薄壁箱梁约束扭转二次剪力流的分解计算方法研究  

Research on Resolution Calculation Method for Secondary Shear Flow of Thin-walled Box Girders under Restrained Torsion

作　　者：张元海[1] 周鹏杰 林丽霞[1] ZHANG Yuanhai;ZHOU Pengjie;LIN Lixia(School of Civil Engineering,Lanzhou Jiaotong University,Lanzhou 730070,China)

机构地区：[1]兰州交通大学土木工程学院,甘肃兰州730070

出　　处：《铁道学报》2021年第4期183-190,共8页Journal of the China Railway Society

基　　金：国家自然科学基金(51968040)。

摘　　要：为合理计算薄壁箱梁约束扭转时的二次剪力流并揭示其分布规律,提出一种对二次剪力流进行分解的计算方法。从分析微元体的纵向平衡出发,分别建立悬臂板和闭合箱室上二次剪力流及二次扭矩的实用计算公式。引入剪应力系数,以反映二次剪应力对总剪应力的提高程度,并结合简支箱梁数值算例,详细分析悬臂板宽度变化对剪应力系数和二次扭矩的影响规律。研究结果表明:箱梁横截面上的最大剪应力发生在腹板内,其剪应力系数可达到2.3;随着悬臂板相对宽度的增大,腹板上产生最大剪应力的位置趋近于腹板底部;悬臂板在约束扭转中承受很大的二次扭矩,甚至会超过闭合箱室承受的二次扭矩;对于箱室高宽比h/b较大的箱梁,当悬臂板宽度与闭合箱室宽度之比为0.65时,悬臂板承受二次扭矩的作用得到充分发挥。In order to calculate reasonably the secondary shear flow and reveal its distribution law in the thin-walled box girders under restrained torsion,a calculation method for the resolution of the secondary shear flow was proposed.Based on the analysis of the longitudinal equilibrium of differential bodies,the practical formulas for the secondary shear flow and secondary torsion moment on the cantilever slabs and closed box cell were established,respectively.The shear stress coefficient was introduced to reflect the increasing degree of total shear stress due to secondary shear stress.A numerical example of simply supported box girder was given to analyze the influence of width variation of the cantilever slab on the shear stress coefficient and secondary torsion moment.The results show that the maximum shear stress at cross section of a box girder occurs in the webs,with the corresponding shear stress coefficient of up to 2.3.The location of the maximum shear stress on the webs approaches the bottom of the webs with the increase of the relative width of the cantilever slabs.The cantilever slabs bear remarkable secondary torsion moment in the box girder under restrained torsion,which can even exceed that of closed box cell.For the box girder with relative large height-width ratio h/b of box cell,the role of cantilever slabs in bearing the secondary torsion moment can be fully exerted when the ratio of cantilever slab width to closed box cell width equals 0.65.

关 键 词：薄壁箱梁 约束扭转 二次剪力流 二次扭矩 剪应力系数 

分 类 号：U448.213[建筑科学—桥梁与隧道工程]