Modification in Response of a Bridge Seismically Isolated with Lead Rubber Bearings Exposed to Low Temperature

This study investigates the response modification in a bridge seismically isolated with lead rubber bearings (LRBs), due to change of ambient temperature from 20 degrees C to -30 degrees C. Accordingly, a large-size LRB was tested after being conditioned at corresponding temperatures and changes in its hysteretic properties were noted. Use of analytical tool in modeling nonlinear response of the tested LRB was justified by comparing the experimentally observed and analytically obtained force-displacement curves. Then, verified analytical representation of an LRB was employed in nonlinear response history analyses conducted to quantify the change in response of a representative LRB isolated bridge when subjected to bidirectional ground motion excitations at 20 degrees C and -30 degrees C. Analyses results are also employed to assess the use of property modification factor, lambda, to change isolator properties in order to represent low temperature behavior. It is revealed that for the selected ground motion records, the average isolator force remains almost the same for both ambient temperatures. Moreover, using property modification factor will result in accurately estimated isolator displacements, but overestimated isolator forces, in an average sense.