Finite-Element Analysis and Strength Model for IC Debonding in FRP-Strengthened RC Beams

Abstract

Intermediate crack (IC) debonding is one of the most dominant failure modes associated with reinforced concrete beams strengthened with fiber-reinforced polymer (FRP) plates. To obtain a better understanding of the mechanism of IC debonding, a comprehensive finite-element (FE) model based on the smeared-crack method is proposed to predict IC debonding failure. This model adopts a crack band model for concrete and incorporates a bond–slip relationship between the steel bars and surrounding concrete, as well as between the FRP plates and concrete substrate. The proposed model is found to be capable of accurately predicting the appearance, development and distribution of cracks in concrete. Furthermore, the concentration of interfacial slip and abrupt changes in the interfacial shear stress and FRP plate strain due to cracking can be predicted accurately, and IC debonding is successfully captured. Comparisons between the numerical and experimental results of 35 beams confirm that the proposed FE model is appropriate for predicting the IC debonding of the strengthened beams. Finally, a simple and accurate model of the FRP debonding strain is proposed based on the FE interfacial shear stress distribution. The accuracy of the model is verified by comparing the strength model with the results of 116 beam tests.