An analytical cohesive crack modeling approach to the edge debonding failure of FRP-plated beams

This paper focuses on the prediction of edge debonding for a beam retrofitted with a Fiber-Reinforced Polymer plate. This failure mechanism, also known as plate-end debonding, stems from the concentration of interfacial stresses arising at the termination of the strengthening plate. Early models of edge debonding adopted failure criteria based on interfacial stresses. However, due to the typically catastrophic nature of this failure mechanism, approaches based on Linear Elastic Fracture Mechanics (LEFM) became increasingly established. In this paper, the problem is addressed by means of the Cohesive Crack Model (CCM) and of the Finite Fracture Mechanics (FFM). These models are able to bridge the gap between the stress- and the energy-based approaches and nevertheless have been used in a limited number of analytical studies to date. Based on a cohesive interface law with linear softening, closed-form solutions are derived for the interfacial stresses and the load–displacement curves, as well as for the ultimate load. It is found that LEFM usually overestimates the debonding load, thus justifying the need for the proposed approach; on the other hand, debonding load estimates based on FFM are in excellent agreement with the CCM predictions. Finally, a parametric analysis highlights the effect of the geometry/material properties on the structural response, as well as the ductile-to-brittle transition and the possible occurrence of structural instabilities depending on the test controlling parameters.