Shear behavior of box‐section concrete beams reinforced by FRP bars and FRP stirrups

Abstract A few research studies are available on the behavior of reinforced concrete (RC) box section beams with fiber‐reinforced polymer bars (FRP) and FRP stirrups. Consequently, the behavior of these beams needs to be investigated. This article studies experimentally, numerically, and analytically the effect of some variables on the behavior of RC box section beams. This article investigates many variables, such as the shear span‐to‐total depth ratio, the flexural FRP reinforcement ratio, and the FRP vertical and horizontal web reinforcement ratio. The experimental program consists of nine simply supported reinforced concrete box section beams. The numerical models using the nonlinear finite element program ANSYS V.15 are carried out. The results are compared to the experimental results using load‐deflection curves, crack patterns, failure loads, and failure modes. The shear capacities based on Egyptian ECP 208‐2019 and ACI 440‐2015 codes are compared to each other and to the experimental results. The findings show an adequate agreement between the experimental, numerical, and analytical results for the range of the studied parameters. The results reveal that increasing the shear span‐to‐depth ratio by 50% decreases the carrying capacity, toughness, and displacement ductility by 2%, 28%, and 12%, respectively. The increase in main FRP reinforcement rebars by 20% increases the carrying capacity and toughness by 59% and 62%, respectively. Increasing vertical FRP stirrups by 79% increases the failure load and toughness by 26% and 15%, respectively, and displacement ductility increases only by 0.8%. The increase in horizontal FRP stirrups by 79% increases the failure load, toughness, and displacement ductility by 33%, 8%, and 4%, respectively. Both Egyptian and American codes are conservative in some cases and unconservative in others, while the numerical results are unconservative.