath the basement comprises 161 lead rubber
bearings (LRBs) with a maximum diameter of 1.5 m, 54 natural rubber bearings (NRBs) with amaximum diameter of 1.3 m, 4 flat sliders, along with 82 steel dampers and 48 viscous dampers. The
maximum isolation displacement is 60 cm and the separation between the superstructure and thesurrounding retaining wall is designed to be 80 cm. The He Xin Building at Hualien Tzu Chi Hospitalis an 11-story SRC structure with a 1-story basement, as shown in Fig. 1(b). The isolation systeminstalled at B2F utilizes 74 LRBs, 14 flat sliders, and additional damping devices [1]. This building is
noteworthy for being the first base-isolated structure equipped with the strong motion monitoring
system of the Central Weather Bureau (CWB) in Taiwan. Its seismic responses measured during
previous earthquakes in Taiwan are discussed in detail in Section 4. The Taichung Tzu Chi Hospital,
completed in 2008, is a 14-story SRC structure with a 2-story basement, as illustrated in Fig. 1(c). The
isolation system implemented at B3F adopts 325 LRBs with a maximum diameter of 1.5 m and 88
viscous dampers. Currently, the tallest base-isolated building is a precast reinforced concrete (RC)residential building with a total height of 133.2 m (B3F~38F) and an aspect ratio of 3.17 [2], as
presented in Fig. 1(d). The isolation system installed underneath 1F consists of 43 LRBs with amaximum diameter of 1.5 m. The separation between the superstructure and the surrounding retaining
wall is designed to be 50 cm. The elastic period before isolation and the effective period after isolation
under the design basis earthquake (DBE) shaking are 3.29 s and 5.18 s, respectively.

63

(a) Taipei Tzu Chi Hospital(b) Hualien Tzu Chi Hospital(c) Taichung Tzu Chi Hospital(d) The tallest base-isolated building

Figure 1 Base-isolated building cases using LRBs in Taiwan
In Taiwan, the mid-story isolation technique has been widely implemented for seismically isolatedbuildings due to its architectural advantages in the aspects of aesthetics and functionality as well as its
easy maintenance and inspection after construction. In mid-story isolation design, the isolation system
is incorporated into the mid-story (typically installed on the top of the first story, as shown in Fig. 2(a))
rather than at the base of the building. Therefore, it is essential to recognize that the dynamic behaviorof a mid-story isolated structure can be more complex compared to that of a base-isolated structure.
Assuming the superstructure to be a single-degree-of-freedom system is inappropriate and may not be
conservative for the preliminary design of mid-story isolated buildings. The modal response spectrum
analysis that appropriately considers the contribution of higher modes, rather than the equivalent lateralforce procedure provided for base-isolated buildings, is more applicable. Most importantly, nonlinear
response history analyses considering appropriate ground motions for the final design check arerequired. These findings underscore the necessity for meticulous attention to detail in mid-story
isolation design [3–5]. In Taiwan, the highest mid-story isolation system is installed above the fourthstory of an RC residential building (B6F~16F), as illustrated in Fig. 2(b). This system utilizes LRBs
with a maximum diameter of 1.2 m. Furthermore, the Civil Engineering Research Building at National
Taiwan University is a 9-story precast RC structure, featuring a 1-story basement and 2-story
penthouses, as depicted in Fig 2(c). Above the first story, there is an isolation system comprising 19
LRBs with a maximum diameter of 0.9 m, as well as 6 viscous dampers with a maximum stroke of±50 cm and a maximum force of 100 tons. It is noteworthy that the height of the isolation layer is 3.2
m, facilitating educational and engineering visits.

(a) Typical mid-story isolation
design(b) The highest mid-story isolation (c) The Civil Engineering ResearchsystemBuilding

Figure 2 Seismically isolated building cases that adopt mid-story isolation design64Concerning the application types of seismic isolators in Taiwan, in addition to the above-mentioned
LRBs, high-damping rubber bearings (HDRBs) and friction pendulum bearings (FPBs) are being used
increasingly. For example, the Chunghwa Post information center, Fig. 3(a), which will be completed
in 2023, is a base-isolated building with an 11-story height and a 2-story basement. The isolation
system is composed of 24 HDRBs and 8 viscous dampers that are installed at B1F. Friction pendulum
bearings have proven effective in addressing the challenge of eccentricity between the center of massof the superstructure and the center of rigidity of the isolation system, especially when dealing withconsiderably irregular structures, due to the feature of their lateral effective stiffness proportional to theimposed axial load [6]. Three iconic irregular buildings in Taiwan have utilized friction pendulum
bearings. (1) Taipei Performing Arts Center (Fig. 3(b)): A 12-story steel structure with one basement.
The base isolation system is composed of 89 FPBs, in which the maximum type of bearing is 2.2m indiameter. The maximum isolation displacement is 700 mm. (2) Tao Zhu Yin Yuan Mansion (Fig. 3(c)):
A 21-story base-isolated structure with a 5m-height roof out-rigger truss, a 3-story roof protrusion, anda 4-story basement. The isolation system consists of 48 FPBs. (3) The Southern Branch of National
Palace Museum (Fig. 3(d)): The base isolation system is composed of 210 FPBs, in which the
maximum type of bearing is 1.9 m in diameter and the maximum horizontal displacement capacity is
500 mm. The superstructures of these cases are architecturally and structurally complex and irregular,
making friction pendulum bearings a valuable choice for the isolation system.

Chunghwa Post information center(a) Chunghwa Post Information Center(b) Taipei Performing Arts Center(c) Tao Zhu Yin Yuan Mansion(d) The Southern Branch of the National Palace
MuseumFigure 3 Seismic isolation design cases using HDRBs and FPBs
In Taiwan, the first seismically isolated bridge was designed and constructed on National Freeway No.
3. Additionally, there are another 8 bridges on the same freeway that have successively implemented
seismic isolation design. These isolation systems incorporate the use of LRBs [7, 8]. Moreover,Taiwan’s bridge seismic design specifications have undergone several revisions since 1987 [9, 10]. To
meet the seismic requirements of the latest specification version, the Freeway Bureau of the Ministry65

of Transportation and Communications initiated a comprehensive evaluation of the seismic capabilityof existing bridges and their retrofitting efforts after the 1999 Chi-Chi Earthquake. As a result, theDong-Shan Bridge on National Freeway No. 3 was retrofitted with the addition of seismic isolation
bearings to the existing rigid piers [11]. However, many other critical facilities in Taiwan, such as hightech factories and emergency centers, have gradually become aware of the effectiveness of seismic
isolation technology and have considered adopting such technology for safety and functionality
purposes [12]. To achieve a higher performance level for existing aseismic structures, applying seismic
isolation technology to the housed critical equipment can yet be regarded as one of the most efficient,practical, and cost-effective strategies. An often-seen case is to incorporate seismic isolators into araised floor system, i.e., an isolated raised floor system. The sloped rolling-type bearings (SRBs)
developed by NCREE, as illustrated in Fig. 4 (a), feature constant horizontal acceleration control
performance regardless of earthquake intensities and frequency properties [13, 14]. It has beenpractically applied in the internet data center of the National Center for High-performance Computing,the internet data center of the National Disasters Prevention and Protection Commission, the antiquestorage cabinets of the Institute of History and Philology, Academia Sinica, the supercomputer of theCentral Weather Bureau, the network and telecommunication servers of Chunghwa Telecom, the data
storage equipment of Chunghwa Post, and the high-precision equipment of several semiconductor
factories, etc., as shown in Fig. 4(b).

.
(a) Schematic view of SRBs(b) Practical applications of SRBs
Figure 4 Seismic isolation for equipment or facilities
In the study of SRBs, a review of the literature indicates that SRBs designed with single sloping angles
and damping forces face challenges in simultaneously controlling horizontal transmitted accelerationand isolation displacement effectively [15]. Consequently, several strategies have been developed toaddress this issue. These strategies include passive adjustments with linearly or stepwise variable
parameters [16, 17], enhancements in a semi-active manner [18, 19], and integration with earthquake
early warning information [20, 21]. Furthermore, certain studies have explored combining SRBs withadded inerters to enhance their performance and resilience [22].
2. RECENT REVISIONS OF TAIWAN SEISMIC DESIGN SPECIFICATIONS ANDCOMMENTARY ON BUILDINGS WITH ISOLATION SYSTEMSIn Taiwan, passive control technology has been accepted as a viable means to limit or eliminate
earthquake-induced damage by academics, design professionals, and government officials. To properly
promote and facilitate the adoption of passive control technology for buildings, the Taiwan Seismic

66

Design Specifications and Commentary of Buildings was updated and expanded from its previous
version to include the design of buildings with seismic isolation and damping systems in 2005 [23].
This design code provided not only analysis procedures for passively controlled buildings but also test
requirements for passive control devices.
In the recent two decades, NCREE has formed a committee composed of academics, design
professionals, and government officials to continuously revise and update the design code for buildings.
At first, in 2011, the design code for buildings with seismic isolation and damping systems was revised
toward a more reasonable and practicable goal [23, 24]. The main modified specifications andcommentaries for buildings with seismic isolation systems were as follows:(1) Appropriate design requirements and methods should be considered corresponding to different
structural performances.
(2) Mid-story isolation design requires nonlinear dynamic analysis procedures due to the complex
dynamic behavior caused by the flexibility of the substructure below the isolation system.
(3) The minimum total lateral force for seismic isolation design at long periods does not need to belimited to the lower bound used in conventional design.
(4) The varied vertical stiffnesses of elastomeric bearings in compression and tension should beconsidered carefully for the design.
(5) The total design displacement DTD and the total maximum displacement DTM should not be lessthan 1.1 times the design displacement DD and the maximum displacement DM, respectively. It isalso suggested that DTM should be less than 1.5 times DTD, and DTD should be less than thedisplacement value corresponding to a shear strain of 200% if the isolation system is composedof elastomeric bearings.
(6) Under DBE shaking, elastic base shear force without considering ductile reduction, Vs, is used
for the design of the superstructure (i.e., the maximum story drift of the superstructure should notexceed 0.005), while 1.25 times the elastic base shear force, Vb = 1.25 Vs, is used for the designof the substructure.
(7) Vs should be distributed rationally over the height of the superstructure using a modified method.
(8) Nonlinear dynamic analysis procedures should use appropriate simulated ground motions.
Average response values can be used if at least seven simulated ground motions are analyzed;
otherwise, maximum response values should be used.
(9) For elastomeric bearings, vertical compression stresses under usual and instant conditions shouldbe less than 150kg/cm2 and 300kg/cm2. An instant small tensile force response on a few bearings
is allowable but should be less than 10kg/cm2.
(10) In prototype testing of elastomeric bearings, vertical stress versus lateral strain can be used inaddition to the vertical load versus lateral displacement test if the following conditions are met:
(1) the test specimen is an elastomeric bearing, (2) the design compression considering dead andlive loads as well as earthquake-induced force is not greater than 200kg/cm2, and (3) DTM is not
greater than a lateral displacement corresponding to 250% of the total rubber layer thickness.
More importantly, several significant revisions were considered and adopted by the committee recently,
as summarized below:
For seismically isolated structures, the effects of the variability in mechanical properties of seismic
isolation units and their influence on the structure are considered in the design code. Since themechanical behavior of seismic isolation units may vary due to factors such as manufacturing andtesting processes, an overall bounding analysis for the isolation system is used to consider variations67

of design parameters, including the effective stiffness of the isolation system at DD and DM (KeD, KeM),
and the equivalent damping ratio of the isolation system at DD and DM (ξeD, ξeM) [25]. The variationsof ±15%, corresponding to the acceptance criteria for the performance test, shall be analyzed by thedesign professionals.
The test requirement for seismic isolation units makes a significant revision in the definition andpurpose for comprehensively considering quality control, feasibility, and promotion. Three tests are
required to verify the quality of a seismic isolation unit before installation, including prototype,production, and performance tests.
(1) The purpose of the prototype test is to verify the production ability of the manufacturer.
(i) At least two identical seismic isolation units of the same type and size shall be tested toprovide the report of the mechanical properties of the specimens. Specimens used for
prototype tests shall not be installed in the structure.
(ii) The prototype test shall be conducted by certified laboratories that are capable of carryingout tests for seismic isolation units in Taiwan.
(iii) If the seismic isolation units are (1) similar in size as well as identical in material and type,(2) identical in design and manufacturing processes, and (3) the prototype test report of thesimilar seismic isolation units within the last five years in Taiwan can be provided by the
manufacturer and has been approved by the design professionals, the prototype test is not
required to carry out again.
(2) The purpose of the production test is to ensure the stability of quality control in each process,from production to final assembly, by the manufacturer.
(i) Before delivery to the site, the production test requires the assessment of the basic
performance of each seismic isolation unit since each unit is essential to structural safety
and behavior.
(ii) Production tests shall be conducted by the manufacturer or certified laboratories that arecapable of carrying out tests for seismic isolation units.
(3) The purpose of the performance test is to verify that the mechanical properties of the seismic
isolation unit samples meet the design requirements of the design professionals.
(i) Before installation to the structure, the performance test requires the test program to follow
the characteristics of the seismic isolation unit samples as determined by design
professionals.
(ii) The performance test shall be conducted by certified laboratories that are capable ofcarrying out tests for seismic isolation units in Taiwan.
3. THE LARGE-SCALE DYNAMIC MULTIAXIAL TESTING FACILITIESIn 2009, NCREE established the Multi-Axial Testing System (MATS) at the Taipei laboratory in
Taiwan [26], as shown in Fig. 5. MATS is one of the few global full-scale testing systems for
conducting large compression and shear force experiments on specimens such as seismic isolators [27]and wall-type damping devices [28, 29]. To meet the increasing requirement of domestic andinternational research and tests for full-scale seismic isolation and velocity-dependent damping devices
with long stroke and high velocity, the bi-axial dynamic testing system (BATS), which possesses highperformance lateral and vertical dynamic control capacities, was subsequently established at the Tainan
laboratory in Taiwan in 2017, as shown in Fig. 6. Recently, BATS has been utilized to investigate

68various responses due to near-fault ground motions, including the behavior of structural components[30], seismic isolation devices [31], and viscous dampers with long stroke and high velocity.

Figure 5 MATS at the NCREE Taipei laboratory
BATS, as shown in Fig. 6(a), mainly serves to examine full-scale critical structural members, such ascolumns and seismic isolators, subjected to both horizontal deformation and a vertical compression
load in a dynamic manner. It mainly comprises a steel reaction frame, a moveable steel table, four
horizontal hydraulic actuators to drive the table longitudinally, seven hydraulic actuators to exert thecompression load vertically, four hold-down hydraulic actuators to balance the table to have more
redundancy for control, and four lateral hydraulic actuators to guarantee that the table has the desired
longitudinal motion during testing. Details of the main components of BATS are illustrated in Fig. 6(b).
Four dynamic longitudinal actuators with a maximum force capacity of 2 MN are installed andconnected between the table and foundation in the horizontal direction. A static vertical actuator witha maximum force capacity of 30 MN and six dynamic vertical actuators each with a maximum force
capacity of 5 MN are mounted on the foundation to support the table in the vertical direction. The
maximum longitudinal stroke, velocity, and force capacity of BATS are ±1.2 m, ±1 m/s, and ±4 MN,
respectively. The maximum vertical stroke and velocity are ±62.5 mm and ±0.15 m/s, respectively.
The maximum vertical compressive force is 60 MN, which includes a total dynamic force of 30 MN
and a static force of 30 MN. The stroke and force capacities of each of the four hold-down actuators
are ±62.5 mm and +2.0 M, respectively. In other words, BATS also has a vertical tension force capacityof 8.0 MN. For each of the four lateral actuators, the stroke and force capacities are ±5.0 mm and +1.0
MN, respectively.
Hold-down actuator (4)Reaction frame
Table

Foundation
Longitudinal actuator (4)Vertical actuator (7)Lateral actuator (4)Hardline1(a) Overall appearance69

TableHold-down actuator (4)Lateral actuator (4)Longitudinal actuator (4)Vertical static actuator (1)Vertical dynamic actuator (6)(b) Key components
Figure 6 BATS at the NCREE Tainan laboratory
Before making BATS available for public use, it is crucial to determine its key parameters, such as
inertial force (effective mass) and system friction force (friction coefficients), and to gain insights into
its dynamic performance. Consequently, a series of tests were conducted to comprehend thesefundamental parameters and assess the dynamic performance of BATS. To achieve this, themathematical model and iteration methodology have been proposed to identify and mathematicallydescribe the dependency of the friction performance of BATS on total normal forces (and that of theshear force of the specimen on vertical compression loads) and horizontal excitation rates. This isaccomplished by iterating the results of horizontal triangular and sinusoidal reversed loading tests [32,33]. The vertical compression loads are 0 MN and 10 MN for triangle wave cyclic loading tests withdifferent horizontal displacements and velocities as well as sine wave cyclic loading tests with variedhorizontal displacements and excitation frequencies. Based on the results, the average effective massof the platform was calculated as 96.69 tons and the relationship between the horizontal excitation rates
and the system friction coefficients under a specific vertical compression load was obtained, as shownin Fig. 7.

System friction coefficient

0.006

test data

0.005

curve fitting formulas (10 MN)
curve fitting formulas (0 MN)

0.004
0.003
0.002
0.001
0

0

200

400

600

Excitation rate (mm/s)

800

1000

Figure 7 Iteration results for the system friction coefficients of BATS
To verify the rationality and applicability of the identified system friction force (friction coefficients)
and inertial force (effective mass) of BATS, small-size isolator tests were conducted. The shear force
responses were also directly measured using a shear force measurement system [34] to eliminate any
interference of friction and inertial force induced by BATS. The shear force measurement systemcomprises an NRB or several NRBs connected in parallel that transmit the vertical load applied to thespecimen, an intermediate plate that connects the system with the specimen, a reaction frame fixed at
the top of the BATS reaction block, and four prestressed rods that transmit the horizontal force fromthe specimen to the reaction frame, as shown in Fig. 8. Therefore, the shear force applied to thespecimen is the sum of the force changes of the four prestressed rods and the NRB (or NRBs). In other70words, the specimen is connected in series with the parallel prestressed rods and the NRB (or NRBs)
in the horizontal direction.
direct force measurement system
BATS reaction blocknatural rubber bearing (NRB)
reaction frame
steel intermediate plate

prestressed rod
Δ
BATS table(a) Experimental setup(b) Overall appearance

Figure 8 The designed direct force measurement system and verification test setup
0.2

0.5

0.15

0.4
0.3

Force (MN)

Force (MN)

0.1
0.05
0
-0.05
-0.1

Ffeedback
Fdirect
Fidentified

-0.15
-0.2
-100

-50

0

Displacement (mm)

50

0.2
0.1
0
-0.1
-0.2

Ffeedback
Fdirect
Fidentified

-0.3
-0.4
-0.5
-400

100

-300

-200

-100

0

100

Displacement (mm)

200

300

400

(a) Vertical compressive Stress: 20 MPa, shear strain:(b) Vertical compressive Stress: 20 MPa, shear

100%, frequency: 0.25 Hz

strain: 350%, frequency: 0.182 Hz

Figure 9 Comparison of hysteresis loops using different approaches
The specimen used in the measurement system was an LRB with a diameter of 500 mm and a totalheight of 197 mm. The tests aimed to provide a comparison of the identification results, as shown in
Fig. 9. In those figures, Ffeedback is the force feedback directly from the actuators, Fidentified is Ffeedback
modified by the identified effective mass and the relationship between the horizontal excitation rates
and the system friction coefficients (see Fig. 7), and Fdirect is the force measured by the shear force
measurement system. The comparison illustrates that both the friction force and the inertial force weremodified, as depicted in Fig. 9(a). In Fig. 9(b), the comparison with a larger displacement amplitudeand higher maximum excitation rate shows that Fidentified is consistent with Fdirect. This reaffirms thereliability of the proposed mathematical model for BATS and underscores the feasibility of the
proposed direct force measurement strategy.
4. STRONG MOTION MONITORING OF A SEISMICALLY ISOLATED BUILDING AND
NEAR-FAULT EFFECT
Taiwan is seismically active, housing a total of 36 active faults [35]. This geological condition leads toapproximately 8.6 million people, comprising one-third of the population, residing within a tenkilometer radius of these fault lines. The potential impact of near-fault effects on buildings andinfrastructure poses a critical concern for human life and property safety in Taiwan. For example, theHe Xin Building at Hualien Tzu Chi Hospital was installed with a structural monitoring system, as
shown in Fig. 10, which includes 26 accelerometers and 4 displacement transducers [1, 36]. The

71

accelerometers are installed at the center and corners of specific floors and measure both the horizontal
responses in the longitudinal and transverse directions. Additionally, the displacement transducers are
installed across the isolation interface, monitoring isolation displacement in both horizontal directions
between the basement floor (B1F in Fig. 10(a)) and foundation layer (B2F in Fig. 10(a), at the centerand corners. On February 6, 2018, an earthquake with a Richter magnitude of 6.0 struck Hualien Cityand caused an intensity scale of seven. The epicenter was located merely 5.3 km deep andapproximately 18.3 km northeast of the Hualien County Government. This earthquake led to thedislocation of the Milun Fault, which is only 2 km from the Hualien Tzu Chi Hospital. Remarkably,
there was no structural or facility damage, and malfunction reported for the seismically isolatedbuilding. From the acceleration measurement results of the structure in the longitudinal direction, as
shown in Fig. 11, the near-fault ground motion phenomenon and the upward transmission of theexcitation with an enlarged period, owing to the function of the isolation system, along the structure
floors was observed. This evidence practically serves to validate the functionality and efficacy of theseismic isolation design in mitigating the impact of the earthquake.

B1

11F

5F
4F

B1F
B2F

CH1~CH26: AccelerometerCH27~CH30: Displacement transducer

CH1~CH26: AccelerometerCH27~CH30: Displacement transducer(a) Front view(b) Plan view
Figure 10 The structural monitoring system
Unfortunately, due to damage to the displacement transducers, the isolation displacement records forthe 2018 earthquake are unavailable. Thus, a numerical model was established. Through numericalanalysis, the displacement response of the isolation system to the 2018 earthquake is illustrated in Fig.
12. The maximum displacements correspond to the actual record of the pushed distance of thesounding flower nursery, which is contacted by part of the extended paving. As indicated in Fig. 12,
the maximum longitudinal displacement is 285 mm, corresponding to a peak ground acceleration of
266 gal. However, according to the original design, the maximum isolation displacement was projected
to be 240 mm, at a corresponding effective peak acceleration of 330 gal. This observation suggests thatthe isolation displacement exceeded the design expectation, underscoring that additional isolation
displacement was induced by the near-fault ground motion.
As mentioned above, the seismic isolation design against near-fault ground motions remains
challenging, considering that the near-fault ground motions containing long-period velocity pulses may
result in a dramatic displacement demand on the isolation system and an unacceptable force transmitted
to the superstructure. For example, several studies have suggested the implementation of viscousdamping devices to the seismic isolation system to potentially reduce the large displacement and, as aresult, the huge inertia force demand on the superstructure. However, on the other hand, the isolation
effectiveness against far-field ground motions may be questioned. Thus, some research works haveproposed the design method by the isolation system composed of multilinear hysteretic bearings andviscous dampers with various damping exponents against both near-fault and far-field ground motions.

72

Additionally, considering the huge demand for near-fault ground motions, designing a superstructure
by its pure elastic behavior is not rational. The force-controlled concept is then employed to reduce thetransmitted force to the superstructure by ductility reduction factors specified in various design codes.

