Algorithmic implementation of a generalized cohesive crack model

Smeared fictitious crack models can be regarded as generalized cohesive cra ck models. The classic fictitious crack models, i.e. the fixed crack, multi ple fixed crack, rotating crack and microplane model, are based on differen t assumptions for the orientation of developing cracks. A smooth transition between the extreme cases, the fixed crack and the rotating crack model, i s provided by the adaptive fixed crack model. In this approach, the critica l direction of failure is uniquely identified based on Mohr's hypothesis. T hus, the critical direction depends on the character of the failure criteri on and the type of loading. The numeric implementation of the adaptive fixe d crack model has given rise to some subtle questions. It is shown that eve n for a classical fixed crack concept, the algorithmic tangent stiffness ma y have to include components of crack rotation, depending on the imposed st rategy for the global equilibrium iteration scheme. (C) 1999 Elsevier Scien ce B.V. All rights reserved.