Shear Behavior of Precast Concrete Box Culverts Reinforced with Glass Fiber-Reinforced Polymer Bars under Concentrated Load

This research evaluated the structural behavior of precast concrete box culverts (PCBCs) reinforced with glass fiber -reinforced polymer (GFRP) bars, both experimentally and theoretically. Four full-scale specimens with a span of 1500 mm (59.06 in.), a rise of 1500 mm (59.06 in.), and a joint length of 1219 mm (48 in.) were prepared, along with one specimen with a span of 1800 mm (70.87 in.). Four specimens were reinforced with GFRP bars, and one specimen with steel bars as a reference. The PCBCs were tested up to failure under a concentrated load over a contact area of 250 x 600 mm (9.8 x 23.6 in.) on the top slab. The load plate simulated the footprint of the truck wheel load (87.5 kN [19.67 kip] CL -625 truck) according to the Canadian Highway Bridge Design Code. The investigated test parameters were the longitudinal reinforcement stiffness (GFRP versus steel), the longitudinal GFRP reinforcement ratios, specimen clear span, and slab thickness. Two-way shear failure was observed in all the tested specimens as a result of the concentrated load acting on the top slab. The test results revealed that increasing the longitudinal reinforcement ratio, as well as increasing the top -slab thickness, resulted in higher load -carrying capacity, lower deflection, and lower concrete and reinforcement strains. The experimental shear strengths were compared to the values predicted using current code provisions for two-way shear resistance equations. The results show that the punching -shear resistance equation in CSA S806-12 provided good yet conservative predictions of the shear capacity of the PCBCs'top slab. The Canadian Highway Bridge Design Code does not provide an equation for two-way shear design of FRP -reinforced concrete members. The two-way shear equation available for steel -reinforced concrete members was modified to take into account the characteristics of FRP bars. The modified equation produced predictions consistent with the experimental results. Moreover, the findings of this study demonstrate the feasibility and effectiveness of using GFRP bars as internal reinforcement for PCBCs as an alternative to steel bars.