为分析车道荷载作用下薄壁箱梁的畸变效应，研究应力放大系数在薄壁箱梁中的分布规律，以畸变角和畸变广义翘曲位移作为节点位移，基于畸变控制微分方程的齐次方程的初参数解，将薄壁箱梁划分为梁段单元，推导其单元刚度矩阵和等效节点荷载列阵。使用Fortran语言并参考平面杆系结构计算程序FRAME2编写，得到可用来分析薄壁箱梁畸变效应的梁段有限元程序，用程序分析箱梁在车道荷载作用下的畸变内力和应力放大系数的变化规律。结果表明：车道荷载作用下变截面三跨连续箱梁桥的畸变翘曲应力在集中荷载作用处产生突变，此处取得最大和最小值，应力放大系数沿纵向分布规律与畸变翘曲正应力沿纵向分布相似，均沿跨径对称分布；应力放大系数的最大值出现在集中荷载作用处，该截面顶板处的正应力放大系数为1.080，底板处的正应力放大系数为1.180，考虑应力放大系数的取值时不应考虑弯曲应力值较小的点。

In order to analyze the distortion effect of thin-walled box girder under lane load, the distribution law of stress amplification coefficient in thin-walled box girder was studied. The distortion angle and distortion generalized bending displacement were taken as node displacements. Based on the initial parameter solution of the homogeneous equation of the distortion control differential equation, the thin-walled box girder was divided into beam segment elements, and its element stiffness matrix and equivalent node load array were derived. Using Fortran language and referring to the calculation program FRAME2 for planar frame structures, a finite element program for beam segments that can be used to analyze the distortion effect of thin-walled box girders was obtained. The program was used to analyze the variation laws of the distortion internal forces and stress amplification factors of box girders under lane loads. The results show that the distortion warpage stress of three-span continuous box girder with variable cross-section under the action of lane load has a sudden change at the place of concentrated load, where the maximum and minimum values are obtained, the longitudinal distribution of stress amplification factor is similar to the longitudinal distribution of distortion warpage normal stress, both of which are symmetrically distributed along the span, the magnification factor of normal stress at the top and bottom of the section is 1.080 and 1.180 respectively. The points with smaller bending stress should not be considered when the magnification factor is taken into account.