Numerical analysis of debonding behavior of <scp>FRP</scp> sheets bonded to concrete focusing on mortar skin

Abstract This paper proposes a novel simple method for finite element analysis (FEA) to simulate the debonding behavior of fiber‐reinforced polymer (FRP) sheets bonded to concrete. This study focuses on the mortar skin of the concrete surface layer, which fails during FRP sheet debonding. We conducted three‐point flexural tests on thin specimens that imitate the material composition of the mortar skin to examine its characteristics. In addition, tests on specimens impregnated with primers were performed. Results indicated that the strength of the mortar skin near the concrete surface increased, with the application of an epoxy primer significantly enhancing the strength. Furthermore, tensile constitutive laws of the mortar skin were derived from the tests by performing an inverse analysis with FEA. A new simple method was proposed for numerical analysis to incorporate mortar skin properties into FEA simulations, replicating the debonding behavior of FRP sheets. The proposed method was applied to numerically reproduce existing bond tests across nine specimens with varying FRP sheet stiffnesses, bond lengths and resin type. The analysis results closely matched the experimental load–slip relationships, crack patterns, strain distributions, and bond stress–slip relationships, confirming its effectiveness in simulating FRP sheet debonding.