Numerical Simulation of the Seismic Performance of RC Bridge Piers Retrofitted With UHPC in Chloride‐Rich Environments

Chloride‐induced deterioration compromises the seismic performance of reinforced concrete (RC) bridge piers, whereas the mechanical effectiveness of ultrahigh‐performance concrete (UHPC) jacketing across different deterioration states remains insufficiently quantified. This study presents a fiber‐section numerical framework to evaluate the cyclic response of UHPC‐retrofitted rectangular RC bridge piers. Component‐level validation against an uncorroded UHPC–RC composite column and corroded circular RC bridge piers produced peak‐load errors of 3.03%–12.11% and captured the principal hysteretic trends. Parametric analyses considered jacket thicknesses of 30–50 mm, nominal UHPC compressive strengths of 100–150 MPa, service times from 45 years (T45) to 85 years (T85), and horizontal loading orientations from 0° to 90°. During 85 years, the normalized surviving residual yield force (SRYF) and peak force of the pier decreased by 23.3% and 18.7%, respectively. At 55 years and under, with a loading angle of 0°, increasing jacket thickness from 30 to 40 mm and nominal UHPC strength from 100 to 150 MPa increased the stiffness at 18.75 mm by 7.5% and 11.0%, respectively. Loading orientation produced pronounced nonmonotonic variations in cumulative energy dissipation. At the final plotted point, the value under 90° loading was 53.7% higher than that under 0° loading. In contrast, the value under 75° loading was 84.3% lower. The findings support a condition‐based retrofit assessment that jointly considers the existing deterioration state, required jacket contribution, and direction‐dependent seismic demand. Because the service‐life cases represent independently assigned deterioration states, the results quantify the mechanical contribution of UHPC jacketing but do not demonstrate reduced chloride ingress or postretrofit corrosion rates.