薄壁箱梁在保向力作用下的弯扭屈曲

Flexural-Torsional Buckling of Thin-Walled Box Girder in the Action of Directional Loads

薄壁杆件弯扭屈曲计算是薄壁结构设计中的一个重要内容.本文针对高宽比较大的简支薄壁箱梁,考虑弯扭屈曲变形中腹板的受力特征,将腹板由剪力滞导致的翘曲位移假设为三次抛物线规律分布函数,利用能量变分原理推导出薄壁箱梁在保向力作用下的弯扭屈曲控制微分方程,根据伽辽金法予以求解,得到了简支薄壁箱梁弯扭屈曲的临界荷载和临界荷载系数.通过分析表明,扇形惯性矩对临界荷载影响很小;荷载沿梁高方向的作用位置、翼缘宽度、腹板高度和梁跨度是影响临界荷载系数的主要因素;剪力滞效应的影响程度对跨度和腹板高度的变化较为敏感.

Flexural-torsional buckling calculation of thin-walled girders is an important content in the design of thin-walled structure. According to the stress characteristics of webs in the flexural-torsional deformation for simple thin-wall box girder with larger high-width ratio, the shear lag displacement of webs was supposed for three-times parabolic distribution function. The governing equation of flexural- torsional buckling of thin-walled box girder in the action of directional loads was set by means of energy variational principle and solved by Galerkin method. The critical load and the coefficients of the critical load for the flexural-torsional buckling problem of simple thin-walled box girder were obtained. The analysis show that the affection for the sector inertia moment on critical load is very smalls load position along the beam depth direction, flange width, web height and beam span are the main factors to influence the critical load coefficients; the role of shear lag effect is obvious for the change of span and web height.