斜拉桥Π形结合主梁施工过程剪力滞系数变化规律
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U441;U448.27

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重庆市自然科学基金(CSTC 2010BB6048)


Shear-lag coefficient of Π shaped composite girder in construction stages of cablestayed bridge
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    摘要:

    斜拉桥中的Π形主梁宽高比很大,剪力滞问题非常突出。针对斜拉桥施工过程中结构、荷载与位移边界条件等不断变化的情形,提出一种能同时考虑结合梁剪力滞变形与弯曲变形耦合影响、适用于复杂荷载与边界条件的每节点两个剪力滞自由度的Π形结合梁单元。在单元公式推导中,假定钢梁与混凝土翼板纵向位移沿横向为3次抛物线分布,相同横向坐标的钢梁翼缘板和混凝土桥面板呈相似的剪力滞位移曲线变化规律。按悬臂施工过程中的动态结构和动态剪力滞边界条件分析了在桥面板自重荷载、斜拉索张拉荷载及二期恒载等作用下的Π形结合梁斜拉桥中主梁截面剪力滞效应及其随施工过程变化的规律,并将计算结果与现场实测数据进行对比,结果表明:斜拉桥中结合梁主梁截面的剪力滞效应随施工过程荷载及位移边界条件的变化呈正负剪力滞交替变化,相较于桥面板自重等竖向荷载,斜拉索张拉荷载对主梁剪力滞效应的影响更明显;与靠近悬臂前端梁段截面的剪力效应相比,靠近桥塔附近梁段截面的剪力滞效应亦更加明显;随着施工步骤增加,Π形结合梁主梁截面剪力滞系数变化逐渐减小。相对斜拉桥成桥阶段,悬臂施工阶段的剪力滞效应更值得关注。

    Abstract:

    Width to height ratio Π shaped girder of cable stayed bridge is very big, and the shear lag problem is very outstanding. For considering the variation of load and boundary conditions in construction process, a beam element with two shear-lag degrees of freedom at each node is established to take the coupling effect of shear lag and bending deformation of composite girder into account, which is suitable for the complex load and boundary conditions. In the formula derivation, it is assumed that the longitudinal displacements of the concrete slab are described by a third-power parabolic function, and the steel flanges share the same displacements with concrete slab at the same abscissa. The shear-lag effects of Πshaped composite girder in a cable-stayed bridge during the construction process is analyzed by using the proposed method. The dead weight of decks, tensioning loads and secondary dead load are considered in analysis according to the dynamic shear-lag boundary conditions during the construction process. The numerical analysis results were compared with measured ones. It was shown that the shear lag of main girder alternates with positive and negative effect along with the changes of load increments and boundary conditions in different construction stages. Comparing with the vertical loads such as the dead weight of decks, the cable-tensioning loads have a much more obvious effect on the shear lag of the main beam. The shear lag effect at the sections near the towers is more obvious than that at the other sections. As the construction continuing of the bridge, the shear lag coefficients of the Πshaped composite beam are gradually decreasing. In addition, it should pay more attention to the shear lag effect in the cantilever construction stages than that in the final structure.

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郭飞,周世军.斜拉桥Π形结合主梁施工过程剪力滞系数变化规律[J].土木与环境工程学报(中英文),2020,42(3):100-105.

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  • 收稿日期:2019-09-06
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  • 在线发布日期: 2020-06-13
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