Anisotropic and Unilateral Damage Application to Concrete

Abstract

The effect of the nucleation and growth of microvoids and/or microcracks (damage) on the overall response behavior of a wide class of materials is now clearly understood. The damage of materials occurs when atomic bonds break at the microstructural level. These microscopic alterations react upon the macroscopic thermomechanical materials properties, elastic softening, decreased conductictivity, plastic yield surface alteration, etc. For concrete, the experimental behavior analysis (concrete is assumed initially isotropic) let us say the principal following phenomena: A loss of stiffness beyond a certain stress point due to damage which is strongly anisotropic due the directionality of the defects (induced anisotropy) A permanent or irreversible strains with the loss of material stiffness (which are due to growth of damage) A stiffness recovery with the change from the damaging loading in traction to a compression loading called “unilateral bahavior” (the damage can be active or inactive, when the microcracks are respectively open or closed) A dissymetric behavior between traction and compression and a softening behavior during traction and compression.