中文摘要：

确立了分别基于开裂强度准则和断裂韧性准则的由三点弯曲实验确定混凝土材料抗拉软化关系的方法。该方法应用扩展的黏聚裂纹模型，通过使模拟的荷载-裂纹口张开位移（stress-cmck width relationship，Load-CMOD，P-CMOD）曲线与三点弯曲实验获得的P-CMOD曲线吻合来确定相应的混凝土抗拉软化关系参数。求解中的所有参数均由三点弯曲实验结果确定，其优点是只需用简单的位移控制试验机完成弯曲实验，与单轴拉伸实验相比，实验成功率更高、更容易实现。

英文摘要：

A method to solve tension softening relationship of concrete obtained from a three-point bending test is presented. The method is based on the extended fictitious crack model, by fitting the theoretical calculated stress-crack width （Load-CMOD, P-CMOD） relationship to the experimentally determined P-CMOD curves to obtain the tensile softening relationship. All inputted parameters used in the calculation were directly obtained from the three-point bending test. The advantage of the present method is that the displacement bending test is easier to carry out than the uniaxial tension test. Also, the percentage of tests that can successfully obtain the tension softening relationship among the total tests is higher than that by uniaxial tension.