在混凝土类软化材料断裂研究中，裂纹端部损伤区被简化为具有黏聚应力分布的非线性裂纹，该黏 聚力对裂纹扩展有阻抗作用。裂纹体的应力强度因子是断裂力学标志载荷作用与几何构型因素的量化表达指标； 黏聚力形成的阻抗强度因子数值，与黏聚裂纹长度和材料极值拉伸应力存在数量关系。通过双K断裂判据，以 带切口的三点弯曲梁为断裂力学模型，分析了裂纹黏聚阻力对断裂过程的影响规律，计算该弯曲梁结构断裂试 样的最大承担载荷；其结果比较符合实验数据。

In the fracture study of softening materials,the damage area of crack tip is regarded as a piece of nonlinear crack with cohesive force.The cohesive force has resistant effect on the crack extension.The stress intensity factor of crack solids is a fracture mechanics index that denotes the effect of loading and crack geometry.The resistant SIF of cohesive force has relationship with the values of length of cohesive crack and ultimate tension stress.Through the double-K fracture criterion and fracture model of three point bending beam, the effect of crack cohesive force on the fracture process is analyzed.For maximum loading of bending beam with crack,the calculation approach is presented and the results are well fitted with concrete tested data.

王利民（1962－），男，山东章丘市人，博士，山东理工大学交通学院教授