桥梁缆索钢丝疲劳性能影响因素试验

为研究桥梁缆索钢丝的疲劳与腐蚀疲劳性能，采用不同强度等级新钢丝、服役7年的斜拉桥拉索钢丝和人工加速腐蚀钢丝开展了缆索钢丝疲劳与腐蚀疲劳试验；根据典型疲劳断口宏观形貌特征，探究了缆索钢丝的疲劳断裂机制；采用威布尔分布函数拟合了缆索钢丝的应力-疲劳寿命曲线，对比了不同钢丝应力-疲劳寿命曲线的差异，揭示了强度等级、应力比、腐蚀损伤和腐蚀疲劳损伤4个关键因素对缆索钢丝抗疲劳性能的影响规律，并建议了相应的疲劳强度曲线。试验结果表明：钢丝未发生腐蚀时抗疲劳性能良好，随着强度等级的提高，缆索钢丝的疲劳强度显著增大，对应的疲劳极限也逐渐上升；缆索钢丝的疲劳强度随应力比的增大而显著减小；腐蚀和腐蚀疲劳损伤均会大幅降低缆索钢丝的疲劳强度，腐蚀疲劳损伤对缆索钢丝剩余疲劳寿命的影响大于单一腐蚀损伤；新钢丝的疲劳裂纹起源于表面划痕或材料不均匀处，对于带腐蚀和腐蚀疲劳损伤的钢丝，蚀坑处存在显著的应力集中，疲劳裂纹源形成于钢丝表面蚀坑处，多源裂纹萌生与裂纹不规则扩展的几率增大；桥梁缆索抗疲劳设计与安全评估时应综合考虑钢丝强度等级、应力比、腐蚀和腐蚀疲劳损伤的影响，试验采用国内桥梁缆索广泛使用的钢丝，得到的疲劳强度可供桥梁缆索抗疲劳设计与寿命预测时参考。

Experiments on factors affecting fatigue performance of bridge cable steel wires

To study the fatigue and corrosion fatigue performance of bridge cable steel wires, fatigue and corrosion fatigue experiments of cable steel wires were conducted by using new steel wires of different strength grades, cable steel wires of a cable-stayed bridge in service for seven years, and steel wires treated with artificially accelerated corrosion. According to the macroscopic morphology characteristics of typical fatigue fractures, the fatigue fracture mechanism of cable steel wires was explored. The Weibull distribution function was adopted to fit the stress-fatigue life curves of cable steel wires, and differences in the stress-fatigue life curves of different steel wires were compared. The influences of four key factors including the strength grade, stress ratio, corrosion damage, and corrosion-fatigue damage on the fatigue resistance of cable steel wires were revealed, and the corresponding fatigue strength curves were suggested. Test results show that the uncorroded steel wires have excellent fatigue resistance. With the increase in the strength grade, the fatigue strength of cable steel wires increases significantly, and the corresponding fatigue limit improves gradually. The fatigue strength of cable steel wires decreases significantly as the stress ratio improves. Both the corrosion damage and corrosion-fatigue damage significantly reduce the fatigue strength of cable steel wires, and the remaining fatigue life of cable steel wires is greatly affected by the corrosion-fatigue damage than the single corrosion damage. The fatigue cracks of the new steel wires derive from the surface scratch or uneven places of the material. For the steel wires with corrosion damage and corrosion-fatigue damage, the stress concentration is significantly found at the corrosion pit, the fatigue cracks are originated from the corrosion pit on the steel wire surface, and the probabilities of multi-source crack initiation and irregular crack propagation increase. The influences of strength grade, stress ratio, corrosion damage, and corrosion-fatigue damage of steel wires should be considered comprehensively in the bridge cable fatigue resistance design and safety assessment. The steel wire widely used in bridge cables in China is used in the test, and the fatigue strength obtained can be referenced by the fatigue resistance design and life prediction of bridge cables.