中文摘要：

以薄壁箱梁的弯曲理论为基础，从分析翼缘板的面内剪切变形和弯曲剪力流的分布规律入手，从理论上证明二次抛物线是箱形梁剪力滞效应分析中的合理翘曲位移函数。选取剪力滞翘曲位移函数时，对悬臂板和底板引入修正系数，并考虑翘曲正应力的平衡条件。对箱形梁横截面上新出现的广义内力给出明确定义并称之为剪滞力矩，从分析正应力在翘曲虚位移上的虚功出发，揭示所定义的剪滞力矩即为相应于剪力滞广义位移的广义内力。对简支箱梁和连续箱梁模型的应力计算表明，计算值与实测值吻合良好，从而证实该文的分析方法和建立的公式是正确的。挠度计算表明：剪力滞效应使简支箱梁和连续箱梁算例的跨中挠度分别增大12％和19％，工程实践中必须认真对待。

英文摘要：

Based on the flexural theory for thin-walled box girders, quadratic parabola is proved to be reasonable as the warping displacement function in shear lag effect analysis of a box girder through investigating the in-plane shear deformation and the shear flow in the flanges. Modified factors for the cantilever and bottom slabs are introduced in the warping displacement function for shear lag and the equilibrium condition for warping stresses is also considered. The new generalized internal force is defined explicitly and named as shear lag moment, which is proved to be the generalized moment corresponding to the generalized displacement for shear lag, through analyzing the virtual work done by the normal stress on the virtual warping displacement. Simply supported and continuous box girder models are analyzed and the calculated results are in good agreement with the test results, which validates the proposed method and formulas. For the simply supported and continuous box girder models, shear lag effect increases the mid-span deflections by 12% and 19%, respectively, which should be treated seriously in practice.