Interface Shear Capacity of Basalt FRP-Reinforced Composite Precast Concrete Girders Supporting Cast-in-Place Bridge-Deck Slabs

Using composite precast concrete bridge girders supporting cast-in-place bridge-deck slabs is a cost-efficient method because it merges precast and cast-in-place elements while maintaining the monolithic construction’s integrity and continuity. In terms of horizontal shear transfer in composite girders, there is a lack of experimental data on the performance of full-scale fiber-reinforced polymer (FRP)-reinforced composite girders. This study explored an innovative and sustainable approach using noncorroding basalt fiber–reinforced polymer (BFRP) as shear transfer reinforcement in precast concrete bridge girders supporting cast-in-place concrete bridge-deck slabs. Five full-scale composite reinforced concrete T-beams measuring 4,200 mm in length, 420 mm in depth, and 250 mm in width were designed, cast, and tested until failure. The main experimental variables evaluated were the interface shear reinforcement type (BFRP versus steel stirrups), the interface shear reinforcement ratio (0.32% versus 0.48%), and the interface shear reinforcement shape (stirrups versus bent bars). The test results were analyzed in terms of ultimate horizontal shear stress, deflection, slippage, and shear reinforcement strain. The experimental results indicated that the BFRP shear reinforcement provided reasonable shear transfer capacities compared to steel when provided across rough concrete interfaces. In addition, the existing equations in North American bridge design guidelines yielded overly cautious predictions of the BFRP bars’ interface shear strength. The study conclusively demonstrates the viability and potential of using BFRP bars as shear connectors in composite precast concrete girders supporting cast-in-place bridge-deck slab applications.