Simple Triaxial Strain-Softening Models for Smeared Cracking

The smeared cracking models have the advantage that they can capture the influences of all the triaxial stress and strain components on the fracture process provided that the triaxial stress-strain relation is known. Unfortunately, formulation of this relation, which Is needed for finite element programs, is a difficult problem of constitutive modeling. There is in the literature a huge number of models trying to adequately model fracture of concrete and similar materials in general triaxial situations. A whole book would be required to describe all of them and their modifications and possible extensions. In this section, we just touch the simplest models for smeared cracking, focusing on tensile stress states. Although they do not suffice to describe the complete behavior of concrete at complex triaxial stress states and histories, such as those with high compression stresses parallel to the crack planes, they are adequate for many practical instances of tensile cracking.