Toward the response of coastal bridges with updated RC shear key properties under the multi-hazard action of earthquakes and tsunamis

Coastal bridges are significantly endangered by the combined effects of earthquakes and tsunamis. The accurate prediction of bridge responses in such scenarios is vital to ensure their security. Reinforced concrete (RC) shear keys, which serve as sacrificial bridge components, can effectively mitigate inertial loads from superstructures, and thus safeguard pier columns. Previous research has shown that their mechanical properties can differ considerably under cyclic and persistent impacts. Therefore, this study focused on the seismic-tsunami responses of a simple-support coastal bridge equipped with RC shear keys. A horizontal failure shear key was incorporated because of its distinct performance observed previously. The OpenSees platform was employed to conduct the numerical work, with an updated material framework developed to modify the shear key behavior before the tsunami analysis. Natural ground motion records were selected to demonstrate the dynamic analysis, and the records were scaled using spectral accelerations (S_a) to account for the various damage states of shear keys resulting from superstructure collisions. The tsunami wave impact was modeled using the second-order solitary wave theory, with different wave conditions employed to consider the immersed conditions. The calculation results were compared for the bridges with and without updated shear key properties, showing distinctions in terms of time-history and maximum responses at certain seismic levels. Based on the analysis results, this study is expected to provide a reliable estimation of the seismic-tsunami responses of coastal bridges.