Figure 11 Longitudinal acceleration response
histories under the 2018 earthquake
5. FUTURE CHALLENGESTECHNOLOGYTO

Figure 12 Isolation displacements and theircomparisons to the actual surface record

APPLICATIONOFSEISMICISOLATION(1) In the aspect of design:
Near-fault ground motions usually cause larger seismic design demands, which is particularly true
for structures with long periods of vibration, e.g., high-rise buildings and seismically isolated
structures. In Taiwan, at present, for static and dynamic analyses, how to practically determine
seismic design demands for which the near-fault effect is reasonably considered is still a criticaland debatable issue. Although some seismic isolation design strategies at the expense of a larger
isolation displacement demand have been proposed, the sacrifice of property lines due to this issue
is still unacceptable to owners and architects, even though the advantages of seismic isolation
design over other conventional earthquake-resistant designs are understood. To practically
overcome this problem, developing more robust devices and combined systems that can better
meet multiple performance objectives at different seismic demands may be still required in the
future.
(2) In the aspect of promotion:
In Taiwan, there are many design professionals who have experience in practically designingseismically isolated structures, and NCREE has much experience in dynamically testing projectspecific seismic isolation units. Peer design review has also been carried out by nationally credibleorganizations for years. However, Taiwan still lacks peer review processes for relevant tests andconstruction, not to mention professional certification. To address this issue, the Chinese Societyof Seismic Isolation (CSSI) attempted to establish a certification program of tests of seismic73isolation units and construction of seismically isolated structures, of which the expense should be
funded by owners. In addition, the establishment of a complete program of regular and irregular(after earthquakes) inspection, maintenance, and management of seismic isolation systems as well
as all components passing through the seismic isolation interface after construction has also been
attempted, of which the expense should be funded by resident’s committees. Currently, CSSI is
endeavoring with the relevant government agencies to get an extra floor area ratio bonus forseismically isolated structures if their design and test results, as well as the inspection, maintenance,and management plans, are approved and certified. If feasible, this plan will be beneficial andpositive in the promotion of seismic isolation technology in Taiwan in the future.
6. CONCLUSIONS
Passive control technologies have been widely implemented in all kinds of structures in Taiwan sincethe 1999 Chi-Chi earthquake. At present, more than 200 building projects have adopted seismic
isolation systems. It is necessary to note that many organizations and industries in Taiwan have adopted
seismic isolation technology to safeguard their critical equipment and facilities. In Taiwan, many
research projects have been actively launched to further understand the actual behavior of the existing
devices and systems, as well as to develop more advanced solutions. Considering feedback frompractical engineering experience and reviews from academic communities, the seismic isolation
provisions in the Taiwan Seismic Design Specifications and Commentary of Buildings arecontinuously modified, aiming for a more reasonable and practicable approach.
With the establishment of BATS in Taiwan, the improvements in seismic isolation technology can besupported in the academic community. Additionally, the demand for conducting prototype, production,and performance tests on full-scale seismic isolators in both industry and government can beadequately met. As a result, NCREE is well-equipped to provide superior seismic experimental
services to government agencies, academia, and industries both domestically and internationally. This
commitment proves beneficial in enhancing public safety and resilience against earthquake disasters.
Moreover, the near-fault effect on buildings and infrastructures is a significant issue of human life andproperty in Taiwan. The seismic isolation design against near-fault ground motions remains
challenging. Therefore, in Taiwan, these issues are currently being addressed through extensive
numerical and experimental studies to mitigate the risks associated with the near-fault effect.
Over the past two decades, there has been a significant increase in the application of seismic isolation
technology in various structures throughout Taiwan. However, the inspection, maintenance, andmanagement of seismically isolated buildings are still in the early stages of development, with limited
practical application in this area. In response to this, CSSI has collaborated with the Japan Society ofSeismic Isolation to facilitate the exchange of ideas and information through workshops and training
programs. This collaboration aims to further enhance the development of comprehensive inspection,
maintenance, and management practices for seismically isolated buildings in Taiwan.
REFERENCES[1] Lin, M.C., Ko, C.Y., Chang, K.C. and Tserng, H.P., “Investigating Real Seismic Responses of Isolation
Structure under Earthquake Attacks: A Case Study of He Xin Building in Hualien Tzu Chi Hospital”, StructuralEngineering, 25(3), 25-26, 2010 (in Chinese).

74[2] Liou, S.K., “Seismic isolation design and quality control of elastomeric bearings, Proc. of the Conference on
Design and Construction of Seismically Isolated Buildings: A Case Study of Lan-Hai Project (38 stories/133m)”,
Taipei, Taiwan, 2010 (in Chinese).
[3] Wang, S.J., Hwang, J.S., Chang. K.C., Lin, M.H. and Lee, B.H., “Analytical and experimental studies on
mid-story isolated buildings with modal coupling effect”, Earthquake Engineering & Structural Dynamics,
42(2), 201-219, 2013.
[4] Wang, S.J., Lee, B.H., Chuang, W.C. and Chang, K.C., “Optimum dynamic characteristic control approachfor building mass damper design”, Earthquake Engineering & Structural Dynamics, 47(4), 872-888, 2018.
[5] Wang, S.J., Lee, B.H., Chuang, W.C., Chiu, I.C. and Chang, K.C., “Building mass damper design based on
optimum dynamic response control approach”, Engineering Structures, 187, 85-100, 2019.
[6] Earthquake Protection System, Inc. (EPS) Friction PendulumTM Bearings, Vallejo, California, 1985.
[7] Hwang, J.S., Chang, K.C., Ye, M.H. and Chen, C.C., “The Investigation on the Seismic Isolation Design of
Taiwan’s First Bridge”, Structural Engineering, 9(2), 15-30, 1994 (in Chinese).
[8] Tang, C.P., Li, W.S. and Ke, H.H., “The Studies and Applications of Seismic Design, Seismic Isolation
Technology and Energy Dissipation Systems for Bridge Structures”, Structural Engineering, 17(2), 33-52, 2002
(in Chinese).
[9] Ministry of Transportation and Communications, “Seismic Design Specifications of Highway Bridges,
Ministry of Transportation and Communications”, Taipei, Taiwan, 2009, 2015, 2018 (in Chinese).
[10] Ministry of Transportation and Communications, “Seismic Evaluation and Retrofitting Design of Highway
Bridges”, Ministry of Transportation and Communications, Taipei, Taiwan, 2020 (in Chinese).
[11] Chen, Y.X., Hsiao, T.J., Wu, M.S., Peng, K.Y. and Chen, G.L., “Seismic Isolation Retrofit and Foundation
Replacement of Freeway Bridge”, Structural Engineering, 36(1), 63-74, 2021 (in Chinese).
[12] Wang, S.J., Chang, K.C., Hwang, J.S., Huang, Y.N., Lin, W.C. and Yang, C.Y., “Recent progress in Taiwan
on seismic isolation, energy dissipation, and active vibration control”, New Zealand Society for Earthquake
Engineering (NZSEE) Annual Conference and Anti-seismic Systems International Society (ASSISi) 15th World
Conference on Seismic Isolation, Energy Dissipation, and Active Vibration Control of Structures, Wellington,
New Zealand, April 27-29, 2017.
[13] Wang, S.J., Hwang, J.S., Chang, K.C., Shiau, C.Y., Lin, W.C., Tsai, M.S., Hong, J.X. and Yang, Y.H.,“Sloped multi-roller isolation devices for seismic protection of equipment and facilities”, Earthquake
Engineering & Structural Dynamics, 43(10), 1443-1461, 2014.
[14] Wang, S.J., Yu, C.H., Lin, W.C., Hwang, J.S. and Chang, K.C., “A generalized analytical model for slopedrolling-type seismic isolators”, Engineering Structures, 138, 434-446, 2017.
[15] Wang, S.J., Sung, Y.L., Yang, C.Y., Lin, W.C. and Yu, C.H., “Control performances of friction pendulum andsloped rolling-type bearings designed with single parameters”, Applied Sciences, 10(20), 7200, 2020.
[16] Wang, S.J. and Sung, Y.L., “Control performance of sloped rolling-type isolators designed with stepwise
variable parameters”, Smart Structures and Systems, 27(6), 1011-1029, 2021.
[17] Wang, S.J., Sung, Y.L. and Hong, J.X., “Sloped rolling-type bearings designed with linearly variable damping
force”, Earthquakes and Structures, 19(2), 129-144, 2020.
[18] Chen, P.C., Hsu, S.C., Zhong, Y.J. and Wang, S.J., “Real-time hybrid simulation of smart base-isolated raised
floor systems for high-tech industry”, Smart Structures and Systems, 23(1), 91-106, 2019.
[19] Chen, P.C. and Wang, S.J., “Improved control performance of sloped rolling-type isolation devices using
embedded electromagnets”, Structural Control and Health Monitoring, 24(1), e1853, 2016.
[20] Hsu, T.Y., Dai, P.S. and Wang, S.J., “Numerical study on smart sloped rolling-type seismic isolators integrated
with early prediction of peak velocity”, Engineering Structures. 246, 113032, 2021.

75

[21] Hsu, T.Y., Huang, C.H. and Wang, S.J., “Early adjusting damping force for sloped rolling-type seismic
isolators based on earthquake early warning information”, Earthquakes and Structures, 20(1), 39-53, 2021.
[22] Lai, Y.A., Wang, S.J. and Hsu, T.Y., “Acceleration-based design procedure for sloped rolling-type bearings
with an added rotational inerter”, Structural Control and Health Monitoring, 2023, 3694995, 2023.
[23] Building Administration Division, “Seismic Design Specifications and Commentary of Buildings”,
National Land Management Agency, Ministry of the Interior, Taipei, Taiwan, 2005, 2011, 2022 (in Chinese).
[24] Chang, K.C., Hwang, J.S., Wang, S.J. and Lin, W.C., “Progress of seismic isolation and energy dissipationin Taiwan – application, research and design”, The 14th World Conference on Seismic Isolation, Energy
Dissipation and Active Vibration Control of Structures (14WCSI), San Diego, U.S.A., September 9-11, 2015.
[25] Wang, S.J., Lee, H.W., Yu, C.H., Yang, C.Y. and Lin, W.C., “Equivalent linear and bounding analyses ofbilinear hysteretic isolation systems”, Earthquakes and Structures, 19(5), 395-409, 2020.
[26] Lin, T.H., Chen, P.C. and Tsai, K.C., “The multi-axial testing system for earthquake engineering researches”,
Earthquakes and Structures, 13(2), 165-176, 2017.
[27] Nishi, T., Suzuki, S., Aoki, M., Sawada, T. and Fukuda, S., “International investigation of shear displacement
capacity of various elastomeric seismic-protection isolators for buildings”, Journal of Rubber Research, 22(1),33-41, 2019.
[28] Li, C.H., Tsai, K.C., Su, L., Lin, P.C. and Lin, T.H., “Experimental investigations on seismic behavior anddesign of bottom vertical boundary elements in multi-story steel plate shear walls”, Earthquake Engineering &Structural Dynamics, 47(14), 2777-2801, 2018.
[29] Chou, C.C., Tseng, W.H., Huang, C.H., Tsuang, S., Chang, L.M. and Chen, Y.H., “A novel steel leverviscoelastic wall with amplified damper force-friction for wind and seismic resistance”, Earthquakes andStructures, 210, 110362, 2020.
[30] Lin, J.L., Chen, W.H., Hsiao, F.P., Weng, Y.T., Shen, W.C., Weng, P.W., Chao, S.H., Chung, L.L. and Hwang,
S.J., “Effects of hysteretic models on the seismic evaluation of a collapsed irregular building from bidirectional
near-fault ground motions on a shake table”, Earthquakes and Structures, 247, 113087, 2021.
[31] Sawada, T., Nishi, T., Murota, N., Mori, T., Fukuda, S. and Aoki, M., “Dynamic behavior of actual size
elastomeric sliding bearings for seismic isolation buildings”, 14th annual Fall Rubber Colloquium, Hannover,Germany, November 8-10, 2022.
[32] Lin, W.C., Liu, C.L., Wang, S.J., Yang, C.Y., Yu, C.H., Lin, C.C., Lu, L.Y., Hwang, J.S. and Chang, K.C.,“Performance Identification of the Bi-Axial Dynamic Testing System”, National Center for Research on
Earthquake Engineering. Report No. NCREE-2022-001, Taipei, Taiwan, 2022. (in Chinese).
[33] Lin, W.C., Yu, C.H., Yang, C.Y., Lin, C.C., Peng, S.K. and Wang, S.J., “Investigation of the Essential
Parameters of the Bi-Axial Dynamic Testing System in the Tainan Laboratory”, 2022 NCREE Research
Programs and Accomplishments, 85-88, 2023.
[34] Yu, C.H., Lin, W.C., Wang, S.J. and Yang, C.Y., “Approaches to Improve Force Measurement of a Biaxial
Testing System”, 2021 NCREE Research Programs and Accomplishments, 57-60, 2022.
[35] CGS. “Active fault map of Taiwan”, Central Geological Survey (CGS), Ministry of Economic Affairs, New
Taipei City, Taiwan, 2021 (in Chinese).
[36] Yu, C.H., Wang, S.J., Yang, C.Y., Lin, W.C. and Chang, K.C., “Study on the Actual Responses of Seismically
Isolated Structures in the Hualien TzuChi Medical Center”, 2018 NCREE Research Programs andAccomplishments, 93-96, 2019.

76

APPLICATION OF SEISMIC BASE-ISOLATION TECHNOLOGY IN INDIA

Pravin Jagtap1 and Vasant Matsagar2
1 Principal Project Scientist, Multi-Hazard Protective Structures (MHPS) Laboratory, Department of Civil Engineering,
Indian Institute of Technology (IIT) Delhi, Hauz Khas, New Delhi - 110 016, India.
2 Dogra Chair Professor, Multi-Hazard Protective Structures (MHPS) Laboratory, Department of Civil Engineering, Indian
Institute of Technology (IIT) Delhi, Hauz Khas, New Delhi - 110 016, India.

ABSTRACTThis document discusses the status of the application of seismic base-isolation (BI) technology in India.
The Indian construction industry has slowly started implementing base-isolation technology tosafeguard the infrastructure from the looming threat of earthquake events. In India, the pace of
application of seismic base-isolation technology is still slow due to a lack of awareness about theperformance benefits of the base-isolation technology amongst the stakeholders. However, as an effectof over the time increase in awareness about financial and other advantages of the base-isolation
technology and the introduction of design guidelines for base-isolated structures through IndianStandard (IS) codes, it is envisioned that the number of projects in India will be increased soon,
especially in the localities of high seismic activities.

KEYWORDS: Buildings, Base-Isolation, Base-Isolators, Earthquake, Energy, Sustainable.

1. INTRODUCTION
Devastating effects caused by earthquakes have been witnessed by several countries worldwide,
including India, in history. Prediction of earthquakes is not possible, being an uncertain event. The
inappropriate occurrence of these events causes hindrances to achieving sustainable development goals,
slows down growth, and pushes down the economic status of any country. Hence, it becomes essential
to safeguard the lives, buildings, and infrastructure from the looming threat of an earthquake.
Base-isolation (BI) is now a well-evolved passive vibration control technology, and through its wide
applications worldwide, it has been established that it is one of the few available concepts to mitigate
structural responses both at member and global levels (Madhekar and Matsagar, 2022). In seismicbase-isolation the damaging effect of the ground motion is absorbed at the isolation plane and hence
reduces the force demand on structures sitting above isolators. The period of the structure is primarily
lengthened when base-isolated, thus improving its performance during an earthquake event. In the77

conventional design approach, one needs to rely on the inelastic action of the various structuralelements to dissipate the earthquake-caused energy. In addition to safeguarding the primary structure,
seismic base-isolation also offers protection of the contents and secondary systems housed in thebuildings; since, the seismic forces transmitted to the primary structure are reduced considerably. Inview of the effective level of protection offered by base-isolation, the reduction in post-earthquake
damages and, hence, a decrease in the post-earthquake repairing cost can be assured.
Looking into the benefits offered by seismic base-isolation technology, the Indian construction industry
has also started implementing this mature technology, particularly in areas of high seismicity, throughseveral government, private, and industrial projects in the last few decades. Brief information aboutsome of the base-isolated projects that are completed, under construction, and upcoming in India is tobe compiled and disseminated through this document to the scientific and public domain. Perhaps due
to lack of public awareness about seismic performance benefits of base-isolation, lack of knowledge
on base-isolation technology amongst design engineers and stakeholders, uncertainty regarding theadditional financial costs for adopting base-isolation, uncertainty regarding easy availability of baseisolators, non-availability of clear design guidelines through Indian Standard (IS) seismic design codes
for base-isolated structures for long time the popularity of application of seismic-base isolation in India
remained slow and taking time to elevate.
2. BASE ISOLATION DESIGN STANDARDS AND CODES IN INDIAThe International Organization for Standardization (ISO) is an international body involved in thedevelopment of international standards. ISO composes experts and representatives from the national
standards organizations of member countries. In India, the Bureau of Indian Standards (BIS) is thenational standards body that develops and publishes the Indian Standard (IS) codes for theirimplementation in design practice. In the year 2022, the BIS, India, published the IS code forearthquake resistance design of buildings using base-isolation technology. The objective of this code
is to reduce the extent of earthquake damage through base-isolation of buildings. IS 1893 (Part 6): 2022
mainly covers requirements for design of base-isolated buildings. This standard proposes the buildings
shall be designed and constructed to resist earthquake induced displacements and forces. The
provisions of this standard are applicable only to regular Reinforced Concrete (RC) buildings and steelframe buildings.
The major part of India's land area is prone to moderate to strong earthquake shaking, and there areseveral critical structures already built and under construction in these areas. Therefore, theimplementation of earthquake-resistant design is of paramount importance and essential, especially inthe zones of high seismic activity. The general provisions for earthquake resistance of buildings arelaid down in the BIS publication IS 1893 (Part 1): 2016. Figure 1 shows the Seismic Zone Map ofIndia as included in the IS 1893 (Part 1): 2016. As per this map, India's land is categorized into four
seismic zones, viz. Zone - II, III, IV, and V. The Highest level of seismic activity is expected in ZoneV; whereas, the lowest level of seismic activity is expected in Zone II, as categorized by the standard.

78

Image Source: IS 1893 (Part 1): 2016

Figure 1 Seismic Zone Map of India as per IS 1893 (Part 1): 2016

3. BASE-ISOLATION PROJECTS IN INDIAAs discussed herein, the Indian construction industry has started adopting base-isolation technology
slowly in view of the benefits offered by this technology to safeguard structures from devastating
earthquake effects. In view of the increasing awareness and availability of detailed design guidelines
in the form of IS code to help structural design engineers, the construction industry in India is expected
to gear up, and more projects with the implementation of base-isolation technology are anticipated tocome up in India. Details of some of the building projects that are functional, under construction, andunder consideration in India are reported in this document.
3.1 Bhuj Hospital Project, Bhuj, Gujarat
On the unfortunate morning of India's 52nd Republic Day, Friday, 26th January 2001, a powerfulearthquake (measuring 7.7 on the Richter scale) struck the Bhuj city in Kutch region of the state ofGujarat in India (Sharpe, 2002). The best estimates suggest that at least 20,100 human casualties
happened that unfortunate morning. As reported, this earthquake has also destroyed the Bhuj District
Hospital, killing almost all of its 178 patients. Hospitals are lifeline structures, and their continuousfunctioning is always desired; hence, the Government of India has planned to replace a 300-bed
hospital and decided to use seismic base-isolation technology while accepting the offer of design
expertise from the New Zealand government. Bhuj Hospital became the first base-isolated hospital79

building in India. A ceremony of laying the foundation stone for the hospital building took place on
Tuesday, 2nd October 2001, and the hospital building was inaugurated on Wednesday, 14th January
2004, by the then Prime Minister of India after construction. The Bhuj Hospital building is supported
by a combination of 280 lead-rubber and sliding isolation bearings. All the isolation bearings required
for this project are manufactured and supplied by Robinson Seismic Limited, New Zealand. Figure 2
shows the pictorial views of the completed Bhuj hospital structure and base-isolation units installed in
the structure.
(b)

(a)

Image Source: http://civilenggseminar.blogspot.com

Image Source: https://www.hospitalmanagement.net

Figure 2 View of the (a) Completed Bhuj Hospital Structure and (b) Base-Isolators Installed in the
Structure
3.2 Base-Isolated Structures at IIT Guwahati, Assam
Two numbers of three-storied RC framed buildings with identical structural configurations areconstructed at the Indian Institute of Technology (IIT) Guwahati campus, one with base-isolation using
four lead plug bearings and the other with the conventional foundation to study the behaviour of baseisolated buildings under real earthquakes (Dubey et al., 2008). These structures are the outcome of acollaborative research project between IIT Guwahati and Bhabha Atomic Research Center (BARC),
Mumbai, India. Figure 3 shows the pictorial view of the structures and architectural details (plan andfront elevation) of the demonstration structures, showing plan dimensions, location of isolators andother relevant details. Different properties of isolators used in the base-isolated structure are describedin Table 1.
Table 1: Properties of Lead Plug Isolators (Dubey et al., 2008)
Model
Property
Value
Mass
0.5 TonVertical Stiffness
188960 kN/m
Post-Yield Stiffness
796 kN/m
Base-Isolated Structure
Ratio of Post to Pre-Yield Stiffness
0.0463(Lead Plug Isolators)
Effective Damping
0.1056
Yield Strength25.38 kN
Effective Horizontal Stiffness
1292.085 kN/m

80

3300

(c)

2500

3300

4500
1000

Isolators

1200

(a)
300

Fixed-Base

Base-Isolated

Structure

Structure

GIS sheet
2100

300
Parapet Wall

3300

3300

3300

300

1200
600

Base Isolator(b)Ground Level

Figure 3 (a)Architectural Details (b) Sectional Elevation and (c) Pictorial View of Structures at IIT
Guwahati Campus

3.3 Indira Gandhi Hospital Project, Dwarka, New Delhi
Figure 4 shows the photograph of a currently functional 750-bed Indira Gandhi Hospital Project,
Dwarka, New Delhi. This project was conceptualized and developed by the Public Works Department(PWD), New Delhi, for the Directorate General of Health Services (DGHS), Government of National
Capital Territory (NCT) of Delhi. The Reinforced Cement Concrete (RCC) structure of the hospitalbuilding has three interconnected blocks: (i) Outpatient Department (OPD), (ii) ward, and (iii)emergency block. This structure is constructed in Seismic Zone-IV of India, which is one of the most
severe earthquake zones in India; hence, the continuous functionality requirement of this hospital
structure is achieved by adopting the base-isolation technology. Table 2 summarizes some of thestructural details and information of the constructed hospital facility. All the blocks of the hospital
structure are base-isolated with a combination of Lead-Rubber-Bearings (LRB) and sliding bearings.
In total, 440 numbers of base-isolation units are placed below the structure to decouple it from theseismic forces generated during earthquake events. The details of the isolators, along with theirproperties considered in modelling, are described in Table 3. Necessary endorsement to the structuraldesign of the base-isolated hospital structure is provided by the communicating author at IIT Delhi. As
per the design, the base-isolator units required at a hospital construction site are supplied by Dynamic
Isolation Systems, USA. L&T Construction was involved in the execution of construction work at thesite.

Sr. No.
1
2
3

Table 2 Construction Details of the Hospital Structure
Hospital Blocks
Number of Floors
Emergency Block
2 Basement (B) + Ground (G) + 5
Ward Block
2B+G+8OPD Block
2B+G+581

Covered Area
36,226 m2
31,455 m2
25,325 m2

Sr.
No.
1
2
3
4
5

BaseIsolator
Category
BG - A
BG - B
BG - C
BG - D
BG - E
Total

Table 3 Block wise Details of the Installed Base-Isolators
Emergency Block
Ward
OPD
Block
Block
Block
Block
Block
(A1, A2)
(A3)
(A4)
23
2
16
28
0
38
12
0
52
14
46
13
0
43
12
13
0
0
3
54
24
1
5
29
12
144
28
21
155
92

Total
Isolator
Units
69
116
114
70
71
440

Image Source: https://twitter.com/AamAadmiParty

Figure 4 Pictorial View of the Indira Gandhi Hospital Structure, Dwarka, New Delhi
3.4 Sardar Patel Bhavan, Patna, Bihar
Sardar Patel Bhavan, Patna, Bihar is the first building in the state of Bihar that is constructed with baseisolation technology. This building utilizes a combination of lead-rubber-bearings (LRB) and sliding
bearings to isolate the base of the structure from the superstructure. Patna, the state capital of Bihar,
falls in Seismic Zone-IV of India. Sardar Patel Bhavan is planned to house the police headquarters andthe state's emergency operation centre; hence, the undisturbed functioning of this building is very
important in case of emergency situations such as earthquakes. The main building block of the Sardar
Patel Bhawan is a B+S+6 storied RCC framed structure. The entire building of the Sardar Patel Bhavan
is supported by a total of 308 number of base-isolators. The Building Construction Department (BCD)of the Government of Bihar led the project activities till its successful completion in the year 2018.
Contribution in structural design and production testing services are provided by the communicating
author at IIT Delhi for this structure. Dynamic Isolation Systems, USA, has manufactured and supplied
the required number of base-isolators, and the construction work of the Sardar Patel Bhavan iscompleted by Ahluwalia Contracts (India) Limited. Figure 5 demonstrates the structural framing
section showing a level of base-isolation of the Sardar Patel Bhavan and a photographic view of thecompleted and functional structure.

82

(a)
Z

3.9

Fifth Floor

3.9

Sixth Floor

3.85

Terrace Floor

Fourth Floor

Open to Sky Court-Yard

3.9

Third Floor

3.9

Y

3.9

Second Floor

Isolator
3.9

First Floor

1.5

Stilt Floor

2.5

Isolation Level

Basement
All dimensions are in meter(b)

Image Source: Building Construction Department, Government of Bihar

Figure 5 (a) Structural Framing Showing Isolation Level and (b) Pictorial View of the Sardar Patel
Bhavan, Patna, Bihar
3.5 Resistoflex Showcase Building Project, NOIDA, Uttar Pradesh
The recently constructed RC mid-rise (B+S+5) Resistoflex showcase building (Figure 6) located in the
National Capital Region (NCR) is entitled India's first base-isolated corporate building structure (plandimension: 27.78 m × 10.05 m) developed in collaboration with the communicating author at IIT Delhi.
The objective of this landmark project is to demonstrate base-isolation technology and provide
adequate information among stakeholders to adapt the BI techniques, especially for important
structures (located in Seismic Zones IV and V of India). The structure is designed to be operational andwill continue to remain functional even in the case of severe earthquakes predicted for Seismic ZoneIV of India (Panda et al., 2023). The showcase building structure is erected on the fourteen number ofDouble-Curvature Friction Pendulum Bearings (DCFPB). The schematic diagram, picture, and typicalforce-deformation behaviour of DCFPB is shown in Figure 6. For the considered RC framed building,the base isolators are decided to be placed at stilt level to isolate the superstructure from ground level.
The DCFPBs are modelled at the stilt level of the building and are designed for design basis earthquake(DBE) and maximum considered earthquake (MCE) by following the guidelines of the in-force
versions of the IS 1893, and ASCE/SEI-7 at the time of design. It is noteworthy to mention that the lift
core in the building is designed and constructed as a hanging structure with the provision of appropriate
space at bottom and around its periphery to allow the movement of isolation units when active. The
showcase building structure is being visited by several national and international fraternities (Figure 6),
which serves the intended purpose of this structure, which is to disseminate base-isolation technology.

