Seismic fragility of reinforced concrete bridge columns utilizing ductile fiber-reinforced concrete covers

The seismic resistance of reinforced concrete (RC) bridge piers reduces over time due to gradual deterioration processes, such as reinforcement corrosion. Using a ductile fiber reinforced concrete (FRC) reinforcement cover may mitigate deterioration. However, current methodologies for estimating deterioration and capacity reduction cannot be applied to bridge piers with cover made of a ductile FRC that behaves differently from conventional concrete. This article utilizes a systematic framework that combines corrosion and seismic analyses to address this limitation. The seismic fragility of an example bridge column with a ductile FRC cover was estimated using the framework and compared to that of a column with a conventional concrete cover. A detailed pitting corrosion model, which explicitly accounted for differences in cover crack patterns of concrete and a ductile FRC, was developed to estimate the rebar mass loss as a function of time. Seismic fragility functions were constructed by nonlinear response history analyses, incorporating rebar mass loss, at discrete times during the life span of the bridge. The results indicate that improved durability of the RC bridge pier enabled by FRC cover translates into a lower probability of seismic damage over time compared to the pier with a conventional concrete cover.