Study on time-varying seismic vulnerability and analysis of ECC-RC composite piers using high strength reinforcement bars in offshore environment

As the main seismic component of a bridge, seismic damage to the bridge pier has a greater effect on its subsequent service. In the offshore chloride environment, the issues (e.g., reinforcement bar corrosion and attenuation of concrete strength) of piers caused by chloride ion seriously curtail the normal service life and deteriorate the anti-seismic property of bridge structures. The engineered cementitious composite (ECC)-reinforced concrete (RC) composite pier with high strength reinforcement bars (HSRB) is expected to solve the above problems. This study aims to clarify the time-varying seismic vulnerability (SV) of the HSRBECC-RC composite pier during its full life cycle (FLC). Based on OpenSees, the refined finite element analysis models of RC pier, ECC-RC composite pier, and HSRBECC-RC composite pier have been established. Moreover, using the nonlinear time-path dynamic analysis method, the influence of chloride ion erosion on the time-dependent seismic vulnerability (SV) of these different piers in different service life and different peak ground acceleration (PGA) were analyzed from a dynamic point of view. The research shows that the exceeding probability (EP) of the same damage level increases with the enhancement of service time and PGA and with the increase of destruction, the exceeding probability (EP) of slight damage (DL-1), moderate damage (DL-2), serious damage (DL-3), and complete collapse (DL-4) decreases in turn; the corrosion degree of chloride ion to piers is small during the early service period, the time-varying vulnerability curve of the bridge piers is almost the same as that of a new bridge, and during later service, as the extent of chloride ion corrosion deepens, exceeding probability (EP) under severe damage (DL-3) and complete collapse (DL-4) is increased, and the seismic performance is significantly enhanced.