83

(a)

(b)

(b)

(b)

(b)

Figure 6 (a) Pictures of Base-Isolated Resistoflex Showcase Building and (b) Visitors from Several
Sectors

Figure 7 Details of DCFP Bearings Installed at Resistoflex Showcase Building
3.5.1 Seismic monitoring of showcase building
A unique feature through seismic monitoring is added to the Resistoflex showcase building while
integrating the data acquisition system and accelerometer sensors to instantly convey to all stakeholders
and occupants through mobiles and the internet about the incoming and happening seismic activity,
which in turn makes the building seismically smart. To monitor the response of the base-isolatedbuilding, a LabVIEW® GUI code has been developed, where there will be continuous data acquisition(Figure 8) through a series of sixteen uniaxial accelerometers and a data acquisition system. Table 4
presents the installation of uniaxial accelerometers at different locations, i.e., column number, direction,
and above or below the isolation level, in the showcase building. This table shows that eightaccelerometers are installed below the isolation level, i.e., at the basement and ground floor.
Additionally, eight accelerometers are installed above the isolation level, i.e., at the ground, 4th, and 5th
floors. The direction of the accelerometers is aligned along both the horizontal directions of the building.
Figure 9 shows the recorded forced vibration data at 4th and 5th floors of the Resistoflex building during

84the recent earthquake activity.
Table 4 Installation of Uni-Axial Accelerometers at Different Locations
ColumnAccelerometer
Location
Direction
DAQ Channel
NumberNomenclature
A01
Along X
CH0
Basement
C14 (BIL)
A11
Along YCH1
A40
Along X
CH14
Basement
C13 (BIL)
A41
Along Y
CH15
A21
Along X
CH2
GroundC13 (BIL)
Floor
A12
Along Y
CH5
A02
Along X
CH4
GroundC13 (AIL)
Floor
A03
Along Y
CH3
A13
Along XCH6
GroundC1 (BIL)
Floor
A14
Along Y
CH7
A20
Along XCH8
GroundC1 (AIL)
Floor
A21
Along YCH9
A22
Along X
CH10
4th Floor
C13 (AIL)
A23
Along Y
CH11
A30
Along X
CH12
5th Floor
C13 (AIL)
A31
Along YCH13
* AIL = Above Isolation Level; BIL = Below Isolation Level

Figure 8 Continuous Data Acquisition through Developed LabVIEW® GUI Code85

Figure 9 Recorded Forced Vibration Data at 4th and 5th Floor Levels of the Resistoflex Building

3.6 Government Lalla Ded Hospital Additional Block Project, Srinagar, Jammu and Kashmir
This is an ongoing G+6 story building project at Srinagar, the summer capital of Jammu and Kashmir.
The project was approved in 2017 under the Jhelum and Tawi Flood Recovery Project (JTFRP). Thisis a critical infrastructure project in Seismic Zone V of India; hence, the World Bank has recommended
the use of base-isolation technology and funded the project. When completed, the project will stand asa groundbreaking endeavour in the Jammu and Kashmir region. The functioning of the additional
block is anticipated to boost the hospital's capacity from 500 to 900 beds. Under the design stage, thelead-rubber bearings at around 41 locations are proposed to be used to base-isolate the additional block
structure. The LD hospital structure is located on the bank of the Jhelum river; thereby, in the event of86

a river flood, the hospital structure partly submerges into the flood water; hence, to avoid the immersionof base-isolators in flood situation, the level of base-isolation is proposed to be at first-floor level of thestructure. The executing agency, Jammu and Kashmir Project Construction Corporation (JKPCC) is
coordinating the activity. Endorsement to the design of the base-isolated structure is under process withthe communicating author at IIT Delhi. The sectional elevation and numerical model of the additional
block structure prepared for design purposes are shown in Figure 10.
(a)

(b)

Figure 10 (a) Sectional Elevation and (b) Numerical Model of the LD Hospital Additional Block
Structure
3.7 Guru Teg Bahadur Hospital Project, Shahdara, Delhi
Guru Teg Bahadur Hospital is a large hospital situated at Dilshad Garden, Shahdara, Delhi, India, andis affiliated with the University College of Medical Sciences, University of Delhi. The 500-bed newward block with eight stories of RCC framed structure building includes a service basement and has atotal floor area of 28,734 m2. It is constructed using base-isolation technology to maintain its
continuous functionality even after devastating seismic events. The new ward block structure caters toadditional facilities for gynaecology and paediatric services. This additional ward is also connected at
all floors with the existing ward block by providing a connecting corridor and ramp. The newly
constructed ward also has green building features to make it an energy-efficient building, which
improves the quality of the indoor environment. Figure 11 shows the image of the base-isolated
hospital structure and a picture of the lead-rubber bearing being installed at the site.

87

(b)

(a)

Image Source: https://gtbh.delhi.gov.in

Figure 11 (a) Images of Guru Teg Bahadur Hospital and (b) Lead-Rubber Bearing Installation at Site

3.8 Lok Nayak Jai Prakash Narayan (LNJP) Hospital Project, New Delhi
The Lok Nayak Jai Prakash Narayan (LNJP) Hospital, New Delhi, is a multispecialty hospital founded
in 1930. As reported, the hospital gets a daily footfall of around 4,000 patients not only from Delhi butfrom neighbouring states as well, for example, Uttar Pradesh, Bihar, Haryana, Punjab, Rajasthan,
Uttarakhand, and Himachal Pradesh. The newly constructed Outpatient Department (OPD) at the
LNJP hospital has state-of-the-art facilities comparable with the established private multispecialty
hospitals in Delhi. Base-isolation technology is implemented to ensure the continuous functionality of
the hospital after earthquake events. Figure 12 shows the picture of LNJP hospital and one of the baseisolator units installed in the hospital structure.
(b)

(a)

Image Source: https://lnjp.delhi.gov.in

Figure 12 (a) LNJP Hospital Structure and (b) Installed Base-Isolator Unit in the Hospital Structure

3.9 Walker Military Hospital Project, Shimla, Himachal Pradesh
The famous Walker Military Hospital, Shimla, Himachal Pradesh, was gutted in an unfortunate fire
event in 1998. As it was a wooden structure, the blaze spread quickly, leaving little scope to control thefire. The entire building was engulfed in flames as the thick coating of paint applied to the woodelements made the structure more inflammable. The reconstruction of the 100-bed five-storey hospital88was planned while implementing the base-isolation technology and installation of lead-rubber bearings,
which makes the hospital structure one of its kind in the state of Himachal Pradesh. Figure 13 shows
the model of the planned 100 bedded base-isolated Walker Military Hospital structure.

Figure 13 Model of the Planned 100-Bedded Base-Isolated Walker Military Hospital Structure

3.10 Cancer Hospital Projects, AssamAs reported, the Assam Cancer Care Foundation (ACCF) is a joint partnership between the
Government of Assam and Tata Trusts. It was set up in December 2017 to create a first-of-its-kind,
three-level cancer grid in the state. With a plan to set up 17 cancer hospitals in the state, it is the largest
cancer care network in South Asia. The distributed care model was conceptualized by the Trusts andthe Government of Assam to create patient-centric cancer institutions to deliver standardized andaffordable care closer to patients' homes. The ACCF is expected to benefit 50% of cancer patients in
Assam. Most of the part of Assam state falls under a seismically active region, and hospitals are lifeline
structures. It is important to safeguard them from the devasting effects of earthquakes; hence, utilizationof seismic base-isolation technology is the best fit here. Triple-pendulum base-isolator units are
installed in the eight number of completed base-isolated hospital structures as of now at Barpeta, Tezpur,
Dibrugarh, Lakhimpur, Jorhat, Darrang, Kokrajhar, and Silchar in the state of Assam. The base-isolator
units are designed, manufactured, and supplied by M/s Earthquake Protection Systems (EPS),
California, USA. The structural design and construction work of the hospital structures is taken up by
the Engineering Design and Research Centre (EDRC) wing of L&T and L&T Construction,
respectively. The activity of endorsement of the structural design of the base-isolated hospital structures
is facilitated by IIT Madras. Figure 14 shows some of the photographs during construction and after
completion of the hospital structures at Dibrugarh and Tezpur.

89

(a)

(c)

(b)

(c)

Figure 14 Photographs of the Hospital Structures at (a) Dibrugarh, (b) Tezpur, and (c) During
Construction Images

3.11 Ireo Business Park Project, Gurugram, Haryana
A 2B+G+6 storied business park structure at Gurugram, Haryana, is a commercial building developedby Ireo Private Limited, Gurugram. The built-up area of the commercial building structure is around
92,903 m2 in plan. The structure primarily contains office spaces and is mainly utilized for commercial
activities. Commercial building structures are the places that a significant population visits every day
for multiple reasons, such as for employment, important meetings with the senior team, or socializing
with colleagues. These spots are important for those who would like to increase their current business
operations or begin a new one. Uninterrupted operations of the commercial structures are always
anticipated; hence, base-isolation technology is adopted to safeguard the Ireo Business Park structurefrom uncertain earthquake events. The commercial building structure is constructed using precast
construction technology and is supported on 258 DCFPBs located at the upper basement level. The
isolator units are designed, manufactured, and supplied at the site by HIRUN International Company
Limited, Taiwan. Figure 15 shows some of the photographs of the Ireo Business Park building during
and after the construction stage.

90

(b)

(a)

Figure 15 Photographs of the (a) Ireo Business Park, Gurugram and (b) Isolator Units and its
Installation
3.12 Shrem Fairmont Airport Hotel Project, Mumbai, Maharashtra
A premium luxury hotel and commercial building project (3B+G+11) of the Shrem Group is underconstruction in Mumbai, Maharashtra. The Shrem Group is a developer in hospitality, real estate andinfrastructure. The developer has specific project requirements with a focus on high customer comfort
and safety standards. Due to increased vibration activities in the metropolitan area and in view of themission to increase comfort, the developer demanded the use of base-isolation technology to mitigate
the local vibrations and protect the structure from unforeseen earthquakes. The building has been underconstruction as a composite structure since 2018, and its completion is planned for 2024. GERB
Vibration Control Systems Pvt Ltd, NOIDA, India, has taken up this project to design, manufacture,and supply the base-isolators. Around 515 steel spring element base-isolators are installed at the upper
basement level of the structure, having 92,903 m2 plan area. As of now, most of the major construction
activities of the building have been completed, and finishing work is in progress. Figure 16 showssome of the details of the Shrem Fairmont Airport Hotel Project.

91

(b)

(b)

(a)

(b)

Figure 16 Details of the (a) Proposed Shrem Fairmont Airport Hotel Project and (b) Isolator Units
and its Installation
4. CONCLUSIONS
Details of some of the critical base-isolated building structures that are functional and underconstruction are provided herein in this document. Application of base-isolation technology is slowly
taking pace in India, especially in the healthcare industry. There is still enormous potential for adopting
this technology in residential, commercial, and industrial structures. It is envisioned that due to theavailability of Indian standards for the design of base-isolated buildings and an increase in awarenessabout the financial and other benefits offered by base-isolation technology, the Indian constructionindustry will adopt this technology more effectively and comfortably, especially in the seismic zones
of high severity.
5. ACKNOWLEDGMENTS
The authors gratefully acknowledge the support of L&T Construction (Buildings and Factories),
Chennai, India; GERB Vibration Control Systems Pvt Ltd, NOIDA, India, Resistoflex Dynamics
Private Limited, NOIDA, Uttar Pradesh, India; Mr Raman Dogra, and Mr Gaurav Ghosh for sharing
and allowing to compile the above project information in this document.
REFERENCES[1] ASCE/SEI-7 (2016). "Minimum Design Loads for Buildings and Other Structures", StructuralEngineering Institute (SEI), American Society of Civil Engineers (ASCE), Reston, Virginia (VA),
United States of America (USA).
[2] Dubey, P. N., Reddy, G. R., Vaze, K. K., Ghosh, A. K., Kushwaha, H. S. and Deb, S. K. "Performanceof Base-Isolated RCC Framed Building under Actual Earthquake", Journal of Structural Engineering,92

Volume 35, Number 3, 195-201, 2008.
[3] IS 1893: Part-1 (2016). "Criteria for Earthquake Resistant Design of Structures: General Provisions andBuildings", Bureau of Indian Standards (BIS), New Delhi, India.
[4] IS 1893: Part-6 (2022). "Criteria for Earthquake Resistant Design of Structures: Base Isolated
Buildings", Bureau of Indian Standards (BIS), New Delhi, India.
[5] Madhekar, S., and Matsagar, V. "Passive Vibration Control of Structures", CRC Press, Taylor andFrancis Group, Boca Raton, Florida (FL), United States of America (USA), 2022.
[6] Panda, J., Singh, V., Jain, R. and Matsagar V., "Seismic performance assessment and benefit-cost
analysis of mid-rise reinforced concrete base-isolated building using double-curvature friction
pendulum bearings", Structure and Infrastructure Engineering, DOI: 10.1080/15732479.2023.2275698,
2023.
[7] Sharpe, R. D. "Kiwi Technology to Protect Indian Hospital from Earthquakes", Paper No. 2.5, Annual
Conference, New Zealand Society for Earthquake Engineering (NZSEE), Napier, New Zealand, 2002.

93

SEISMIC ISOLATION IN TÜRKİYE
Mustafa Erdik
Professor Emeritus, Dept. Of Earthquake Engineering, Bogazici University, Istanbul, Türkiye

ABSTRACTThis paper provides a brief survey of the current state and the challenges faced in seismic isolation
applications. The utilization of the technique of seismic isolation for new structures and retrofit ofexisting structures is developing at a high rate in the country. A new seismic isolation design codefor buildings is prepared. As of 2023, there are about 200 structures (constructed or underconstruction) with seismic isolation. The list includes hospitals, buildings, airport terminals, LNG
storage tanks, bridges and viaducts, sports arenas, and schools. Most of the recent activity seems
to have focused on viaducts and hospital buildings as the Ministry of Health made it mandatory touse seismic isolation for public hospitals in the high earthquake hazard zones of Türkiye. After the
recent earthquakes, the interest and demand in seismic isolation applications have substantially
increased. The training of engineers for the proper use of seismic isolation techniques is needed forthe healthy development of applications.
KEYWORDS: Türkiye, Earthquake, Isolation, Codes
1. INTRODUCTION
Earthquake is a threat to human lives and assets. Population growth and increasing urbanization inearthquake-prone areas suggest that earthquake impacts on human populations will continue in the
coming decades. Although, seismic design codes have been successful in controlling the damage
to structures, and in provision of life safety, the non-structural and business losses kept increasing.
In most buildings (especially the museums) the contents are generally more costly and valuable
than the buildings themselves. The post-earthquake operational continuity of hospitals,
communication centers, poliçe, and fire stations and other critical facilities needs to be ensured.
Conventional construction techniques that can protect the structure itself, may result in very highfloor accelerations that damage non-structural components and contents. As such, the use of
seismic isolation techniques is needed to ensure "fully operational" performance.
Türkiye has suffered a high amount of casualties and loss of property due to earthquakes over many
centuries. The seismic isolation technology has been applied at an accelerated pace for earthquake
protection after the 1999 Kocaeli Mw7.4 Earthquake. Today, there exist about 200 structures(constructed or under construction) with seismic isolation, including hospitals, schools, airport
terminals, storage tanks, bridges, viaducts, and sports arena. Most of the recent activity havefocused on hospital buildings (Erdik et al, 2015). In 2017, Engineering News Record (ENR)

94

selected the largest 10 base isolated buildings in the world (https://www.enr.com/articles/42366the-10-largest-base-isolated-buildings-in-the-world). The ranking was based on the total closed
floor area. Three of these largest base isolated buildings are located in Türkiye.
These developments on seismic isolation also necessitated the preparation and enforcement of anational official design code for seismic isolation applications on buildings in 2019.
The 2020 Elazığ earthquake and the catastrophic February 6, 2023 earthquakes served as a test of
the performance base isolated hospitals and indicated the problems associated with the state ofapplications. These earthquakes also served to increase the interest and demand in seismic isolation
applications. With a current number of qualified engineers, it is difficult to meet such a demand.
The training of engineers for the proper and correct utilization of seismic isolation techniques, aswell as licensing, needs to be considered for the healthy development of applications.
2. OVERVIEW OF THE SEISMIC ISOLATION IN TÜRKİYE
The status of the seismic isolation applications in Türkiye is documented sevearal publications (e.g.
Yenidogan et al. (2014), Erdik et al. (2015, 2018), Erdik (2015, 2017 and 2019) and Sadan (2023).
The following overview represents a summary of these papers.
The total number of seismic isolation applications in Türkiye, especially for hospitals, hassignificantly increased after the 1999 Kocaeli and Düzce and 2011 Van earthquakes, where, a large
number of hospitals were damaged beyond repair and have led the Turkish Ministry of Health toenact a regulation in 2013 to enforce that the “Hospital Buildings, located in seismic zones 1 and 2with a number of bed capacity over 100 should be constructed with base-isolation”.
As of 2021, there are 102 isolated structures in Türkiye, of which 65 are hospitals, 8 are bridges,
and 3 are industrial facilities (Figure 1) encompassing about 45,000 isolation units (Sadan, 2023).
Most of these seismic isolation applications for hospitals involve large buildings encompassing
isolation units in the order of 1000. About 60% of these isolation units were curved surface friction
and 40% were elastomeric type.

Figure 1. Distribution of the seismically isolated structures in Türkiye (After, Sadan, 2023)

95

The isolated structures include the Adana Integrated Health Campus which houses 1,550 beds infour building units supported by 1,512 base isolators (Figure 2a). The 790,000 square meter, 2,354bed Başakşehir Health Campus hospital complex sitting on 2040 isolator units, is currently thelargest base-isolated building in the world (Figure 2b). Başıbüyük Training and Research Hospitalin İstanbul was retrofitted with seismic isolation (Figure 3a) and currently represents the largest
hospital in the world, retrofitted with seismic isolation. The hospital complex is composed of
sixteen 2-13 story blocks with a total area of 113.000 meter square and a 750-bed capacity. Recent
seismic isolatiıon applications also involve residential/commercial building complexes, such as theMavera Comfort Apartments, with 16 isolated apartment blocks covering 170,000m2 andencompassing 454 lead rubber isolators (Figure 3b). In addition to numerous bridges and viaducts,
there also exist exemplary seismic isolation applications for historical buildings, liquid storage
tanks, and jetties.

Figure 2. (a) Adana Integrated Health Campus and (b) Başakşehir Health Campus

Figure 3. (a) Başıbüyük Training and Research Hospital and (b) Mavera Comfort Apartments
The Turkish Association for Seismic Isolation (TASI - https://did.org.tr/en/) was founded in 2006
with a mission of increasing the awareness and applications of seismic isolation technologies tomitigate earthquake losses. TASI is a member of ASSISi (Anti-Seismic Systems International
Society) and has established strong ties with other sister organizations, especially with the JapaneseSociety of Seismic Isolation (JSSI). The ever-increasing efforts of TASI include several nationaland regional conferences including the 10th ASSISi World Conference on Seismic Isolation,
Energy Dissipation and Active Vibration Control of Structures held in Istanbul in 2007 and therecent (Nov. 2023) 18th World Conference on Seismic Isolation (18WCSI) in Antalya.

96

In response to the advances in seismic isolation technology and the increased number of seismic
isolation applications, TASI prepared a guideline (TASI, 2008) entitled “Seismic Isolation Design
Code for Buildings”, which was adopted by the Istanbul Seismic Risk Mitigation and Emergency
Preparedness Project (ISMEP, www.ipkb.gov.tr) for the seismic isolation design of new andretrofitted hospitals. In 2018, a design code on Seismic Isolation Design for Building Structures,
essentially based on ASCE 7-16 (2016), is prepared by a committee consisting of academicians
and professional engineers. The code considers 475-year (DBE-Design Basis Earthquake) and
2475-year (MCE-Maximum Credible Earthquake) ground motion levels for the seismic isolation
design. The analysis methods of (a) Equivalent Lateral Force (ELF), Mode Superposition, andNonlinear Time History Analysis are to be used depending on the properties of the building andisolation system. The code considers different performance objectives of Continued Functionality
and Limited Damage / Immediate Occupancy at different earthquake ground motion levels.
Türkiye’s first full-scale dynamic seismic isolator testing facility, ESQUAKE was established on
the premises of Eskisehir Technical University in 2018. The testing capacity of ESQUAKE
accommodates Static Vertical Load of 20,000kN, Dynamic Vertical Load of 15,000kN, Horizontal
Load of 2,000kN, Displacement of ±60cm, and Velocity of 1m/s.
There exist several facilities in Türkiye that produces elastomeric and curved surface friction typeisolation units. Among them, TIS (tis.com.tr/en/seismic-isolation) has provided seismic isolation
units for 64 projects at home and 32 projects abroad.
4. PERFORMANCE
EARTHQUAKES

oOF

THE

ISOLATEDHOSPITALS

IN

FEB..

6,

2023

Figure 4. Isolated Hospitals in the February 6, 2023 Earthquake affected region (Erdik, 2023b)
On Feb. 6, 2023, a magnitude Mw7.8 earthquake struck in south-central Türkiye, followed by amagnitude Mw 7.7 event about 9 hours later. M7.8 earthquake that ruptured more than 300km fault
with fault offsets more than 8m. The death toll from the Türkiye earthquakes has reached 50,783,
with more than 107,204 injured and 297 missings. At least 15.73 million people and 4 million

97

buildings were affected, 345,000 buildings were destroyed and more than 2 million residents in theaffected provinces were evacuated to nearby provinces. The earthquakes caused about $103.6
billion of direct damage (Erdik et al, 2023a). The Feb. 6 earthquakes affected 10 base isolated
hospitals in the region as illustrated in Figure 4.
With the exception of Doğanşehir (#3) and Elbistan (#5) Hospitals, all other hospitals have posed
to earthquake ground motion with isolation system displacement demands less than 20% of theavailable capacities. This percentage was 85% and 50% respectively for the Doğanşehir (#3) andElbistan (#5) Hospitals (Erdik, 2023b). As reported in TASI (2023), among these hospitals,
Battalgazi (#1)\ Elbistan (#5), Hatay (#9), and Adana (#10) hospitals provided continued
functionality with some minor non-structural damages. Kahramanmaraş (#4) Adiyaman (#6)
Düziçi (#7) Osmaniye (#6) under construction and not open to service. There was extensive NonStructural damage in Doğanşehir (#3) and Malatya Merkez (#2) hospitals mostly due to improper
detailing of the nonstructural elements, constructional problems and blocked seismic gaps (moats)and their cover plates. The damaged non-structural elements included cladding, partition walls,
ceilings, mechanical/electrical equipment, utility distribution systems, medical equipment, andother furnishings.
5. CHALLENGES IN SEISMIC ISOLATION OF STRUCTURESThe number of seismically isolated structures is increasing yearly in Türkiye. Although the superior
earthquake performance of seismically isolated structures over the conventionally built ones isknown, the developers still consider the isolation system as a cost-increasing application. This
understanding needs to be rectified.
Currently, the seismically isolated building design is more controlled compared to the conventional
ones because of the mandatory peer review system. However, apart from the BSc degree in Civil
Engineering no further qualification is needed for the designer and the the peer review system isonly concerned with code conformity issues. In the absence of a professional engineering systemin the country, the training of engineers for the proper and correct utilization of seismic isolation
techniques, as well as their licensing, needs to be considered for the healthy development ofapplications. It is further believed that a thorough peer reviewing system is essential and eventually,
the design process needs to be transformed into a professional engineering undertaking.
In general, it should be kept in mind that the appropriate use of seismic isolation technology
requires adherence to the following points. Otherwise, the seismic safety of the isolated structure
may possibly be lower than that of the conventional one.
1- A rational and functional architectural design.
2- A reliable assessment of the design basis ground motion, particularly in near-fault conditions(e.g. Erdik et al, 2023a)
3- A dependable, robust, and resilient design to ensure post-earthquake functionality.
4- A careful selection, design, manufacturing, testing, installation and maintenance of the seismic
isolation units,
5- A good construction implementation for both structural and non-structural elements, with properquality assurance and control.

