Study on Aging Performance of BFRP Cables in Long-Span Sea-Crossing Cable-Stayed Bridges Under the Coupling Effect of Light, Heat, Water, Salt, and Prestress

The anti-aging performance of stay cables in complex marine environments is directly related to the long-term service safety of sea-crossing cable-stayed bridge structures, and it has been recognized as one of the key issues for the priority evaluation of the structural performance of sea-crossing cable-stayed bridges with Basalt Fiber Reinforced Polymer (BFRP) cables. In this paper, the coupled aging effects of ultraviolet radiation, salt spray, temperature and humidity, and prestress on BFRP cables were taken into consideration. Accelerated aging tests involving the coupling of light, heat, water, salt, and prestress were carried out to simulate the actual marine service environment. The anti-aging performance of BFRP cables was investigated by combining the analysis of macro mechanical properties with the characterization of micro structural morphology. The results of the study were as follows: (1) With the increase in aging duration, the tensile strength and ultimate fracture strain of BFRP cables decreased gradually. The degradation rates of tensile strength and ultimate fracture strain of BFRP cables exhibited a decreasing trend, characterized by an initial rapid phase followed by a gradual slowdown under the coupled aging effects of light, heat, water, salt, and prestress. (2) Compared with the significant decrease in tensile strength, the elastic modulus of BFRP cables showed an insignificant decrease. The elastic modulus of BFRP cables was observed to exhibit a trend of initial decrease, subsequent increase, and another decrease, with an overall reduction. (3) Temperature and prestress were verified to exert a considerable influence on the anti-aging performance of BFRP cables. The influence of temperature on the degradation of aging performance of BFRP cables was found to be greater than that of prestress. (4) The degradation in the anti-aging performance of BFRP cables under coupled aging effects was confirmed to originate from the initiation and propagation of microcracks in the resin matrix, which were caused by the combined actions of prestress, photochemistry, and hydrolysis. Meanwhile, the damage to the fiber–resin interface was accelerated by chloride ions in seawater under high-temperature conditions, which ultimately led to a reduction in the anti-aging performance of BFRP cables.