Experimental Study on a New Connection Joint between Prestressed High-Strength Concrete Piles and Cap

To address issues such as stress concentration, complex construction, and insufficient deformation resistance faced by the connection joints between prestressed high-strength concrete pipe piles and pile caps under seismic action, this study developed a novel direct reinforcement insertion connection system. Based on the Guohe Bridge project along the S209 Highway in Luyi County, Zhoukou City, China, full-scale specimens with two configurations (Z1: conventional welded connection and Z2: proposed insertion connection) were subjected to unidirectional cyclic loading tests and finite element analysis. Results indicate that, compared with the traditional welded connection, the Z2 insertion connection exhibits a 12% increase in critical load capacity. Under 900 kN lateral loading, displacements measured 39.0 mm (pile) and 42.7 mm (cap), with no load-displacement curve separation observed throughout testing. The reinforcement stress gradient rate in Z2 decreased from 2.68 to 0.32 MPa/mm, with peak tensile stress reduced from 385.0 to 192.3 MPa, and no distinct tension-compression transition zones were identified. Both field tests and numerical simulations confirm the reliability of the new connection system, demonstrating enhanced ductility and coordinated deformation capacity in pile-cap joints.