Seismic performance of UHPC precast double-column piers with socket connections

Ultra-high performance concrete (UHPC) offers excellent seismic toughness, but its use as a full structural material remains underexplored. In this study, the UHPC cast-in-place double-column pier and the UHPC precast socket-connected double-column pier were designed and fabricated. Seismic performance was evaluated through quasi-static loading tests, analyzing failure modes and mechanical responses. Both piers experienced flexural failure. However, the precast pier demonstrated a 16.5% increase in ultimate load capacity and a 4.5% increase in cumulative energy dissipation compared to the cast-in-place pier. The superior seismic performance of the precast pier is attributed to the shear keys in the socket section, which enhance joint anchoring, and the UHPC columns embedded in the foundation and cap beam, which fully utilize the mechanical properties of the material. Finite element analysis was conducted to investigate the influence of factors such as socket depth, axial load ratio, grout strength, and rebar properties on the seismic performance of the piers. Results indicate that grout strength and longitudinal rebar strength have a substantial effect on the yield capacity and ultimate load capacity of the piers. Finally, displacement angle limits for UHPC double-column piers at various performance levels were proposed based on seismic design codes. Research on UHPC precast piers is expected to promote the adoption of precast methods and advanced materials in bridge substructures, providing strong support for bridge design in seismic regions.