A unified framework for concrete damage and fracture models including sizeeffects

A unified approach is given for isotropic and anisotropic damage formulatio ns for concrete fracture. The formulation encompasses the classical fixed a nd rotating smeared crack models, but also more refined approaches based on the microplane concept. Higher-order strain gradients are introduced to av oid the boundary value problem from becoming ill-posed at the onset of soft ening. Again, this has been accomplished in a unified setting. By analysing a geometrically identical anchor bolt of three different sizes it is shown that higher-order strain gradients also introduce a proper size effect in the model.