Punching-Shear Strength of Normal and High-Strength Two-Way Concrete Slabs Reinforced with GFRP Bars

This paper investigated the punching-shear behavior of two-way concrete slabs reinforced with glass fiber-reinforced polymer (GFRP) bars of different grades. A total of 10 full-scale interior slab-column specimens measuring 2,500 x 2,500 mm with thicknesses of either 200 or 350 mm and 300 x 300 mm square column stubs were fabricated with normal and high-strength concretes. The specimens were tested under monotonic concentric loading until failure. The effects of concrete strength as well as reinforcement type and ratio were evaluated. The test results revealed that increasing the reinforcement ratio resulted in higher punching-shear capacity, lower reinforcement and concrete strains, and lower deflections. In addition, the high-strength concrete increased the punching-shear capacity, significantly reduced concrete strains, increased strains in the GFRP reinforcing bars, and reduced deflection due to the high tensile strength and modulus of elasticity. The test results and results from literature were used to assess the accuracy of the punching-shear provisions of fiber-reinforced polymer (FRP) design codes and guides. Despite the 60 MPa limit of the Canadian standard punching-shear equation, it yielded good predictions for specimens with concrete strengths of 71-75.8 MPa. (C) 2013 American Society of Civil Engineers.