Numerical modeling and design sensitivity of seismic behavior of UHPC-NSC bridge piers with the longitudinal grooved contact surface

Normal strength concrete (NSC) has low structural and durability resistance to meet the comprehensive performance requirements of modern construction. The reinforced concrete bridge column quickly degrades, particularly when exposed to environmental compartments, causing the concrete to deteriorate and the reinforcement to corrode. The phenomenon significantly reduced the durability and load-bearing capacity of the column, which impacted the functionality of the bridge and threatened its recovery operation. The superior behavior of advanced cementitious ultra-high-performance concrete (UHPC) has drawn increasing benefits among the construction industries. However, the high cost of UHPC has developed a concern that resulted in its small-scale application. Therefore, incorporating UHPC with NSC has the potential to balance the low performance of NSC and the economic cost of UHPC. Therefore. This study incorporates UHPC and NSC in a large-scale two-column bridge pier and investigates its seismic performance. The study aims to understand the general behavior, failure modes, and effect of design parameters of developed UHPC-NSC bridge columns with longitudinally grooved contact surfaces through finite element analysis. The pushover response of the UHPC-NSC twocolumn with a typical geometry and gravity load of a representative bridge was investigated. A comprehensive parametric study was carried out to evaluate the effect of interface groove geometry, longitudinal reinforcement ratios, core NSC compressive strength, and reinforcement grade on the characteristic behavior of the columns. The study shows that the capacity of the composite UHPC-NSC bridge column under gravity load is 11 % higher than the conventional NSC concrete. The UHPC-NSC column with 300 x 300 mm interface groove, reinforced with 4 % HRB500 longitudinal rebars, can sustain over 80 % of the peak capacity up to 5 % drift. A higher axial load ratio of up to 14 % can increase the capacity of the UHPC-NSC two-column by 75 %, which has a more significant impact than what is often observed on NSC piers.