Seismic Safety Assessment of Base-Isolated Buildings Using Lead-Rubber Bearings

Lead-rubber bearing (LRB) is a well developed and implemented isolation technology. One of the design challenges is to prevent LRBs from buckling during strong earthquake shaking. Although detailed component behavior of LRB under combined axial and shear loads has been well investigated, the seismic performance of base-isolated buildings with LRBs has not been systematically examined. In this study, the robust finite element model of the LRB, which accounts for the axial and shear coupling, has been used to examine the seismic performances of two prototype buildings, each with different LRB geometric properties, structural periods, and axial loads. The results of nonlinear dynamic analyses show that the axial and shear coupling response of the LRB play an important role in the safety of base-isolated buildings. A simple amplification factor of 2.5 is proposed to increase the axial capacity of the LRB when the shear deformation reaches the maximum total displacement. The results show that such a simple amplification factor can produce low probability of failure of LRB buildings during strong earthquake shaking.