Shear stress and angular strain prediction of concrete panels reinforced with GFRP bars

Glass fiber-reinforced polymer (GFRP) bars are an alternative for reinforcing shear walls since tensile strength and density of GFRP bars are two times higher and four times lower, respectively, than those of conventional steel reinforcing bars. However, no models are reported in the available literature to predict the shear stress (τ) − angular strain (γ) curve of concrete panels reinforced with GFRP bars subjected to diagonal tension. This study proposes analytical models to estimate τ-γ for concrete panels and walls reinforced with GFRP bars. The suggested prediction models of concrete panels with GFRP bars were generated from the analysis of the τ-γ curve measured during diagonal tension tests of 21 concrete panels subjected to unreversed cyclic quasi-static loads. The study included the analysis of the test results of square concrete panels having 600 mm on each side and 100 mm thick with reinforcement ratios of 0.125 % and 0.25 % using GFRP bars with helical wrapping (GFH) and GFRP bars with sand coating (GFS). Benchmark panels reinforced using steel welded wire mesh (WWM) were also included to perform a comparative assessment. In the study, the parameters τ and γ associated to the limit states of concrete diagonal cracking, strain hardening, maximum and ultimate shear strength of the τ-γ curves were defined. The measured results showed that the parameters τ and γ can be calculated as a function of the reinforcement ratio, the design tensile stress of the reinforcement and its modulus of elasticity. This study also presents correlation equations to approximate the values of τ and γ between panels and walls.