Performance Improvement of Multi-Span Simply Supported Bridges Using Optimized Compound restrainers

This paper is aimed at improving seismic performance of bridges by providing an optimized compound restrainer model. Introducing the characteristics of the compound restrainer as well as a mechanical model, a computer code has been developed in order to optimize performance of the compound restrainer via the optimization method of feasible directions of Zoutendiijk. A real 3-span simply supported bridge has been used for case study. Nonlinear time history analyses were performed to assess the performance of the existing bridge. The evaluation of the seismic response of the existing bridge showed significant vulnerabilities in the bridge responses especially by failure of the bearings. To assess the performance of the proposed restrainer element, the bridge was subjected to the same ground motion records after being retrofitted with the conventional restrainers and then the compound restrainer as well as the optimized compound restrainer. The results show that although the conventional restrainers are capable of restricting the lateral displacement of the bridge, they impose considerable forces on the abutments and hence in sum they substantially decrease the capability of the structure to dissipate the hysteresis energy during earthquakes. It is illustratively concluded that moreover to augment happened in the energy dissipation capability of the optimized compound restrainers compared to the initial compound restrainers; it also resulted in the reduction of forces imposed on the abutments. It illustrated the effect of optimization in devising a more convenient restrainer design.