Degradation in Flexural Capacity of CFRP Strengthened RC Beams Anchored by Fiber Bundles Under Seawater Wet-Dry Cycle

To address the issue of deterioration and delamination of the bonding interface between Carbon fiber-reinforced polymer (CFRP) and reinforced concrete (RC) beams under environmental effects such as salt erosion and wet-dry cycle in coastal environments, which leads to a reduction in flexural bearing capacity, additional anchoring at the CFRP ends can effectively enhance the anti-delamination capability and bearing capacity of the interface. To investigate the degradation pattern of the flexural performance of RC beams strengthened with additionally anchored CFRP under seawater wet-dry cycling conditions, four-point loading tests were conducted on CFRP-strengthened RC beams with fiber bundle anchorage at their ends after 0, 60, 120, 180, and 240 wet-dry cycles. Additionally, comparison groups were established to explore the influence of different fiber bundle anchorage configurations. The test results indicate that as the number of wet-dry cycles increases, the bond and anchorage performance at the interface deteriorates, and the failure mode of the strengthened beams gradually changes from fiber bundle anchor shear fracture to pull-out failure. The cracking, yielding, and ultimate loads of the beams progressively decrease, with reductions of 39%, 23%, and 10%, respectively, after 240 cycles. Under the same number of wet-dry cycles, a greater number of in-line anchor bundles results in stronger anchorage effects. Compared to non-anchored specimens, full-length anchored specimens exhibit fiber breakage failure, with a 48% increase in load-bearing capacity. Specimens with in-line triple-anchor, triangular anchorage, and in-line double anchor configurations demonstrate similar force and deformation behaviors, with approximately a 25% increase in load-bearing capacity and a CFRP utilization rate of around 75%. In contrast, U-shaped hoop anchorage only results in 5% increase in load-bearing capacity, with a CFRP utilization rate of 66%. Finally, based on the comprehensive test data and analysis, a degradation coefficient for the ultimate load of FRP-strengthened beams with additional in-line double anchor configurations is provided.