基于断裂力学和损伤理论的混凝土开裂模型

New concrete cracking model established based on fracture mechanics and damage theory

依据宏观断裂力学和细观损伤理论,研究混凝土断裂过程区对断裂韧度的影响.在双参数模型的基础上,将细观的损伤本构模型运用于描述宏观断裂过程区的应力分布,并建立改进的混凝土开裂模型.以力学实验为基础,采用ABAQUS分析软件对不同龄期、不同初始裂缝深度的混凝土梁开裂过程进行模拟.数值模拟结果表明,应力强度因子和裂缝尖端位移都随着龄期的增加而增加.但是在同一龄期,初始缝高比对应力强度因子和裂缝尖端位移的影响并不明显.采用改进模型进行的数值模拟结果与实验结果吻合良好,表明该开裂模型能准确描述混凝土的临界开裂,可以作为评价混凝土开裂与否的理论判据.

According to macro-fracture mechanics and meso-damage theory, the influence of fracture process zone on the fracture toughness of concrete was studied. Based on two-parameter model, the mesodamage constitutive model was employed to represent the stress distribution of the macro fracture process zone. And an improved cracking model of concrete was established. Based on mechanical tests, the frac ture processes of concrete beams with different pre-crack depth at different ages were simulated using ABAQUS. The numerical simulation results indicate that both critical stress intensity factor （Ks） and crack tip opening displacement （CTOD） increase with the increase of curing age. While at the same age, the initial crack depth has no clear influence on Ks and CTOD. It is found in this research, using the improved cracking model, the numerical simulation results agree well with the experimental results. It proves that the improved model can accurately describe the critical cracking behavior of concrete, and be applied to evaluate concrete cracking as a theoretical criterion.