Influence of foundation flexibility on the seismic response of low-to-mid-risemoment resisting frame buildings

Recent studies show that the effects of soil–structure interaction (SSI) may be detrimental to the seismic response of structure and neglecting SSI in analysis may lead to un-conservative design. The objective of this study is to simulate the performance of multi-story building-foundation systems through a Winkler-based approach. Four typical steel moment resisting frame (MRF) buildings on three soil types with shear wave velocities less than 600m/s subjected to actual ground motion records of varied hazard levels are modeled with and without SSI. It is observed that the performance level of models supported by flexible foundation, particularly in an intense earthquake event,may alter significantly in comparison to fixed-base structures.Moreover, for MRFs on soft soil, the nonlinear foundation is found to have a significant effect on the force and displacement demands. This is indicating the necessity for consideration of flexible foundation behavior in the modern design codes in order to accomplish a more economic yet safe structural design.