Analytical and Experimental Study on Using Yielding Steel Shear Keys in Girder-Slab Bridges Supported on Rubber Bearings

In girder-slab bridges supported on conventional rubber bearings, shear keys are usually designed to support the girders against lateral seismic loads. Shear keys are relatively stiff elements and transfer the lateral load of the superstructure to the substructure during an earthquake. Due to relatively large mass of superstructure, the lateral seismic load could damage the substructure. In this paper, an innovative idea is proposed in which the conventional shear keys are replaced with yielding steel shear keys with high ductility. During an earthquake seismic energy is dissipated within the proposed shear keys resulting in significant reduction of seismic demand on the substructure. Experimental study has been conducted to evaluate the behavior of the proposed shear keys. Test results indicate that these shear keys can sustain large inelastic deformation without strength degradation under cyclic loading. A two span concrete bridge has also been analyzed to evaluate the performance of bridges equipped with the proposed shear keys. The results of analyses indicate that seismic demand on substructure reduces by about ۵۰ percent if conventional shear keys are replaced by the proposed shear keys.