98

As evidenced by the inadequate earthquake performance of some of the isolated hospitals toprovide continued functionality in the February 6 earthquakes, there exists ample room for thefurther development of these points in Türkiye.
The logistical challenges for the seismic isolation applications encompass the following issues.
1- Although the isolator production in the country is developing, their generally inadequate
production capacity leaves room for the import of isolators from foreign manufacturers withassociated timing and cost problems.
2- Lack of knowledge, in developers, contractors, and engineers, on the selection, procurement,
testing, and installation stages of the seismic isolation process results in delays in the construction
schedule.
3- The highly limited number of in-country testing facilities, with the capability to provide realtime testing to large-scale isolators, necessitate resting in other countries with inherent schedulingand cost issues. Furthermore, the testing process requires the preparation of official regulations
concerning the selection and licensing of testing facilities.
6. PROSPECTS IN SEISMIC ISOLATION OF BUILDINGS
6.1 Base Isolated Modular Construction
Essentially all of the isolated buildings in Türkiye cast-in- place R/C structures. The isolation plane
is located above the foundation at the basement and the isolator distribution follows and matcheswith the distribution of columns and the shear walls, thereby unreasonably increasing the number
of isolation units used in the seismic isolation system. Yet, the current trend in the world is the
reduce the the number of isolation elements through structural design and also through the use of
precast/prefabricated/modular building elements.
It is expected that the use of base isolated modular construction will serve to realize high speed andlow cost constructions for mass housing, dormitories, schools, and hospitals. Most conventional
modular buildings around the world are built as a system of modules that are eventually connected
laterally to a cast in-situ or prefabricated core that serves as the primary lateral load resistingelement. To form the building, the prefabricated modules can be stacked strategically to resist thelateral loads, to enable the load transfer between modules in both horizontal and vertical directions,bolted plates can be used. The main benefits and features of modular building units (modules) are:
• The modules can be designed to encompass all essential components of a building (i.e. utility andelevator shafts, stairs, corridors)• The modules are constructed in a quality controlled production facility and can include piping,cabling, and kitchen and bathroom equipment.
• The modules can easily be removed for reuse.
The seismic behavior of precast buildings depends on the characteristics (i.e., strength, stiffness,ductility, and deformation capacity) of the connections between the precast structural members andthe foundation. One of the reasons of the inadequate performance of precast buildings in pastearthquakes has been poorly designed and/or poorly built connections.
Using base isolation, the assembly of prefabricated modules alone could be used as a structural
system to realize a structurally feasible low-cost construction. As a result, the structure would not99require a structural core and can behave as a purely modular system. The isolators can be placed
under the mat foundation in an optimum number and distribution. Seismic base isolation, utilized
in precast or modular buildings, will have the potential to reduce the ductility demand under seismic
loading, thus making it possible to design and build them with better seismic performance.
Furthermore, the low period of vibration associated with modular structures allows for a wide
separation of fixed base and isolated periods thereby ensuring the full benefit of seismic isolation.
An illustrative application of base isolated modular building construction is provided in Figure 5.

Figure 5. A schematic view of the Base Isolated Modular Construction
6.2 Low Cost Isolation Units
The developments in seismic isolation technology have led to several innovative isolation units. In
this connection, Fiber reinforced elastomeric isolators (FREIs) were proposed as low-cost isolation
devices for widespread utilization, especially for base isolated modular construction describedabove.
FREI bearings use generally carbon fiber mesh instead of steel plates used in SFRI (Steel
Reinforced Elastomeric Isolator). They provide isolation using the same principle of having a low
lateral stiffness as SREI bearings; however, the fibers have the advantage of decreased weight andcost, which could potentially broaden the uses of base isolation. Furthermore, due to the increased
damping provided by the fiber strands, additional means to add damping to the system are notneeded and the cost of production of FREI is much lower than SREI since no vulcanization process
is needed. In addition, the performance of the FREI is shown to be superior to that of the SREI inview of the horizontal stiffness and vertical stiffness of the isolator and that it is possible to produce
an FREI that matches the behavior of an SREI (Moon et al. 2002)
The concept of FREIs is promising. Since 1999, FREIs have been investigated extensively
experimentally, analytically, and numerically, with all studies reporting favorable findings. The
primary challenge for practical applications is the lack of a standard and comprehensive design
guideline for FREIs. It is believed that increased application of FREIs will encourage
manufacturers to enter the market (Van Engelen, 2019).

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ACKNOWLEDGEMENTS
I have freely used the contents of the studies that were made by Dr. Bahadır Şadan, Dr. Cüneyt
Tüzün Ömer Ülker, Mehmet Özcanlı and Dr. Cem Yenidogan. For which, I am grateful.
REFERENCESASCE 7-16 (2016), Minimum design loads for buildings and other structures, Standard, American Societyof Civil Engineers, Reston, Va.
Erdik, M., Tuzun, C., Ulker, O. (2015), Evaluation of seismic isolation applications of health care facilities
in Turkey, Proc. 14WCSI, San Diego (CA), USA
Erdik, M. (2015), State of the Art on App., R&D and Design Rules for Seismic Isolation and Energy
Dissipation for Bldgs, Bridges, Cultural Heritage and Plants in Turkey, Proc. 14WCSI San Diego, CA.
Erdik, M. (2017). State of the art on application, R&D and design rules for seismic isolation and energy
dissip. for Bldgs., bridges, cultural heritage and plants in Turkey. Proc. of the NZSEE conference.
Erdik, M., Ülker, Ö., Şadan, B. And Tüzün, C. (2018). Seismic isolation code developments and significant
applications in Turkey. Soil Dynamics and Earthquake Engineering, 115, 413-437.
Erdik, M. (2019). State of the art on application, R&D and design rules for seismic isolation and energy
dissip.in Turkey. Proc. 16WCSI, St.Petersburg, Russian Federation.
Erdik, M., B. Şadan, C. Tüzün, M.B. Demircioğlu Tümsa, Ö. Ülker and E. Harmandar (2023a), Near-Fault
Earthquake Ground Motion and Seismic İsolation Design, in Seismic Isolation, Energy Dissipation and
Active Vibration Control of Structures, Ed.by G.P. Cimellaro, Springer
Erdik, M. (2023b), Design Basis Ground Motion for Isolated Structures, Proceedings of the 18WCSI#
Antalya, Türkiye (to be published).
Moon, B-Y., G.-Ju Kang, B.-Soo Kang, J. M. Kelly (2002), Design and manufacturing of fiber reinforced
elastomeric isolator for seismic isolation, J.of Materials Processing Technology 130–131 (2002) 145–150
Sadan, B. (2023), State of the Art in Application of Seismic Isolation and Energy Dissipation in Turkey, in
Seismic Isolation, Energy Dissipation and Active Vibration Control of Structures, Ed.by G.P. Cimellaro,
Springer
TASI (2008), Draft Earthquake Resistant Design Code for Seismic Isolation (Submitted to the Ministry of
Public Works), Turkish Association for Seismic Isolation
TASI (2023), The Response of Seısmıcally-Isolated Hospıtals in the Kahramanmaras Earthquakes ofFebruary 6, 2023. An Observatıon Report by the Turkısh Assocıatıon For Seısmıc Isolatıon.
TBDY-2018, Türkiye Bina Deprem Yönetmeliği (Turkish Earthquake Resistant Design Code for Buildings)(https://www.resmigazete.gov.tr/eskiler/2018/03/20180318M1.pdf)
Van Engelen, N. C. (2019), Fiber-reinforced elastomeric isolators: A review, Soil Dynamics and Earthquake
Engineering 125 (2019).
Yenidogan, C. and M. Erdik (2014), "The State of Art in Seismic Isolation and Energy Dissipation
Applications in Turkey", The Japan Society of Seismic Isolation, Menshin (83), 49-59, 2014-02.

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EXPERIENCE OF USING SEISMIC ISOLATION SYSTEMS IN RUSSIA

Aleksandr A. Bubis,
JSC «SRC «Construction» TSNIISK named after V.A. Kucherenko
Head of earthquake engineering research center, Ph.D

Albubis@gmail.com
ABSTRACTThe main direction of seismic isolation systems and other dynamic seismic protection systems
design are the adaptive systems and non-stationary systems (systems with switchable elements
and dynamic parameters which could be changing during an earthquake), nonlinear systems
and some combination of those and other systems. The article outlines practical methods forcalculating and designing of seismic isolation of multi-story buildings for areas with 7-9 points
seismicity. The systems presented in the article developed in and currently used in Russia areeconomically and socially efficient. They allow, compared with traditional designs, to increase
the seismic reliability of structures, reduce the cost of anti-seismic measures, reduce damage
from earthquakes, and clarify assessments of investment and insurance risks.
KEYWORDS: Base isolation system, Base isolated buildings, Response control, Isolator,
Damper
1. PPINCIPLE and BRIEF HISTORY of SEISMIC ISOLATION DEVELOPMENT
Seismic isolation refers to structural mechanisms for reducing seismic impact on the part of thestructure located above the foundation by installing any systems or elements between the partof the structure and the foundation. In contrast to traditional methods of seismic protection,
which consist in increasing the strength of materials and cross-sections of structural elements
and connections, seismic isolation is aimed at significantly reducing dynamic loads on
structures.
The first attempts to seismically isolate buildings date back to around the third century AD. At
the base of Central Asian minarets and a number of other buildings, ancient architects laid soft
layers made of reed pillows and plastic clay as pliable elements.
With the emergence and development of the theory of seismic resistance (1900–1925),
considerable attention was paid to the problem of seismic isolation of structures. For example,
in 1925 M. Viscordini described the designs of roller seismic isolation supports and support
columns with spherical upper and lower ends. However, despite the clarity and simplicity of
the idea of seismic isolation, it did not become widespread at that time, since the static method

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used at that time to assess the seismic resistance of structures made it difficult to assess the
dynamic properties of the structure and did not allow to quantify the effect of seismic isolation.
Since the mid-1950s, there has been a widespread transition from the static to the spectral
method of calculating structures for seismic impacts. When using this method, the seismic loads
on the structure are first estimated, taking into account the dynamic properties of the structure,and then, within the framework of the d'Alembert principle, a static calculation of the structure
for the effect of these loads is performed.
The dependence (Tj) ( is the coefficient of dynamism that depends on the period of
oscillations of the structure TJ according to the j-th form) is called a “spectral curve” in theliterature. This curve is constructed using data on the behavior of mass construction structures(residential and industrial buildings of medium rise with a relatively rigid structural scheme)
during destructive earthquakes and has a clearly expressed monotonically decreasing character.
Such a decreasing dependence was the basis for the construction of seismically isolated
structures.
Attempts to seismically isolate individual buildings have been made since ancient times. The
mass introduction of seismic stress reduction systems into practice should be attributed to the70s of the twentieth century. One of the pioneers in the field of seismic isolation in construction
was Russia and the USSR.
In 1959, in Ashgabat (Turkmenistan, USSR), a house with an earthquake-insulated foundation
was built for the first time according to the project of engineer F.D. Zelenkov. The house had astrong frame foundation, to which a system of beams was suspended on metal rods, which were
supporting elements for a 4-storey building (Fig. 1).

4
1

A)
B)
C)
D)
Figure 1 A)Cross-section of a reinforced concrete frame-seismic shock absorber of a buildingin Ashgabat: B,C,D) Different type of Kinematic supports types
The regular systems of the Russian domestic seismic insulation were developed at the V.A.
Kucherenko Central Research Institute starting from the late 50s. In the 1980s and 1990s,
seismic isolation systems began to be used in the United States, Japan, and New Zealand; in thefirst years on single objects, and after the earthquakes in Kobe (Japan) in 1995 – on a massive
scale in the above-mentioned countries, as well as in Italy, China, and other countries.
Over the past 30 years, seismic isolation has become quite widespread in our country and abroadin the construction of not only buildings, but also such critical structures as reservoirs, bridges,
dams, airports, stadiums.

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In Russian practice, there are more than a dozen implemented types of seismic isolation devices.
However, the introduction of seismic isolation systems into the practice of earthquake-resistantconstruction did not have an appropriate theoretical basis. As a result, buildings with flexible(seismic-isolated) lower floors collapsed during the earthquakes in Scopla, Bucharest and
Mexico City. To a certain extent, this limited the spread of seismic isolation and prompted thestart of serious research in this area. As a result of the research carried out in recent decades,
the concept of earthquake-resistant construction of seismically isolated buildings has been
formed, the main provisions of which are as follows.
1) Seismic isolation provides a significant reduction in inertial loads on the structure, but at thesame time there are significant mutual displacements of the seismically isolated parts of thestructure. These displacements can reach 0.5 m or more. Such displacements can lead to thedestruction of the supporting elements or the fall of the structure from them, and eventually to
its complete collapse. As a result, when assessing the seismic resistance of seismically isolated
structures, their kinematic calculation, i.e. the determination of mutual displacements ofseismically isolated parts of the structure, becomes decisive.
2) Evaluation of the kinematic characteristics of seismic isolation requires the correct setting of
the design impact, in particular, distortions of the calculated accelerograms in the long-period
region must be excluded. Such distortions are present in most known records, and their use
makes the calculation results random and gives an erroneous impression of the seismic
resistance of the structure.
3) In order to limit the mutual displacements of the seismically isolated parts of the structure, itis necessary to install damping devices between them.
This concept is the basis for the design and use of effective seismic isolation systems inearthquake-resistant construction.
2. BRIEF OVERVIEW of SEISMIC INSULATION SYSTEMS of BUILDINGS andSTRUCTURESAt present, dozens of monographs of scientists and hundreds of articles on seismic isolation ofbuildings and structures have been published in Russia. A detailed classification of seismic
isolation devices is given in the works of Y.M. Eisenberg, I.G. Horowitz, T.Zh. Zhunusov, L.Sh.
Kilimnik, G. Mtsverri, V. Robinson, O.A. Savinov, T.A. Sandovich, R. Skinner, V.I. Smirnov,
A.M. Uzdin, Y.D. Cherepinsky, V.G. Yaremenko. The analysis of seismic insulation systemsof bridges is also available in the reviews of I.O. Kuznetsova and Z.G. Khuchbarov. Therefore,
this review provides only a brief classification of seismic isolation systems according to theprinciple of their operation during an earthquake and, accordingly, according to the type ofequations describing the behavior.
All seismic isolation systems are divided into stationary and adaptive. Stationary systems retain
their elastic-damping characteristics in the process of oscillations, while adaptive systems
change their parameters, adapting to the loading regime (seismic action). For adaptive systems,
there are no nonlinear steady-state modes of motion and it is impossible to construct anamplitude-frequency response (AFR). In contrast to adaptive systems, steady-state modes ofoscillation are possible for stationary systems and the corresponding methods for analyzing theequations of motion, in particular, the construction of frequency responses, are applicable.

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Stationary seismic isolation systems can be divided into systems with and without restoring
force. The last type of seismic isolation is carried out by the arrangement of a seismic isolation
sliding belt (seismic belt). In these systems, a load exceeding the friction force in the seismic
belt cannot be transmitted to the seismically isolated part of the structure. Systems with aseismic isolation sliding belt have two features from the point of view of their design. Firstly,
significant residual displacements are possible between the seismically isolated parts of such
systems, and their assessment is one of the tasks of the structure calculation. Secondly, thesystem of differential equations describing the behavior of the structure is special because thedeterminant of the stiffness matrix of the system is zero. This circumstance must be taken into
account when decomposing the equations of motion into forms of vibrations.
The structures of the seismic isolation belt have been proposed by many specialists, but they
have been studied in the most detail in the works of L.Sh. Kilimnik, L.A. Soldatova and V.P.
Chudnetsov. According to their proposals in the 1980s-1990s. Several seismically isolatedbuildings were built in Bishkek (Kyrgyzstan) and Petropavlovsk-Kamchatsky. On the basis ofthese research and developments, the V.A. Kucherenko Central Research Institute preparedrecommendations for the construction of a seismic isolation sliding belt in civil engineering.In
turn, seismic isolation systems with restoring force are divided into elastic and gravitational. In
the former, the restorative force is the elastic force, and in the latter, the force of gravity.
Seismic insulation foundations on elastic supports are widely used in construction practice.
These include buildings with flexible underfloors that have been massively damaged byearthquakes, as well as buildings with rubber supports. Rubber supports are currently the main
seismic isolation elements used in Russia and in the world. Seismic isolation with the use ofelastic seismic isolation supports is the simplest and most developed, and its use with the correct
selection of system parameters is quite effective.
Seismic isolaton foundations based on kinematic supports of the gravity type (KS) are proposedby a number of authors. The use of such foundations is typical for Russia and the CIS countries.
The most famous in this field are the kinematic supports of V.V. Nazin, A.M. Kurzanov, Y.D.
Cherepinsky (Fig. 1 B,C,D). Buildings on such supports were built in PetropavlovskKamchatsky, Navoi, Yuzhno-Sakhalinsk, Sochi and other seismically dangerous regions of the
CIS countries, but the most significant disadvantage of the operation of such foundations is theuneven loading of supports. In the patent literature there are more than a hundred proposals forthe construction of gravitational kinematic foundations. Such an abundance of proposals is
explained by the fact that a change in the rolling surface of the supports of such a foundation
can lead to a change in the dynamic characteristics of the system as a whole, and, accordingly,
to a new technical solution. This review provides a detailed classification of gravity-isolating
seismic foundations (Fig. 2) and their general characteristics.
At the suggestion of V.T. Yaremenko, gravitational seismic isolation foundations are divided
into suspended and supporting. In suspended foundations, the building is installed on the upper
foundation slab, which is suspended on rods from the frame structure, rigidly connected to thelower foundation slab. This type of foundation includes the above-mentioned seismic isolation
foundation by F.D. Zelenkov (Fig. 1 A). In support foundations, the upper foundation slab rests
on kinematic supports. The general equation of motion of a building on kinematic foundations
with an arbitrary skating surface was obtained by A.M. Uzdin, A.A. Dolgoy and A.N. Gunchev.
Some special cases of motion of structures on kinematic supports are considered in the articles
by B.N. Kvasnikov and S.N. Kouzakh.

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From the point of view of the type of equations of motion of the system, the behavior of thestructure near the resting position is important. A building on free supports can be described bylinear equations with small oscillations, but in the case of jammed supports, such linearization
is in principle impossible. All jammed supports can be divided into two types – positive andnegative stiffness.
For the first time, the mass construction of buildings with seismic isolation systems in the formof switch-off elements and stops of movement limiters was carried out in the late 70s during
the construction of the Baikal-Amur Mainline. An entire city of railroad workers, 82 buildings
in total, was built up with earthquake-insulated buildings (Fig. 2).

Figure 2 Earthquake-isolated large-panel houses in Severobaikalsk with metal switchable
elements.
Seismic insulation with the use of flexible supports (reinforced concrete or metal posts orframes) in the lower floors, with switchable energy-absorbing elements in the form of
reinforced concrete diaphragms, with metal switchable elements, with stops-limiters ofexcessive displacements were developed by Prof. Y.M. Eisenberg, V.I. Smirnov and otherstudents and collaborators (M.M. Deglina, H.N. Mazhiev, A.M. Melentyev, S.K. Uranova(Fig.2).
Systems with changing (self-adjusting) dynamic characteristics during an earthquake areadapted to seismic impacts through the use of special structural elements that increase therigidity of the structure in the initial state and are switched off when a certain threshold level ofseismic vibration amplitudes of the structure is reached. At the same time, all vertical loads
from self-weight and seismic loads must be fully absorbed by the supporting structures of thestructure in a state when the redundant rigid connections are switched off.
Seismic isolation with switchable braces contains: a rigid element - a stop, a displacement
limiter (a tie panel, buttress or other rigid structure) and switchable elements. The basic idea ofsystems with switchable connections is that the switchable element is rigidly attached to thecoupling element and to the main load-bearing structure (transom, floor, etc.), providing a rigid
connection between the overlying floors and the foundation up to certain threshold values ofseismic load and displacement. After these thresholds are exceeded, the switchable element is
destroyed, and in the breaking limit, the connecting element plays the role of a damper.
The design embodiment of redundant switch-off elements can be different and is accepted
depending on the required scheme of operation in the building and the fracture deformation
diagrams. In the case of buildings with frame lower floors and with rigid upper floors, the roleof switching links can be performed by:- Weakly reinforced stiffening diaphragms with slots. Under horizontal seismic impact,
cracks and inelastic deformations develop in the diaphragm piers;106

- Metal plates with electric rivets welded to the stops of the movement limiters. In case of
seismic impact, there is a step-by-step destruction of welded rivets (multiple changes in
the periods of natural vibrations of the building in the process of seismic action);- Metal plates with variable cross-section. The cross-section change is calculated for theappearance and accumulation of plastic deformations from cycle to cycle under seismic
action with subsequent destruction;- Metal rods that work only in tension. In this case, significant plastic deformations candevelop in the switch-off elements, and the switch-off can occur repeatedly. It depends
on the number of rods to be installed.
Depending on the design scheme and the height of the building, the switchable connections canbe placed either horizontally or at the height of the building. After an earthquake, the backup
elements of seismic isolation are restored to their original state.
3. SEISMIC INSULATION of BUILDINGS with the USE of KINEMATIC SUPPORTS
In Russia, the use of seismic insulation of buildings on kinematic supports is most widespreadin two seismic regions of Siberia. In the Irkutsk region, 77 residential buildings were built forthe period from 1984 to 2003, in the Kemerovo region - 15 houses were built for the period
from 1997 to 2003. A diagram of seismic isolation in these buildings is shown in Fig. 3.
The Kinematic Support Element (KSE) is a truncated tetrahedral pyramid with a spherical lower
part. At the bottom, the KSE rests freely on the support part, and at the top it is hinged to theoverhead part. The hinged connection with the superstructure provides mobility in thehorizontal plane in all directions. The swivel joint is made in the form of a binding anchor anda small square steel plate. The swivel joint is also a displacement limiter, as the binder creates
an increasing resistance to the rotation of the KSE. The gravitational force that keeps the KSE
in a state of stable equilibrium determines its horizontal stiffness and depends on the weight ofthe superfoundation structure, the height of the KSE, and the radius of curvature of the heel.
The size of the KSE depends on the magnitude of the vertical load, the strength of the material
and the intensity of seismic impact.

Kinematic Support
Element

Elastoplastic damper

Figure 3 Diagram of the building on kinematic support elements
Most of the houses built in Russia on the KSE belong to multi-storey housing construction. For
example, residential buildings in Irkutsk and Novokuznetsk (Fig. 4-5). Reducing seismic loads
makes it possible to increase the number of storeys, improve planning solutions, and reduce theconsumption of materials in structures. The installation of KSE in the basement allows you tocreate an open layout and place car parking.

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Figure 4 Buildings on kinematic supports in Irkutsk

Figure 5 Building on kinematic supports in Novokuznetsk

Figure 6 Design of Combined Sliding Supports
In the 1970s, other types of kinematic supports were proposed and applied. In Sevastopol, V.V.
Nazin used supports in the form of columns with spherical ends. Later, these columns were
improved in Kamchatka by Y.I. Bezrukov. A.M. Kurzanov proposed columns with flat ends
and specific inclined displacement limiters.
Prof. S.V. Polyakov, Ph.D. L.SH. Kilimnik (TsNIISK) and Ph.D. L.A. Soldatova were engaged
in the study and implementation of seismoinsulation systems - sliding supports using Teflonstainless steel pairs.
An earthquake-insulating sliding belt is made in the form of a series of supports located between
the foundation of the building and the above-ground structures, usually at the intersection of
longitudinal and transverse walls (Fig. 6). Each support has two plates made of stainless steel
and fluoroplastic-4. Due to the low coefficient of friction in the supports (f=0.05-0.1), when theinertial loads exceed a certain level, the building begins to slip relative to the foundation. From
this moment on, the forces from seismic loads in the load-bearing structural elements practicallydo not change. To ensure the reliability of buildings, the system provides elastic and rigid
limiters for horizontal and vertical movements.

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Sliding supports, such as the one shown in Fig. 6, were used for buildings up to five storeyshigh.
4. APPLICATION of SEISMIC INSULATION in the FORM of RUBBER-METALSUPPORTS in the REINFORCEMENT of BUILDINGSThe use of seismic insulation in the form of rubber-metal supports was carried out during thereconstruction of the building of the Central Bank of the Russian Federation, a historical andarchitectural monument built in 1934 in Irkutsk (Fig. 7).

Figure 7 The Central Bank of the Russian Federation in the Irkutsk Region
The structural solution refers to the so-called buildings with an incomplete frame. The loadbearing structures of the western and northern parts of the building are the exterior brick walls,
the internal transverse walls and two longitudinal rows of brick pillars. In the central part of thebuilding, the internal frame is made of monolithic reinforced concrete with circular columns(Fig. 8).

Figure 8 Plan of the first floor of the bank building. Location of seismic isolation supports inthe building plan
In terms of its space-planning and structural solutions, the building materials used, the building
did not comply with the current anti-seismic regulatory requirements. Taking into account thefact that the building is a historical monument and traditional methods of seismic reinforcement
are not applicable, TsNIISK together with the specialists of Irkutsk Promstroyproekt developedand implemented a project to increase the seismic resistance of the bank. A total of 110 seismic
poles were installed. Each pole is designed for a load of 2500 kN. All supports have the same
dimensions: diameter 510 mm, height 216 mm.

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It should be noted that this was the first and very successful experience in the installation ofseismic insulation in the form of rubber-metal supports in a non-earthquake-resistant existingbuilding.
Prior to the 1995 Kobe earthquake in Japan, more earthquake-insulated buildings had been built
in Russia and the CIS than in any foreign country. Moreover, the seismic isolation systems
developed by our specialists are inexpensive and easy to implement.
Statistics shows that the dynamics of the implementation of seismic protection in constructionin Russia has slowed down, and the crisis phenomena of the 1990s and 2000s have had anegative impact on the use of seismic isolation. It should be noted that designers and builders
have recently become interested in seismic insulation of buildings again.

Figure 9 Seismic isolated high rise Hotel (left) and Olympic university (right) in Sochi
Seismic isolation systems are actively introduced into the practice of earthquake-proof
construction in Russia (Fig. 9). This is evidenced by many unique objects using seismic
isolation systems. Their design and construction is conducted in the Russian Federation withthe participation of specialists from the Research Center of Earthquake Engineering, which isthe part of the Research Institute of Building Construction and Russian Association ofEarthquake Engineering. Among such objects it is necessary to note the high-risebuilding Akhmat-Tower in Grozny city (Chechen Republic) (Fig.10), "Kommunar" Cinema in
Novokuznetsk (Fig.11) and others.

