Tension-Compression Damage Model with IMPL-EX Algorithm for Micromodeling of Masonry Structures

A tension-compression continuum damage constitutive model was recently proposed by some of the authors and applied to the continuous micro-modelling of masonry structures. The model features two damage parameters, for tensile and compressive stress states, to handle the unilateral effect of masonry. It was also demonstrated how the 2-parameter model can represent, even if in an approximate manner, the dilatancy of mortar joints, which is something that is not explicitly handled by damage models as it is with plasticity models. To overcome the convergence issues that arise from the softening behaviour of masonry, the proposed model is here improved by implementing a mixed implicit-explicit (IMPL-EX) constitutive integration algorithm. This work discusses the theory of the constitutive model, its implementation in OpenSEES, and its usage in OpenSEES solver and STKO pre- post- processor for the analysis of masonry structures via the micro-modelling approach.