Seismic response of a mid-story isolated structure considering SSI in mountainous areas under long-period earthquakes

At present, there is not much research on mid-story isolated structures in mountainous areas. In this study, a model of a mid-story isolated structure considering soil-structure interaction (SSI) in mountainous areas is established along with a model that does not consider SSI. Eight long-period earthquake waves and two ordinary earthquake waves are selected as inputs for the dynamic time history analysis of the structure. The results show that the seismic response of a mid-story isolated structure considering SSI in mountainous areas can be amplified when compared with a structure that does not consider SSI. The structure response under long-period earthquakes is larger than that of ordinary earthquakes. The structure response under far-field harmonic-like earthquakes is larger than that of near-fault pulse-type earthquakes. The structure response under near-fault pulse-type earthquakes is larger than that of far-field non-harmonic earthquakes. When subjected to long-period earthquakes, the displacement of the isolated bearings exceeded the limit value, which led to instability and overturning of the structure. The structure with dampers in the isolated story could adequately control the nonlinear response of the structure, effectively reduce the displacement of the isolated bearings, and provide a convenient, efficient and economic method not only for new construction but also to retrofit existing structures.