对于矩形截面梁,当截面所承受的弯矩和所选配的钢筋面积已知时,需对钢筋和混凝土的最大应力进行校核(按允许应力法)。这种核算应力的方法,在有关教科书中已有介绍。笔者采用和教科书中同样的假定,导出了矩形截面梁受压区高度系数和内力臂系数,使用起来颇感方便。现以双截面梁为例予以推导, For rectangular section beams, the maximum stress of reinforcement and concrete shall be checked (by permissible stress method) when the moment to be borne and the area of ​​the reinforcement to be selected are known. This method of accounting for stress has been introduced in the relevant textbooks. Using the same assumptions as in the textbook, the author derives the height coefficient and the internal arm coefficient of the compression section of a rectangular cross-section beam, which is quite convenient to use. Now double beam as an example to be derived,