Comparison study of seismic-tsunami performance for coastal bridges with different RC sacrificial shear keys

Simple-support bridges are employed in offshore regions as integral component of coastal transportation networks. However, these bridges are vulnerable to the combined effects of earthquakes and ensuing tsunami waves due to weak lateral resistance. Reinforced concrete (RC) shear keys have been widely utilized to strengthen bridges by providing extra constraints to the superstructure. While the seismic performance of RC shear keys has been extensively studied, their effectiveness under the sequential action of both hazards remains seldom addressed yet. Therefore, this study aims to compare the seismic-tsunami response of bridges with different RC shear keys. To this regard, a novel envelope curve model was developed for the diagonal failure shear key, with emphasis on their distinct behaviors under seismic and tsunami impacts. OpenSees platform was employed, with natural ground motions and second-order solitary wave theory adopted for seismic and tsunami modeling, respectively. The shear key under each hazard was simulated using an Update Material approach to account for the distinct mechanical property. Subsequently, a parametric study was carried out to compare various factors, including shear key failure modes and strength, as well as wave conditions. The analysis result showed that the maximum strength of RC shear keys can significantly affect bridge performance, while the failure mode also contributes. In addition, the wave condition can largely affect the time-history and maximum deformation depending on water depths. Furthermore, the recommendations for shear key design against sequential seismic-tsunami hazards were provided.