用损伤法计算混凝土断裂过程区的等效缝长

Calculation of Equivalent Crack Length of Concrete Fracture Process Zone by Damage Mechanics

在混凝土结构宏观裂缝前缘存在一定范围的断裂过程区,若考虑其影响,则裂缝失稳扩展的临界缝长已不再是初始缝长a0,而是最大荷载对应的等效临界缝长ac,即ac=a0+Δae,其中Δae是断裂过程区的等效裂缝长度。损伤力学认为混凝土从开始受力到最终破坏的整个过程就是一个损伤产生、积累、发展的过程。在计算断裂过程区等效缝长时,应考虑混凝土初始损伤及σ-ε曲线上升段对计算结果的影响。本文运用灰色理论计算了楔入劈拉实验试件的初始损伤D0和损伤阈值Df,并基于虚拟裂缝模型原理,运用损伤力学理论,对初始裂缝为a0的混凝土楔入劈拉试件进行研究,推导得到了断裂过程区的等效缝长Δae及对应的损伤度。

There is certain fracture process zone in front of macro crack in concrete structure. Considering its impact, critical equivalent crack length of instable expansion is no longer initial crack length a0, but the equivalent critical crack length ac corresponding to the maximum load, that is ac =a0 ＋ Aao , in which Aae is equivalent crack length of fracture process zone. Damage me chanics considers that the whole process of concrete from beginning of force action to final fracture is a process of formation, accumulation and development of the damage. In calculating equivalent crck length of fracture process zone, the influence of concrete＇s initial damage and a-ε curve＇s upward segment on calculated results should be conidered. By use of grey theory, this paper calculates initial damage Do and damage threshold Dt of specimens in wedge-splitting experi ment. Based on virtual crack model principle and damage mechanics theory, the concret＇s wedgesplitting specimen with initial crack a0 was studied and the equivalent crack length Aao in fracture process zone and corresponding range of damage degree were deduced.