中文摘要：

选取剪力滞效应引起的附加挠度作为广义位移，在定义新的剪力滞广义力矩的基础上，将箱梁的剪力滞变形状态从初等梁挠曲变形状态中分离出来，作为一种独立的基本变形状态进行分析。应用能量变分法建立关于附加挠度的控制微分方程和边界条件，给出微分方程的初参数解。从分析翼缘板的面内剪切变形入手，证明二次抛物线是剪力滞翘曲位移函数的合理模式。为进一步分析变高度连续箱梁等复杂结构的剪力滞效应，提出一个8自由度的梁段单元。对一有机玻璃制作的变高度3跨连续箱梁模型及混凝土简支箱梁的计算表明，计算值与实测值及有限元结果均吻合良好，从而验证提出的分析方法和梁段单元是可靠的。计算表明，剪力滞效应使该3跨连续箱梁模型在集中荷载和均布荷载作用下中跨跨中截面的挠度提高幅度分别达到22．3％和23．9％，工程实践中必须认真对待。

英文摘要：

The additional deflection caused by shear lag effect was adopted as generalized displacement to describe the shear-lag deformation state. Based on the new generalized moment for shear lag defined in this study, the shear-lag deformation state was separated from the flexural deformation state of elementary beam as a fundamental deformation state for analyzing. The governing differential equation and corresponding boundary condition for the additional deflection were established by applying the energy variational principle, and then the initial parameter solution of the differential equation was given. The quadratic parabola was proved to be the reasonable form of the shear-lag warping displacement function mode according to the investigation of the in-plane shear deformation of flanges. A beam-segment finite element with 8 degrees of freedom is proposed to analyze the shear lag effect in complex continuous box girder with varying depth. A plexiglass model for a three-span continuous box girder with varying depth and a simply supported concrete box girder were analyzed and the calculated results were in good agreement with both test results and finite element results, validating the reliability of the method and the element presented. The increase in mid-span deflection for the three-span continuous box girder model due to shear lag reached 22.3% and 23.9% under the concentrated and uniformly distributed loads, respectively, which should be treated seriously in engineering practice.