Dynamic Response and Damage of Prefabricated UHPC Tall-Pier Bridges Subjected to Near-Fault Hanging-Wall Ground Motions

This study investigates the influence of the comprehensive effect of hanging-wall near-fault ground motions on the seismic behavior of prefabricated tall-pier reinforced concrete bridges with ultra-high-performance concrete (UHPC) socketed reinforcement connections. A refined finite element model of a prototype bridge was developed and subjected to nonlinear time-history analyses under four seismic fortification levels (frequent, basic, rare, and very rare earthquakes), using representative hanging-wall ground motions and code-specified design ground motions as inputs. Key seismic response indicators—including pier displacement, ductility, drift ratio, residual drift, internal forces, and girder displacement—were systematically evaluated to elucidate the damage evolution and failure mechanisms under the comprehensive effect of hanging-wall ground motions. The results demonstrate that the hanging-wall effect significantly amplifies the seismic response of the bridge. Compared with design ground motions, the average displacement ductility coefficient of piers and the girder displacement under rare earthquakes increase by 186%–209% and 182%–198%, respectively. The responses of central piers and mid-span girders are substantially higher than those of side piers and side-span girders, exhibiting a pronounced “middle-high, side-low” spatial distribution. The seismic performance of the structure exhibits nonlinear evolution across fortification levels, with the most significant increase in damage indices occurring at the rare earthquake stage. The comprehensive effect of hanging-wall ground motions aggravates damage severity without altering the spatial distribution of damage regions. Under the seismic intensities considered in this study (up to 0.6g PGA), no stress concentration or abrupt stress transition is observed at the UHPC socketed connection regions, verifying the seismic reliability of the prefabricated connection system. During the low‑intensity elastic stage, the spectral characteristics of bridge response under hanging‑wall and design ground motions show minor differences. As seismic intensity increases to rare and very rare levels, stiffness degradation, nonlinear damage, and period elongation occur, leading to a marked divergence in spectral evolution. The low‑frequency pulses of hanging‑wall motions significantly amplify the nonlinear dynamic response and damage development of the bridge. This study provides valuable guidance for the seismic design of prefabricated bridges in high-intensity seismic zones and offers a theoretical and technical reference for the seismic design of prefabricated UHPC tall-pier bridges.