Modeling NSM FRP strengthened RC beams under fatigue due to IC-debonding

Abstract

This paper presents an analytical model proposed to predict the flexural fatigue behavior and fatigue life of reinforced concrete (RC) beams strengthened with near-surface mounted (NSM) fiber reinforced polymer (FRP) reinforcements subject to intermediate crack-induced debonding failure. In deriving this model, a trilinear behavior is assumed for the bond-slip relationship of FRP-concrete interface. Based on a model previously developed for strengthened beams under monotonic loading, the proposed fatigue model considers the fatigue bond heterogeneity by imposing a degradation law for the peak interfacial shear stress. Theoretical solutions to the flexural behavior throughout the fatigue life are obtained by imposing appropriate boundary conditions. The predicted fatigue life under debonding failure mode and flexural behavior (e.g., tensile strain of the NSM reinforcement) are further verified by comparisons with existing experimental data, where good agreement is reached. The subsequent parametric study shows that higher concrete compressive strength and bond strength of NSM improves the flexural behavior under fatigue and elongates the fatigue life. The diameter and Young’s modulus of the NSM reinforcement have insignificant effect on the fatigue flexural behavior.