大跨度叠合梁斜拉桥非线性稳定研究

为研究大跨度叠合梁斜拉桥非线性稳定的变化规律和失稳过程，以主跨360 m的西固黄河大桥主桥为研究对象，通过有限元数值模拟计算结构在典型施工阶段、成桥及运营阶段的非线性稳定安全系数及其失稳模态；重点分析结构在成桥状态下从初始加载直至达到其极限承载力这一过程中斜拉索应力、索塔等效应力变化和结构关键部位的荷载 位移曲线。结果表明:主桥施工典型阶段、成桥及运营阶段的非线性稳定安全系数均满足设计要求，结构失稳均以索塔纵桥向失稳和主梁面内失稳为主；主桥从初始加载直至达到其极限承载力这一过程中，部分斜拉索发生断裂，主梁和索塔连接部位出现塑性区，失稳破坏过程合理；索塔和主梁的荷载 横向位移曲线表现出较为明显的非线性效应。

Research on Nonlinear Stability of Long-span Composite Girder Cable-stayed Bridge

In order to research the variation law and the instability process of the nonlinear stability of long-span composite girder cable-stayed bridge, the Xigu Yellow River Bridge with 360 m main span was selected as the study object. The nonlinear stability safety factor of the typical construction stage and operation stage of the bridge was calculated by finite element simulation and the structural instability mode was obtained. At the same time, the stress changes of the stay cable and pylon and the load displacement curves of the key control point during the bridge from the beginning to the ultimate load-carrying capacity were analyzed. The results show that the nonlinear stability safety factor of the typical construction stage and the operation stage of the main bridge meet the design requirements, and the structural instability is reflected in longitudinal instability of pylon and in-plane instability of main beam. Part of the stay cable are broken and the connection location of main beam and pylon appears plastic area during the bridge from the beginning to the ultimate load-carrying capacity. The damage process is reasonable. The load-lateral displacement curves of tower and girder show obvious nonlinear effects.