Experimental evaluation of longitudinal seismic performance of bridge restrainers at in-span hinges

A specimen consisting of two box girder reinforced concrete blocks representing the adjacent spans of a reference bridge at an in-span hinge was constructed and tested under incrementally increasing input excitation to investigate the impact between adjacent bridge spans at in-span hinges, to evaluate the efficacy of restrainers in reducing relative displacements across the hinges, and to examine the effects of restrainer stiffness and gap on the response of the hinge-restrainer system. Cable restrainers were used to connect the two blocks, the number and gap of which were varied during the experiments. The experimental results indicated that impacts between the adjacent frames produce acceleration levels significantly higher than what is typically assumed in design. In all the restrained system cases, restrainers were capable of reducing hinge relative displacements and preventing span unseating. However, restrainer yielding occurred under strong input motions, especially when the restrainer gap was set to zero.