由于斜拉索护套自然老化和受损破裂等原因，暴露在自然环境中的斜拉索钢丝容易发生腐蚀破坏，并且承受交变荷载作用，因此有必要对环境腐蚀下钢丝多尺度疲劳损伤演化机理展开研究。通过钢丝室内加速腐蚀试验研究腐蚀坑分布特性，采用分形理论建立钢丝腐蚀坑时变概率模型，探讨钢丝锈蚀程度评定方法。开展多组多系列钢丝腐蚀疲劳试验，确定不同锈蚀程度下钢丝疲劳寿命与循环应力之间的关系，基于Goodman准则对S-N曲线进行修正，分析腐蚀坑对疲劳寿命的影响，提出基于分形维数的腐蚀疲劳寿命预测新方法；建立一种新的多尺度腐蚀疲劳裂纹扩展模型，对钢丝三维腐蚀疲劳裂纹扩展进行分析并验证模型有效性；选取合适的损伤变量建立钢丝腐蚀疲劳损伤非线性演化方程。综合考虑受载状况、工作环境、结构体系、材料特性、钢丝断裂等随机性因素，提出斜拉索腐蚀疲劳可靠度及耐久性评估方法，完善斜拉桥全寿命设计理论，为在役斜拉桥的损伤诊断提供理论依据。

Due to natural aging and cracking of stay cable sheath, stay cable wires exposed to the natural environment are prone to corrosion damage and subjected to an alternating load. It is necessary to investigate the evolution mechanism of multi-scale fatigue damage of wires under environmental corrosion. According to the indoor accelerated corrosion test of wires, the distribution characteristics of corrosion pits are studied. The time-varying probability model of corrosion pits is established based on fractal theory. The evaluation method of corrosion degree of wires is discussed. Multi-group and multi-series corrosion fatigue tests are conducted. The relationship between fatigue life of wires and cyclic stress is established under different corrosion degrees. The S-N curves of wires are modified by the Goodman criterion. The effect of corrosion pits on fatigue life is analyzed. A new method of corrosion fatigue life prediction based on fractal dimension is proposed. A new multi-scale corrosion fatigue crack growth model is created. The three-dimensional corrosion fatigue crack growth of steel wires is analyzed and the validity is verified. The appropriate damage variable is selected to establish the nonlinear evolution equation of corrosion fatigue damage of wires. The assessment method on corrosion fatigue reliability and the durability of stay cables will be carried out when random factors on loading condition, working environment, structure system, material properties and wire fracture are taken into account. The whole life design theory of cable-stayed bridge is improved, and it provides the theoretical basis for damage diagnosis of cable-stayed bridges.