Seismic performance of an LRB-isolated structure with EIMD under near-fault pulse-like ground motions

Abstract

Under near-fault pulse-like ground motions, base-isolated structures (BIS) are prone to isolation bearing failure due to excessive base floor displacement. To mitigate this risk, hybrid base isolation systems, which incorporate passive dampers with isolation bearings, offer a promising solution. This paper proposes a novel hybrid base isolation system that combines an electromagnetic inertial mass damper (EIMD) with a lead-rubber bearing (LRB), aiming to reduce the base floor displacement while further improving the isolated superstructure’s seismic performance. Firstly, the force-displacement relationship of the bearing is described by the Bouc-Wen hysteretic model and a linear damping model, while a linearized mechanical model is adopted for the EIMD. The motion equations of a 10-storey LRB-isolated building model with EIMD are subsequently established. Next, the influence of the inertance-to-mass ratio on the natural period of the LRB-isolated building model with EIMD is investigated. Then, based on the average seismic responses of the LRB-isolated building model with EIMD subjected to 18 near-fault pulse-like ground motions, the control law of EIMD on the base floor displacement, superstructure interstory drift and absolute acceleration is studied. Finally, the nonlinear time-history responses of the LRB-isolated building model with EIMD and with viscous damper (VD) are compared, and the superiority of EIMD’s performance is demonstrated.