人字形桥梁中薄壁直箱梁结构性能的矩阵分析

人字形桥梁由于采用了薄壁箱梁结构,其约束扭转、畸变效应及剪力滞比较突出。另外,人字形桥梁分叉结构的相互联系和制约作用,又使得约束扭转效应更加显著。同时随着宽翼缘箱梁结构使用的增加,人字形桥梁结构中薄壁直线箱梁仅以初等梁理论每个节点只有6个自由度的计算方法难以较好把握结构的受力行为。因此,本文基于初等梁理论及梁格理论分析方法的基础上,通过增加自由度的分析方法,在考虑初等梁受力特性的基础上同时考虑约束扭转、畸变角、畸变翘曲及剪力滞效应等薄壁箱梁结构的受力特点,并建立每节点10个自由度的人字形薄壁箱梁空间有限元分析单元,推导出单元的刚度矩阵及编制出相应的有限元分析程序,以解决宽翼缘薄壁箱梁的结构性能分析问题。通过算例分析表明,验证了本文方法的可靠性,便于实际应用,具有较高的工程使用价值。

Matrix Analysis of Structure Behaviors of Thin-walled Straight-line Box Girders in the Y-shape Bridges

The adoption of the thin-walled box girder to the Y-shape bridge makes the restrained torsion effect,distortion effect and shear lag effect prominent.Owing to the mutual connection and restriction between the branching structures of the Y-shape bridge,the restrained torsion effect is more conspicuous.With the increasing use of the wide-wing thin-walled box girder structure,it is difficult to have good knowledge of the stessed behaviors of the Y-shape bridge structure by calculation with 6 degrees of freedom at each node of the thin-walled straight box girder on the basis of the elementary beam theory.This paper applies the elementary beam theory and the analytical method of grillage simulation,takes into account the mechanic properties of restricted torsion,distortion corner,distortion warping and shear-lag effect of the thin-walled box girder based on the mechanic properties of the elementary beam,and builds the space finite element with 10 degrees of freedom at each node of the thin-walled box girder by increasing the degrees of freedom.The stiffness matrix of FEM is deduced and the FEM analysis procedure is composed in order to solve the problem of analyzing the behavior of the structure of the wide-wing thin-walled box girder.The computational example proves that the proposed method is dependable,practical and of high value in engineering construction projects.