Two-Way Shear Strength of GFRP-Reinforced Precast Concrete Box Culverts under Vertical Concentrated Loading

The purpose of this study was to investigate the two-way shear strength of precast concrete box culverts reinforced with glass fiber–reinforced polymer (GFRP) bars. The investigations included testing four full-scale specimens reinforced with GFRP bars under truck wheel load in accordance with current Canadian design codes. The load was applied to the top slab at three different distances: d (effective depth), 1.5d, and 2.5d from the tip of the haunch to the edge of the load plate. One of the specimens was placed and tested on an aggregate bedding material instead of the rigid floor of the test laboratory. Following experimental testing, a theoretical study was conducted to evaluate experimental shear strength to predicted values using different provisions of several North American and international design standards. Two-way shear failure in the top slab occurred in all tested box culverts, indicating that GFRP-reinforced concrete box culverts are critical in shear under traffic wheel loads. The behavior of the tested box culverts was significantly affected by changing the load location or testing the specimen on an aggregate bedding material. On the other hand, the available two-way shear equations conservatively predicted the two-way shear strength of the top slab of the box culverts. Moreover, the two-way shear action equation used in the Canadian standards considers only the cracking strength of concrete. Therefore, an equation has been proposed to consider the characteristics of the GFRP bars and shear span to effective depth ratio. The proposed equation accurately predicted the two-way shear strength and may be considered in future provisions. Finally, the findings demonstrated the feasibility and efficiency of using GFRP bars as internal reinforcement in concrete box culverts.