GRADIENT-ENHANCED DAMAGE MODELING OF CONCRETE FRACTURE

Classical continuum damage theory for quasi-brittle fracture exhibits an extreme sensitivity to the fineness and orientation of the spatial discretization in finite element simulations. This sensitivity is caus ed by the fact that the mathematical description becomes ill-posed at a certain level of accumulated damage. The ill-posedness can be remove d by the use of a gradient-enhanced damage model, In this model, highe r-order deformation gradients give rise to a non-local effect, which r egularizes the localization of deformation and thus renders numerical analyses mesh-objective. The mesh objectivity of the gradient-enhanced damage approach is demonstrated by the application to two concrete fr acture experiments: a double-edge notched bar subjected to a uniaxial, tensile load and a single-edge notched beam under anti-symmetric four -point loading. Both the initiation and the propagation of damage can be simulated. Particularly the latter aspect calls for an appropriate definition of the strain measure which governs the evolution of damage . (C) 1998 John Wiley & Sons, Ltd.