Consistency of Bond–Slip Models in Simulating the Bond between ETS-FRP Bars and Concrete and the Shear Contribution of the Strengthening System

Abstract

Predicting the shear contribution of a fiber-reinforced polymer (FRP) strengthening system in a reinforced concrete (RC) beam strengthened using the embedded through-section (ETS) method remains challenging due to the complex shear mechanisms involved. The present study proposes a new approach that analyzes the shear resistance mechanism for ETS-FRP strengthening bars by investigating their bonding behavior with concrete. First, the consistency of existing bond models and parameters for simulating the bond profile for ETS-FRP bar-to-concrete joints was studied using a simplified finite discretization method (FDM). After validation using pullout tests, the maximum bond stress, slip at peak bond stress, and slip at complete debonding were found to be consistent for all bond laws. This allows researchers and engineers to conveniently obtain suitable bond parameters for their designs. A bonding-based approach coupled with the FDM that considers various bond rules and crack compatibility for analysis of the ETS shear contribution was then developed. The proposed approach can analyze the behavior and failure progress for single ETS strengthening elements. Based on corroboration using 46 sets of beam data, the proposed method was found to more accurately predict the ETS-FRP shear contribution than current shear design models. The results of this study indicate that using the proposed method, the ETS shear resistance can be reliably estimated by applying bilinear, trapezoidal, and nonlinear bond laws considering the compatibility of nonuniform crack widths.