Efficient Constitutive Model for Continuous Micro-Modeling of Masonry Structures

Masonry is a composite material often modeled as an equivalent homogenous material. However, the complexity of its micro-structure leads to complex mechanical responses, which are almost impossible to capture accurately with homogenous constitutive models. Micro-modeling can be used in these scenarios, allowing for the explicit modeling of microstructural components, leading to an accurate capturing of their interaction. Its main drawback is the computational cost, which often makes this approach suitable only for the simulation of small specimens. This is especially true due to strain-softening leading to severe instabilities and non-convergence of the solution. The objective of this work is to propose a simple yet effective constitutive plastic-damage model for the microstructural components of masonry. It is based on a damage model previously developed by the authors. For a better representation of the cyclic response of masonry, plasticity is added using a simplified implementation that does not strictly follow the rules of standard elastoplasticity, allowing an explicit computation of the stress tensor from the strain tensor without the need for an iterative loop at the material level. To reduce the numerical issues related to strain-softening and thus improve the stability of the solution, an IM-PLEX integration algorithm is adopted.