Simulating quasi-brittle failures including damage-induced softening based on the mechanism of stress redistribution.

There have been extensive analytical and numerical studies on crack propagation and softening behavior in quasi-brittle materials, such as concrete, rock and bone, based on the smeared crack model or the discrete crack model, each of which has advantages and disadvantages. It is well known that stress redistribution has an important effect on cracking behavior and may be taken as the physics mechanism. Using the principle of superposition, the theoretical explanation is provided for stress redistribution during the progressive fracture process. Although this explanation deals with problems of linear elastic fracture mechanics, it is a clue of modeling softening behavior. Then, it is shown that the above stress redistribution based method satisfies the necessary condition that the specimen returns to the unstressed state whenever all the external forces are removed. Finally, a new model for simulating quasi-brittle softening is established via a kind of "sub-element" methodology. Numerical examples show the effectiveness of the above subelement method in modeling the behavior of block media with quasi-brittle block-block interfaces. [ABSTRACT FROM AUTHOR]