交变荷载与侵蚀环境耦合作用下斜拉索腐蚀疲劳损伤机理与寿命预测模型研究

The stay cable system have been exposed to the natural environment under cyclic loading, so they are susceptible to environmental corrosion, especially for the anchorage zone with complicated structures and concentrated force. These damage will endanger the safety of cable-stayed bridge. This project puts the serve safety of long-span cable-stayed bridge as the breakthrough. On the bases of meso-damage mechanics theory, a series of accelerated corrosion experiments are carried out for the cable wires under cyclic loading. The corrosion fatigue damage mechanism and evolution rules are studied of the stay cable under coupled alternating stress and corrosive environment. The effects are revealed of the alternating stress on the cable corrosion fatigue performance. Then a prediction model of the residual life and the evaluation method of damaged safety are proposed for the stay cable. This research can provide theoretical basis for evaluating the technical condition, prolonging life and improving anticorrosion design of the stay cable. Compared with other scholars' research, there are two features and innovation in this project. One is the equivalent damage theory and decoupling method of cyclic loading and environmental parameters. They can achieve a breakthrough of the corrosion fatigue test benchmark for the cable. The other is a prediction model of the residual life of damaged cable based on the equivalent depth and growth rate of corrosion fatigue crack. It is expected to promote the research of the cable damage safety evaluation from macro scope to microscope.

斜拉桥拉索系统长期承受交变荷载并暴露于自然环境中，特别是构造复杂、受力集中的锚固区极易遭受侵蚀性环境的腐蚀，危及桥梁运营安全。本项目以大跨径斜拉桥服役安全性为突破点，以细观损伤力学理论为基础，开展交变荷载与侵蚀性环境耦合作用下拉索加速腐蚀试验研究，探索拉索腐蚀疲劳细观损伤机理与演化规律，揭示交变应力对拉索腐蚀疲劳损伤的耦合作用机理，建立腐蚀疲劳损伤拉索的剩余寿命预测模型与破损安全评价方法，从而为科学评价斜拉桥拉索技术状况、延长拉索使用寿命和改进拉索防腐蚀设计提供理论依据。与国内外同行研究相比较，本项目研究特色在于：1）提出交变荷载与环境参数的耦合损伤等效理论与解耦方法，以实现拉索腐蚀疲劳试验研究基准（Benchmark）的突破；2）建立基于腐蚀疲劳裂纹等效深度与扩展速率的拉索剩余寿命预测模型，有望推进拉索破损安全评价研究从宏观向细观尺度发展。

斜拉桥、悬索桥、吊杆拱桥缆索系统长期承受交变荷载并暴露于自然环境中，特别是构造复杂、受力集中的锚固区极易遭受侵蚀性环境的腐蚀，危及桥梁运营安全。本项目研究以桥梁缆索结构长期性能与服役安全为突破点，以细观损伤力学理论为基础，采用人工加速腐蚀试验、理论模型、数值仿真以及工程应用等研究方法，通过开展交变荷载与侵蚀性环境耦合作用下拉索加速腐蚀试验，研究桥梁拉吊索钢绞线、钢丝在盐雾、酸雨、电化学环境分别与静态应力、交变应力耦合作用下的应力腐蚀、腐蚀疲劳损伤特性，对影响拉吊索长期性能与服役寿命的荷载与环境参量及其耦合因子开展研究，进一步结合实桥现场检测结果对在役桥梁开展了拉吊索系统可靠性及剩余寿命评估的研究。.本项目取得的重要结果如下：（1）提出了基于拉索损伤等效的人工加速腐蚀疲劳实验相似准则，并据此建立交变荷载与盐雾、酸雨、电化学等侵蚀环境参数的解耦方法，实现了拉索腐蚀疲劳试验研究基准（Benchmark）的突破；（2）揭示了拉索在交变荷载与侵蚀性环境耦合作用下的腐蚀疲劳损伤演化机理，建立拉索腐蚀疲劳细观损伤演化模型；（3）基于细观损伤力学理论揭示了拉索腐蚀疲劳裂纹等效深度与扩展速率的变化规律，提出拉索剩余寿命预测模型与破损安全评价方法，推进拉索破损安全评价研究从宏观向细观尺度发展。.本项目研究的科学意义在于：（1）开展的腐蚀疲劳试验实现了交变荷载与盐雾、酸雨、电化学腐蚀环境的耦合作用与腐蚀疲劳损伤的解耦，实现桥梁缆索结构腐蚀疲劳试验基准（Benchmark）的突破；（2）从细观尺度上建立了基于腐蚀疲劳裂纹等效深度与扩展速率的拉索剩余寿命预测模型，为科学评价桥梁缆索结构长期性能与安全、延长拉索使用寿命和改进拉索防腐蚀设计提供理论依据。