荷载横向变位下箱梁剪滞效应分析

Analysis of the shear lag effect of a box girder with varying lateral loading locations

为了研究荷载横向变位下对箱梁剪滞效应的影响,对箱梁底板、顶板及悬臂板分设不同的纵向位移差函数,采用二次抛物线作为箱梁翼缘板的纵向位移沿梁宽分布函数,基于能量变分原理,建立了考虑剪滞效应的箱型梁控制微分方程;分析了荷载在箱梁顶板横向变位下底板、顶板及悬臂板应力的变化规律,根据对简支箱梁在均布荷载作用下跨中剪力滞系数的计算结果,随着作用在顶板的荷载从肋板向顶板中心移动,顶板经历一个产生正剪力滞效应和无剪力滞效应,最后到产生负剪力滞效应的变化过程,而底板及悬臂板在荷载移动过程中始终保持正剪力滞效应.计算结果和有限元数值模拟结果吻合较好,验证了理论的可靠性,与以往的研究相比更能正确地反映结构剪力滞效应的变化规律.

In order to construct a study on the shear lag effect of a box girder with varying lateral loading locations,three longitudinal displacement differential functions for a trapezoidal section box girder were assumed and a quadratic parabola was adopted as the function of longitudinal displacement of flange slab along the flange width.The governing differential equation of the box girder was proposed based on the energy-variational principle.The variation of the stress on the top,bottom,and cantilever slabs of the box girder with varying lateral loading locations was investigated.Based on the calculation results for the simply supported beam under a uniformly distributed load,the whole changing process of the top plate reflecting from positive shear lag to no shear lag,and then to a negative shear lag was analyzed.This was done with varying the symmetrical loading on the top plate moving from the webs to the top plate center,and the shear lag effects on the bottom and cantilever slabs of the box girder remained positive.When comparing the calculation results with the results obtained from the finite element method,the proposed method proved to be reliable.Compared with previous studies,this method can reflect the transformation of the shear lag effect more accurately.