波形钢腹板多室箱梁部分斜拉桥剪力滞效应分析

Analysis of Shear Lag Effect in Extradosed Bridge with Multi-cell Box Girder and Corrugated Steel Webs

为了解波形钢腹板多室箱梁部分斜拉桥剪力滞效应对结构受力的影响,以某(58+118+188+108)m单箱四室波形钢腹板部分斜拉桥为背景,采用有限元法建立空间有限元模型,在跨中偏载和对称荷载作用下,计算主跨箱梁有索段和无索段顶底板混凝土正应力,分析各截面的剪力滞分布规律。结果表明:箱梁跨中截面混凝土顶板、底板正应力分布极不均匀,具有明显的剪力滞效应,箱梁混凝土顶板、底板剪力滞系数随距集中荷载作用点距离的增大急剧减小,截面顶板剪力滞效应均比底板大;箱梁顶底板均呈现正剪力滞效应,混凝土横隔板可以改善箱梁截面正应力分布,减弱剪力滞效应;顶底板剪力滞系数在无索段范围内急剧减小,有索段内急剧增大,车辆活载只在局部范围内引起较大的剪力滞效应,设计中应考虑此效应引起的不均匀应力。

To examine the influence of shear lag effect on the load bearing condition of the extradosed bridge withmulti-cell box girder and corrugated steel webs, an extradosed bridge with four-cell box girder and steel corrugated webs was cited as an example. The extradosed bridge has four spans of 58, 118, 188 and 108m. The spatial finite elementmodel of the bridge was established, under the action ofmid-span eccentric load and symmetrical load, the normal stresses of concrete in the top and bottom plates of themain span box girder, including both the sections with cables and the sections without cables, were calculated, and the distribution law of the shear lag in each cross section was analyzed. The results show that the normal stress distribution in themid-span cross section of the top and bottom plates of the box girder was not uniform, with obvious shear lag effect. The shear lag coefficient of the base plate sharply reduced when the distance to the action point of the concentrated loads was increased, and the shear lag effect in the top plate cross section was bigger than that in the bottom plate. The shear lag effects in the top and bottom plates of the box girder were all positive shear lag effect. Concrete diaphragms can help improve the distribution of normal stress in the cross section of box girder and reducing the shear lag effect. The shear lag coefficients of the top and bottom plates were sharply reduced in the sections without cables, but the shear lag coefficients of the sections with cables were sharply increased. The live loads of vehicles can only induce great shear lag effect in local regions, and the non-uniform stresses induced by such effect should be considered in the design.