考虑拉索抗力退化的斜拉桥体系可靠度评估

疲劳损伤和大气腐蚀作用致使斜拉索性能退化,影响斜拉桥运营期的安全水平.为了分析拉索抗力退化对斜拉桥体系可靠度的影响,建立了斜拉索抗力退化的串并联概率模型,提出基于机器学习的斜拉桥时变体系可靠度分析方法.以经典斜拉桥和某大跨度双塔混凝土斜拉桥为工程背景,研究了考虑拉索抗力退化的结构时变体系可靠度.研究结果表明:对于稀索体系的小跨度斜拉桥,随着斜拉索抗力的逐步退化,桥梁结构体系的主要的失效路径为由梁和塔的弯曲失效逐渐转变为由拉索腐蚀引起的拉索强度失效;当拉索抗力退化后的可靠度低于主梁关键截面可靠度时,结构体系可靠度将显著降低;对于密索体系的大跨度斜拉桥,在拉索疲劳和腐蚀共同作用下,该斜拉桥体系可靠指标将在29年降低到5.2.

System Reliability Assessment of Cable-stayed Bridges Considering Cable Resistance Degradation

Fatigue damage and atmospheric corrosion lead to the degradation of cable performance, which affects the lifetime safety risk of the cable-stayed bridge. In order to investigate the influence of cable resistance degradation on the system reliability of cable-stayed bridges, a series-parallel probability model of the cable resistance was established. A framework for time-variant system reliability evaluation of cable-stayed bridges was presented based on machine learning. Both a typical bridge and a long-span cable-stayed bridge were selected as prototypes to investigate the influence of the cable degradation on their structural system reliability indices. Numerical results show that the dominant failure sequence of the short-span bridge with short-spacing cables changes from the bending failure of girders and pylons to the tensile failure of cables due to the cable corrosion. As a result, the structural system reliability significantly decreases in the period that the cable reliability is inferior to the one of the critical girder. For the long-span bridge with long-spacing cables, the system reliability index decreases to the threshold value 5.2 in the 29-year service period taking into account both fatigue and corrosion.