Abstract: In order to study the characteristics of stress distribution and deformation of box girder bridge with variable cross section, the element stiffness matrix of box girder with variable cross section is derived based on the restrained torsion differential equation of box girder.Based on the analysis of the project, three load distribution conditions are set up, and the bending moment and warping displacement of box girder with variable cross-section are calculated, the stress amplification effect is also studied.The results show that the curves of moment changing with longitudinal distance in case 1 and case 2 are similar and show “W” shape.In condition 3, the trend of change was just opposite, myopia presented “M” type, and both the value and the range of change were small.The warping displacements are mainly concentrated at the end and the middle of the side span, and show an anti-symmetric distribution with the mid-span section as the boundary.In case 1 and case 2, the values of the generalized warpage displacement in mid-span and right-span are basically the same.The curve of warping double moment shows the law of attenuation from the peak point to the two sides, and the extreme value appears at the position of the center fulcrum and the action point of the concentrated load.The maximum normal stress of warpage occurs in the section under the action of concentrated load. The stress magnification coefficients of the four control sections are less than 1.41 under three loading conditions.

Key words: variable cross section, continuous box girder, constraint Twist, stress amplification factor

摘要： 为研究变截面箱梁桥的应力分布特征和变形规律,根据箱梁约束扭转微分方程,推导出了变截面箱梁单元刚度矩阵。基于此,依托跨四港联动大道项目进行实例分析,设置了3种荷载分布工况,计算出了不同工况下变截面箱梁的弯矩和翘曲位移,并对应力放大效应进行了探究。结果表明:工况1和工况2中弯矩随纵向距离变化曲线数值和趋势均较为类似,呈现出“W”型。工况3变化趋势恰好相反,近似呈现出“M”型,且数值和变化幅度方面均偏小。翘曲位移主要集中在边跨端部和跨中位置处,以跨中截面为界表现出反对称分布。工况1和工况2中广义翘曲位移在中跨及右跨数值和变化趋势基本一致。翘曲双力矩曲线呈现出由峰值点向两侧衰减的规律,在中支点位置处和集中荷载作用点处均出现极值。翘曲正应力极值均出现在集中荷载作用的截面。3种荷载施加工况下,4个控制截面的应力放大系数均未超过1.41。

关键词: 变截面, 连续箱梁, 约束扭转, 应力放大系数