箱梁剪应力计算及分布规律的研究

Shear Stress Calculation of Box Girder and Distribution Laws

为了准确计算箱梁在弯曲时的剪应力,反映箱梁截面剪应力的分布规律,在薄壁杆件弯曲分析的基础上推导了薄壁箱梁弯曲剪应力的实用计算公式.结合具体的算例计算了不同悬臂宽度的箱梁弯曲剪应力大小以及分布规律.研究结果表明:箱梁腹板最大弯曲剪应力发生在腹板中性轴以上部分,而且箱梁底板上承受的剪应力比顶板要大;在荷载不变的情况下,随着悬臂板宽度的增加,悬臂板与顶板上的剪力流之和基本不发生变化,但悬臂板上的剪力流逐渐增加,而顶板上的剪力流逐渐减小,悬臂板上的剪力流占总剪力流的比例由原来的51%增加到65%.在设计箱形截面尺寸时,应计入剪应力的影响,不应采用薄底板,顶板和悬臂板应分别采用不同的厚度,与此同时还应加强其配筋及构造措施,防止在后期使用过程中发生破环.

In order to calculate the shear stress of box girder in bending situation and detect the shear stress distribution of the box girder cross-section,the calculation formula of thin-walled box girder is deduced based on the analysis of bending shear stress calculation formula of thin-walled box girder. The bending shear stress and the distribution law of box girder with different cantilever width are calculated by using the formula in this paper. The results show that: the maximum bending shear stress occurs at the center axis of the part above the web,and the shear stress under the box girder bottom is larger than that in the roof; when the load is constant,with the increase of the width of the cantilever plate,sum of shear in cantilever plate and the roof does not change,but the shear flow in cantilever plate increases gradually,while shear flow in the roof decreases,and shear flow in cantilever plate to total shear flow ratio increases from 51% to 65%. In order to design the box girder,shear stress should be considered and the thin bottom plate should not be used,top plate and a cantilever plate should adopt different thickness at the same time to prevent the occurrence of broken ring in the late stage of the process.