Glass reinforced plastic (GRP) liner-enhanced load-bearing performance of reinforced concrete box culverts: Experimental and numerical investigation

Reinforced concrete (RC) drainage box culverts are critical to urban infrastructure; however, prolonged service exposure increases their vulnerability to cracking and deterioration, compromising structural safety. This study combines laboratory three-edge bearing tests (TEBT) and finite element analysis (FEA) to evaluate the mechanical properties. It systematically investigates the pipe structural behavior of RC box culverts before and after rehabilitation with GRP liner. The load-bearing performance, failure mechanisms, and deformation responses were comprehensively analyzed. Experimental and numerical results indicate that the GRP liners markedly enhance the load capacity, stiffness, and ductility of the culvert. Compared to the unreinforced culvert, the GRP-rehabilitated specimen achieved a 67 % increase in ultimate load (53.6 kN versus 32.1 kN), and 3.6 times increase for the initial stiffness. The unreinforced culverts primarily exhibited bending and shear-induced cracking failures, while the reinforced specimens predominantly showed interface debonding and cracking. FEA predictions agreed within 5 % of experimental results. Based on the FEA results, the effects of GRP elastic modulus, wall thickness, mortar strength, interface bonding condition, and liner placement were further evaluated. Sensitivity analysis showed that interfacial bonding strength had the greatest influence on structural performance with a sensitivity index of 74.7 %, followed by liner position and thickness. This study provides theoretical insight and engineering recommendations for the repair design and material selection optimization of RC box culverts. • Experiments and FEA were conducted on RC box culverts before and after rehabilitation. • GRP reinforcement improved ultimate load by 67 % and initial stiffness by 3.6 times. • Interfacial bonding was identified as the most influential factor affecting reinforcement. • Design strategies for effective GRP reinforcement are proposed for culvert rehabilitation.