Predictive modeling of bond strength and failure strain in FRP-to-concrete joints considering groove classification

Externally bonded reinforcement on grooves (EBROG) is an effective method for strengthening concrete structures with fiber-reinforced polymer (FRP) composites. Groove classification, based on variations in depth, width, spacing, and direction, offers a wide range of design options for EBROG joints. Although several equations have been proposed to predict the interfacial bond strength or failure strain in FRP-to-concrete joints, their accuracy remains limited due to the lack of consideration for groove classification. This study proposes a predictive model for FRP-to-concrete interfacial bond strength and failure strain considering varying groove classifications based on non-linear regression analysis. The proposed model was developed using experimental data from 194 single-lap shear tests reported in the literature, with 111 specimens used for model development and 83 for validation. Results indicate that the proposed model achieves high accuracy in predicting the failure strain of FRP-toconcrete joints across different groove classifications, with a coefficient of determination (R²) of 95% and a coefficient of variation (CV) of 8%. A case study of 240 scenarios examined design parameter optimization. Results show FRP failure strain decreases with higher concrete strength and FRP stiffness. Among groove classes, 5@15 mm performed best, providing optimal FRP utilization and overall structural efficiency.