Soil-structure Interaction At TheEl Centro Terminal Substation

Abstract

The objective of this paper is to report on possible soil-structure effects that may have affected previously recorded earthquake motions at the instrument site housed in the Terminal Substation Building in El Centro, California. This site was selected for this study as more strong motions accelerograms have been recorded at this site than at any other site in the United States. The soil-structure effects were analyzed using the pseudo three-dimensional plane strain finite element program FLUSH. The comparison of recorded and computed motions revealed the existence of interaction effects that may be attributed to the underlying soft soils and the very stiff structure of the El Centro Terminal Substation Building. These effects are strong at high frequencies (i.e. from 8 to 10 Hertz). As expected, it was also observed that at the higher frequencies and accelerations, soil nonlinearity had a significant influence on the recorded motions. INTRODUCTION During an earthquake, the ground shaking is typically recorded by a strong motion accelerograph. Such records may be made at locations in the free field (i.e. away from nearby structures) or within buildings. Typically, the recording made within a building will be influenced by the inertial forces generated by the structure. However, the nature and magnitude of this soil-structure influence has only been investigated recently (Crouse et al. [1]; Luco et al. [2]; Moudud [3]). This study reports on the possible soil-structure interaction effects that may have influenced motions recorded within the Terminal Substation Building in El Centro, California. This accelerograph station has contributed more records to the current library of strong motion data than any other station in the western United States. Thus it would be relevant and pertinent that the influence of SSI effects be examined for this site. Transactions on the Built Environment vol 3, © 1993 WIT Press, www.witpress.com, ISSN 1743-3509 582 Soil Dynamics and Earthquake Engineering