Figure 10 Seismic isolated hi-rise building in Grozniy city.

110Figure 11 Seismic isolated building of Communar Theatre in Novokuznetsk city (left) and inprocess (middle)
Seismic isolation is used in cases: high-rise construction, historical monuments, uniquestructures of airports in Gelendzhik (Fig.12), Magadan, Yelizovo (Fig.13). After the publicationof a new edition of the Russian codes, seismic protection systems have found application in
medical, educational, and residential buildings. Standard solutions were developed for seismic
protection of structures whose own seismic resistance is lower than the seismicity of the site.

Figure 12 Gelendzhik airport building (LRB, sliders, Hysteretic dampers)
The building of the new city complex of Gelendzhik airport has overall dimensions in terms
about 155.0 by 85.0 m. The height of the building is variable, near 25 meters. The structuralscheme of the constructed airport complex is a mixed frame-wall with steel-reinforced concrete
columns and a spatial structural coating. The structural scheme of the projected airport complex
consists from located below the planning mark underground floor, pavilions inside the airport
complex, the coating in the spatial structure form, supported by 9 internal columns (locatedinside the airport complex) and 4 external structural support elements and unique facade
structures consisting of a set of inclined vertically oriented trusses.

Figure 13 Elizovo airport building (Steel Hysteretic dampers, left) and calculation model(right)The building of the airport complex Elizovo in Kamchatka region has a round toroidal planwith a courtyard. The building has 2 3 floors in part floors in part 33-5, 4 floors in buildings
part 23-10 (SPA area). The dimensions of the outer diameter of the building is about 173 m, the111

size of the inner diameter of the building is 88 m. The height of the highest elevation of the roofis 30.05 m. The Roof is covered with decorative lamellas.
The inclusion of damping devices in the structural system makes it possible to reduce therigidity of the building and thereby reduce the value of the dynamism coefficient, shifting fromthe area of their increased values on the graph of the dynamism coefficient in the calculation of
LSM (Spectral Method) and increasing the damping capacity of the entire system (Fig. 14).

Figure 14 Damping effects in airport building.

Figure 15 School building in Sochi (dampers and sliding supports)
Including buildings designed: hospitals (dampers) and schools (seismic isolation) in
Novokuznetsk, hospitals in Simferopol (dampers), Krasnodar, Petropavlovsk-Kamchatsky,112

Nikolaevsk-on-Amur (seismic isolation), residential buildings in Baikalsk, Tomsk, schools in
Sochi (Fig. 15) with dampers, Angarsk (Fig. 16), Alexandrovsk-Sakhalinsky (with seismic
isolation).

Figure 16 School building in Angarsk. Re-constructed with LRB.

Figure 17 Bandy Ice stadium in Irkutsk (sliders).

Figure 18 Anapa airport control towers testing model and real building (LRB)
For calculations and optimization of seismic isolation systems, the most important problem isthe correct task of seismic impact. At the same time, it is of fundamental importance to take
into account the correlation between the amplitude and the prevailing period of seismic impact.
When designing seismic isolation systems, it is necessary to take into account that traditional
structures of seismic insulation foundations are practically devoid of reserves of bearing
capacity. This fact must be taken into account when calculating earthquake-insulated buildings,
assigning an increased level of design load compared to conventional buildings, as well as indesign, introducing additional redundancy elements into the system. For calculation on 1st stageof Isolated building construction used method of base separation (Fig. 19). The source seismic
action is “filtrated” by specially developed software. This method allows design building withinstalled bearings in the elastic formulation. All inelastic deformations and hi damping involves
in software modulation.

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The comparative analysis of the results obtained for the three models, representing building
with LRB, leads us to the following conclusions:Figure 19 Base separation method of isolated buildings construction design.
In the high-frequency range (frequency range above 0.5-1 Hz) values of response spectra
obtained for multi-mass models don’t exceed the values of response spectra obtained for the
single-mass oscillator. In the low frequency range, on the contrary, the values of response
spectra obtained for multi-mass models may have higher values.

Accel, sm/sec2

The result of solving the system of equations is a set of records of accelerations, velocities anddisplacements at the level of the top of the seismic insulating layer - a modified dynamic effectthat acts on the superstructure. From the modified dynamic action, the spectrum of theacceleration reaction is constructed, which is then used to calculate the superstructure. The
discrepancy between the results obtained for dual-mass and multi-mass models is negligible.
Response spectra for multi-mass models are well correlated with each other (Fig. 20,21).

Accel, sm/sec2

Time, sec
Figure 20 Time history Acceleration Buharest (Up) and filtrated acceleration for different
isolation types and sizes.

Natural period, sec
Figure 21 Spectral response Buharest (Up) and response of filtrated acceleration with different
LRB isolation sizes.

114

Seismic isolation is one of the most effective methods of ensuring the seismic resistance ofbuildings and structures. The use of seismic insulating foundations is most effective for seismic
protection of rigid buildings with a pitch period of less than 0.3–0.5 s.
REFERENCES
1. Belash T.A. Optimization of energy absorption parameters in structures on seismic insulating
foundations: Author. dis. Doc. techn. Sciences. - St. Petersburg: PGUPS, 1996.
2. Eisenberg J.M. Structures with switch-off connections for seismic areas. М. Stroyizdat. 1976.229 p.
3. Eisenberg J.M. Spectra of the state of systems with degrading stiffness and their application forassessing the seismic response of structures // Express information of VNIIIS. Sir. Earthquakeresistant construction. – 1981. – No.6. – p.24–29.
4. Eisenberg J.M. Experimental methods in research and development of earthquake-resistant
structures. Construction and architecture//Express information VNIINTPI. Sir. Earthquake-resistantconstruction. – 1997. – No. 1. – p.4–9.
5. Eisenberg J.M., Smirnov V.I., Dashevsky M.A. 1995. («Seismic Isolation of Buildings. New
Applications and Design Rules in Russia.») International Post-SMIRT Conference Seminar on
Seismic Isolation. Santiago, Chile. pp. 457-463.
6. Eisenberg J.M., Smirnov V.I, Uzdin A.M. 1997, («Progress in Applications and Development Rules
for Base Isolation and Passive Energy Dissipation of Civil Buildings, Bridges and Nuclear Reactors
in the Russia Federation.»), International Post-Smirt Conference Seminar on Seismic Isolation,
Passive Energy Dissipation and Active Control of Seismic Vibration of Structures, Taormina, Sicily,
Italy,. pp. 97-112.
7. Goldenblat I.I., Nikolaenko N.A. Calculation of structures for the action of seismic and impulsive
forces. – M.: Gosstroyizdat, 1961.
8. Smirnov V.I. 1981. Reducing the seismic response of buildings with a flexible lower floor throughthe use of additional switch-off rigid elements. Sat. VNIIIS, ser.14, vyp.12. 13-17 p.
9. Eisenberg J., Smirnov V., Senkin S., Vasilyeva A. Progress of Application and R&D for Seismic
Isolation and Passive Energy Dissipation for Civil and Industrial Structures in Russia and Other
Former USSR Countries//7th International Seminar on Seismic Isolation, Passive Energy Dissipation
and Active Control of Vibrations of Structures. Assisi, Italy, October 2-5, 2001.
10. Eisenberg J.M. Earthquake and blast response spectra of reinforced concrete structures with variablemechanical parameters as a result of damages//Proc. of Japan Earthquake Engineering Symposium,
Tokyo, 1966.
11. Eisenberg J.M. Effect of damages on the estimation of earthquake and blast action on reinforced
concrete structures//International Symposium on the effects of repeated loading of materials andstructural elements. RILEM, Mexico City, 1966.
12. Eisenberg J.M., Smirnov V.I, Uzdin A.M. Progress in Applications and Development Rules for Base
Isolation and Passive Energy Dissipation of Civil Buildings, Bridges and Nuclear Reactors in the
Russia Federation//International Post-Smirt Conference Seminar on Seismic Isolation, Passive
Energy Dissipation and Active Control of Seismic Vibration of Structures, Taormina, Sicily, Italy,
1997. – p.97-112.
13. Tyapin A.G. Half-infinite 3d frequency domain elements in SSI analysis//Proceedings of the 10-th
European Conference on Earthquake Engineering. – Vienna, Austria, 1994. – Vol. 1. – p.571–574.

115

CURRENT STATE AND CHALLENGES OF
SEISMICALLY ISOLATED STRUCTURES IN ITALY
Paolo Clemente1 and Chiara Ormando2
1

Former Research Director, ENEA, Rome, and Adjunct Professor, Sapienza University, Rome, Italy
2
Researcher, ENEA, Rome, Italy

ABSTRACTThis paper summarises the development and application of seismic isolation in Italy,
highlighting the importance of a suitable specific technical code. The main criteria on which
the current Italian technical code for construction is based are illustrated, and the results of an
extensive investigation about the economic aspects and some optimization criteria arereported. The problem of applying base isolation for the seismic retrofit of existing buildings
is addressed, keeping them operational during the works in order to reduce the inconvenienceto the inhabitants as much as possible. In this regard, safety criteria are discussed andpractical solutions are proposed. The importance of the correct application of base isolation is
finally emphasized, and the results of an extensive study on the behaviour of seismic isolation
systems subjected to low energy seismic actions are reported. In particular, a systemcomposed of HDRBs only, one composed of CSSs and one composed of HDRBs and SDs are
considered. In the second and third cases, the onset of motion of the system is linked tofriction, which must not be too high, while, in the first case, the behaviour depends on theincrease of the stiffness of the rubber as the angular deformation decreases.
KEYWORDS: Base isolation, Design of seismic isolation systems, Optimization of seismic
isolation systems, Seismic behaviour, Structural health monitoring.
1. INTRODUCTION
Japan is one of the first countries in the world for the number of applications of seismicallyisolated structures. But only some people know that seismic isolation started in Europe in the
70s of the twentieth century, and some interesting pioneering applications were realized in
Italy [1][2][3].
The very first one referred to a viaduct in northeastern Italy, the Somplago Viaduct. It wasunder construction when the area was hit by severe seismic events on September 15th, 1976.
The very good behaviour of this bridge caused a rapid increase in the application of antiseismic systems to new bridges and viaducts in Italy.
The first seismically isolated building in Italy was the fire command building in Naples, completed in 1981. Neoprene bearings are at the top of reinforced concrete towers and support a
reticular beam from which a steel structure is suspended, while floor dampers and shocktransmitter units are inside the building. The seismic isolation, not considered in the first design, was inserted to retrofit the original design after the November 23rd, 1980, CampanoLucano earthquake (M = 6.9). A few years later, in 1985, a second fire command building,116

close to the first one, was protected using similar devices. In 1991, the Telecom Italia Centreof the Marche Region at Ancona was completed. It was protected by 297 High Damping
Rubber Bearings (HDRBs). A release test was performed on one of the five buildings with an
initial displacement of 110 mm.
The absence of a suitable technical code for seismically isolated structures slowed the use of
seismic isolation in Italy for several years. In 1998, the guidelines for seismically isolated
structures [4] were issued, but they required a very complicated and time-consuming approval
process by a special committee of the Ministry of Infrastructures. Finally, a suitable seismic
design code was issued in 2003, after the October 31st, 2002, Molise earthquake (M = 5.4) [5].
During this event, the Francesco Jovine School building in San Giuliano di Puglia collapsed,causing the death of 27 children and a teacher. The new Italian seismic code included design
rules for seismic isolation and energy dissipation systems, whose use was allowed without
any additional approval.
The new code encouraged the implementation of seismic isolation, especially when high levelof safety was required, which could not be obtained with traditional techniques. This happens
especially for strategic structures, such as buildings for civil protection purposes, and relevant
structures, such as schools and hospitals. In these kinds of buildings, the contents can be very
valuable, so the construction cost of the structure is only a low percentage of the total value.
On the contrary, the safety requirements are lower for ordinary buildings, and the construction
cost increase due to base isolation does not encourage its use.
In 2008, all the revised technical codes, issued separately in the past, were included in the
new Italian Technical Code [6]. This became the only valid code in July 2009, after the
L’Aquila earthquake, and was finally updated in 2018 (NTC-2018) [7].
The most important challenges of seismic isolation in Italy referred the economic evaluations,the application to existing buildings keeping them operational during the works, and the behaviour recorded under real earthquakes in Italy.
2. SEISMIC ISOLATION IN ITALY: TECHNICAL AND ECONOMIC
EVALUATIONS
According to NTC-2018, when using seismic isolation, Zero Earthquake-Damage Buildings(ZEDB) are realized [8], and no ductility requirements are needed for the structural elements.
As a result, the substructure and the superstructure remain in an elastic range and can be modelled as linear elastic systems [9].
A suitable decoupling of motion is obtained if the ratio between the fundamental vibration
period of the isolated building (Tis) and that of the superstructure considered as fixed base(Tfb) is Tis/Tfb ≥ 3. Still, to obtain a suitable reduction of the seismic acceleration in the structure, it should be Tis > 2 s. The seismic action is evaluated with respect to a reference period,
which coincides with the nominal life for ordinary structures (usually 50 years) but can beamplified for relevant and strategic ones by means of a use factor equal to 1.5 and 2.0, respectively. This means that the seismic action is not amplified directly but acting on the return
period. For isolated structures, the Italian Code considers two ultimate limit states:• The life safeguard limit state (SLV), associated with an exceedance probability of 10% in
the reference period. This limit state is used to check the substructure and the superstructureusing the same material factor γM of non-isolated buildings. A behaviour factor q ≤ 1.5 isallowed for seismically isolated buildings, but for the substructure q = 1.0 is to be preferred.
The design spectra are obtained by putting η = 1/q in the relations that define the elastic
spectra, where=η
10 ( 5 + ξ ) is a damping coefficient which reduces the response spectrum amplitudes and ξ the damping factor.

117• The collapse limit state (SLC), associated with an exceedance probability of 5% in the reference period, will be used to check the isolation devices.
The total seismic effects on the structure are calculated as a linear combination of the effectsof the three components of the seismic action, E =+Ei 0.3E j + 0.3Ek (with i, j and k, equal
to x, y and z, respectively, and permuted). The vertical component Ez must be considered if
the ratio between the vertical stiffness (Kv) and the equivalent horizontal stiffness of the isolation system (Kesi) is Kv/Kesi < 800. The seismic effects are combined at the SLV with those of
the structural loads G1, the permanent non-structural loads G2 and the variable loads Qkj(ψ2j < 1 is the variable load factor) as follows: G1 + G2 + E + ∑ j ψ 2 j QKj .

()

For elastomeric isolators, the checks refer to the angular strains due to shear only
( γ s ≤ γ s ,max =2 ), the total angular strain ( γ t ≤ γ t ,max =5 ), the device instability ( V ≤ Vcr 2 ,where V is the vertical load on the device and Vcr is its critical vertical load), and the stress inthe steel laminates ( σ s ≤ f yk , where σs and fyk are the stress and the nominal tensile resistanceof the steel laminates, respectively). A suitable graphic procedure for the optimum design canbe used, in which the four previous design conditions are represented on the (De, Ve) planewhere they define an admissible area for the solution (Fig. 1). The minimum point in which
the design curve intersects the admissible area represents the optimum solution [10].
In HDRBs+SDs systems, the locations of SDs are chosen to optimize the dynamic behaviourof the structure. The choice can also be influenced by the vertical loads acting on the columns,
and SDs can be inserted under the columns with anomalous vertical loads (very high or very
low compared to most columns). The values of the vertical loads influence the friction forces
and so the onset of motion of the isolation system. Friction is the main parameter also for
Curved Surface Sliders (CSS), in which the vertical load varies from device to device andcould varies a lot during the quake [11].
The good performance of seismic isolation systems under strong earthquakes has been testified in several cases. Now it is important to guarantee a correct use of seismic isolation to
avoid unexpected behaviours and wrong applications [12].
200

Design curve

160

Admissible
Area

Ve (dm3)

120
80
40
0

400

500

600

700
De (mm)

800

900

1000

Figure 1. Graphic procedure for the optimum design of HDRBs.
The Italian code allows designing the superstructure with the effective seismic action, which
is much lower than that to consider for a fixed base building. So, the cost of base isolation canbe balanced by savings in the superstructure. The reduction of the spectral amplitudes is related to the change in the fundamental vibration period and the damping ratio. If Tˆ = Tis T fb andηˆ = ηis η fb are the ratios between the values of the vibration period and the damping coeffi-

cient for the isolated structure and those for the corresponding fixed base one, then the spec-

118

tral acceleration reduction when using seismic isolation, for Tis ≤ TD is (TD = value of T where
the zone of constant velocity ends in the elastic spectrum):Sˆe=Se,is (Tis ) ηˆ=Se, fb (T fb ) Tˆ

Without losing generality, the value of Tfb can be assumed equal to TC, which is the value of T
where the zone of constant acceleration ends, if T fb ≤ TC . The relation Sˆe ηˆ =1 Tˆ is represented in Fig. 2 by the upper curve. If Tis > TD , the spectral acceleration reduction is:
ˆ
S=
e

ηˆ TD
⋅
Tˆ 2 T fb

In Fig. 2, the corresponding curves are plotted for different values of T fb TD . They all startfrom the curve relative to Tis ≤ TC at the abscissa corresponding to Tis = TD.
1.0
Tis < TD
Tis<TD
Tis > TDTfb/TD=0.2, Tfb/TD = 0.20
Tis>TD,
Tis > TDTfb/TD=0.25, Tfb/TD = 0.25
Tis>TD,
Tis > TDTfb/TD=0.3, Tfb/TD = 0.30
Tis>TD,
Tis > TDTfb/TD=0.4, Tfb/TD = 0.40
Tis>TD,
Tis > TDTfb/TD=0.6, Tfb/TD = 0.60
Tis>TD,

Se/η

0.8
0.6
0.4
0.2
0.0

1

3

5
T

7

9

Figure 2. Elastic spectra ratios.
The economic suitability of seismic isolation depends on several factors, among which are theearthquake intensity and the soil characteristics, but also the shape and the size of the building. A comprehensive numerical analysis was carried out by Clemente & Buffarini [13] withreference to reinforced concrete buildings. The authors concluded that:• The difference between the cost of a building designed with a fixed base and the samebuilding designed with base isolation is, in general, very low; furthermore, if well designed,a base isolated building costs less than a fixed base one.
• Differences are certainly negligible for buildings in high seismicity areas (i.e., where ag ≥0.20 g on rigid soil with probability of exceedance of 10% in 50 years), where the solution
with base isolation could be even less expensive. Base isolation could also be convenient
for medium and low seismicity areas, especially for irregular and special buildings.
• One should account for the larger useful area due to the smaller size of columns in the solution with base isolation, which translates into higher value for the building.
A parallel analysis was performed also for masonry buildings, obtaining quite similar results[14]. The use of seismic isolation is certainly suitable if one refers the comparison to the life
span of the building. In fact, correctly erected seismically isolated buildings will not need reparation work, even after an earthquake of the same intensity as the design one.
Obviously, a suitable comparison between traditional and base isolated buildings should bemade by referring to the same structural target in terms of the degree of safety. In other words,
one should design the fixed base building in the elastic range. In this case, the convenience ofseismic isolation in terms of construction cost becomes very high.

119

3. SEISMIC ISOLATION OF EXISTING STRUCTURES
Seismic isolation is very suitable for the retrofit of existing structures because it allows the
choice of the design spectral amplitude for which the superstructure remains in the elastic
range. This is pursued by fixing a suitable period of vibration. Consequently, retrofit interventions in the superstructure can be limited or even avoided [15]. Unfortunately, the applicationof seismic isolation in the retrofit of existing structures is not always easy and represents oneof the challenges of the next future.
Devices can be inserted inside the vertical elements, columns or walls, or between the existing
foundations and new sub-foundations, or even between two new sub-foundations [16].
The first technique is to be preferred when the existing foundations are in good conditions or
can be easily improved (Fig. 3). It is also the most common technique used in reinforced concrete buildings, where one isolator is put for each column to guarantee a suitable transfer ofthe gravitational loads in service conditions. The columns could be enlarged to contain thedevices and ensure an adequate stiffness of the columns themselves, if necessary.
In masonry buildings, where isolators are usually placed at the wall crossings and at intermediate locations, if necessary, suitable structures must be realized to transfer the actions fromthe masonry walls to the devices and from these to foundations.
With reference to the elevation, isolators should be placed at the top of the first level, if possible. So, the entire building will be protected, and the displacements during an earthquake will
not interfere with the functionality of the floor below. Furthermore, the existing deck justabove the isolation interface can be good rigid diaphragm. All the devices must allow the horizontal displacements. They can also be inserted at different levels, but the superstructure
must be completely separated from the substructure. Stairwells and the elevator shaft could
influence the positioning of the isolators.

(a)

(b)

Figure 3. Typical insertion of the devices along a column: (a) cutting of the column (courtesy
FIP Industriale); (b) temporary structure to unload an entire column (courtesy G&P Intech).
Hydraulic jacks are used to transfer the loads during the retrofitting works between temporary
elements connected to the upper and the lower structural element, respectively (Fig. 3b). To
adhere again the vertical elements, flat jacks are inserted under each isolator, and injectedwith resin.
The real challenge is to keep the building operative during the intervention, guaranteeing atleast the same safety degree that characterized the structure before the retrofit intervention.
This can be pursued by keeping the devices blocked using additional steel profiles, which canbe inserted between the upper and the lower plates of the devices (Fig. 4a) or of the columns(Fig. 4b). The increment of the cost with reference to a simple isolation system varies between 2% and 5%. Obviously, all the additional elements can be reused.

120

The creation of a new sub-foundation is needed when the existing foundations are not in goodcondition or are insufficient. This situation is typical of old reinforced concrete buildings. Isolators are inserted between the old and the new foundation structures (Fig. 5a).
On the contrary, the creation of two new foundations is to be used when foundations do notexist at all, as usually in old masonry buildings. Usually, continuous concrete beams compose
the upper new foundation, while the lower one is made by plinths, which must be connectedto each other. The devices are placed between them (Fig. 5b).

(a)

(b)

Figure 4. Locking profiles (a) between the device plates with vertical bolts and (b) on thecolumn.

(a)(b)

Figure 5. Seismic isolation with (a) a new sub-foundation (courtesy G. Mancinelli) and (b)two new sub-foundations (courtesy FIP Industriale and R. Vetturini).
The isolation interface can also be placed below the existing foundations, without touchingthem. The Seismic Isolation Structure for Existing Buildings (SISEB) works exactly like this(Fig. 6). A trench is excavated at one side of the building, then horizontal pipes are inserted
by means of pipe jacking, creating a discontinuity between the foundations and the soil. The
pieces of pipe are composed of a lower and an upper cylindrical sector, respectively, connected by removable elements that are then replaced by isolation devices. Internal and externalvertical walls complete the construction [17][18].
Seismic isolation is also a very good system for the retrofit of bridges. Actually, just substituting of the existing bearings with seismic isolators could sometimes be enough to retrofit abridge. The reduction of the seismic effects on the piers allows avoiding further interventions
on them.

