Seismic performance analysis of socket-connected prefabricated UHPC pier columns

Ultra-High Performance Concrete (UHPC) provides a promising solution to challenges in current prefabricated bridge piers, such as excessive segment weight, construction complexities, and inadequate durability. This study proposes a socket-connected prefabricated UHPC bridge pier system that enables lightweight, high-strength structures while enhancing lifecycle economic efficiency. A cast-in-place (CIP) UHPC pier (CIP-2) and a socket-connected prefabricated UHPC pier (PC) were constructed with a socket embedment depth of 1.0D (where D is the pier diameter). A CIP C50 concrete pier (CIP-1) was also built as a reference specimen. Quasi-static tests were conducted to observe their failure modes and obtain seismic performance metrics, such as hysteresis curves, skeleton curves, and stiffness degradation. Test results showed that, compared to CIP-1, the CIP-2 exhibited substantial improvements in seismic performance. The ultimate load-bearing and deformation capacities increased by 68.19 % and 15.77 %, respectively, due to the superior material properties of UHPC. The PC further improved load and deformation capacity by 20.69 % and 22.41 % over CIP-2, due to the enhanced interface performance of the socket connection. Finite element analysis (FEA) was conducted to investigate the effects of socket embedment depth and axial compression ratio. Results indicate that an embedment depth less than 0.85D compromises structural capacity. A depth of 1.0D is recommended to ensure reliable load transfer and accommodate construction tolerance. Increasing the axial load ratio improved the peak strength due to enhanced confinement but significantly reduced post-peak ductility and accelerated stiffness degradation. Statistical analysis of 54 UHPC pier specimens was performed to define drift ratio thresholds for damage states. The lateral drift limits for "basically intact," "minor damage," "moderate damage," "severe damage," and "complete failure" were established as 1/300, 1/140, 1/50, 1/40, and 1/30, respectively. This study offers a comprehensive evaluation of seismic performance and provides design guidance for prefabricated UHPC bridge piers.