Energy dissipating shear key for precast concrete girder bridges

This paper presents an economical solution to improve the seismic response of simply supported precast concrete girder bridges under transverse excitation. This solution employs an energy dissipation system, which consists of conventional elastomeric bearings that transfer gravity load to the substructure, and energy dissipating shear keys that replace conventional shear keys on bent caps and abutments. The proposed shear key, which is a yielding steel damper, transfers a good portion of the seismic load to the substructure, while dissipating the seismic energy through inelastic deformation. An experimental study on four full scale specimens is conducted to evaluate the behavior of the proposed shear keys under cyclic loading condition. The specimens with good ductility and energy dissipation capacity are identified. These specimens were able to sustain large inelastic deformation without any strength degradation under cyclic loading. The nonlinear time history response of a three span precast concrete girder bridge, with and without the proposed shear key, is also studied. The results of analyses indicate that seismic demands on the substructure are greatly reduced when conventional shear keys are replaced by the proposed shear keys.