Two-Parameter Kinematic Approach for complete Shear Behaviour of Deep FRC Beams

While tests of deep fiber-reinforced 1 concrete (FRC) beams have shown that steel fibers enhance the crack control and shear strength, the modeling of these effects in a simple and rational manner remains a challenging problem. Because FRC features enhanced tension behavior, it is not well suited for the traditional strut-and-tie approach which neglects the tension in the concrete. Therefore, this paper proposes an alternative approach which focuses on the displacements in the critical shear cracks. The displacements are described with a kinematic model with two degrees of freedom, and are used with appropriate constitutive relationships to estimate the shear contribution of the fibers. This kinematics-based approach is validated with experimental data, and it is shown to capture adequately the complete pre- and post-peak behavior of deep FRC beams. It is also shown that the model predicts well the effect of beam aspect ratio, fiber volume ratio, longitudinal reinforcement ratio and concrete strength on the shear strength of deep FRC beams.