Conventionally, structural designers are concerned about the safety of buildings, bridges, and other civil

engineering structures that are subjected to earthquakes. The recent history of earthquakes reveals that

strong earthquakes, such as the 1994 Northridge earthquake (U.S.A.), 1995 Kobe earthquake (Japan),

and 1999 Chi-Chi earthquake (Taiwan), can cause some badly designed structures or buildings to fail or

collapse, and also cause some well-designed structures to malfunction due to the damage or failure of the

equipment housed in the structure or building. Both the failures of structures and equipment, also

known as structural and nonstructural failures, respectively, can cause serious harm to the residents or

personnel working in a building. For the case where the equipment is part of a key service system, such as

in hospitals, power stations, telecommunication centers, high-precision factories, and the like, the lives

and economic losses resulting from the malfunctioning of the equipment can be tremendous. Thus, the

maintenance of the safety of structures and attached equipment during a strong earthquake is a subject of

high interest in earthquake engineering. In this regard, base isolation has been proved to be an effective

means for protecting the structures and attached equipment, which is made possible through reduction

of the seismic forces transmitted from the ground to the superstructure (Yang et al., 2002).