箱桁组合钢梁斜拉桥剪力滞效应分析

Shear Lag Effect of Steel Box-Truss Composite Girder of Cable-Stayed Bridge

以某在建大跨度公铁两用斜拉桥为背景,建立了箱桁组合整体有限元模型。对整体钢箱桥面的剪力滞效应进行了分析,并研究横隔板间距、桥面板厚度和箱梁截面高度等参数对桥梁剪力滞效应的影响规律。结果表明:箱桁组合钢梁中整体钢箱桥面存在一定的剪力滞后现象,边跨由于应力水平较低和支座处受力复杂导致剪力滞后效应较明显,过渡墩支点处最大应力不均匀系数为9.27;中跨大部分节段剪力滞后效应较小,顶板应力不均匀系数在1.06左右,底板应力不均匀系数在1.09左右,顶板应力均匀程度高于底板;从中跨跨中向桥塔方向,应力不均匀系数逐渐减小;随着横隔板间距、桥面板厚度和截面高度的增大,顶、底板应力不均匀系数减小,其减小值在5%以内。

To analyze the shear lag effect of the overall box girder bridge deck, a finite element model of overall steel box- truss composite girder was established, which took a long span rail-cum-road cable stayed bridge in the construction as the research object. The influence rule of the transverse diaphragm distance, bridge deck thickness and cross-section height on the shear lag effect was also studied. The research results show that there are shear lag phenomena in the steel box-truss composite girder. Due to the low stress level and the bearing stress complexity, shear lag phenomena are more evident in the side span than in other areas. The uneven coefficient of maximum stress is 9.27 at the point of transition pier. The shear lag effect of most segments of middle span is small; the uneven coefficient of stress is 1.06 at top plate of and 1.09 at bottom plate; the stress uniformity of the top plate is higher than that of the bottom plate. The uneven coefficient gradually decreases from the middle section of middle span to the section near the tower. The stress uneven coefficient of top and bottom plates decreases with the increase of transverse diaphragm distance, bridge deck thickness and cross-section height, meanwhile its decreasing range is less than 5%.