A continuum model for in-plane analysis of masonry: an approach based on failure mode classification

In this paper, a multi-failure continuum model for in-plane analysis of masonry structures is introduced. The model is based on a recently-proposed single-surface multi-failure strength domain, and is here implemented in an elasto-plastic framework to perform nonlinear incremental static analyses on masonry walls. As a key feature of the model, the activated failure mechanism(s) can be identified and the corresponding plastic strains evolution computed. In particular, the distinction between crushing failure, joint failure (horizontal, vertical, and diagonal) and mixed joint-block failure is guaranteed by means of specific weights assigned to each failure mode. This amounts to a classification procedure which selects the active failure modes based on the information provided by the stress state. As a further novelty of this work, ad hoc nonassociated flow rules are then chosen to characterize each failure mode independently, so allowing a straightforward tracking of their nonlinear evolution. Well-known numerical examples are used to show the capability of the approach. From these, the proposed continuum model appears accurate and the tracking of the plastic strains related to the considered failure modes allows a straightforward interpretation of the results.