Craft - a plastic-damage-contact model for concrete II. Model implementation with implicit return-mapping algorithm and consistent tangent matrix

A computational strategy for the evaluation of stresses in a finite element implementation of a new plastic-damage-contact model is described. As part of this strategy a new return-mapping algorithm is developed which fully couples plasticity to directional damage on one or more damage surfaces, and which ensures that local and total constitutive relationships are simultaneously satisfied. In addition, an associated consistent tangent matrix is derived. The performance of the model, as implemented with this new strategy, is explored in a range of 2D and 3D examples which include analyses based on direct and indirect fracture tests, a mixed mode fracture test, shear-normal tests in which aggregate interlock is significant and a reinforced concrete test in which cracking, aggregate interlock and crushing all contribute significantly to the behavior. It is concluded that the consistent computational approach gives solutions with good equilibrium convergence properties. Furthermore, it is concluded that the new model, as implemented in the finite element code, is able to represent a wide range of the behavior of plain and reinforced concrete structures.

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