Effects of unbounded media on seismic responses of FPS‐isolated structures

Base isolation protects buildings against severe earthquakes. The reduction in seismic loadings on the building can be achieved by inserting horizontal soft isolation elements between the superstructure and foundation. The efficiency of the isolator in reducing seismic energy imparted to a structure is very dependent on the flexibility of the supporting soil. The effects of radiation damping and the flexibility of the soil medium should be taken into account. This paper presents the interactive behavior of a FPS-isolated building and the soil with an unbounded region during earthquakes. To yield more accurate results, a rigorous procedure in the time domain accounting for radiation damping for the unbounded soil and the FPS-isolated building has been developed. Significant differences between the system with and without radiation damping and the flexibility of supporting soil have been observed in this study. Numerical results also reveal that interaction effects between the isolated building and the unbounded soil medium is very important. Copyright © 2004 John Wiley & Sons, Ltd.