Performance Assessment of a Bridge Seismically Isolated with Lead Rubber Bearings at Low Temperature

This study investigates the variation in structural response of a bridge seismically isolated with lead rubber bearings (LRBs), when subjected to ground motion excitations at low ambient temperature. For this purpose, first, a full-scale LRBwas conditioned at -20 degrees C, -10 degrees C, 0 degrees C and 20 degrees C temperatures for 24 h and tested under dynamic conditions in order to determine the change in its characteristic strength and post-yield stiffness. Recorded force-displacement curves were then utilized to represent the deteriorating hysteretic behavior of the LRB in case of different temperatures. Seismically isolated bridge was idealized by a single-degree-of-freedom model and analyses were performed by OpenSees structural analysis program. Nonlinear response history analyses (NRHA) were conducted considering the strength deterioration of the LRB due to the lead core heating during cyclic motion. In the analyses, eleven pairs of ground motion records, selected and scaled to represent a target spectrum, were used. Response quantities assessed in the analyses were maximum isolator displacement and maximum isolator force for the isolation system and maximum acceleration for the bridge deck. It is revealed that as the ambient temperature decreases, the amount of amplification in maximum isolator forces and accelerations can be up to 30%.