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Seismic Isolation in Buildings to Be a Practical Reality: Behavior of Structure and Installation Technique

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Seismic Isolation in Buildings to Be a Practical Reality: Behavior of Structure and Installation Technique Journal of Engineering and Technology Research Vol. 3(4), pp. 99-117, April 2011 Available online at http:// www.academicjournals.org/JETR ISSN 2006-9790 ©2011 Academic Journals Full Length Research Paper Seismic isolation in buildings to be a practical reality: Behavior of structure and installation technique A. B. M. Saiful Islam*, Mohammed Jameel and Mohd Zamin Jumaat Department of Civil Engineering, University of Malaya, Kuala Lumpur, Malaysia. Accepted 17 February, 2011 Although a great deal of research has been carried out regarding seismic isolation, there is a lack of proper research on its behavior and implementing technique in low to medium seismic region. The basic intention of seismic protection systems is to decouple the building structure from the damaging components of the earthquake input motion, that is, to prevent the superstructure of the building from absorbing the earthquake energy. This paper reviews a number of articles on base isolation incorporation in building structure. Lead rubber bearing (LRB), high damping rubber bearing (HDRB), friction pendulum system (FPS) have been critically explored. This study also addressed the detail cram on isolation system, properties, characteristics of various device categories, recognition along with its effect on building structures. Meticulous schoolwork has also been accomplished about installation technique for various site stipulations. The entire superstructure is supported on discrete isolators whose dynamic characteristics are chosen to uncouple the ground motion. Displacement and yielding are concentrated at the level of the isolation devices, and the superstructure behaves very much like a rigid body. Rigorous reckoning illustrated the isolation system as very innovative and suitable in buildings to withstand the seismic lateral forces and also contributed to safety ensuring flexibility of structures. Key words: Seismic protection, base isolation, idealized behavior, hysteresis loop, ductility, installation technique. INTRODUCTION To minimize the transmission of potentially damaging elements can actually help to minimize earthquake earthquake ground motions into a structure is achieved damage to buildings, considering the tremendous forces by the introduction of flexibility at the base of the structure these buildings must endure in a major quake (Cheng et in the horizontal direction while at the same time al., 2008; Islam and Ahmad, 2010). Contrasting the introducing damping elements to restrict the amplitude or conventional design approach based on an increased extent of the motion caused by the earthquake somewhat resistance (strengthening) of the structures, the seismic akin to shock absorbers. In recent years this relatively isolation concept is aimed at a significant reduction of new technology has emerged as a practical and eco- dynamic loads induced by the earthquake at the base of nomic alternative to conventional seismic strengthening. the structures themselves (Micheli et al., 2004, , Islam et This concept has received increasing academic and al., 2010a, 2010b). Seismic isolation separates the professional attention and is being applied to a wide structure from the harmful motions of the ground by range of civil engineering structures. To date there are providing flexibility and energy dissipation capability several hundred buildings in Japan, New Zealand, United through the insertion of the isolated device so called States, India which use seismic isolation principles and isolators between the foundation and the building technology for their seismic design. structure (Ismail et al., 2010). It may come as a surprise that the rubber foundation Invention of lead rubber bearing (LRB, 1970's) and high damping rubber bearing (HDRB,1980's) gives a new dimension to the seismic base isolation design of BI structure (Islam, 2009; Hussain et al., 2010). ICBO *Corresponding author. E-mail: [email protected]. Tel: (1997) included design specification for isolated +60102573287. Fax: +60379675318. structures as in Uniform building Code, UBC 1997. A 100 J. Eng. Technol. Res. significant amount of both past and recent research in the SEISMIC ISOLATION COMING TO REALITY area of base isolation has focused on the use of elastomeric bearings, such as HDRB and LRB (Islam et Seismic isolation is intended to prevent earthquake al., 2011a, 2011b). Providakis (2008) investigated damage to structures, buildings and building contents. seismic responses of multi- storied buildings for near fault One type of seismic isolation system employs load motion isolated by LRB. Dall’Asta and Ragni (2006, bearing pads, called isolators. They