121

Figure 6. Seismic Isolation Structure for Existing Buildings.
4. THE CHECK UNDER LOW ENERGY EARTHQUAKES
Nowadays, seismic isolation is one of the best techniques to protect structures against earthquakes and, when applicable, should be preferred to other techniques. Anyway, a correct use
is to be recommended to avoid failures, which could discourage its use in the future.
One of the topics to consider is the behaviour under low energy earthquakes, such as far fault
or just weak events. While seismic isolation systems showed very good performances during
several strong events in several countries, the behaviour under low energy excitation has beenstudied in depth only recently [19] [20]. The seismic sequence that hit Central Italy from August 2016 to January 2017 offered a suitable occasion. Some buildings with different seismic
isolation systems were selected for comparison, in particular two seismically isolated buildings of the Civil Protection Centre at Foligno and other base isolated ones at L'Aquila, whichwere more than 30 km from the epicentral areas. All the events with magnitude equal to or
greater than 4.0 were selected and classified based on the energy at the basement of eachbuilding, evaluated by means of the Arias intensity [21]. The variation in the resonance frequencies, the peak accelerations and the maximum relative displacements were particularly
pointed out.
In the first building of the Civil Protection Centre, the isolation system is composed of
HDRBs only [22][23][24][25]. It is well known that the shear modulus of the elastomer increases when the shear deformation γ gets lower (Fig. 7a). Consequently, the first resonancefrequency gets higher and could become close to those of the superstructure. If this occurs,
the decoupling of motion cannot be guaranteed. In the studied building, this did not happen
due to the very high stiffness of the superstructure, whose first resonance frequency is 3.4 Hz.
It is worth noting that the contribution of the seismic isolation system was also apparent underambient vibrations only. In Fig. 7b, the first resonance frequency is plotted versus IA: it varies
a little around a medium value, equal to that obtained under ambient vibrations (about 1.9
Hz), up to a value of IA and then decreases when IA increases. The resonance frequency isalways much higher than the design one (0.38 Hz).
In Fig. 8a, the maximum accelerations at the three levels (L0 = basement, L1 = just above theisolation interface, L2 = top of the building) are plotted versus IA for all recorded events. For
low values of IA, the acceleration at L1 was often greater than that at L0. Just the opposite
occurred for higher values of IA. In Fig 8b, the maximum relative displacements between L1and L0 and between L2 and L1 are plotted versus IA for the recorded earthquakes. Due to thedeformability of the ground floor columns, below the isolation interface, the drift between L1

122and L0 is always higher than that between L2 and L1. The difference increases very muchwith IA.
The observed behaviour can be interpreted as follows. For low energy earthquakes, the isolation system is subject to very low shear strains, for which the shear modulus of the rubber ismuch higher than that at shear strains greater or equal to one. The first resonance frequencies
get higher and could become equal to those of the superstructure.
2.5

16

G/G1= γ–0.43

2.0

f (Hz)

G / G1128

40
2.E-03

1.5
1.0
0.5

2.E-02γ

2.E-010.0
1.E-04

2.E+00

1.E-02(a)IA (cm/s)

1.E+00

1.E+02(b)

Figure 7. Isolation system with HDRBs only: (a) normalised shear modulus vs shear strainand (b) first resonance frequency vs IA.
1.E+00

1.E+01

1.E-01a (g)d (mm)

1.E+00

1.E-02

1.E-01

a2max
a2max
a1max
a1max
a0max
a0max

1.E-03
1.E-04
1.E-04dd1-0,max
1-0,maxdd2-1,max
2-1,max

1.E-02IA (cm/s)

1.E+00

1.E-02

1.E+02(a)

1.E-03
1.E-04

1.E-02IA (cm/s)

1.E+00

1.E+02(b)

Figure 8. Isolation system with HDRBs only: (a) maximum accelerations at the three levels
and (b) maximum relative displacements be-tween L1 and L0 and between L2 and L1 vs IA.
The second case study refers to residential buildings seismically isolated by means of curved
surface sliders (CSS) [26]. It is well known that the friction coefficient decreases when thevertical load gets lower (Fig. 9). For this reason, the friction coefficient in seismic conditions(vertical load NE) could be much lower than that under the vertical loads corresponding to thestatic limit state (vertical load NULS). Therefore, the static friction could be very high so thatthe onset of motion could not occur under low energy events [27].
In Fig. 10 the resultant inertial force at each instant is compared with the maximum theoretical friction force (red circles) for two different buildings. In the first case (Fig. 10a), relative
to a reinforced concrete building, the inertial force gets higher than the friction force at someinstant, so the isolation system is put in action. In the second one (Fig. 10b), relative to awooden building, the friction force is always greater than the inertial one, and the system is
not activated. Actually, if friction is very high, the isolation system could not be put in action,and the structure could behave as a fixed base building.

123

0.10
0.08

µst

0.06
0.04
0.02
0.00

NULS

NE

0.0

0.2

0.4

N/Nu

0.6

0.8

1.0

Figure 9. CSSs: friction coefficient vs normalized vertical load.
R.C. building

5250

Wooden building

Fy (kN)

5250

Fy (kN)Fx (kN)
-5250

5250

Fx (kN)
-5250

5250

-5250

-5250

(a)

(b)

Figure 10. Isolation system with CSSs: maximum theoretical friction force (red circles) andresultant inertial force (blue line) for (a) a r.c. building and (b) a wooden building.
The last case study is represented by a second strategic building of the Civil Protection Centre, seismically isolated by means of HDRBs and SDs [28][29]. In Fig. 11 the first resonancefrequency is plotted versus IA. As in the first case of isolation system made of HDRBs only, itvaries a little around a medium value up to a value of IA and then decreases when IA increases.
But this time, the initial value is equal to that of the superstructure (about 3.5 Hz), which is
obviously much higher than the design one. In Fig. 12a the accelerations obtained at the threelevels (L0 = basement, L1 = just above the isolation interface, L2 = top of the building) areplotted versus IA for all recorded events. It is apparent that for low values of IA, the acceleration at L1 is almost always greater than that at L0, while the opposite occurred for higher values of IA. In Fig 12b, the maximum relative displacements between L1 and L0 and between
L2 and L1 are plotted versus IA for the recorded earthquakes. The drift between L1 and L0 isalways higher that between L2 and L1 and the difference increases very much with IA. One
can conclude that for an isolation system composed of HDRBs + SDs, the onset of motion isgoverned by the static friction of the sliding devices. During the motion, the stiffness of therubber determines the effective resonance frequency, which could become very high and close
to the first resonance frequency of the superstructure.
In all cases, the seismic effects in the superstructure could be higher than those evaluated in
the design phase. This occurrence should be accounted for in the design of a seismically isolated structure.
It is worth reminding that the isolation system has a horizontal stiffness low enough to allow
the relative displacements required in case of earthquake but high enough to avoid vibrations

124

under very low horizontal actions, such as wind, traffic-induced, or ambient vibrations. In
other words, the stiffness should be calibrated accurately to avoid unexpected behaviours.
4.5

f1 (Hz)

3.0

1.5

0.0
1.E-04

1.E-02IA (cm/s)

1.E+00

1.E+02

1.E+00

1.E+01

1.E-01

1.E+00d (mm)a (g)Figure 11. Isolation system with HDRBs+SDs: first resonance frequency vs IA.

1.E-02

1.E-01

L0 x
L1 x
L2 x

1.E-03
1.E-04
1.E-04

1.E-02

1.E+00IA (cm/s)

L1 – L0 (x)1.E-02

1.E+02(a)

1.E-03
1.E-04

L2 – L1 (x)1.E-02(b)IA (cm/s)

1.E+00

1.E+02

Figure 12. Isolation system with HDRBs+SDs: (a) accelerations at the three levels and (b)maximum relative displacements between L1 and L0 and between L2 and L1 vs IA.
5. CONCLUSIONS
Nowadays, seismic isolation can be considered one of the best protection technique against
earthquake, especially for strategic structures for which full integrity and operability after
even very strong earthquakes are required, but also for residential buildings. Fortunately, thenumber of applications is increasing remarkably in several countries.
One of the most important challenges for the future is the wide use of seismic isolation to retrofit existing structures, keeping the structures operational during the works. The most usedtechniques for new and existing buildings have been shown, as well as new solutions to keep
the building operational during the retrofit intervention. These should guarantee at least thesame safety level that the structure had before the retrofit intervention.
In order to encourage the application of base isolation in the future, its correct use is to berecommended. The actual behaviour shown during earthquakes is indeed of fundamental importance for future developments. The observed behaviours in Italy pointed out the importance of analyzing the characteristics of the isolation system under low energy earthquakes
at the site, such as far fault earthquakes. In fact, the behaviour of isolation devices under low
vibrations is quite different from that assumed under the design earthquake at the ultimate
limit state.

125

REFERENCES[1] Clemente P (2017) Seismic isolation: past, present and the importance of SHM for the future. J. of

Civil Structural Health Monitoring, 7(2):217-231, Springer, https://doi.org/10.1007/s13349-0170219-6.
[2] Clemente P, Martelli A (2019) Seismically isolated buildings in Italy: State-of-the-art review andapplications. Soil Dynamics & Earthquake Engineering, 119:471-487, Elsevier Science Ltd,
https://doi.org/10.1016/j.soildyn.2017.12.029.
[3] Clemente P (2023). Applications and recent studies on seismic isolation in Italy. In: Cimellaro
G.P. (ed) Seismic Isolation, Energy Dissipation and Active Vibration Control of Structures. WCSI
2022 (Proc. of the 17WCSI, Turin, 11-15 Sep 2022). Lecture Notes in Civil Engineering, Vol.
309, 3-16. Springer, Cham. Invited lecture, online 07.01.2023. https://doi.org/10.1007/978-3-03121187-4_1.
[4] LG (1998) Linee guida per progettazione, esecuzione e collaudo di strutture isolate dal sisma.
Consiglio Superiore dei Lavori Pubblici – Servizio Tecnico Centrale, Available online:
https://cslp.mit.gov.it/normativa/circolari-e-linee-guida (accessed on 5 May 2023).
[5] OPCM 3274/2003 (2003) Primi elementi in materia di criteri generali per la classificazione
sismica del territorio nazionale e di normative tecniche per le cotruzioni in zona sismica.
Ordinanza del Presidente del Consiglio 3274 of 20/03/2003, G.U. 105 of May 8, 2003,
Supplemento Ordinario 72.
[6] NTC 2008 (2008) Norme Tecniche per le Costruzioni. DM MIT 17 January 2018, Supplemento
Ordinario n. 8 alla Gazzetta Ufficiale, 2018, Serie Generale n. 42 of 20 February 2018. Available
online: https://www.gazzettaufficiale.it/eli/gu/2018/02/20/42/so/8/sg/pdf (accessed on 5 May2023).
[7] NTC 2018 (2018) Aggiornamento delle Norme Tecniche per le Costruzioni. DM MIT 17 January
2018, Supplemento Ordinario n. 8 alla Gazzetta Ufficiale, 2018, Serie Generale n. 42 of 20
Available
online:February2018.
https://www.gazzettaufficiale.it/eli/gu/2018/02/20/42/so/8/sg/pdf (accessed on 5 May 2023).
[8] Clemente P, Bongiovanni G, Buffarini G, Saitta F (2018) Zero Earthquake-Damage Buildings: thechallenge for sustainability and resilience in seismic areas. Int. J. of Earthquake and Impact Engineering, 2(4):322-338, Inderscience Publishers, https://doi.org/10.1504/IJEIE.2018.10020824.
[9] Scafati F, Ormando C, Clemente P, Buffarini G (in press) Designing Base Isolated Buildings according to the Italian Technical Code: a Benchmark for Comparison. In: Seismic Isolation, Energy Dissipation and Active Vibration Control of Structures. WCSI 2023 (Proc. of the 18WCSI,
Antalya, 6-10 Nov 2023). Springer, Cham.
[10] Tripepi C, Clemente P (2021) Graphic Procedure for the Optimum Design of Elastomeric Isolators. Practice Periodical on Structural Design and Construction, 26(1):04020058, ASCE,
https://doi.org/10.1061/(ASCE)SC.1943-5576.0000547.
[11] Saitta F, Clemente P, Bongiovanni G, Buffarini G, Salvatori A, Grossi C (2018) Base isolation ofbuildings with curved surface sliders: basic design criteria and critical issues. Advances in Civil
Engineering, 2018:1569683, 14 pages, Hindawi, https://doi.org/10.1155/2018/1569683.
[12] Martelli A, Clemente P, De Stefano A, Forni M, Salvatori A (2014) Recent development andapplication of seismic isolation and energy dissipation and conditions for their correct use. Geotechnical, Geological and Earthquake Engineering, 34:449-488, Springer Nature,https://doi.org/10.1007.978-3-319-07118-3.
[13] Clemente P, Buffarini G (2010) Base isolation: design and optimization criteria. J. of Seismic
Isolation and Protection Systems, 1(1):17-40, Mathematical Science Publisher,https://doi.org/10.2140/siaps.2010.1.17.
[14] Clemente P, Bontempi F, Boccamazzo A (2016) Seismic Isolation in Masonry Buildings: Technological and economic issues. In: Modena C., da Porto F. & Valluzzi M.R. (eds), Brick andBlock Masonry: Trends, Innovation and Challenges (Proc. 6th Int. Conf. IB2MAC, 26-30 Jun
2016, Padua), 2207-2215, Taylor & Francis Group, London, UK.
[15] Saitta F, Clemente P, Buffarini G, Bongiovanni G (2017) Vulnerability analysis and seismic retrofit of a strategic building. J. of Performance of Constructed Facilities, ASCE, 31(2),126https://doi.org/10.1061/(ASCE)CF.1943-5509.0000948.

[16] Buffarini G, Clemente P, De Flaviis A, Ormando C, Salvatori A (2023) Seismic retrofit of r.cbuildings with base isolation. In: Cimellaro G.P. (ed) Seismic Isolation, Energy Dissipation and
Active Vibration Control of Structures. WCSI 2022 (Proc. of the 17WCSI, Turin, 11-15 Sep
2022). Lecture Notes in Civil Engineering, Vol. 309, 969–977. Springer, Cham,https://doi.org/10.1007/978-3-031-21187-4_85.
[17] Clemente P, De Stefano A (2011) Application of seismic isolation in the retrofit of historicalbuildings. In: Brebbia C.A. & Maugeri M. (eds), 8th World Conference on Earthquake ResistantEngineering Structures, ERES 2011 (Chianciano, 7-9 Sep 2011), 41-52, WIT Press, Southampton,
UK, 120:1746-4498, https://doi.org/10.2495/ERES110041.
[18] De Stefano A, Clemente P, Invernizzi S, Matta E, Quattrone A (2015) Innovative technique forthe base isolation of existing buildings. In: Papadrakakis M., Papadopoulos V., Plevris V. (eds),
Computational Methods in Structural Dynamics and Earthquake Engineering (5th International
Conference COMPDYN 2015, Crete Island, Greece, 25–27 May 2015), 1:377-387, NTUA, Athens, Greece, ISBN: 978-960-99994-7-2.
[19] Clemente P, Bongiovanni G, Buffarini G, Saitta F, Scafati F (2019) Monitored Seismic Behaviorof Base Isolated Buildings in Italy. In: Limongelli M, Celebi M (eds), Seismic Structural Health
Monitoring, 115-137, Springer Tracts in Civil Engineering. Springer, Cham,https://doi.org/10.1007/978-3-030-13976-6_5.
[20] Buffarini G, Clemente P, Ianniruberto U, Ormando C, Scafati F (2023) Observed seismic behaviour of base isolation systems in Italy. In: Cimellaro G.P. (ed) Seismic Isolation, Energy Dissipation and Active Vibration Control of Structures. WCSI 2022 (Proc. of the 17WCSI, Turin, 11-15
Sep 2022). Lecture Notes in Civil Engineering, Vol. 309, 599–610. Springer, Cham, online
07.01.2023. https://doi.org/10.1007/978-3-031-21187-4_50.
[21] Arias A (1970) Measure of earthquake intensity. In: Hansen R. (ed.), Seismic Design of Nuclear
Power Plant, Massachusetts Inst. of Tech. Press, Cambridge, Mass.
[22] Clemente P, Bongiovanni G, Buffarini G, Saitta F, Castellano MG, Scafati F (2019) Effectiveness of HDRB isolation systems under low energy earthquakes. Soil Dynamics & Earthquake Engineering, 118:207-220, Elsevier Science Ltd, https://doi.org/10.1016/j.soildyn.2018.12.018.
[23] Clemente P, Di Cicco A, Saitta F, Salvatori A (2021) Seismic behaviour of the base isolated Civil
Protection Operative Centre at Foligno, Italy. J. of Performance of Constructed Facilities,
34(4):04021027, ASCE, https://doi.org/10.1061/(ASCE)CF.1943-5509.0001589.
[24] Salvatori A, Di Cicco A, Clemente P (2021) Monitoring of base isolated building subjected to far
fault earthquake. In: Rainieri C, Fabbrocino G, Caterino N, Ceroni F, Notarangelo MA (eds) Civil
Structural Health Monitoring. CSHM 2021. Lecture Notes in Civil Engineering, 156:311-338,
Springer, http://doi.org/10.1007/978-3-030-74258-4_21.
[25] Salvatori A, Di Cicco A, Clemente P (2019) Seismic monitoring of buildings with base isolation.
In: Papadrakakis M., Fragiadakis M. (eds), Computational Methods in Structural Dynamics andEarthquake Engineering (7th ECCOMAS Thematic Conf., COMPDYN 2019, Crete Island,
Greece, 24–26 June 2019), ID 19221. https://2019.compdyn.org/proceedings/.
[26] Scafati F, Ormando C, Clemente P, Bongiovanni G (2022) Observed behavior of buildings seismically isolated with CSSs under a low energy earthquake. J. Civil Structural Health Monitoring,12(2):225–243, Springer, https://doi.org/10.1007/s13349-021-00539-z.
[27] Ormando C, Clemente P, Ianniruberto U, Scafati F (2021) Onset of motion of CSS isolation systems. Practice Periodical on Structural Design and Construction, 26(3), ASCE,
https://doi.org/10.1061/(ASCE)SC.1943-5576.0000580.
[28] Salvatori A, Bongiovanni G, Clemente P, Ormando C, Saitta F, Scafati F (2022) Observed seismic behaviour of a HDRB and SD isolation system under far fault earthquakes. Infrastructures
2022, 7(2):13, MDPI, Basel, Switzerland, https://doi.org/10.3390/infrastructures7020013.
[29] Clemente P, Bongiovanni G, Ormando C, Scafati F (in press) Influence of friction in the seismic
behaviour of HDRB+SD isolation systems. In: Seismic Isolation, Energy Dissipation and Active
Vibration Control of Structures. WCSI 2023 (Proc. of the 18WCSI, Antalya, 6-10 Nov 2023).
Springer, Cham. Invited lecture.

127

RECENT APPLICATIONS OF SEISMIC ISOLATION IN NORTH AMERICA

I.D. Aiken1 and C.J. Black2
1 Principal, SIE, Inc., Berkeley, California, USA
2 Associate, SIE, Inc., Berkeley, California, USA

ABSTRACTThe number of seismically-isolated building projects continues to grow at a steady, albeit slow rate in
the U.S., and applications in Canada are starting to appear. Many projects are architecturally notable,
and many also involve increasingly large isolation displacements. The use of isolation for sensitive andcritical equipment is becoming more common, and in some cases is extending to state-of-the-art threedimensional protection. The paper gives an overview of a selection of recent notable projects anddiscusses recent trends in design and applications.
KEYWORDS: seismic isolation, buildings, industrial, sensitive equipment, three-dimensional USA,
Canada.

1. INTRODUCTION
The first seismically-isolated building in the U.S. was completed in 1985. This was a new, four-story
building, the Foothill Communities Law & Justice Center in Rancho Cucamonga, California thatutilized high-damping rubber bearings. Soon after, the first seismic isolation retrofit in the U.S. and theworld was completed, the Salt Lake City & County Building in Salt Lake City, Utah. These and otherearly projects initially positioned the U.S. at the forefront of the use of the technology. It is now
estimated that there are about 200 seismically-isolated buildings in the U.S., and while not nearly the
number that have been completed in various other countries, isolation has continued to be used at a
steady, albeit slow, pace with many notable applications and distinctive projects.
The use of seismic isolation for buildings in Canada has taken place much more recently with the firstbuilding, the retrofit of an historic school building in Vancouver, B.C., being completed in 2017.
Isolation is now being used for a number of notable projects currently underway and is being actively
considered by engineers and owners for numerous others.
This paper gives an overview of a selection of recent seismic isolation projects in both countries andprovides some observations on trends regarding the use of the technology and applications.

128

2. OVERVIEW OF RECENT PROJECTSThe following sections briefly describe a selection of projects that have been completed within the last
several years or which are currently under construction, in the categories of architecturally notable newbuildings, retrofits, essential facilities, data centers, and several categories of non-building applications:equipment, industrial and artwork.
2.1 Architecturally Notable New Buildings
A series of recent building projects in the Los Angeles area have taken advantage of the structural
flexibility possible with the use of seismic isolation to achieve dramatic architectural forms. The newhome of both the NFL Los Angeles Rams and the Los Angeles Chargers, SoFi Stadium features a
sweeping roof structure covering more than 120,000 m2, supported on 53 pendulum isolation bearings
atop massive “blade” columns (Figs. 1.a and b). The stadium is within meters of the NewportInglewood Fault, and the isolation bearings were designed for a maximum displacement of 2.03 m.

(a) Exterior view of stadium(b) Roof structure with isolators at top of blade columns

Figure 1 SoFi Stadium, Inglewood, California, USA (photos: SoFi Stadium)Two other dramatic architectural examples are the Academy Museum of Motion Pictures (Fig. 2.a)and the (W)rapper building (Fig. 2.b). The Academy Museum is a spectacular 45.8 m diameter steel
and glass orb supported on just eight isolators with a maximum displacement of 750 mm, while the(W)rapper is a unique, 17-story, 73 m tall steel building with no columns or regular framing, instead ahelical band exoskeleton supports the structure and achieves entirely column-free interior spaces. The(W)rapper isolation system comprises 18 triple friction pendulum bearings.
Both the Lucas Museum (Fig. 2.c), and the David Geffen Galleries of the Los Angeles County Museumof Art (LACMA) (Fig. 2.d) feature impressive free-form architectural designs, with isolation not only
facilitating the architectural and structural forms, but also providing the highest level of protection to
the valuable art and contents to be housed in both complexes. All the projects of Fig. 2 have utilized
triple pendulum isolation bearings.

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(a) Academy Museum of Motion Pictures(b) The (W)rapper

Los Angeles, California, USA

Los Angeles, California, USA(photo: Renzo Piano Building Workshop)(image: Eric Owen Moss Architects)(c) Lucas Museum, Los Angeles, California, USA(image: Lucas Museum of Narrative Art)(d) David Geffen Galleries, LACMA, Los Angeles, California, USA(image: Atelier Peter Zumthor & Partner / The Boundary)

Figure 2 New seismically-isolated buildings, Los Angeles, California, USA
2.2 Retrofit Projects
The use of isolation for the retrofit and upgrade of historic buildings in the U.S. has always been asignificant sector of application, and in recent years that has expanded into Canada. The first Canadianbuilding isolation project was the retrofit of the Lord Strathcona School in Vancouver (Fig. 3.a). This130

1,800 m2, three-story timber/masonry/stone building used 30 elastomeric and flat sliding bearings andwas completed in 2017. Currently underway is the retrofit of Centre Block, the main building of theCanadian Parliamentary complex (Fig. 3.b). The project includes the addition of a new, undergroundvisitor welcome center, and will see the transfer of the building onto nearly 600 isolators [1].
Construction is currently underway on the seismic upgrade of the Salt Lake Temple of The Church of
Jesus Christ of Latter-day Saints (Fig. 4.a). The temple, originally constructed over 40 years andcompleted in 1893 will be supported on 98 triple pendulum bearings with a maximum displacementof 1.52 m (60 in.). The massive, granite walls of the temple required an innovative underpinning andload transfer approach, with the isolators either side of the axis of the walls (Fig. 4.b).

(a) Lord Strathcona School(b) Centre Block, Canadian Parliament

Vancouver, British Columbia, Canada

Ottawa, Ontario, Canada (photo: Wikipedia)

Figure 3 Heritage building seismic isolation retrofits, Canada(a) Temple Building(b) Load transfer and isolator placement(image: Wikipedia)(image: Intellectual Reserve, Inc.)

Figure 4 Salt Lake Temple, The Church of Jesus Christ of Latter-day Saints, Salt Lake City, Utah, USA
2.3 Essential Facilities
Along with the retrofit of historic buildings, isolation has also been consistently used in the U.S. foressential facilities. The following examples in Figs. 5, 6, and 7 show some notable recent examples.
The Loma Linda University Medical Center in Southern California is a 100,000 m2 new hospitalbuilding, comprising two patient towers of 16 and 7 stories (Fig. 5.a). The hospital is located within a
few hundred meters of the San Jacinto Fault (see Building “5”, Fig. 10) and is exposed to extremely
severe near-field shaking. As a result, the isolation system has been designed to accommodate not only131

large horizontal displacements (1.07 m) using triple pendulum bearings and fluid viscous dampers, butalso to provide isolation in the vertical direction (Fig. 5.b). The hospital construction is complete, withdesign details included in the basement to allow the implementation of the vertical isolation system inthe coming years.
The other essential facility examples of Figs. 6 and 7 are all in the state of Oregon. Figs. 6.a and b.
show a new operations center for Oregon’s largest energy utility company, and a new headquarters for
the Oregon state government Treasury. Both projects have been recently completed and opened in
2021, and both utilize isolation systems with a combination of elastomeric and flat sliding bearings.
Along with utility networks, transportation systems are also increasingly regarded as essential facilities,
and Fig. 7 shows the currently under-construction main terminal building expansion of Portland
International Airport [2]. The roof structure is isolated at the tops of architecturally impressive Ycolumns using a total of 68 curved-surface sliding bearings. The use of isolation not only made possible
the dramatic architecture but also achieved above-code functionality protection for the facility.

(b) Isolation system components(a) Hospital building general view

Figure 5 Loma Linda University Medical Center, Loma Linda, California, USA (images: Ref [5]).

(a) Utility company operations center, Tualatin, Oregon, USA(b) Treasury Resiliency Building, Salem, Oregon, USA

Figure 6 Essential facilities, Oregon, USA (photos: PGE; GBD Architects)

132

(b) Terminal interior with Y columns(a) Exterior view, main terminal building

Figure 7 Terminal Roof, Portland International Airport, Portland, Oregon, USA (images: ZGF Architects)
2.4 Data Centers
Seismic isolation has been used for a number of data centers in the last several years. Two recent
examples are shown in Fig. 8, a 4-story, 16,000 m2, center in Silicon Valley, northern California, and a
2-story, 6,000 m2 project in southern California [3]. Both projects utilize triple pendulum bearings andhave been designed for maximum displacements of approximately 800 mm, with the Santa Clara
project additionally including fluid viscous dampers to limit the maximum displacement.

(b) Data center, Irvine, California(a) Data center, Santa Clara, California

Figure 8 Seismically-isolated data centers, California, USA (images: (a) NTT/Gensler ; (b) TGS/LPA).
2.5 Computer and Electrical Equipment
A major new hydroelectric project in the Canadian province of British Columbia, the Site C Clean
Energy Project has made extensive use of state-of-the-art isolation systems to provide enhanced
seismic performance of both critical electronic equipment and electrical distribution equipment. Fig.
9.a shows an example of 3-D seismic isolation platforms used to protect spillway gate control
equipment critical to dam safety against 1/10,000 year Maximum Earthquake shaking (a total of 39
platforms of varying sizes are used on the project) and Fig. 9.b shows wire rope isolators used to protect
high-voltage electrical distribution equipment [4].

