在施工过程中施工误差对大跨径斜拉桥极限承载力影响的研究

Research on Ultimate Bearing Capacity for Long-Span Cable-Stayed Bridges due to Construction Deviation During Erection

在斜拉桥施工过程中由于不可避免地产生几何尺寸和索力的误差时,主梁和主塔也会产生偏离理论纵轴线的误差,当悬臂施工过程中悬臂长度增大时斜拉桥主梁就会发生出平面的变形。当前斜拉桥跨径已经突破千米,如果施工误差引起悬臂施工中主梁的平面外偏移,则必然降低结构的安全性。文中综合考虑影响斜拉桥几何非线性的因素,同时计及材料非线性,基于Monte Carlo思想对斜拉索索力随机误差进行了模拟,利用大型通用有限元程序ANSYS对千米级斜拉桥按照第二类稳定问题的求解方法对其施工过程进行了模拟分析,主要考察了斜拉桥处于最大双悬臂和中跨最大单悬臂状态时的最不利施工工况下结构的极限承载力,给出了不同施工误差下大跨径斜拉桥荷载安全系数的比较和分析结论。

It is inevitable that deviations will occur on the geometry of deck and pylon, tension of cable forces during construction. Especially, as growing of deck cantilever, the deck will be deformed transversely due to the deviations. If efficient measures can not be taken for adjustment in time, it will make the deck difficult for closure, even result reducing security of whole structure for thousand-meter scale cable-stayed bridges. In this paper,based on geometric and material nonlinearities and Second Stability Theory, considering cable force errors simulated with Monte Carlo method and out of plan deck deformation, the ultimate bearing capacity of whole structure was checked according to the worst construction cases of the longest double-cantilever and the longest single-cantilever stage of the middle span. Through comparison and analysis under different construction deviations for a long-span cable-stayed bridge, the relative structural safety coefficient was given.