多室箱形梁非线性有限元分析

本文将单箱多室箱梁离散为若干个空间梁段单元，梁段单元的弯曲、扭转及其横截面翘曲均采用三次插值函数描述，其拉压变形采用线性插值。为了计算箱梁顶、底板的面外弯曲，剪力滞后及横截面畸变，采取横向有限条的概念，从梁段单元截取单位厚度的空腹桁架；取桁架的每根杆件为一平面梁单元，用三次插值函数描述其位移，单元节点位移参数用三次多项式表示为箱梁梁段单元节点位移参数的函数。箱梁各横隔板取为有结点转角的四结点平面单元，用基于连续介质力学的Ｕ．Ｌ．列式虚功增量方程，考虑剪切变形影响建立各种单元的弹塑性平衡方程。按照上述思路编制了计算程序，计算结果与模型测试结果接近。

NONLINEAR FINITE ELEMENT ANALYSIS OF THIN-WALLED MULTICELL BOX GIRDERS

Thin-walled multicell box girder is separated into space beam elements and the displacement field of the beam elements are developed based on the assumption of plane section and Cartesian co-ordinate system. Bending, torsion, torsional warping, cross-sectional distortion, distortional warping and shear lag effects of the box girder are interpolated us- ing cubic polynomials while the axial displacement is specified by linear interpolation. The transverse finite strip method conception has been employed to compute the out-of-plane displacement of the wall, cross-sectional distortion and shear lag effects of box girder. The unit width box girder is thus sectioned from the box girder elements and treated as a vieren deel truss. Every rod of the truss is then considered to be a plane beam element with its displacement described by Hermitian interpolations. The nodal displacement parameters of the plane beam are expressed as the functions of the nodal displacement of the box girder element by cubic polynomials. The transverse diaphragms of the box girder are treated as four-node plane elements considering nodal transformation angles. The plastoelastic equilibrium equations are derived from the Updated Lagrangian virtual incremental formulations based on continuum mechanics in consideration of shear deformation. According to the above-mentioned train of thought, a computer program has been compiled. The computed results are in good agreement with the experimental ones.