The Effects of Soil-structure Interaction on the Seismic Performance of a Base-isolated 13-Story RC Building Founded on Soft Soil

Abstract

Base isolation (BI) is a proven technique for reducing seismic demands on buildings, enhancing resilience, and maintaining post-earthquake functionality with minimal repairs. However, its effectiveness on soft soil remains uncertain due to soil–structure interaction (SSI), which can alter the building’s fundamental period and compromise the benefits of BI. This issue is critical, as many densely populated, high-seismicity cities are located on soft soil. This study investigates a 13-story building equipped with a lead–rubber bearing (LRB) isolation system on soft soil using nonlinear time-history analysis (NLTHA) that explicitly incorporates SSI effects. The results show that the BI system significantly increased the fundamental period by approximately 114% and reduced base shear by up to 47%. In addition, inter-story drift and peak acceleration were reduced by up to 49% and 48%, respectively. On the other hand, SSI increased base shear by up to 52% in the fixed-base model and approximately 76% in the base-isolated model. SSI also increased peak acceleration by up to 14% and 13% in the fixed-base and base-isolated models, respectively, highlighting its adverse impact on structural performance. Nevertheless, the BI system remained effective in mitigating seismic demands even in the presence of SSI. These findings emphasize the importance of incorporating SSI in seismic analysis and support the applicability of BI systems for high-rise buildings on soft soil.