133

(a) 3D seismic isolation platforms for electrical and(b) Wire rope isolators for 500 kV electrical equipment

electronic control equipment

Figure 9 Equipment seismic isolation, Site C Clean energy Project, Peace River, B.C., Canada

3. TRENDS
Whilst the total number of seismically-isolated buildings in the U.S. over time has not progressed as
significantly as in some other countries, many of the applications that have been completed are
structurally or architecturally significant, and among those projects that have been completed in recent
years a number of general trends can be observed:
•

•
•
•
•

Design displacements for isolation systems have tended to increase over time. This has been
due not only to changes (generally increases) in seismic hazard estimations, but also the greateruse by designers of longer-period isolation systems. Fig. 10 is indicative of this change inmaximum design displacement over time, showing the inland region of southern California
east of Los Angeles that includes a number of isolated buildings. Building “1” is the firstisolated building in the U.S., and Building “6” is the Loma Linda University Medical Center(Fig. 5). It can be seen that design displacements, originally in the range of 380-550 mm haveincreased to as much as 1.07 m over about 25-30 years. These large displacements present
significant design challenges and push the performance limits of isolation devices.
Many recent projects with large displacement requirements have utilized triple pendulum
bearings.
A number of low-rise (2-3 story) steel-framed buildings have used a combination ofelastomeric and flat sliding bearings.
Fluid viscous dampers continue to be used together with pendulum or elastomeric bearings, tomoderate large displacement demands.
The use of isolation for non-building applications, such as computer systems, sensitive andcritical equipment and artwork has increased. These systems have recently included highperformance 3-D capabilities.

Interest in seismic isolation in Canada is growing with more engineers now exploring isolation for both134

new and retrofit construction, and its use even in areas of relatively low seismicity is proving to be bothtechnically and economically viable, particularly for retrofit applications.

4. SUMMARY
It is nearing 40 years since the design and completion of the first seismically isolated buildings in the
U.S. The rate of adoption of the technology has not matched that of some other countries, nonethelessmany notable seismic isolation projects have been completed and continue to be undertaken, withapplications pushing the state-of-the-art in terms of seismic protection objectives. The use of seismic
isolation for buildings in Canada has started to emerge in the last decade and it is expected that isolation
will see increased use in future years, not only in high, but also low-to-moderate seismic regions of thecountry.

Figure 10 Maximum design displacements for seismically-isolated buildings in inland southern
California, 1984-2016. (image: adapted from Google Earth).
REFERENCES[1] Bebamzadeh, A., Sherstobitoff, J. et al., “Canada’s Parliament Hill Centre Block Base Isolation Seismic
Upgrade: Impact of Vertical Ground Motions,” Proc. 12th National Conf. on Earthquake Engineering, EERI, Salt
Lake City, USA, June-July, 2022.
[2] Zimmerman, R., “Seismic Isolation of the Terminal Core Rood at the Portland International Airport," Proc.
17WCSI, ASSISi, Turin, Italy, September, 2022.
[3] Richardson, S. and Lindorfer, K., “Seismic Isolation in the U.S. Mission Critical Sector," Proc. 17WCSI,ASSISi, Turin, Italy, September, 2022.
[4] Aiken, I., Black, C. et al., “3D Seismic Isolation for Operational Level Protection of Critical Electrical
Equipment and Electronic Control Equipment for the Site C Clean Energy Project, Proc. 17WCSI, ASSISi, Turin,
Italy, September, 2022.

135

SEISMIC ISOLATION IN CHILE

R. Retamales1 and R. Boroschek2
1
2

Principal, Seismic Intelligence SpA, Santiago, Chile, rodrigo@seismicintelligence.com

Professor, Department of Civil Engineering, University of Chile, Santiago, Chile, rborosch@uchile.cl

ABSTRACTThe continental territory of Chile is located on the subduction zone between the Nazca and SouthAmerican plates. In the last fourteen years, three earthquakes with moment magnitudes Mw larger than
8.2 struck the Chilean territory. Earthquakes with Mw > 7 occur every 5 years in average, converting
Chile in one of the most seismically active countries in the world. The economical and physical losses,
in addition to business interruptions, have motivated authorities, investors, and stakeholders to request
the use of seismic protection technologies, such as seismic isolation and energy dissipation in theirprojects, aiming at improving the seismic performance of structures including hospitals, datacenters,
bridges, wharfs, and industrial, office and residential buildings, among many others. Nevertheless, inrecent years the protection technologies have been applied mainly in hospitals, datacenters, andeducational facilities. This paper summarizes the observations of structural and nonstructural seismic
performances of base isolated structures, some of which have been instrumented for more than 30
years. The expected seismic performance of isolated structures designed according to Chilean practices
is also discussed and analyzed. The observed and expected seismic performances have been considered
for continuous calibration of the Chilean standard for seismic design of isolated structures. The main
characteristics of the Chilean standard and professional practice, and its differences with the US andEuropean standards and practices, are also described and analyzed.
KEYWORDS: Seismic isolation, Energy dissipation, Code development, seismic performance,
seismic monitoring, structural and nonstructural performance

1. INTRODUCTION
The continental territory of Chile is located on the subduction zone between the Nazca and SouthAmerican plates. In the last fourteen years, three earthquakes with moment magnitudes Mw larger than
8.2 struck the Chilean territory. Earthquakes with Mw > 7 occur every 5 years in average, converting
Chile in one of the most seismically active countries in the world. The economical and physical losses,
in addition to business interruptions, have motivated authorities, investors, and stakeholders to request
the use of seismic protection technologies such as seismic isolation and energy dissipation in theirprojects, aiming at improving the seismic performance of structures including hospitals, datacenters,

136

bridges, wharfs, and industrial, office and residential buildings, among many others.
1.1 Seismic Activity
Table 1 summarizes the destructive seismic events (Mw~8) that have struck Chile in the last 445 years.
As observed in Table 1, thirty-one destructive events have been observed in this timespan, resulting indamaging capable events occurring, in average, every 14.5 years within the Chilean territory. In
addition, three events with Mw>8 have been observed in the last 14 years. Among the recent
earthquakes, the most damaging one was the Mw 8.8 El Maule Earthquake in 2010, with an aftermathof 521 fatalities and 33 billion US dollar in direct losses, equivalent to 15% of 2010 Chilean grossdemographic product, GDP. The health system network experienced economical losses close to 3
billion US dollars, and 10 primary health hospitals needed to be evacuated, demolished, and rebuilt.
Among the fatalities, 15 occurred in structures with engineered design; 180 approximately were causedby the tsunami following the main shock; and the remaining fatalities occurred in structures without
seismic design, mainly adobe self-construction houses in rural areas. With regards to economic losses,
90% of them were associated to nonstructural damage given the strict code that rules structural seismic
design [1]. Chile is affected not only by large magnitude events but also frequent and moderate seismic
events. Fig. 1 shows the frequency for earthquakes with Mw larger than 5 and 6 per year between 2004
and 2020 [2].
Table 1 Earthquakes with Moment Magnitudes larger than 8 in Chile
Approx.
Approx.
Date
Magnitude
Date
Magnitude
Location
Location
1570

Feb. 8

8.0 – 8.5

Concepcion

1906

Aug. 16

7.9

Valparaiso

1575

Dec. 16

8.5

Valdivia

1922

Nov. 10

8.4

Vallenar1604

Nov. 24

8.5

North Arica

1928

Dec. 1

8.4

Talca

1647

May. 13

8.5

Valparaiso

1939

Jan. 24

8.0 – 8.3

Chillan

1657

Mar. 15

8.0

Concepcion

1943

Apr. 6

8.3

Illapel1730

Jul. 88.8

Valparaiso

1950

Dec. 98.0

Calama1737

Dec. 24

7.5 – 8.0

Valdivia

1960

May. 22

9.5

South Chile

1751

May. 25

8.5

Concepcion

1966

Dec. 28

8.1

Taltal1796

Mar. 30

7.5 – 8.0

Copiapo1985

Mar. 3

7.8

Central Zone

1819

Apr. 3-11

8.3

Copiapo

1995

Jul. 30

8.0

Antofagasta

1822

Nov. 19

8.5

Valparaiso

2001

Jun. 23

8.4

South Peru

1835

Feb. 20

8.0 – 8.5

Concepcion

2005

Jun. 13

7.8

Tarapaca

1837

Nov. 78.0

Valdivia

2010

Feb. 27

8.8

Center-South1868

Aug. 13

8.5

Arica

2014

Apr. 1

8.2

Iquique

1877

May. 98.0

lquique2015

Sep. 16

8.3

Canela Baja

1880

Aug. 15

7.5 – 8.0

IllapelFrom the data shown in Fig. 1, it can be inferred that, in average, and removing aftershocks, 45 and 5
seismic events with Mw greater than 5 and 6 are observed every year in the territory, respectively. Awareof this situation, authorities, stakeholders, investors, and owners are demanding the use of seismic
protection technologies in their projects. The high number of moderate events imposes requirements137

on the selection and design of the seismic protection technologies, which are not only designed foraccommodating MCE demands as in ASCE/SEI 7-22 [3] but also for service level earthquakes.
Another important characteristic of Chilean earthquakes is related to their durations. Fig. 2 shows thehorizontal accelerations recorded in Concepcion City during the Mw 8.8, 2010 El Maule earthquake.
In Fig. 2 it can be observed that during approximately 120 sec the acceleration threshold of 0.05g isexceeded. Similarly, the acceleration of 0.1g is approximately exceeded during 90 sec, and the 0.2g
acceleration threshold is approximately exceeded during 20 sec.

Figure 1 Frequency for seismic events with Mw larger than 5 (left) and 6 (right).

Figure 2 Exceedances of acceleration thresholds
1.2 First Applications of Seismic Protection Technologies in Chile
Seismic isolation in Chile began in 1992, when one structure in the Andalucia Condominium (Fig. 3),
was seismically isolated by University of Chile Professors Sarrazin and Moroni [4] to introduce thistechnology in developing countries. The isolated building, shown in Fig. 3, is a 4-story confined
masonry structure mounted on 8 high damping rubber bearings. The first level considers reinforced
concrete shear walls. The building has a 10x6 m floor footprint. The weight of the structure is 1,630
kN. The typical slab thickness is 10 cm. The structure’s roof is a wooden truss. The isolators are 315
mm in diameter and 320 mm in height. The thickness of the rubber layers is 6.7 mm. Four isolators
were located in the corners of the building and two at the middle of each long side. The isolators havea vertical load capacity of 350 kN at 200 mm lateral displacement (100% strain). An extensive test
series was carried out at the University of California, Berkeley [4]. The design period of the isolatedbuilding was 2 sec. The base isolated and one of the fixed base buildings were instrumented. The
response of the building during the 2010, Mw 8.8 El Maule earthquake was successfully recorded [5].

138a) Isolated (left) and fixed baseb) Plan view isolated structurec) Elevation isolated
instrumented structure (right)
structure
Figure 3 Andalucia Condominium: first isolated structure in Chile
The second structure that incorporated seismic isolation in Chile was the Marga-Marga bridge, shownin Fig. 4 [6]. This bridge, that spans 368 m, consists of 4 steel girders mounted on 36 high damping
rubber bearings. The height of the tallest reinforced concrete pier is 32 m. Rubber bearing sizes vary
among 850x500, 700x500, and 500x500 mm2. All isolators are 302 mm in height, with 204 mm ofrubber, 16 steel shims 3 mm in thickness, and two 25 mm thick mounting plates. The design
displacement was 156 mm. Two prototypes of each type and all production bearings were tested at the
University of Chile. This bridge was fully instrumented by the University of Chile since its construction,using an array of 24 accelerometers.
The first application of seismic isolation in a large structure was the La Reina Military Hospital,
developed in 2001 (Fig. 5). The total cost of the structure was 112 million US dollars, the number ofbeds 330, and the total constructed area was 88,000 m2 approx. The clinical and emergency services
were located in a base isolated structure in order to protect the investment and the functionality of theirservices. The structural system of this building consists of a moment-resistant frame system with anapproximate built area of 50,000 m2 distributed in 5 levels, including a basement level for parking. The
highest level of the structure corresponds to a mechanical floor. The dimensions in plan are 126x115
m. The column spacing is 9 m in both directions. The floor height is 5.75 m at the basement level and
4.5 m at the upper levels. The building’s columns have a typical section of 800x800 mm, except in thebasement level, where the typical column section is 1100x1100 mm. The beams have a typical sectionof 600x900 mm, except in the ceiling of the basement level, where the beams have a 600x1100 mm
section. The stronger system at the basement level was requested for an elastic design and to control
the story drift at this level. The structure is mounted on 164 seismic isolators located at the ceiling of
the basement level, 114 of these isolators were manufactured using high damping rubber. The isolators
are 700 and 900 mm in diameter and were made of 20 rubber layers of 8 mm of thickness and 4 mm
thick steel shim plates. The remaining isolators have a 150 mm in diameter lead core to increase its
energy-dissipation capacity. These isolators are 900 mm in diameter and are located in the perimeterof the structure, in order to control torsional effects. The design displacement was 240 mm. The
damping provided by the isolation system was nearly 12%. The period of the isolated structure wasnearly 2.5 sec.

139

Figure 4 Marga-Marga bridge: firstseismically isolated bridge in Chile

Figure 5 La Reina Military Hospital

1.3 Current Applications of Seismic Protection Technologies in Chile
Between 1992 and 2010 approximately 10 isolated structures were built in Chile. The 2010 earthquake
triggered the demand for using seismic isolation technologies. Currently, approximately 200 isolated
structures are built. Fig. 6 summarizes the types of structures incorporating isolation technologies andtheir proportion to the total. It is observed that most isolated structures correspond to health facilities
and residential buildings. Fig. 7 shows the type of technology used for seismically isolating structures.
Although most existing applications consider high damping rubber systems (HDRB), the trend isdrastically changing, given that all new hospitals (with built area larger than 40,000 m2, approximately)
consider natural rubber (RB) and lead rubber bearings (LRB) by government specifications, and theirruption in the market of comparatively lower cost friction pendulums (FP) technologies, that are also
applicable to relatively low mass structures such as data centers and control rooms. In addition, it isexpected to increase the demand for using this type of technology given the recent evidence ofcontinued functionality of hospitals isolated with friction pendulums, that were struck by the Mw 7.8
and 7.5, 2023 Kahramanmaraş earthquakes in Türkiye. In consequence, the percentages shown in Fig.
7 are expected to change quickly in the upcoming years.
Low-income
housing andfamily dwellings
6%

Industrial
facilities
12%

Other
3%

Health facilities
25%

LRB/RB
20%

Educational
facilities
6%

FP
5%
HDRB
75%

Datacenters
6%
Residentialbuildings
24%

Bridges9%
Office buildings
9%

Figure 6 Isolated structures in Chile

Figure 7 Type of isolation
technology

By year 2010 most existing seismically isolated structures in Chile were buildings of relatively low

140height, mainly health care facilities. In the last decade the application of protection devices rapidly
expanded to other types of structures such as datacenters, museums, laboratories, educational facilities,
industrial facilities (such as LNG tanks, control rooms, and telescopes), and more importantly, to office
and residential buildings. Current trends consider the transition from high damping rubber bearings tolead rubber bearings and frictional pendulum systems, to protect relatively tall buildings, massive
structures in isolated blocks, low mass critical tech infrastructure, and bridges. The incorporation ofisolation devices manufactured worldwide into the Chilean market has resulted in a reduction of 30%
in the cost of the isolators, contributed significantly to increase testing capabilities, and helped with thetechnology transfer. Fig. 8 shows the Torre del Sol condominium, the first of many relatively tallbuildings isolated in Chile. The building, structured using shear bearing walls, was built in Copiapo
City, in a 100 years seismic gap zone. The structure, which spans 19,000 m2 approx. and 19 stories,
was at its time the tallest residential building with seismic isolation in the Americas. A typical floor
covers 53x12.9 m. The total height of the building, including the undergrounds, is 49.6 m. The total
seismic weight of the structure supported by the isolation system is 155,000 kN. The foundation soil
corresponds to a stiff soil with average shear wave velocity in the first 30 m beneath the surface of 598
m/s. For this project, lead rubber bearings were considered. In order to provide stability to the structure
and to prevent tension forces on the isolators, 60x197 cm beams were considered underneath theparking area, on the second underground level. Seismic isolators were arranged at the ends of beams
and, generally, at the ends of bearing walls. To reduce costs, the 45 seismic isolators used in the
structure were all identical. The maximum compressive force on the isolators (considered for design
and for testing) was 8,200 kN, while the tensile force (or minimum compression load) was 0 kN.
Prototypes and all production isolators were subjected to an exhaustive test series combining
compression and shear to validate the properties assumed for the design and to verify the stability of
the isolators during extreme seismic loads. In the design of the isolation system, a series of nonlinear
dynamic analyses were carried out taking into consideration 7 seismic records compatible with thedemands associated with the maximum considered earthquake defined in the Chilean standard for theseismic zone and ground conditions at the building site. A wide variety of seed records were selected
to allow for analysis of the different seismic events to which the structure could be exposed during its
lifetime. The analysis showed that the use of isolation allows for achieving a reduction close to 90% in
the average base shear, story drifts, and floor accelerations of the structure. The good performance ofthe structure is related to the high stiffness and redundancy of bearing walls, which allows forconcentrating nonlinear deformations in the seismic isolation system. Fig. 8 also shows other similar
condominium buildings incorporating isolation systems.
Fig. 9 shows examples of health facilities, office buildings, datacenters, bridges, and viaducts
incorporating seismic isolation technologies. Most hospitals are structured considering reinforced
concrete intermediate moment resistant frames, with typical story heights of 4.0-4.5 m and distance
between columns in the range 7.8-8.5 m. Office buildings are typically structured considering a
combined system of shear walls in the core and columns in the perimeter. Datacenters may be
structured using a variety of structural systems, including reinforced concrete moment resistant frames,
shear walls, steel moment resistant frames, and special concentrically braced frames.
Bridges and viaducts, as shown in Fig. 9d, are typically structured considering simple supported spans,with expansion joints every 4 spans. Girders are typically steel or posttensioned concrete. Bridges and141

viaducts are designed to fulfill both AASHTO LRFD and AASHTO GSSID requirements.

Figure 8 Examples of seismically isolated tall residential buildings in Chile: Torre del Sol (left);
Nunoa Capital (center); and Via Poniente (right)
2. CHILEAN CODE FOR SEISMIC ISOLATION DESIGN
2.1 First Code for Seismic Isolated Structures Design (2003)
The first Chilean code for seismic design of isolated structures, NCh2745, was released in 2003 [7].
The code, mainly based on the requirements of the UBC-97 standard, collected the experience gainedin Chile from the first isolated projects. The seismic demands were determined by the committee basedon data recorded by the national network of accelerometers of the University of Chile. The code
considered Newmark type design spectra. The Peak Ground Accelerations (PGA’s) for the Design
Basis Earthquake (DBE) and for the Maximum Considered Earthquake (MCE) were determinedprobabilistically considering probabilities of exceedance of 10% in 50 years, and 10% in 100 years,
respectively. The ratio between MCE and DBE PGA’s was estimated equal to 1.2. The displacement
branch in the DBE spectra was defined deterministically as the envelope of all historically recorded
data (until 2003), multiplied by a factor equal to 2. Fig. 10 shows a comparison between the DBE code
spectrum and the 5% damping response spectra obtained from earthquakes Mw ≥ 7 affecting coastal
high seismicity zones between 1985 and 2010. The response and design spectra correspond to soil
Type B, characterized by shear wave velocities vs in the range 500 to 900 m/sec. In a similar way, theChilean code considered reduction factors due to damping (B) that differed from the values in UBC 97
and ASCE/SEI standards. Fig. 11 shows the reduction factors as a function of SDOF effective damping
and period, and a comparison between the reduction factors in UBC and Chilean standards.
The Chilean code limited the super-structure story drifts, computed for DBE level and considering, asa maximum, a response modification factor R ranging between 1 and 2, to a value equal to 0.0025 of
the story heigh when modal spectral analysis was performed. This value can be increased to 0.003 if
nonlinear response history analysis is carried out. The displacements and design forces shall be linearly
scaled whenever the shear at the seismic isolation level results below 0.067Ws, where Ws corresponds
to the reactive seismic weight of the isolated structure, for structures located in coastal zones; and0.05Ws for structures located in Central zones between the Pacific Ocean and the Andes Mountains.
In addition, the Chilean code mandates that the vertical frequency of the isolation system shall be atleast 10 Hz.

142a) Health care facilitiesb) Office buildingsc) Datacentersd) Bridges
Figure 9 Isolated structures examples

143

Reduction Factor 1/B

Soil Type B

β = 0,05
β = 0,10
β = 0,15
β = 0,20
β = 0,25
β = 0,30

B

Period T (s)Damping (β)

Figure 10 Comparison response and CodeDBE spectrum

Figure 11 Damping reduction factors in Chilean
code

2.2 First Review of Code for Seismically Isolated Structures Design (2013)
Ten years after releasing the first version of the code, the standard was reviewed in 2013 to include theexperience accumulated during one decade of professional practice and the lessons learnt from the El
Maule 2010 earthquake. In addition, the code revision had the objective of promoting the use of thetechnology and correcting the issues that made difficult applying the code. Among the measures made,the requirements of gap between isolated structures were clarified.
Given the response spectra of the records obtained during the 2010 El Maule earthquake ratified thatthe design spectra considered by the Chilean standard (Fig. 10) were conservative for periods close to
3.5 sec, the TM period for which specific site spectra development is not required was increased from
3.0 to 3.5 sec.
The 2013 standard permits that structural elements located above the isolation system in buildings
structured using reinforced concrete moment resistant frames can be designed and detailed inconformity with the requirements of ACI-318 standard for intermediate moment frames instead of
special moment frames, whenever the criteria for the strong column – weak beam is fulfilled. Similarly,
it removes the need for boundary elements in bearing walls in isolated structures. The structuralelements located under the isolation interface in reinforced concrete isolated structures must meet therequirements of ACI-318 for special moment frames, while 80% of the seismic load is not transferred
to structural walls. The code allows for an increase in the response modification factor for designing
the sub-structure elements from 1.0 to 1.5, in consideration of the intrinsic over-resistance of current
design procedures. The standard establishes that the response modification factor to be considered fordesigning the isolated structure does not need to be less than 1.0, so the design demands will not need
to be greater than the elastic seismic demands. Fig. 12 shows the fragility curves used to support thedecision to use intermediate frames instead of special moment resistant frames [8]. Fig. 12 shows thefragility curves for ultimate rotation capacity of structural elements in isolated (ISO) and fixed base(BF) structures. The curves for the first (Max), 16th (P16) and 50th (P50) percentile ultimate rotation
capacity exceedances are shown. In the figure is observed that the PGA triggering the first ultimate
rotation capacity in a fixed base special moment frame structure is 35% lower than the PGA triggering
the first ultimate rotation capacity in the isolated intermediate moment resistant frame.

