Analytical Study of Effects of Near-Fault Ground Motion on Seismically Isolated Structures

Analytical Study of Effects of Near-Fault Ground Motion on Seismically Isolated Structures

The concept of seismic isolation design is accepted as an effective method for the seismic mitigation of structures. However, in Taiwan, an earthquake prone island, many sites are located in near-fault zones. The recorded seismic waves have near-fault characteristics such as velocity pulses and displacement pulses. These seismic waves may cause excessive displacement demand on the isolation system, and transmit significant acceleration to the superstructure. Consequently, the design of seismically isolated structures located in nearfault areas is challenging. The objective of the study is to develop a suitable design strategy for an isolation system to resist near-field ground motion. The code-specified procedure is examined for their appropriateness of designing seismic isolation system against near-fault ground motions. A design procedure is proposed for the isolation system composed of lead-rubber bearings and viscous dampers. Results show that the proposed procedure can lead to controllable maximum displacement of the isolation system and an acceptable acceleration transmitted to the superstructure.