Design of shear keys for mitigating seismic response due to translational and torsional ground motions

Irregular plan geometries and soil-abutment-structure interaction, as well as the torsional components of ground motions (TGMs) are significant contributing factors that result in excessive torsional demand during seismic events that may lead to premature and asymmetric failure of shear keys. Therefore, a design method that ensures the effectiveness of shear keys in mitigating the seismic response of highway bridges is proposed. The proposed method follows the conventional approach to capacity-protect the substructure components, however, formalizes a practical procedure to specify desired deformation limits associated with i) gap size between the superstructure and shear keys, and ii) ultimate deformation capacity of shear keys. The efficacy of the method is demonstrated through nonlinear response history analyses of a series of example bridges. It is demonstrated that excessive inplane deck rotations and the extent of damage can be limited when the effectiveness of shear keys is maintained throughout the duration of seismic excitation. Furthermore, probable deck unseating may be prevented when the deck displacements are restrained due to shear keys that are designed to remain intact.