荷载横向变位下箱梁顶板与底板的剪滞效应分析

不同于以往荷载作用于箱梁的肋板处时剪力滞效应的研究,考虑当荷载不作用在箱梁的肋板处时顶板与底板位移及剪力滞效应的差异,对顶板与底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,通过能量变分法,研究荷载在顶板横向变位下箱梁顶板与底板的位移,应力及剪力滞效应的变化,根据对于简支箱梁受均布荷载作用下跨中剪力滞效应的计算结果,随着作用在顶板的对称荷载从对称中心向肋板处移动,顶板将经历一个产生负剪力滞效应到无剪力滞效应,再到产生正剪力滞效应的过程。而与此同时底板的剪力滞效应规律受荷载的移动的影响很小,始终保持正剪力滞效应。计算结果与有限元数值模拟结果吻合较好,验证了理论的可靠性,同时也说明当荷载不作用在箱梁的肋板处时,对顶板与底板分设不同的纵向位移差函数的考虑是正确的。

Analyses of the shear lag effect on the top and bottom plates of box beams with varying loading locations

The shear lag effect of the loading not acting on the webs of box beams was investigated.Due to the variation of shear lag effect,different functions of longitudinal displacement differences were respectively assumed for the top and bottom plates of the box beam and a quadric parabolic was adopted as the function of longitudinal displacement along the flange width.By using the energy variational method,the variation of displacement and the stress and shear lag effect on the top and bottom plates of the box beam with varying load locations were investigated.Based on the calculation results,for the simple box beam subjected to uniform load,with the symmetrical loading on the top plate moving from the symmetric enter to the webs,the shear lag effect on the top plate changes from negative to positive,and the shear lag effect on the bottom plate rarely changes and remains positive.The results are in good agreement with those from finite element method.