Experimental and analytical investigations on backbone curve models for RC shear keys under sequential seismic-tsunamic impacts

Reinforced concrete (RC) sacrificial shear keys play a crucial role in enhancing the structure resilience of coastal bridge against lateral impacts induced by seismic-tsunami scenarios. Existing researches have primarily focused on their performance under cyclic effects to simulate seismic impacts during earthquakes. However, their ability to withstand enduring forces under tsunami wave has been rarely studied yet. In this research, an experimental test was carried out to investigate the failure mechanism of RC shear keys under sequential cyclic-persistent effects, in which three typical failure modes of shear keys were considered. Various damage states were introduced to account for the possible damage levels after sustaining seismic impacts. The test results were analyzed by focusing on damage pattern, hysteretic behavior, peak capacity, and strain development, showing great distinctions with respect to different failure modes and corresponding damage stages. Furthermore, the analytical backbone curve models were developed based on the experimental test results. The presented models were validated using the typical strain-stress curve of reinforcement, and exhibited better applicability in characterizing the performance of shear keys under either cyclic or cyclic-persistent sequential effects, comparing to the other approaches that emphasizes on their seismic properties.