Research on the durability performance of CFRP bonded anchors subjected to coupled multi-factor conditions

Large carbon fiber reinforced polymer (CFRP) tendon anchors are bonded anchors, which have durability issues due to degradation of the bond between the anchor and the anchor interface. This paper tests the mechanical behavior of 54 CFRP tendons under various adverse environmental factors and loads through pull-out tests to study the mechanical behavior of the bond interface in the anchorage zone. These adverse factors include freeze-thaw cycles, temperature, temperature-humidity coupling, and temperature-humidity-sustained load coupling. Through testing, the influence of the above adverse environmental factors on the maximum pull-out force and residual bond strength of the bonded interface was obtained. Thus, these findings allowed for the evaluation of adverse environmental factors on the ultimate tensile strength of the CFRP anchors. The results show that after 30 and 50 freeze-thaw cycles, the maximum pull-out force decreased by 6.87% and 22.34% compared to the control group, respectively. Temperature weakens the bonding performance in the short term, but in the long term, post-curing reaction can increase the maximum pull-out force by 13% to 20%. The maximum pull-out force decreased by 6.9% in a temperature-humidity coupled environment, while the residual bearing capacity increased by 42.67% due to increased friction. The maximum pull-out force further decreased by 16.55% under the combined conditions of temperature, humidity, and sustained load. Finally, it was concluded that the combination of multiple factors (temperature, humidity, freeze-thaw, and sustained load) was the most unfavorable condition, leading to a maximum pull-out force decrease of 32.37% and a complete change in the failure mode to interface failure. This study provides an important basis for the durability of CFRP used in tensile members of bridges.