Modeling of shear mechanisms and strength of concrete deep beams reinforced with FRP bars

Abstract

With the growing application of concrete structures reinforced with fiber reinforced polymer (FRP) composite materials, it is necessary to develop more rational mechanical models for their load-carrying capacity evaluation. Firstly, this study numerically analyzed the influences of differences in bond behavior and axial stiffness between FRP and steel bars on the shear behavior of concrete deep beams. It was identified the reinforcement stiffness is the main influencing factor, and an explanation on how the reinforcement stiffness influences the shear performance of deep beams at the mechanism-level was also provided. On this basis, a mechanical cracking strut-and-tie model (CSTM), which theoretically considered the effect of the critical shear crack on the diagonal strut capacity, was proposed to predict shear mechanisms and strength of concrete deep beams reinforced with FRP bars. The proposed CSTM was verified by a shear database of 52 existing tests and compared with predictions of other models. In addition, for purpose of practical design, a simplified CSTM was proposed and verified to be superior to the shear models of CSA S086-12 and ACI 440.1R-15 in terms of safety margin and accuracy.