Combined Effect of Low Temperature and Exposure Time on Seismic Performance of an LRB-Isolated Bridge

Abstract

This study investigates the modification in the seismic response of a base-isolated bridge that is exposed to low temperatures. The isolation system is assumed to be composed of lead rubber bearings (LRBs). The parameters considered in this study (experimental and analytical) are the temperature (0°C, −10°C, and −20°C) and exposure time (3, 6, and 24 h). In the experimental section, a large-sized LRB was subjected to displacement-controlled cyclic motions once it had been conditioned at the desired low temperatures and exposure times. The recorded force–deformation relationships were used to construct deteriorating hysteretic bilinear representations for each loading condition. Then, in the analytical section, several bidirectional nonlinear response history analyses were conducted using the idealized bilinear representations. In the analyses, two sets of ground motion records that were representative of different seismicity levels were selected and scaled in accordance with the codified procedures. The exposure time is a key parameter that needs to be considered in the estimation of the maximum isolator forces (MIFs) that are transmitted to the bridge piers. For the selected parameters, the MIFs of the analyzed bridge model could increase up to 30% with a trend to increase with the increasing exposure time.