2012 NZSEE Paper Template

This research presents the impact of base fixity on seismic analysis including soil-structure interaction (SSI) considering linear and nonlinear soil-foundation interface conditions. A set of inelastic time history analyses using a yielding singledegree-of-freedom structural system with different fixity conditions at the base are used. The base fixity configurations considered are: 1) fixed-base; 2) linear flexible-base; 3) nonlinear flexible-base without uplift; and 4) nonlinear flexible-base with uplift. A suite of 40 ground motions with large-magnitude and moderate-distance is chosen to ensure robustness of the results across realistic ground motions. The examination of SSI effects on the structural response under a design base earthquake (DBE) level, i.e. 500-year return period event, is carried out for all considered scenarios. In addition, the effects of an increase in the seismic intensity up to a maximum credible earthquake (MCE) level, i.e. 2500-year return period event, are also studied for the case of nonlinear flexible-base with uplift. The results illustrate the degree of residual foundation deformation as well as the impact of SSI on structural acceleration, total displacement and ductility. In this context, the importance of SSI effects for a design procedure as well as the difference between linear and nonlinear SSI considerations is highlighted.