Finite element analysis of nonlinear mechanical behavior of series seismic isolation system based on tests

In order to study the nonlinear mechanical behavior of series Seismic Isolation System (SIS) composed of lead-rubber bearing (LRB) and reinforcement concrete (RC) column, 8 groups of SIS finite element (FE) models with LRB were established based on the LRB test and shaking table test of SIS. Firstly, LRB was analyzed using the FE software MARC, and numerical results show that the achieved equivalent stiffness and hysteretic curves are basically identical to the LRB test results. Secondly, 8 groups of SIS models were analyzed with Pushover method and under cyclic loads with different amplitude for the nonlinear mechanical behaviors of SIS, including the relationship curve of force and deformation, characteristic bearing capacity, stiffness, damping ratio and damage characteristics. Then, the effects of aspect ratio of RC column on these mechanical behaviors of SIS were investigated. Finally, the equivalent stiffness from the FEA analysis was compared with that of SIS test, the trends are basically consistent. The results indicate that nonlinear mechanical behaviors of LRB have obvious influences on those of SIS, and the effects of RC column on nonlinear mechanical behaviors of SIS may increase with increasing the aspect ratio of RC column when it is larger than 4. As a result, the damage limit value and safety limit value for aspect ratio of RC column are suggested to be 3.5 and 5, respectively, which offers reference for structure design. ©, 2015, Tumu Gongcheng Xuebao/China Civil Engineering Journal. All right reserved.