Semi-empirical models for predicting mode-II bond indicators between FRP and concrete

The bond behaviour between fibre-reinforced polymer (FRP) composites and concrete is a complex problem that is influenced by material properties, joint geometric configuration and the surrounding environment. The three fundamental bond performance indicators of concern are interfacial fracture energy, bond strength and debonding strain. This paper introduces a new semi-empirical model for predicting interfacial fracture energy (G_f) between externally bonded FRP and intact concrete in terms of the most influential material and geometric parameters, namely concrete's compressive strength and maximum aggregate size, stiffness of FRP composites and bond width and length of FRP composites relative to the dimensions of the concrete member. The prediction of G_f helped generate accurate predictions for the other two bond performance indicators. The present model was developed using non-linear regression analysis before validation using almost one-third of the total database consisting of 425 points, collected from credible publications. The accuracy of the present model of G_f outperformed those of well-known literature. The excellent agreement in trend behaviour of the present model with those reported in related literature works postulated further the model's validity. The estimation of debonding strain and bond strength in terms of fracture energy demonstrated superior accuracy over those provided by different relevant literature models.