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由于薄壁截面抗弯与抗扭的性能良好,箱型梁在梁式结构中广泛得到应用。当箱腹间距较大时,在弯曲荷载作用下,变形已经不服从初等梁的理论,这里存在不同的剪力滞效应。文献[1]、[2]做了详细的探讨与研究。在初步设计中往往仍沿用初等梁理论计算弯曲法向应力σ,因此有必要知道肋处与板中的剪力滞系数λ~e与λ~c。计算λ~e与λ~c的过程中本文仍假定翼缘板的纵向位移函数按三次抛物线的变化规律,利用变分法推演出几种边界条件下箱型梁的剪力滞效应。对简支梁、悬臂梁,在均布与集中荷载作用下,与两跨连续梁在集中荷载作用下,跨径从20m～70m,箱的半宽b=2.0m,2.5m及3m或l/2b=3,4,5时分别给出λ~e与λ~c的计算结果,并绘成图表以便参考。最后对箱型梁剪力滞系数做了有关规范条文上的建议。
Due to the good performance of bending and twisting of thin-walled sections, the box beam is widely used in beam structures. When the box-to-box spacing is large, under the bending load, the deformation has not obeyed the theory of elementary beams, and there are different shear lag effects. Literature [1], [2] made a detailed discussion and research. In the preliminary design, the normal beam bending stress σ is often calculated using the elementary beam theory. Therefore, it is necessary to know the shear lag coefficients λ ~ e and λ ~ c in the rib and the plate. In the calculation of λ ~ e and λ ~ c, this paper still assumes that the longitudinal displacement function of the flange plate changes according to the cubic parabola and the variational method is used to deduce the shear lag effect of the box beam under several kinds of boundary conditions. For simply supported beams and cantilevers, under the action of uniform and concentrated loads, with the span of two beams spanned from 20m to 70m and the half span of b = 2.0m, 2.5m and 3m or l / 2b = 3, 4, 5, respectively, λ ~ e and λ ~ c calculation results, and plotted for reference. Finally, on the box girder shear lag coefficient made on the provisions of the provisions of the recommendations.