Full-Scale Tests of Seismic Cable Restrainer Retrofits for Simply Supported Bridges

Many parts of the central and southeastern United States have recently begun initiating seismic retrofit programs for bridges on major interstate highways. One of the most common retrofit strategies is to provide cable restrainers at the intermediate hinges and abutments in order to reduce the likelihood of collapse due to unseating. To evaluate the force-displacement behavior of the cable restrainer retrofits, a full-scale bridge setup was constructed based on an existing multispan, simply supported steel girder bridge in Tennessee, that has been considered for seismic retrofit using cable restrainers. Seismic cable restrainers were connected to the bridge pier using steel bent plates, angles, and undercut anchors embedded in the concrete as specified by typical bridge retrofit plans. The full-scale bridge model was subjected to monotonic loading to test the capacity of the cable restrainer system and to determine the modes of failure. The results showed that the primary modes of failure are in the connection elements of the pier and girders, and they occur at force levels much lower than the strength of the cable. Modifications to the connection elements were designed and tested. The new connections resulted in a higher strength and deformation capacity of the cable restrainer assembly.