Investigation of Isolator Stiffness and Yield Strength on Seismic Response of Bridges

To investigate the effect of isolation system on bridge response, two types of pier are studied. The bridge without isolator is designed based on AASHTO96 and then the system with and without isolator are modeled in DRAIN-2DX program. The nonlinear time history analyses are preformed on bridges subjected to different earthquake records.To study the effect of stiffness and yield strength of isolator on response of bridge with isolated pier, during the repetitive analyses, the isolator stiffness is varied from 20% to 100% of elastic pier stiffness in each step. The ratio of yield strength to pier tributary mass is varied from 5% to 20%. In each case, the maximum deck displacement, the isolator ductility demand the Pier Protection Index (PPI) and the deck residual displacement are computed and the results are presented in form of diagrams. Finally, based on results obtained from this research, the conclusion are made and the recommendations to design the isolated bridges are presented.