A stress-based gradient-enhanced damage model

One of the shortcomings of nonlocal damage models with a constant length scale parameter is the wrong prediction of damage initiation and propagation in correspondence of a strongly inhomogeneous strain field. This unphysical behavior can be corrected by considering an evolving length scale which is made a function of the stress state. Giry, Dufour and Mazars (2011) have recently proposed an approach, based on an integral nonlocal damage model, which solves the problem of incorrect initiation and propagation of damage as discussed by Simone et al. (2004). In this contribution, a similar approach is presented in a differential damage model, the gradient-enhanced damage model. The underlying idea, which is used to modify the governing equations, is explained. A new formulation of the finite element equations is derived, with attention to C0-continuity requirements. Representative examples will illustrate the performance of the proposed approach. Shortcomings of the model are pointed out and graphically explained using slight variations of the before-mentioned examples.Building EngineeringCivil Engineering and Geoscience