UMAT subroutine code for damaged elasticity

This is a material constitutive model subroutine developed for modelling of isotropic damaged elasticity. The code is written in Fortran programming language and can be used as UMAT subroutine in Abaqus software. The aim of the development was to improve an existing shortcoming in available commercial software fracture model, concrete damaged plasticity. According to this model, the material behaves elastically until the maximum principal stress arrives at the material's tensile strength. After that, the material behavior follows a softening law (in this case a bi-linear softening law) and material's stiffness reduces monotonically until the complete failure. The lower post-peak stress limit is decreased to 0.0001% of tensile strength, which increases the accuracy of the model compared to the similar commercially available models. The details of the model will be explained in an article.