144

Figure 12 Fragility curves for intermediate and special moment resistant frames.
In the case of structures with seismic isolation systems based on frictional pendulums, the 2013
standard establishes mandatory consideration of response history analysis for designing the isolation
system. This measure is based on the difficulties in predicting the behavior of isolators that base their
response on a friction that depends on the vertical load and displacement rate, varying at each secondon the isolators. Consequently, the code requires that response history analyses include the verticalcomponents of earthquakes. Complementarily, the code clarifies the procedures for determining thetotal displacement of structures with this type of isolation system, given that torsion effects arecontrolled given the centers of mass and stiffness coincide at any moment in time.
The 2013 version of the code includes explicit quality control test requirements for rubber and frictional
pendulum isolators, an aspect which previously was left to the discretion of the structural engineer ofrecord. In particular, and in the case of natural rubber or high damping isolators, 100% of the isolators
in a project require testing. For frictional pendulum isolators, testing is required, as a minimum, for
15% of the isolators in the project, but no less than 4 units.
The code is further complemented with clarifications regarding the requirements for P-Delta analysis,load combinations to be considered for the design of isolation systems and structural components,
inspection and maintenance requirements for isolated structures, gap requirements between isolated
and fixed structures and between isolated structures, and requirements for the design of nonstructuralcomponents in isolated buildings, among other clarifications.
2.3 Second Review of Code for Seismically Isolated Structures Design (2023)
The code is currently under review to further introduce improvements and clarifications oriented toease the implementation of seismic isolation technologies. In consequence, what is described in thissection is still under discussion and it may not be adopted. The first topic in discussion is the seismic
demand considered for designing isolation systems. The committee concluded the need to increase theratio between MCE and DBE from 1.2 to 1.4, without consideration of reducing DBE, which will
result in an increase in design displacements. In addition, the committee agreed to consider the verticalground motion component for the analysis and design of all types of seismic isolation systems. The
incorporation of lambda factors in the code is still under discussion, but probably the factors in
ASCE/SEI 7 will be adopted. Procedures and equations to compute load capacity of elastomericbearings will be explicitly included, with instructions for their correct application. Minimum safety

145factors for load and deformation capacities will be explicitly included to uniformize the criteria among
designers. Finally, the committee agreed on the need and convenience to clarify that nonstructuralcomponents in isolated structures do not need to be designed considering component importancefactors Ip greater than 1, even in critical infrastructures. This initiative is expected to result in savings
making attractive the use of seismic isolation.
3. OTHER DESIGN CONSIDERATIONS AND PROFESSIONAL PRACTICE
3.1 Design considerations for health facilities
In addition to the requirements of the Chilean standard, authorities and practitioners consider their own
criteria. In particular, the Ministry of Public Health and the Ministry of Public Works elaborated in2020 a guideline [9] with specific requirements for designing health infrastructure. The guideline
mandates the use of natural rubber and lead rubber bearings, prohibiting the use of high damping rubber
bearings. The prohibition of HDRB is due to its well know and documented scragging, ageing andreliability issues, and the observed manufacturers’ difficulties to fulfill technical specifications testing
tolerances. The use of lubricated sliders is also prohibited. The use of flat dry sliders is allowed, as far
as the service load on individual sliders does not exceed 1,500 kN. The total service load on sliders
shall not exceed 0.25 times Ws, where Ws corresponds to the seismic reactive weight of the isolated
structure. The first requirement results in the use of sliders in zones of stairs, accesses, patios, and low
service loads in general. The second requirement has the objective to define an upper limit to theactivation of the isolation system.
Given that current Chilean code does not include procedures to consider variation in bearing properties
due to scragging, ageing, temperature, velocity, and travel, among others, the guideline recommends
using the lambda factors procedure available in ASCE/SEI 7 for modeling the isolation system.
Similarly, the guideline stablishes that the safety factors for bearing load capacities shall be greater than
3 and 1 for static and seismic load combinations, respectively. The minimum safety factor for total
shear strain of elastomeric bearings is defined equal to 1.5, including shear strains caused by direct
shear and vertical maximum loads, but excluding shear strains due to rotation. This safety factor shallbe computed considering a shear strain capacity of the rubber equal to 0.85εu, where εu, the ultimate
strain of rubber, shall not be considered greater than 600%. This requirement uniformizes the criteria
considered by designers. While tensile stress up to 2Gr are permitted by certain design codes, where Gr
is the shear modulus of the elastomer, the design criteria for health facilities does not allow tension
forces on bearings, given the difficulties for performing laboratory tests for bearings in tension.
Concrete shrinkage effects shall be considered by adding an initial bearing deformation Do equal to 50
mm to the maximum total displacement DTM of the isolation system. This initial deformation shall beconsidered independent of the construction joints considered in the project. The initial deformation
shall be also considered for determining the static bearing load capacity. This requirement has theobjective to consider shrinkage observed in Chilean cements, which is typically in the range 0.8-1.0
mm/m.
The guideline requests performing probabilistic seismic hazard analysis to determine the seismic
demands to consider for designing the structure (DBE) and the isolation system (MCE). The

146

considered spectra shall not fall below the NCh2745 spectra.
The guideline requests that the capitals below and above the isolators shall be at least 90 cm larger thanthe diameter of the bearing, to accommodate the jacks required to jack the structure, if needed, and tohave enough room to distribute capital’s reinforcement. This requirement does not apply in the building
perimeter, around elevators or other singularities. According to the guideline, all building utilities shallbe placed at least 1.5 m away from the bearings, to ease routine and post-earthquake inspections.
Elastomeric bearings shall be protected with a F-120/180 passive fire protection system tested
according to ASTM E119/ISO 834. The maximum temperature measured by the thermocouples placedat the bearing surface shall not exceed 140 ºC. Before fire testing, the fire barrier shall be mechanicallytested to accommodate at least 10 cycles under a displacement equal to ±DTM without exhibiting any
damage. Testing materials only is not allowed. The full constructive solutions shall be mechanically,and fire tested. The fire barrier shall permit the inspection of the bearings every 5 years (maximum) orafter earthquakes with Mw ≥ 6.
Another important requirement raised by the guideline for hospitals is related to the minimum gap
required around the isolated structure. The document requires to control the probability of pounding
between the isolated structure and surrounding structures to be less than 5% for the DBE, and less than
10% for the MCE level.
3.2 Additional Requirements from Professional Practice
In addition to the requirements described in previous sections, practitioners have further considerations
to make safer designs. Among these considerations, limits to maximum pressures on isolators andseismic isolation activation requirements are found. Practitioners typically limit the maximum pressure
on elastomeric bearings to 17-18 MPa for isolators with diameters in the range 70-115 cm. The
activation of the seismic isolation is controlled by limiting the total characteristic strength (QTot) of theisolation system to be, typically, in the range 0.01-0.03 times Ws, to get an isolation system activatedby the moderate earthquakes that frequently affect the territory. Controlling QTot also allows forcontrolling permanent deformations.
Fig. 13 [10] shows the effects of varying the yield force Fy~1.1QTot and the post yield period (T) on thenormalized base shear (V/Ws) and maximum displacement of a SDOF system subject to a set ofChilean ground motions scaled to the NCh2745 spectrum. Typical post yield periods for hospitals andlarge structures are in the range 4-5 sec. In consequence, for typical Fy and T values, the base shears
and displacements are close to 0.1Ws and 300 mm, respectively.
Fig. 14 [11] shows the residual displacements (Dres) as a function of the total characteristic strength ofa model structure. The blue, orange, green and brown dots correspond to soil Types A (vs ≥ 900 m/s),
B (500 m/s ≤ vs < 900 m/s), C (350 m/s ≤ vs < 500 m/s), and D (180 m/s ≤ vs < 350 m/s), respectively.
In Fig. 14 it can be observed that for typical characteristic strengths values the residual displacements
do not exceed 14 mm.

147

Figure 13 Effect of yield force and post yield
period on base shear and maximum displacement

Figure 14 Residual displacements (Dres) as afunction of characteristic strength

4. CONCLUSIONS
The application of seismic isolation technologies is rapidly growing in Chile. Currently, by January2024, the number of structures incorporating protection devices is close to 200. The good performanceof the protected structures during the Mw 8.8, 2010 El Maule earthquake, demonstrated throughout therecorded response of instrumented structures, triggered an increased demand for the use of protection
devices. The use of protection systems has expanded from demonstration and health facilities projects
to datacenters, viaducts, bridges, and office and tall residential buildings. The observation ofinternational experiences and the execution of technology transfer projects have been fundamental forthese developments. Among the future challenges is the continuous improvement of the codes to makeeven more attractive to investors the use of seismic protection technologies.
REFERENCES[1] Miranda, E., Mosqueda, G., Retamales, R. and G. Peckan (2012) Performance of Nonstructural Components
during the February 27, 2010 Chile Earthquake, in Earthquake Spectra, Vol. 28, N° S1, p453-471.
[2] Nunez, I. (2014) Nuevo Peligro Sismico para Chile, thesis for the degree of Civil Engineer, Department ofCivil Engineering, University of Chile (in Spanish).
[3] ASCE/SEI (2022) ASCE/SEI 7-22: Minimum Design Loads for Buildings and Other Structures, American
Society of Civil Engineers, American Society of Civil Engineers.
[4] Moroni, M., Sarrazin, M. and R. Boroschek (1998) Experiments on a base-isolated building in Santiago,
Chile, Engineering Structures, 20(8), p720-725.
[5] Boroschek, R., Retamales, R. and A. Aguilar (2012) Seismic Response of Isolated Structures Subjected to
the Mw 8.8 Chile Earthquake of February 27, 2010, in Proceedings the International Symposium for CISMID
25th Anniversary, Paper N° M-2, Peru.
[6] Boroschek, R, Moroni, MO, Sarrazin, M. (2003) Dynamic characteristics of a long span seismic isolated
bridge. Engineering Structures 25, 1479–1490.
[7] INN (2003) NCh2745: Analysis and design of buildings with seismic isolation, Instituto Nacional deNormalizacion, Chile.
[8] Toledo, T. and R. Retamales (2015) Analisis de vulnerabilidad sísmica de estructuras con aislacion sísmica
detalladas como marcos especiales e intermedios, in Proceedings of XI Chilean Conference on Seismology and
Earthquake Engineering, Achisina (in Spanish).
[9] MOP (2020) Criterios de diseño de calculo estructural, Segundo Programa de Concesiones de148

Establecimientos de Salud, Ministry of Public Works (in Spanish).
[10] Gomez, G. (2019) Metodologia alternativa para diseño de sistemas de aislacion sismica basado en
optimizacion de desempeño sismico, thesis for the degree of Masters in Structural and Earthquake Engineering,
Department of Civil Engineering, University of Chile (in Spanish).
[11] Barra, T. (2020) Analisis de deformaciones permanentes en estructuras chilenas con sistemas de aislacion
sismica de base, thesis for the degree of Civil Engineer, Department of Civil Engineering, University of Los
Andes (in Spanish).

149

CURRENT STATE AND CHALLENGES OF IMPLEMENTING SEISMIC
ISOLATION IN NEW ZEALAND (2023)

D. WhittakerSenior Technical Director, Beca Limited, Christchurch, New Zealand

ABSTRACTThis paper describes the current state of practice and challenges in the application of seismic
isolation (base isolation) of structures in New Zealand. The widely used lead-rubber bearing
technology was invented by New Zealand scientists. Since 2010 New Zealand has experienced
significant earthquake events causing loss of life, serious damage leading to demolition of alarge number of buildings, as well as large economic impacts. These events have resulted in amove away from designing conventional structures and relying on high levels of ductility,
which often result in irreparable damage. Performance-based design approaches set objectives
for achieving resilient seismic behaviour, including specific objectives for acceptable life safety,
damage occurrence and repairability, as well as functional recovery of structures. Owners andengineers in New Zealand are now more often adopting earthquake protection technologies
including seismic isolation and supplemental damping (energy dissipation) systems such as
dissipative braces, viscous dampers and friction sliding devices. The paper provides examplesof recent new and retrofit projects that have incorporated seismic isolation and performancebased design objectives that exceed minimum code requirements. Challenges to the ongoing
implementation of seismic isolation and other related technologies in New Zealand are
discussed.
KEYWORDS: seismic, isolation, New Zealand, current state, challenges

1

INTRODUCTION

New Zealand is a seismically active country located adjacent to the active Hikurangi subduction
zone [ref. Geonet]. The country has been a leader in development of earthquake resistant
structural design methods such as capacity design, ductile design of reinforced concrete and thedevelopment of seismic isolation and other earthquake protective technologies.
This paper summarises recent progress and developments in the application of seismic isolation(base isolation) for seismic protection of structures in New Zealand. Although New Zealandengineers were instrumental in developing seismic isolation technology, including inventing

150

lead-rubber bearings, use of isolation has been until recently predominantly only for significant
public and high importance buildings. Following severe earthquakes in Christchurch in 2010/11
and Kaikoura in 2016, there has been an increase in the application of isolation and other energy
dissipation technologies for earthquake protection of new and existing buildings, not just forhigh importance buildings. Recent examples of new and retrofit structures using isolation andother energy dissipation technologies are summarised. A New Zealand guideline for design ofisolation systems for buildings has been published to assist designers of isolation systems.
2

APPLICATIONS OF SEISMIC ISOLATION IN NEW ZEALAND

2.1 Growth of number of isolated structures
Based on the author’s personal enquiries, as at late 2023, there are now approximately 110
isolated structures in New Zealand. Fig. 1 shows the growth in numbers of isolated structures
over time including the types of structures and isolation technology. Around half of the total
number of structures are bridges and there has been a steady increase in the overall number ofisolated structures from 2010, since the Canterbury earthquakes.

Figure 1. Growth in numbers of structures with seismic isolation in New Zealand.
2.2 Examples of Building Projects with Seismic Isolation
Fig. 2 shows the new 50-bed Children’s hospital recently built in Wellington [ref. McKee Fehl].
The hospital is a three-level 8,000 m2 floor area building supported on 45 Triple Pendulum™
isolators, providing seismic protection to withstand a 1-in-2500-year event in a high seismicity
zone. This required the isolators to accommodate substantial horizontal isolator displacementsof 1500 mm, which is the largest displacement provided in an isolation system in New Zealand
to date.
Fig. 3 shows the Christ Church Cathedral located in the centre of Christchurch which was
extensively damaged by the Canterbury earthquake sequence of 2010/2011. Damage to thelargely unreinforced masonry building included collapse of the bell tower and significant
dislocation of walls in the building. Previous localised strengthening work likely helped thebuilding survive the earthquakes without more extensive collapse. Repair and strengthening of
the cathedral [ref. Christ Church Cathedral] is currently in progress and has included a carefully151managed sequence of external stabilization, insertion of a new ground floor slab and raft subfoundation, new structural walls and tie elements, and extensive re-construction and groutingof the masonry walls. The final stage of the restoration includes retrofit of seismic isolation
under the building to protect the repaired and strengthened building against future earthquakes.

Figure 2. Left: New isolated Wellington Children’s Hospital. Right: Triple Pendulum™
isolator diagrammatic.

Figure 3. Earthquake repair including base-isolation of historic Christ Church Cathedral.
Left: building under repair. Right: graphic of digital model used for engineering analysis.
3

NEW ZEALAND GUIDELINE FOR DESIGN OF SEISMIC ISOLATIONSYSTEMS FOR BUILDINGS

A guideline [ref. Isolation Guideline, 2019 and Whittaker 2020] for the design of seismic
isolation systems for buildings in New Zealand was recently published for trial use by designers.
The Guideline sets a framework and recommendations for designing buildings with seismic
isolation, in accordance with the New Zealand Building Code [ref. Building Performance] andthe Structural Loading Standard NZS 1170.5 [ref. Loading Standard]. It provides displacementbased analysis and design recommendations that supplement the requirements for normalbuildings to account for period elongation and additional damping available in building
structures with isolation systems.
The Guideline covers four prescribed isolated building types from simple to complex. The

152

chapters include: performance objectives for isolated buildings, design limit states and design
philosophies, design spectra for acceleration and displacement demands, analysis methods,
design approaches to be used for the various components of an isolated building; iesuperstructure, isolation system and substructure, detailing of the isolation plane, guidance on
preparing technical specifications for procurement of the isolation system and isolator devices,
recommendations for inspection and maintenance of the isolation system and components. The
content of each Chapter is presented as recommendations (normative) and associatedcommentary (informative).
This project was led by technical societies and funded largely by government agencies. The
Guideline was prepared by national specialists and reviewed by several international experts.
The Isolation Guideline provides both acceleration and displacement spectra for design ofisolated structures. The design spectra are based on NZS 1170.5 [ref. Standards NZ] elastic
acceleration design spectra and derived displacement spectra, including adjustment for theoverall equivalent level of viscous damping in the isolated building system. Once the global
design actions are established, the methodology then determines the required actions for designof the isolation system, substructure and superstructure, in accordance with appropriatematerials design standards (eg for concrete and steel structures).
Although the Isolation Guideline currently has no formal or legal status, is generally regarded
as being the authoritative and accepted guidance for designing isolated buildings in New
Zealand. The Guideline content is relevant for design of structures with other earthquake
protective technologies such as supplemental damping that are also not within the scope ofcurrent New Zealand design codes. Each technology and system type requires specific design
to reflect relevant performance characteristics.
Whittaker [reference 2020] presented examples of acceleration and displacement demands on
isolated structures using the Isolation Guideline document. The behaviour of the typicalisolation system is based on a yielding bilinear hysteretic system, which can be represented by
the generalised expression for an equivalent curved surface slider system given in Equation 1.
The system behaviour for an elastomeric system using lead rubber bearings, can be expressedin a similar equation form representing overall system yield force and elastic restoring force
terms.
𝑉

𝑊 𝑓

∆

(1)

where Vb is the base shear force at the isolation plane
W is the isolated superstructure weight
𝑓 is the friction coefficient (and W𝑓 is the effective yield force of the system)Ris the horizontal displacement of the isolation systemis the radius of curvature for the equivalent curved surface slider system.

The isolation system base shear versus displacement behaviour can be depicted on an
acceleration versus displacement response graph, together with the earthquake acceleration
versus displacement demand spectrum (the so-called “ADRS” spectrum). This ADRS format
plot conveniently allows capacity-demand diagrams, such as the example shown in Fig. 4 (left),153to estimate acceleration and displacement response demands on the isolation system. Also
shown in Fig. 4 (right), is an example parametric design chart (nomogram) that was derived
from the Isolation Guideline by considering a range of typical isolation system parameters at a
Christchurch location, where the ground conditions are typically deep soft soils. The nomogram
considers a practical range of key isolation system parameters including yield level ranging
from 6% to 12% of the isolated weight and post-elastic slope corresponding to a range ofequivalent curved surface isolator radii from 2 m to 6 m. The reference to “CALS” in the
diagram is to an explicit “Collapse Avoidance Limit State” used in the Isolation Guideline,
being a limit state considering survival of a maximum considered rare earthquake. Parametric
nomograms for other locations and site conditions were also reported in Whittaker [2020].

Figure 4. System response graphs in acceleration-displacement format, showing demands
for isolated buildings in Christchurch according to the NZ Isolation Guideline. Left graphshows an example isolation system response against design earthquake demands. Rightgraph shows parametric demands for various levels of system yield and effective radiusof curvature for an equivalent curved surface slider system.
4

CHALLENGES FOR IMPLEMENTATION OF SEISMIC ISOLATION

The following subsections discuss a number of challenges that designers in New Zealand facewhen conceiving and implementing seismic isolation for structures.
4.1 Isolation Versus Other Protective Technologies
It is not easy for designers to compare and quantify the performance benefits and costs of othercompeting technologies such as dissipative braces and supplemental damping systems
including Buckling Restrained Braces (BRBs), friction devices and fluid viscous dampers(FVDs). These systems do not have the beneficial feature of an isolation plane where large
seismic movements can be directed and accommodated. On the other hand, these systems avoid
the cost and complexity that an isolation plane brings.
Table 1 provides a qualitative comparison of some characteristics of different seismic protection
systems, including conventional fixed-base construction, based on the author’s experience.

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Table 1. Comparison of seismic protection systems.
Protective System
Conventional Fixedbase (eg moment
frame, cross-braced
frame or wall)
Seismic Isolation

Fluid Viscous
Dampers

Benefits
Code compliance requirements clear.
Cost savings with high ductility.
Optional performance in excess of code.
Can select ductility and repairability.
Generally best protection possible.
Reduced superstructure sizes and cost.
Protection of structure, building fabric &contents from damage and disruption.
Large reduction of drifts & accelerations.
Concentrates deformation in isolators.
Excellent functional recovery.
Extensive global use and experience.
Design codes / guidelines available.
Can reduce response significantly.
Maximum damping forces out of phasewith elastic forces.
Can be optimised to limit number.

Friction system(part of frame orbraced or rocking
system)Rocking system

Inelastic deformation & damping indevices.
Can also provide re-centering if required.
Proprietary products available.
“Partial” isolation solution

Buckling
Restrained Braces(BRB)

Direct and efficient bracing system.
Well-established international supply.

Potential Disadvantages
Ductility brings damage which can bedifficult or uneconomic to repair.
Large structure sizes in high seismic
zones with low ductility.
Alternative code compliance (in NZ).
Cost premium over conventional.
Requires space for isolation plane / gap.
Cost of isolators and additional
suspended structure over isolation plane.

Must be used with elastic primarystructure to provide re-centering.
No easy path to code compliance.
Typically used in braced configurations
which impacts usable floor area.
Normal application needs many devices.
No easy path to code compliance.
Flag-shaped hysteresis gives limited
additional damping.
Special study for NZ code compliance.
Drifts in superstructure large to achieve
period shift and force reduction.
Alternative path to code compliance.
Attracts large forces and floor
accelerations. Large brace members
impact usable area.

4.2 Which Isolation Technology to Use
Most practicing engineers in New Zealand have limited experience to assess the performance
characteristics, costs and benefits of each isolation technology and which is best suited to theirproject. Engineers are reliant on published case studies and advice from specialists and suppliers.
The two common systems used in New Zealand recently are laminated rubber bearings(including lead) in combination with flat slider bearings and curved surface slider (pendulum)
bearings. Although not common in New Zealand to date, there may be advantages in using
laminated rubber or lead rubber bearings in conjunction with viscous dampers to achieve greater
reduction of superstructure response.
4.3 Knowledge of Structural Engineers
Application of new earthquake protective technologies such as seismic isolation requires
practitioners to develop new knowledge and skills to reliably design building systems
containing them. Design of these systems requires knowledge and consideration of the155following: Using displacement-based design methods and utilising supplemental damping.
 Selecting performance-based design strategies to achieve performance outcomes,
possibly in excess of code minimum requirements.
 considering damage control and repairability, and reducing functional recovery times.
 Meeting sustainability targets including measuring and reducing embodied carbon.
4.4 Building Code Compliance
Many of the available protective technologies are not explicitly covered by design codes andrequire alternative compliance pathways, as well as specialist peer review. The New Zealand
Building Code is performance-based, but compliance is normally achieved following citeddesign Standards, known as Verification Methods. The Building Code also permits complianceusing Alternative Solutions using guidelines or methods that are not cited but may be accepted,
normally with appropriate peer review. These approaches can bring increased risk of noncompliance and unintended outcomes, so care is needed.
4.5 Specification Supply and Testing of Devices
Seismic protection devices are usually proprietary, meaning they are designed andmanufactured by the supplier to meet performance requirements specified by the building
designer. In New Zealand almost all isolation devices are imported from international suppliers
and most prototype and production testing is also carried out overseas by the supplier orapproved test agency, with independent oversight and verification. Designers and specifiers
need to be familiar with these procurement processes to ensure reliable outcomes are achieved.
The New Zealand Isolation Guideline provided guidance for specifying isolation systems anddevices including sample technical specifications for typical isolation devices followinginternational standards such as EN 15129 or ASCE 7-17 Chapter 17.
4.6 Revised New Zealand National Seismic Hazard Model
The seismic hazard in New Zealand has recently been updated [ref. GNS Science 2022]. For
some parts of the country the seismic hazard appears to have increased significantly, perhaps
up to 2 times, compared with the current code hazard maps. These increases in hazard, if
reflected fully in the design standard, will lead to substantial increases in seismic design actions
and displacement demands, as well as costs, in all structures, including those with isolation.
4.7 Earthquake Insurance Availability
The availability of earthquake insurance is relatively high in New Zealand. It is understood that
more than 80 percent of property damage from recent major earthquakes in New Zealand wasinsured. New Zealand has a government-led Earthquake Commission (EQC) fund which
provides first-cover for residential properties, including land damage from earthquakes. As at
2023, this scheme provides first-cover up to around US$200,000 per residential property fornatural disaster events. Most residential property owners purchase additional top-up earthquake
insurance cover, up to an agreed insured value. Commercial properties are generally insured forearthquake damage, under material damage insurance policies. Insurance premiums are likely156

to increase under the influence of sporadic seismic activity and anticipated more extreme
weather events. Hopefully, increases in natural and seismic hazards will lead to greater interestin seismic risk mitigation, such as use of seismic isolation, rather than passing risk to insurers.
Global sustainability pressures will likely also encourage further development and uptake ofseismic resilient and protective technologies such as seismic isolation.
5

CONCLUSION

Seismic isolation remains the premier earthquake protection technology in New Zealand. Useof seismic isolation and other supplemental damping technologies has increased steadily
following recent severe and damaging earthquakes. Owners and engineers are increasingly
recognising the significant performance and life-cycle benefits that these technologies bring to
reducing disruption and improving functional recovery of buildings and their contents. The
benefits include increases in safety, as well as reductions in the frequency and severity ofdamage and downtime to repair any damage that does occur. These trends are likely to continue
with the increased focus on sustainability and increasing earthquake insurance premiums.
A recently published New Zealand guideline for design of buildings with seismic isolation helps
designers of these systems meet the requirements of the national building code. Peer review isa key step in ensuring designs meet national standards and stated performance objectives.
In addition to seismic isolation, other energy dissipation and supplemental device technologies
are now being routinely used in New Zealand, including dissipative braces, fluid viscousdampers, friction slip devices and design using rocking foundations.
Seismic isolation and other supplemental energy dissipation technologies are essential for
protecting buildings and their occupants from future earthquakes in New Zealand.
REFERENCES[1] Building Performance, https://www.building.govt.nz/building-code-compliance/building-code-andhandbooks/[2] Christ Church Cathedral Reinstatement Project https://christchurchcathedral.org.nz/.

[3] GNS Science website https://www.gns.cri.nz/our-science/land-and-marine-geoscience/ourplate-boundary/hikurangi-subduction-zone[4] GNS Science report; 2022/57. doi:10.21420/TB83-7X19, https://nshm.gns.cri.nz/.
[5] https://www.mckeefehl.co.nz/our-projects/the-wellington-childrens-hospital-case-study/[6] New Zealand National Seismic Hazard Model 2022 Revision: model, hazard and process overview,[7] New Zealand Parliamentary Council Office, Natural Hazards Insurance Act 2023.
[8] New Zealand Society for Earthquake Engineering, “Guideline for the design of seismic isolation
systems for buildings”, June 2019. https://www.nzsee.org.nz/wp-content/uploads/2019/06/2825Seismic-Isolation-Guidelines-Digital.pdf.
[9] NZS 1170.5:2004, “Structural Design Actions, Part 5: Earthquake Actions – New Zealand”,
Standards New Zealand.
[10] Whittaker, D., “Guideline for Design of Buildings with Seismic isolation in New Zealand”, 17th
World Conference on Earthquake Engineering, Sendai, Japan, 2020.

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