Performance of RC Shear Keys Under Multi-Hazard Actions of Earthquakes and Tsunamis

Earthquakes and tsunamis pose significant threats to coastal bridges owing to their successive impacts. Isolated bridges are rather susceptible to such hazard chains because of their separated configurations. Reinforced concrete (RC) shear keys are commonly used in such bridges to enhance the resistance of superstructures to lateral impacts, and they often function as sacrificial components for seismic design. While the shear keys subjected to earthquakes have been extensively studied, their performance under sequential seismic-tsunami impacts remain rarely investigated yet. Hence, the current study inspects the variation in shear key properties under different load effects. Experimental test was conducted to the shear key specimen with 1:3 scaling, with the quasi-static loading adopted for the load applying. Three failure modes of shear keys were incorporated to compare their distinctions under such impacts. A loading frame was designed to demonstrate the test and ensure the out-of-plane stability during the test. Special loading protocols were proposed to characterize cyclic (seismic) and persistent (tsunami) forces, with different combinations of the two protocols used to address their initial seismic damages within such scenarios. The test results reveal significant distinctions among different failure modes across various initial damage states, and their performance under two load patterns also shows considerable variations. Based on the test result, analytical envelope curve models were developed for each failure mode and showed good agreement with test results. This study showed that using the same shear key model during seismic and tsunami analysis might result in biased results; and thus the proposed model is more suitable for seismic-tsunami analysis on coastal isolated bridges.