DEVELOPMENT AND APPLICATION OF ISOLATION BEARING ELEMENT CONSIDERING BI-DIRECATIONAL COUPLED INTERACTION

Abstract

Base isolation technology, which introduces isolated bearings between the top of foundation and upper structure, is regarded as an effective method to reduce seismic energy absorbed by the upper structure. Lead rubber bearing (LRB), that is, a representative seismic isolation device, has been widely used in isolated structural systems. An isolation bearing element for simulating the behavior of LRB was developed with the user element subroutine (UEL) feature of ABAQUS, which was further introduced into seismic analysis of the base-isolated structure with LRB. The Bouc-Wen bi-directional coupled restoring force model was adopted in the developed element to describe the nonlinear hysteric characteristics for LRB in the lateral direction. Meanwhile, the strength differences of LRB in the vertical direction were also included in the element. The accuracy of the isolation bearing element was verified by close agreement between numerically predicted hysteresis curves and experimental counterparts. Moreover, the nonlinear earthquake responses of a four-story reinforced concrete structure isolated by LRB with and without the bi-directional coupled interaction of bearing restoring forces were separately explored, and it was revealed that the bi-directional coupled interaction had considerable effects on the seismic responses of the isolated buildings. Once these coupled interaction effects were not taken into account, the displacement of LRB was underestimated while the bearing capacity would be over-predicted, which had a detrimental effect on the design of isolated buildings.