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

This numerical study aims to evaluate the seismic performance of bridges retrotted with a new compound restrainer, and the sensitivity of their responses to likely changes in the characteristics of the restrainerʹs components. The compound restrainer was introduced as a retrot tool for improving the 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, real 2-span and 3-span simply supported plate girder bridges have been used for the 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 retrotted bridges restrained by conventional 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 deciencies 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.