Performance of RC shear keys on coastal bridges under multi-hazard actions of earthquake and sequent tsunami

Reinforced concrete (RC) shear keys are critical components for safeguarding coastal bridges against hazards such as earthquakes and tsunamis. While numerous researches have examined their mechanical properties under cyclic loading, the investigation into their behaviors under the combined impacts of earthquakes and ensuing tsunamis remains limited. In the present study, 12 shear key specimens with 1/3 scaled dimension were tested experimentally. These tests considered three distinct failure modes, including horizontal, diagonal, and sliding failure modes, by varying the geometric and reinforcement layouts. A quasi-static loading approach was employed, alongside a novel hybrid loading protocol including both cyclic and persistent phases to simulate the successive earthquake and tsunami actions. The specimens were assessed under three damage levels (slight, moderate, severe) to represent the varying post-earthquake damages of this component in realistic cases. The comparative analysis on experimental results reveals distinct behaviors across different failure modes. Shear keys with horizontal failure exhibit heightened sensitivity to persistent loading across all damage states, while those with diagonal failure demonstrate significant variations only at the slight damage. In contrast, shear keys with sliding failure show consistent responses to both cyclic and persistent loading. This study is expected to provide further insights into developing numerical models for the shear keys under the dual threats of earthquakes and tsunamis.