This paper discuss the possibility of structural failure prediction through a special kind of gradient-enhanced damage theory in which the material is considered to possess a substructure or microstructure. In these theories the microscopic movements are accounted for by the damage variable and a reformulation of the kinematics (to include the possible "micro-motions") and of some basic governing principles of the classical Continuum Mechanics is necessary. The theory allows an adequate description of the strain-softening and localization behaviors due to the material degradation, Costa-Mattos (1992) and (1995), Fremond (1996), Domingues (1996) and (1999), for example. First, a continuum damage model for quasi-brittle materials is presented. Then, a simple numerical technique, based on the finite element method, is proposed to approximate the solution of the resulting nonlinear mathematical problems. Within this framework, a numerically predicted macro-crack is the set of points in the structure where the damage variable has reached its critical value. One of the main features of such model is that it is valid for any kind of geometry and external loading. This procedure is applied to the analysis of macro-crack initiation and propagation in several structures and the results are compared with predictions of fracture Mechanics.
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