Bond performance of CFRP strengthening and hybrid anchoring systems for RC elements: experimental and analytical studies

ENG- In recent decades, strengthening existing reinforced concrete (RC) structures has become increasingly important due to the high cost of replacing structural elements. Among available solutions, carbon-fiber reinforced polymers (CFRP) applied using the externally bonded reinforcement (EBR) technique are widely used because of their simplicity and efficiency. However, a major limitation of EBR is premature debonding, which prevents full utilization of the FRP tensile capacity. To address this issue, several alternative techniques have been developed, such as near-surface mounted (NSM), externally bonded reinforcement on grooves (EBROG) and in grooves (EBRIG), as well as mechanical anchorage and hybrid bonded (HB) systems. Despite these advances, premature debonding remains a critical challenge, requiring a deeper understanding of bond mechanisms and their evolution. This thesis investigates bond behaviour through single-shear pull-out tests on specimens strengthened with EBR, EBROG, NSM and HB. The results were used to examine the different bond–damage mechanisms and to validate a novel numerical methodology capable of identifying the bond–slip law without assuming a predefined shape. The methodology combines a multilinear representation, a finite-difference formulation, and a metaheuristic optimization algorithm, and was validated against synthetic data generated through finite element models under varying conditions. The thesis then focuses on the HB system to characterize its monotonic and fatigue bond behaviour and to better understand premature failure mechanisms. An experimental program under cyclic pull-out loading was performed to evaluate fatigue damage progression as a function of load level and static capacity