Seismically Resilient Hybrid Precast Concrete Piers with Ultrahigh-Performance Concrete

This paper investigated a novel hybrid precast pier system that utilized ultrahigh-performance concrete (UHPC). The pier combines features of emulative and nonemulative (of cast-in-place construction) systems to balance self-centering and energy dissipation under seismic loading and uses UHPC to maintain that balance with low damage. An analytical model was used to study piers with varying UHPC mixes, properties of which were determined through material testing. Two large-scale pier specimens with UHPC and with varying confinement reinforcement grades were tested under quasi-static cyclic lateral loading. The test results demonstrated that the selected UHPC mix enabled the balance between bending and rocking. The rocking-induced cracking was not prevented by UHPC but was alleviated with a steel case. When the rocking-induced damage was prevented, more than 40% of the total displacement was caused by rocking at smaller drift ratios (<0.5%), enabling self-centering. At larger drift ratios (>4.5%), approximately 80% of the displacement was from bending, enabling energy dissipation. Replacing normal-strength steel with high-strength steel confinement did not improve the flexural capacity or ductility of UHPC.