Prediction of long-term creep deflection of seismic isolation bearings

Abstract

Isolation structures use high damping rubber bearings (HDRBs), lead rubber bearings (LRBs), and natural rubber bearings (NRBs) in order to significantly reduce the seismic forces transmitted from a substructure to a superstructure. The laminated rubber bearing is the most important structural member of a seismic isolation system. We present an analysis of a 1000 hr ongoing creep test conducted at 7.5 and 8.37 MPa in our laboratory. The long term behavior of bridge bearings (e.g., laminated rubber bearings) is determined through compression creep tests subjected to actual environmental conditions. These tests indicate that the maximum creep deformation is about 0.3 to 1.92 % of the total rubber thickness.