Rational prediction of punching shear strength of slabs reinforced with steel or FRP bars

Three two-way slabs reinforced with glass-fibre-reinforced polymer (GFRP) bars were tested, and previous experimental results from two steel-reinforced slabs were used as companion specimens in order to investigate the punching shear behaviour of slabs. The main variables were the slab reinforcement material (steel or GFRP) and the concentration of slab reinforcement around the column. From the experimental results analytical derivation, a rational expression to compute the punching shear strength of two-way concrete slabs was derived. The expression for punching shear strength was further enriched to take into account the elastic modulus of the reinforcement, inclination of the punching crack, flexural reinforcement ratio, size effect and dowel effect. The proposed predictive model was verified by comparison with experimental results, and its accuracy was evaluated through comparisons with various other prediction models. The comparisons confirmed that the proposed model renders fairly accurate and consistent predictions of the punching capacity for either steel- or FRP-reinforced slabs.