A semi-empirical model for bond strength between FRP composites and concrete

An accurate estimate of fibre-reinforced polymer (FRP)–concrete bond is essential for a successful FRP repair. The present work aims at developing a semi-empirical model employing a large database (about 500 data points) collected from various literature works. In the beginning, an iterative regression process was followed to establish the trend in behaviour (of each key parameter against bond strength) and decide on insignificant ones. Then, the different equations were merged and manipulated into a simplified model with three regression constants. These were determined based on two-thirds of the database points using the statistical software SPSS. The key parameters involved in the final simplified model included concrete properties (compressive strength and maximum aggregate size) and mechanical and geometric characteristics of the FRP composites (axial stiffness and bond width and length). The proposed model showed a high fit of the regression database at 0.88 coefficient of determination (R²) with a very limited number of outliers. Moreover, the accuracy of prediction by the present model of the validation database far exceeds that of all well-known semi-empirical and empirical models. The sensitivity of the present model to the changes in the key parameters confirms the trend in behaviours reported in the various experimental works and models.