Seismic soil-structure interaction in buildings on stiff clay with embedded basement stories

The increasingly popular performance-based design approach requires that soil-structure interaction (SSI) analysis become an integral part of the seismic evaluation. This is particularly important for structures with substantial embedment. The primary objectives of this study are twofold: (i) evaluate the SSI effects for buildings with a basement and (ii) evaluate the ability of two analytical methods to account for SSI effects in seismic design - an analytical solution for kinematic SSI and a nonlinear finite element model. Scaled model shaking table tests were performed on a model building with an embedded basement founded in a synthetic stiff clay deposit enclosed in a laminar soil container. The model structure used in this study comprised a simple single-degree-of-freedom structure with a modular box foundation designed to permit consideration of structures with different basement embedment depths. The experimental results showed that the ratio of effective period of the soil-structure system to that of the structure (T/T) decreased for the long-period structure and increased for the short-period structure, with increasing embedment. The results confirm the ability of the analytical techniques to predict with reasonable accuracy the SSI effects for buildings with embedded parts.