Numerical investigation on optimization of lateral constraint and anchorage configurations for GFRP-reinforced concrete utility tunnels

This study investigates the structural behavior of Glass Fiber Reinforced Polymer (GFRP)-reinforced concrete utility tunnels, focusing on optimizing lateral constraint mechanisms and anchorage configurations. A comprehensive finite element model was developed and validated through full-scale testing, demonstrating high accuracy with discrepancies less than 10 % in load-displacement responses. Numerical analysis reveals several significant findings: (1) a quantitative classification of lateral constraint stiffness, where K= 20 kN/mm serves as a critical threshold between weak and strong constraint conditions, leading to distinct failure mechanisms; (2) contrary to conventional understanding in box-girder structures, the eccentricity of lateral constraint distance shows negligible impact on structural behavior; and (3) multiple short GFRP anchors (two 50 mm) demonstrate superior performance compared to a single long anchor (150 mm), challenging traditional anchorage length principles. The optimized configuration combining 20 kN/mm lateral constraint stiffness with + 75 mm anchorage location effectively resolves GFRP reinforcement stress concentration issues. These findings provide valuable insights for developing more efficient GFRP-reinforced underground infrastructure design guidelines.