Experimental study of fatigue behaviour of CFRP-to-concrete bonded joints employing the EBROG strengthening technique

Traditional systems for strengthening concrete structures, such as externally bonded reinforcement-fiber reinforced polymers (EBR-FRP) encounter difficulties associated with premature FRP debonding from the concrete surface. To overcome this challenge, this research introduces a novel strategy referred to as externally bonded reinforcement on grooves (EBROG). This innovative approach aims to efficiently tackle the issue of premature FRP debonding, thereby delaying or averting such occurrences. Despite extensive research on EBROG joints, their behavior under cyclic fatigue loading remains unexplored. In a pioneering effort, this paper provides an empirical exploration into the behavior of carbon FRP (CFRP)-to-concrete bonded joints employing the EBROG installation approach under low and high-cycle fatigue loading by using wide specimens. Twenty-three specimens underwent reinforcement through the EBROG approach with diverse groove dimensions, while an additional five specimens received strengthening via the EBR method. Subsequently, these specimens underwent single-lap shear tests under both monotonic and varying fatigue loading amplitudes. The results revealed that wider concrete specimens exhibited more capacity compared to previous research. Furthermore, the EBROG method significantly extended the fatigue life of CFRP-to-concrete joints within the same loading range as EBR. Conversely, tests indicated that the fatigue life of EBROG specimens is contingent on the loading amplitude and can be enhanced by reducing the maximum load level of cyclic loading. In a pioneering step, the paper introduces a formula to forecast the fatigue life of strengthened FRP/concrete joints employing the EBROG method.