圆弧形底面扁平钢箱梁局部应力分析

Local stress analysis of flat steel box girder with circular arc lower desk

采用从整体到局部、从粗放到精细的两阶段两尺度分析方法,对国内首个圆弧形底面扁平钢箱梁在运营状态下的局部应力进行分析。用大尺度单元建立全桥模型,用小尺度单元建立梁段模型。通过分析全桥模型获得梁段模型的边界约束力。在此基础上,利用梁段模型研究钢箱梁在恒载和活载作用下顶、底板的应力响应。研究表明:圆弧形底面扁平钢箱梁顶、底板均存在剪力滞现象,U肋对跨中截面应力分布的影响大于墩顶附近截面。圆弧形底面钢箱梁的底板正应力不均匀程度略大于折线形底面钢箱梁。

A flat steel box girder with circular arc lower desk was analyzed by two steps with two models,a whole bridge model established by larger scale elements and a segment model established by little scale elements.The whole bridge model was analyzed firstly to determine the boundary condition for the segment model.Then the local stress distributions of the upper desk and the lower desk were studied based on the segment model with the obtained boundary condition under the dead load and the living load.It is found that shear lag effects are significant in the upper and the lower desk and that effects of the ribs on the mid-span section are larger then that on the section near the pier.Comparisons of the lower desk stress distributions between two kinds of the flat steel box girder show that stress distributions of the girder with fold line lower desk are uniform than that of the girder with circular arc lower desk.