Abstract: In order to study the internal mechanism of the static wind instability of the long-span asymmetric suspension bridge, taking a suspension bridge with a main span of 628 m as the background, the corresponding ANSYS finite element model was established to analyze the static wind stability. Considering the nonlinear influence of the structure system and the static load, the instability process and critical state of bridge under static wind load were analyzed by double iteration method. The results show that the instability process of the long-span asymmetric suspension bridge is that the static wind displacement of the main beam increases nonlinearly, which leads to the increase of the relative vertical displacement of the main cable and suspender, and the stress of the main cable and suspender decreases continuously until the main cable and the suspender are close to the relaxation state and lose stability. The static wind instability mode is a complex three-dimensional instability state, in which the main girder is symmetric transverse bending and symmetric torsion, and the vertical displacement also has a great influence on it.The internal mechanism of static wind instability is that the increase of additional wind attack angle leads to the nonlinear increase of lifting moment and lifting force, the torsion deformation of main beam and the vertical displacement of cable, which leads to the decrease of cable stress and even local relaxation, and finally leads to the significant reduction of gravity stiffness of the bridge structure.

Key words: bridge engineering, suspension bridge, asymmetric, static wind stability, instability critical state, instability process

摘要： 为研究大跨非对称悬索桥的静风失稳的内在机理，以主跨628 m的某悬索桥为背景，建立相应ANSYS有限元模型进行静风稳定性分析。考虑到结构体系自身和静力荷载的非线性影响，采用两重迭代法分析了桥梁在静风荷载作用下的失稳过程和临界状态。结果表明：大跨度非对称悬索桥的失稳过程是主梁静风位移非线性增大，导致主缆和吊杆的相对垂直位移增大，使得主缆和吊杆的应力不断减小，直至主缆和吊杆接近松弛形态而失稳；静风失稳形态是以主梁发生对称横弯和对称扭转为主，同时竖向位移也有较大影响的复杂对称弯扭耦合的三维失稳状态；静风失稳内在机理是由于附加风攻角的增大导致升力矩和升力非线性增大，主梁扭转变形和缆索的竖向位移也不断增大从而导致缆索应力下降出现局部松弛化，最终导致该桥梁结构重力刚度大幅降低。

关键词: 桥梁工程, 悬索桥, 非对称, 静风稳定性, 失稳临界状态, 失稳过程