本文从薄壁箱梁的剪力滞效应是由于翼板剪切变形所致这一本质出发,通过分析箱梁在竖向弯曲时翼板的剪力流分布规律,提出利用翼板剪切变形规律来定义其剪滞翘曲函数的方法.针对常见的单室箱梁,定义出截面仅有一个未知翼板剪切变形最大差,各翼板符合剪切变形规律的翘曲位移函数.建立基于变分法的箱梁剪力滞控制微分方程.通过对典型结构的剪力滞效应分析,表明本文分析结果与模型试验值、基于板壳元的数值解以及截面具有3个未知剪切变形最大差的变分解吻合良好.证明本文提出的基于翼板剪切变形规律的剪力滞翘曲位移函数不仅原理明确,而且具有未知变量少,分析精度高的特点.本文剪力滞翘曲位移函数的定义方法适用于各种薄壁截面,可为复杂截面剪力滞翘曲位移函数的定义提供参考.%Through analysis on the distribution law of the shear flow of the box girder under vertical bending, the new method to define the warping displacement function of shear lag is presented on the basis of the mechanism that the effect of the shear lag of the thin-wall box girder is caused by shear deformation of flange-slabs.With respect to the single cell box girder,the new shear-lag warping displacement function is defined, which includes only one unknown maximum angular rotation and conforms to the shear deformation principle.The governing differential equations for shear lag of box girders are established on the variation principles.According to analysis on shear lag of typical structures,it is shown that the results obtained using new warping displacement are in good agreement with the model test results,finite element results and variation results with 3 maximum angular rotations.The new method to define the warping displacement function of shear lag based on the shear deformation law of flange-slabs is featured by explicit principles, less number of unknown variables and high degree of precision.The new method is suitable for any thin-walled structures,especially for complex thin-walled structures.
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