云桂铁路南盘江特大桥主拱圈非线性稳定性评估

为探讨大跨度劲性骨架拱桥主拱圈的非线性稳定性能,以云桂铁路南盘江特大桥为工程背景,运用西南交通大学自主研发的LSB软件建立主拱圈有限元模型,考虑几何与材料非线性的影响,计算施工全过程共46个工况下的结构非线性稳定系数,并评估主拱圈在施工过程中的变化趋势。结果表明:钢管骨架拼装阶段主拱圈非线性稳定系数在2.2~26.3,拼装与拱顶合龙段相邻的19#节段时非线性稳定系数为2.2,钢管骨架合龙时非线性稳定系数为3.9;灌注钢管内混凝土阶段主拱圈非线性稳定系数在2.6~3.8,灌注下弦外侧钢管内混凝土时非线性稳定系数为2.6,随着钢管内混凝土逐渐达到其设计强度,非线性稳定系数保持相对稳定;浇筑外包混凝土阶段非线性稳定系数在2.1~4.6,浇筑边箱底板第3,6,9段外包混凝土时非线性稳定系数为2.1,是施工全过程主拱圈非线性稳定系数的最小值;施工全过程主拱圈失稳形态以面内失稳为主,其非线性稳定系数均大于安全临界值2.0,非线性稳定性能满足要求。

Main Arch Ring Nonlinear Stability Assessment of Nanpan River Super Large Bridge on Yunnan-Guangxi Railway

In order to discuss the nonlinear stability for main arch ring of large span stiff skeleton arch bridge ,taking Nanpan river super large bridge on Yunnan-Guangxi railway as the engineering background,the finite element model of main arch ring was established by using the LSB software independently developed by Southwest Jiaotong University. Considering the influence of geometric and material nonlinearity,the structural nonlinearity stability coefficients under forty-six working conditions during the whole construction process were calculated and their variation trend with the whole construction process were evaluated. The results show that nonlinear stability coefficients of main arch ring at the stage of steel tubular skeletonn assembly is 2.2 ~ 26.3. The nonlinear stability cofficient is 2.2 occuring in 19# lifting segment next to closure segment of vault,while the value of nonlinear stability coefficient at the stage of steel tubular skeleton closure is 3.9. Nonlinear stability coefficients of main arch ring at the stage of pouring concrete into steel tube is 2.6 ~ 3.8. The nonlinear stability coefficient is 2.6 occuring in pouring concrete into outward bottom chord steel tube. With the concrete in steel tube gradually reaching its design strength,the value of nonlinear stability coefficient keeps relatively stable. Nonlinear stability coefficients of main arch ring at the stage of pouring encased concrete range from 2.1 to 4.6. The nonlinear stability coefficient is 2.1 occuring in pouring the 3rd,6th,9th segment encased concrete of edge bottom plates,which is also the minimum value of nonlinear stability coefficient of main arch ring for the whole construction process. Instability modes of the main arch ring are dominated by in.plane instability. The values of the whole construction process are all greater than safety critical value 2.0,nonlinear stability meets requirements.