Bond behavior of GFRP bar-concrete interface: Damage evolution assessment and FE simulation implementations

This study presents a bond damage assessment approach for the glass fiber-reinforced polymer (GFRP) bar-concrete interface. The damage evolution equations are proposed based on the strain equivalence principle of damage mechanics, where the variations of the secant modulus of the bond-slip curve are utilized to evaluate the interface deterioration against slip. Numerical analyses are conducted with the ANSYS finite element (FE) program to simulate the bond behavior of pullout test. Nonlinear material behaviors of the GFRP composite and concrete matrix with respect to plain concrete and fiber-reinforced concrete (FRC) are implemented using appropriate constitutive models. The interfacial bond-slip behavior is implemented using nonlinear spring elements. Numerical predictions are validated by the experimental results and compared with the widely used analytical models accounting for the FRP-concrete bond. Upon this, the bond damage evolution curves are derived thereafter, which are found to strictly follow the lognormal distribution or Weibull distribution. Further comparisons of different specimens are performed to investigate the critical factors and their impacts on the damage evolution, as well as those on the critical bond damage corresponding to the bond strength.