一、问题的提出变高度粱的剪应力τ不仅与剪力Q有关,而且与法向力N和弯矩M以及截面积A和惯性矩I的变化程度有关。苏联吉勃西曼著《预应力钢筋混凝土桥梁理论与计算》和波利万诺夫著《钢筋混凝土桥(设计与计算)》均列出了变高度粱垂直截面的剪应力计算式,但在查对该两书所列的计算式后发现两者所规定的符号(指正负号)各自不同,而且该两者的计算结果也是不一致的。同时波利万诺夫的公式推导中某些算式也是使人费解的。我们曾对两者的计算图式分别进行了公式推导和比较,证实吉氏算式中的c_2项的 First, the problem put forward variable height beam shear stress τ not only Q, but also with the normal force N and bending moment M and cross-sectional area A and moment of inertia I degree of change. The formula for calculating the shear stress in the vertical cross-section of variable-height beams are listed in the article “Theory and Calculation of Prestressed Reinforced-Concrete Bridges” by Bolingovich and Polvvanov’s "Reinforced Concrete Bridges (Design and Calculation) After examining the formulas listed in the two books, it is found that the symbols (sign) prescribed by the two are different from each other, and the calculation result of the two is inconsistent. At the same time, Polynov’s formula to derive some of the formula is also puzzling. We have carried out a formula for the calculation of the two were derived and compared to prove that the Kyrgyz formula in the c_2