Improved seismic response of multi-span bridges retrofitted with compound restrainers

This numerical study aims to evaluate the seismic performance of bridges retrofitted with a new compound restrainer and the sensitivity of their responses to likely changes in the characteristics of the restrainer’s components. Compound restrainer was introduced as a retrofit tool for improving seismic response of multi-span bridges in terms of forces and displacements. The compound restrainer is mechanically an assembly of several elastic and plastic springs. To this end a real 2-span and a real 3-span simply supported plate girder bridge have been used for case study. Nonlinear time history analyses of detailed three-dimensional models have been performed under seismic excitations in order to assess the performance of the existing and retrofitted bridges restrained by conventional restrainers and compound restrainers, numerically. The results show that the compound restrainer is very sensitive to the characteristics of its components. Moreover, while past earthquakes have shown the deficiencies of the conventional restrainers, the compound restrainer seems to be successful in dissipating hysteresis energy in bridges as well as in reducing the internal forces imposed on the substructures.