南京长江五桥主桥结构非线性稳定性研究

南京长江五桥主桥为主跨600m的三塔组合梁斜拉桥,半飘浮体系。为研究该桥在施工和运营阶段的极限承载能力,采用ANSYS软件建立全桥有限元模型,考虑几何与材料非线性,计算施工全过程及主要运营阶段各工况下结构的非线性稳定系数,评估主要构件的承载能力,并探讨桥塔钢壳与斜拉索破断对结构非线性稳定性的影响。结果表明:施工阶段及运营阶段,该桥的整体非线性稳定系数均大于临界值2.0,结构的稳定性能满足要求;三大受力构件中,主梁的承载能力最强,桥塔次之,斜拉索的承载能力相对最弱;桥塔钢壳对提升结构整体稳定性能具有不可忽略的作用;与考虑斜拉索破断时相比,不考虑斜拉索破断时结构的非线性稳定系数显著提高。

Study on Nonlinear Stability of Structure for Main Bridge of Fifth Changjiang River Bridge in Nanjing

The main bridge of Fifth Changjiang River Bridge in Nanjing is a semi-floating cable-stayed bridge with main span of 600 m, which possesses three pylons and composite girder. In order to study the ultimate bearing capacity during construction and operation stages, we established a finite element model of the main bridge by ANSYS software. Taking geometric and material nonlinearity into account, we calculated the nonlinear stability coefficients of structure in various cases including the whole construction process and main operation stages. Moreover, we evaluated the bearing capacity of major components, and analyzed the effects of cable fracture and steel shells of the pylon on the nonlinear stability of structure. The results show that the nonlinear stability coefficients of the integral bridge are all greater than the critical value 2.0 during construction and operation stage, which meet the requirements of structural stability. The bearing capacity of the main girder is strongest, and the bearing capacity of the pylon and cables decreases in a subsequent order. Steel shells of the pylon plays a nonnegligible role in improving the integral stability of structure. Compared with conditions while taking cable fracture into account, the nonlinear stability coefficients of structure significantly increase while disregarding cable fracture.