变截面梁的应力计算及其分布规律研究

为了合理计算预应力混凝土变截面箱形梁的剪应力,客观反映其应力分布状况,首先推导了任意变截面梁剪应力计算的一般公式,在此基础上,考虑箱形梁的梁高、底板厚度、腹板厚度沿跨度的变化,导出了变截面箱形梁的剪应力实用计算公式。应用导出的公式,结合矩形及箱形变截面悬臂梁算例,分析了变截面梁的应力分布状况。研究结果表明,变截面梁横截面上的最大剪应力并不发生在截面重心轴处,而是在重心轴以下区域或梁底缘处;变截面箱形梁的底板受有很大剪应力作用,为了合理设计变截面箱形梁,不应采用薄底板,而且应加强其配筋及构造处理。

STRESS CALCULATION AND STRESS DISTRIBUTION ANALYSIS OF NON-UNIFORM BEAMS

In order to calculate rationally the shear stresses in prestressed concrete box beams with variable cross section and reflect objectively their distribution, general formulas for shear stresses of arbitrary non-uniform beams are derived. The practical simplified formulas for shear stresses of box beams with variable cross-section are presented with the variations of beam depth, thickness of web and base plate. The derived formulas are applied to investigate the stress distributions of cantilever beams with variable rectangular and box cross-section. It is shown that, large shear stress occurs in the base plate of a box beam with variable cross-section, and the maximum shear stress of a non-uniform beam doesn’t exist at the location of gravity axis but in the region below the gravity axis or at the bottom fiber. In the design of box beam with variable cross-section, thin base plate shouldn’t be used, and the arrangement of reinforcements in the base plate should be strengthened.