引入结构仿真模型试验相似理论，提出了钢筋混凝土受弯构件正截面抗裂弯矩的相似比计算方法。根据试验研究成果提出了考虑截面高度、混凝土保护层厚度与配筋率等参数的截面抵抗矩塑性系数计算公式。通过大型钢筋混凝土梁及其模型试验梁的正截面抗裂弯矩对比试验，证明所提公式可用于原型和模型构件之间正截面的抗裂换算，为模型试验设计提供了科研依据。

Leading into the similitude principle of simulation model test of structure, the method is established for calculating the similitude ratio of flexural moment against cracking of the normal section of reinforced concrete flexural members. On the basis of the experimental results, the formula is proposed for calculating the plastic coefficient of sectional resistance moment, in which the height of normal section, the thickness of concrete covering and the percentage of reinforcement are considered. By comparison tests of the flexural moment against cracking of normal section between the large reinforced concrete beams and their simulation model ones, it is proved that the formula can be used for conversion of flexural moment against cracking between prototype and simulation model, and can be used as reference for the design of simulation model test.