Two-Way Shear Behavior of GFRP-Reinforced Concrete Box Culverts with 70 MPa Concrete under CL-625 Truck Loading

Although high-strength concrete is becoming more common in bridge and highway structures, its performance in glass fiber–reinforced polymer (GFRP)-reinforced box culverts under two-way shear remains unexplored. This study aimed to fill that gap and provide insights into their structural behavior. Four full-scale GFRP-reinforced concrete box culverts cast using concrete with a compressive strength (fc′) of 70 MPa were tested under the CL-625 truck wheel load, in compliance with the Canadian Highway Bridge Design Code. The experimental program examined key parameters, including longitudinal GFRP-reinforcement ratio (ρf), top-slab thickness (h), and concrete compressive strength (fc′). The use of concrete with grade of 70 MPa enhanced the performance, reducing deflection by 37% and increasing two-way shear strength by 21% compared to specimens with 40 MPa reported in a previous study. Comparisons revealed, however, that increasing the GFRP-reinforcement ratio (ρf) or slab thickness (h) was more effective for specimens with a concrete compressive strength (fc′) of 40 MPa than specimens with a concrete compressive strength (fc′) of 70 MPa. Experimental two-way shear strengths were assessed and compared to predictions from existing provisions and equations proposed in the literature. The findings provide critical insights into the effectiveness of using concrete with high compressive strength in enhancing the structural performance of GFRP-reinforced concrete box culverts, which are essential for supporting highways and serve as critical elements within bridge systems. This research contributes to advancing design practices for more efficient, durable, and reliable bridge infrastructure elements.