斜拉桥箱形主梁斜腹板的合理厚度分析

Analysis of Reasonable Thicknesses of Inclined Webs of Main Box Girders Used in Cable-stayed Bridges

针对斜拉桥中双箱式主梁,采用三维有限元分析方法,建立具有不同斜腹板厚度(18 cm,24 cm,30 cm,35 cm,40 cm)的5个箱形主梁有限元模型,分析其空间应力分布特点,归纳出斜拉桥中此类双箱单室倒梯形截面的薄弱环节及斜拉桥箱梁在不同斜腹板厚度下的应力变化。考虑到梁段以外附近区域的作用,在其两端截面上施加由平面杆系结构分析所得的端面内力,另外,索力和预加力(梁纵向、横隔梁横向、斜腹板竖向)也施加在相应的位置,分析了不同工况下箱形主梁在自重、索力和预应力作用下的空间应力效应。通过对以上工况计算结果的静力分析,归纳出斜拉桥中此类双箱式截面的应力分布特点,并提出斜腹板厚度的合理化建议。分析表明:斜腹板厚度为30 cm左右时,主梁的应力分布比较合理。

By using the three-dimensional finite element method, five finite element models were established for twin-box girders used in cable-stayed bridges with the inclined webs of different thicknesses of 18 cm, 24 cm, 30 cm, 35 cm and 40 cm. Spatial stresses distribution of the models was analyzed. The weak points of the twinbox single cross hammerhead sections and the stress variations with different inclined web thicknesses were summed up. Considering the action of the zones to adjacent the girder sections, the internal forces were exerted on two-end surfaces , which were obtained by the analysis of the plane structure of linear elements. Moreover, the weight,cable force and pre-stressed force including girder longitudinal, diaphragm transverse and inclined web vertical direction were considered. Based on the above, the three-dimensional stresses of the box girder with different thickness of the inclined web of cable-stayed bridge were analyzed. By the result of above working situation, stresses distribution characteristics of twin-box girders of cable-stayed bridge were indicated, and the reasonable designs were proposed. Analysis shows that the stress distributions of main girder are reasonable when the inclined web thickness is around 30 cm.