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根据已有的断裂实验测试资料和计算结果 ,对比按经典断裂韧度计算式计算的断裂韧度KⅠC和双K断裂准则中的起裂韧度KiniⅠC和失稳韧度KunⅠC,并计算按经典断裂韧度计算式用临界有效裂缝长度代替预制裂缝长度时的KⅠC值 ,认为工程中通常采用的按经典公式算得的KⅠC并不能全面体现混凝土开裂的真实情况。提出工程中宜采用双K断裂准则 ,并综合考虑安全因数进行设计。由于混凝土断裂试验中CMOD较难准确测定 ,提出通过Δ与CMOD的换算 ,以Δc 代替CMODc 计算临界有效裂缝长度ac,从而降低了实验难度。文中还对双K断裂准则中粘聚力的假定分布进行探讨
According to the existing fracture test data and calculation results, the fracture toughness KⅠC and the fracture toughness KiniⅠC and the instability toughness KunⅠC calculated by the classical fracture toughness calculation formula are compared with those calculated according to the classical fracture Toughness calculated by the critical effective crack length instead of pre-crack length KⅠC value that the project is generally used by the classical formula calculated KⅠC can not fully reflect the real situation of concrete cracking. Proposed engineering should adopt double K fracture criterion, and consider the safety factor design. Because it is difficult to accurately determine the CMOD in the concrete fracture test, it is proposed to calculate the critical effective crack length ac by ΔC instead of CMODc through the conversion of Δ and CMOD, thereby reducing the experimental difficulty. The paper also discusses the assumed distribution of cohesion in the double-K fracture criterion