are located strate- 2008), Bhuiyan et al. (2009) covered experimental tests, gically between the foundation and the building structure analytical model and nonlinear dynamic behavior of and are designed to lower the magnitude and frequency HDRB. of seismic shock permitted to enter the building. They Although it is a relatively recent technology, seismic provide both spring and energy absorbing characteristics. isolation for multi storied buildings has been well Figure 1 illustrates the behavior change of structure evaluated and reviewed (Barata and Corbi, 2004; Hong without isolator and with isolator incorporation. and Kim, 2004; Matsagar and Jangid, 2004; The first seismic isolation system was proposed by Dr. Komodromos, 2008; Lu and Lin, 2008; Spyrakos et al., Johannes Calantarients, an English medical doctor, in 2009; Polycarpou and komodromos, 2010). Base isolator 1909. His diagrams show a building separated from its with hardening behavior under increasing loading has foundation by a layer of talc which would isolate the main been developed for medium-rise buildings (up to four structure from seismic shock. The oldest base isolated storeys) and sites with moderate earthquake risk structure of the world, Mausoleum of Cyrus, is shown in (Pocanschi and Phocas, 2007). Nonlinear seismic res- Figure 2. ponse evaluation was performed by Balkaya and Kalkan This technology can be used both for new structural (2003). design and seismic retrofit. In process of seismic retrofit, Resonant behaviour of base-isolated high-rise buildings some of the most prominent U.S. monuments like under long-period ground motions was dealt by Ariga et Pasadena City Hall, San Francisco City Hall, Salt Lake al. (2006) and long period building responses by Olsen et City and County Building or LA City Hall. The seismic al. (2008). Deb (2004), Dicleli and Buddaram (2007), rehabilitation of the Los Angeles City Hall is a landmark Casciati and Hamdaoui (2008), Di Egidio and Contento event in the City's history. For Los Angeles City Hall (2010) have also given effort in progresses of isolated (Figure 3a), in process of seismic upgrading, this high- system. Komodromos et al. (2007), Kilar and Koren rise building was placed atop a mechanical system of (2009) focused the seismic behavior and responses isolators, sliders and dampers called base isolation through dynamic analyses of isolated buildings. Wibowo technology. Later on a few famous isolated buildings et al. (2010) have done the failure and collapse modeling have also been shown in Figure 3. Bhuj Hospital (Figure analysis of weak storey building. The low to medium 3b), New Zealand Assembly Library (Figure 3c) and New earthquake risk region is prone to seismic hazard in the Zealand Parliament (Figure 3d) have been erected on United States too. Many places at the Midwestern areas Lead Rubber bearing type base isolator. Isolation system in US (Southern Illinois, Kentucky, Southern Indiana etc) was also inserted at Te Papa Museum of New Zealand experience low to moderate seismicity. However, for (Figure 3e). Figure 3f shows the practical construction of building construction in these zones, seismic base inserting seismic isolation system in Te Papa Museum isolation can be a suitable alternative as it ensures building. flexibility of building and reduces the lateral forces in a Early concerns were focused on the fear of uncon- drastic manner. Apart from this as the additional cost of trolled displacements at the isolation interface, but these using the system is favorable; these sites can also benefit have been largely overcome with the successful develop- from implementation of this base-isolation system, ment of mechanical energy dissipaters. When used in especially in such buildings as museums, data centers combination with a flexible device, an energy dissipater etc. Though the application of isolator is going to be very can control the response of an isolated structure by familiar all over the world, there is a lack of proper limiting both the displacements and the forces. Interest in research to implement the device practically in low to base isolation as an effective means of protecting medium risk seismic zone especially for local buildings in structures from earthquakes has therefore, been revived Dhaka, Bangladesh region as per the local requirements. in recent years. So, this concern is a very burning matter for this study. The following are the advance developments (Kelly, Site specific earthquake data are also very important in 1998) that have enabled base isolation to be a practical seismic design. This study focused on the detail revise on reality. isolation system, characteristics of various device categories, recognition along with its effect on building (a) The design and manufacture of high quality isolation structures. Thorough schoolwork has also been bearings that are used to support the weight of
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