Semi-Empirical Model for Load-slip Response of Externally Bonded FRP Strengthened Reinforced Concrete Structures

Abstract

Understanding the interfacial bond behavior between externally bonded fiber-reinforced polymer (EB-FRP) and concrete is essential for the effective strengthening of civil structures. Various bond-slip models exist, but most analytical models are too complex for practical engineering, and empirical models lack flexibility across diverse configurations. Furthermore, existing models are generally based on small-scale tests that do not adequately represent real-world construction conditions. This study presents a semi-empirical bond-slip model that integrates experimental observations with fracture mechanics principles to predict debonding behavior. Strain distributions and debonding mechanisms were captured using digital image correlation (DIC) in 24 large-sized EB-FRP strengthened reinforced concrete (up to 915 mm in length, 2 mm in thickness) subjected to single-lap shear tests. The model applies an interfacial analytical approach based on fracture mode II (sliding shear) and uses multivariable nonlinear regression to account for key bond indicators. Validation of the model against a dataset of 1,659 single-lap shear tests reported in the literature confirms the accuracy in predicting load-slip responses. The proposed bond-slip model offers a practical and scalable tool for calculating the debond capacity efficiently, making it valuable for both research and industry applications in large-sized EB-FRP systems

This work was supported by the Ministry of Business, Innovation and Employment (MBIE) Endeavour Fund – Smart Ideas [Project No.: 3724823]; New Zealand’s Centre for Earthquake Resilience (QuakeCoRE) – Disciplinary Theme 2 (DT2) [Project No.: 3724367]; and the University of Auckland Postgraduate Research Student Support (PReSS) [Project No.: AJHZ740]