Near-Ground Lateral Load Tests: Evaluating Ultrahigh-Performance Concrete for Enhanced Shear Performance in Precast Column-to-Pile Shaft Systems

Precast concrete columns connected to pile shaft foundations through socket connections rely on the thin-walled pile shaft for load transfer to the ground, which makes them inherently less effective at resisting the direct shear forces generated by vehicular collisions. This research aims to experimentally investigate the strategic use of ultra-high-performance concrete (UHPC) to address this vulnerability. Two specimens, featuring pile shafts made from normal concrete (NC) and UHPC, respectively, were subjected to quasistatic near-ground lateral loads to replicate the effects of vehicular collisions. The experimental results revealed notable differences in damage mechanisms and overall performance between the two specimens. The specimen with NC pile shaft experienced shaft prying failure and column flexural damage, whereas the specimen with UHPC pile shaft exhibited damage concentrated primarily in the column with minimal damage to the shaft. In addition, the use of UHPC in pile shaft led to 17% increase in the lateral load capacity and more than 60% improvement in deformation capacity. The experimental results presented support the improved shear performance and failure mitigation offered by UHPC in precast column-to-pile assemblies, potentially advancing the design of more resilient bridge systems against vehicular impacts.