The paper approaches the effect of environmentally assisted damage on the fatigue resistance of the tie-down cables from a cable-stayed bridge after the failure of two seven-wire prestressing steel strands from distinct cables. The strands failed where their manufacture protection had been partially removed for anchoring, with the research being performed as support for the repair solutions explored. The experimental program sought to reproduce in-laboratory the service-induced damage in wires and strand samples extracted from the sheath protected parts of the broken strands in order to determine the remanent fatigue life. Thus, data obtained from constant amplitude fatigue tests in the stress range of 200 MPa were correlated with micro- and macro- fractographic analyses of specimens with laboratory-replicate damages by using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) techniques. The fatigue tests confirmed that nominally damage-free wires still preserve after 30 years of service the fatigue strength specified by current standards. Only the strongly damaged wire specimens failed when fatigue tested in the applied stress range of 200 MPa. Infinite fatigue life without any resistant capacity loss was also being found in the moderately damaged wires. From the fatigue tests of the strands, it was noted that the laboratory-reproduced damage was less critical than that induced by the commercial clamping wedges, deliberately used for the strand gripping during testing.

中文翻译：

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环境辅助损伤对斜拉桥使用 30 年后系紧索疲劳强度的影响

本文探讨了在不同缆索的两根七线预应力钢绞线失效后，环境辅助损伤对斜拉桥系留缆索疲劳强度的影响。这些钢绞线因锚固而部分去除了制造保护，因此发生故障，正在进行的研究是为了支持所探索的修复解决方案。该实验计划试图在实验室中重现从断裂绞线的护套保护部分提取的电线和绞线样品中的使用引起的损坏，以确定剩余疲劳寿命。因此，通过使用扫描电子显微镜 (SEM) 和能量色散 X 射线光谱，将在 200 MPa 应力范围内的等幅疲劳试验中获得的数据与实验室重复损伤样本的微观和宏观断口分析相关联。 EDX）技术。疲劳测试证实，名义上无损坏的电线在使用 30 年后仍能保持现行标准规定的疲劳强度。在 200 MPa 的外加应力范围内进行疲劳测试时，只有严重损坏的线材样本才会失效。在中度损坏的电线中也发现了无限的疲劳寿命，而没有任何抵抗能力损失。从钢绞线的疲劳测试中可以看出，实验室再现的损坏不如商业夹紧楔块引起的严重，商业夹紧楔块在测试过程中故意用于夹紧钢绞线。