Assessment of sliding-rubber isolator effect in progressive collapse of bridges under two scenarios

摘要

In this study, performances of 2 types of bridges, with and without seismic isolation, are addressed in 2 damage analysis scenarios, where, in the first, the side column and, in the second, the middle column are removed from the bridge piers. The performance was assessed using nonlinear dynamic analysis, and the time history and maximum structural responses were evaluated. Initially, sliding-rubber isolators were designed according to AASHTO guide specifications, and then the bridges were modeled in OpenSees software package. Additionally, the coefficient of friction for the isolator was considered as a variable due to sudden removal of the columns and the consequent changes in the sliding velocity and axial forces. The results indicate that use of seismic isolation systems caused an increase in all maximum structural responses except that of the base shear. Considering the frictional performance of the isolators, slides in the deck are not caused by yielding of seismic isolators, and the reason for permanent displacements of the deck may be attributed to bridge instabilities in the first scenario. However, decrease in the horizontal stiffness results in increased maximum permanent displacement. In the first scenario, uplift of the deck occurred in the case of isolated bridge.