Due to the inherent complexity of its mechanical behaviour, the analysis of masonry structures is usually performed relying on numerical models. For this aim, several modelling strategies can be adopted, ranging from detailed computationally expensive block-based models to simplified computationally cheap homogeneous continuum models. When homogeneous models are adopted, the choice of the constitutive law is essential to obtain a proper representation of masonry mechanical response, also including the post-peak behaviour. Regarding this latter aspect, which is of particular interest when the mechanical response of masonry structures is investigated, the presence of different constituents in the material, i.e. joints and blocks, plays an important role. In facts, such material heterogeneity leads to different failure mechanisms according to failure taking place in joints, blocks or in both joints and blocks. Accounting for different possible failure typologies within the constitutive law is thus paramount to develop an accurate homogeneous model. In this framework, a mechanism-based damage model for masonry is here proposed. Basing on the multi-failure strength domain for the in-plane behaviour of masonry proposed in [1], three failure typologies are considered in the model, namely block failure, joint failure, and mixed joint-block failure. The model is then extended to the post-peak behaviour by means of an orthotropic damage model inspired by [2], explicitly distinguishing between all the different failure mechanism. The model is implemented in a finite element code and validated on some simple cases aimed at highlighting the role of each failure mechanism within the model response. Finally, applications of the model to the analysis of structural cases are performed and the obtained results critically discussed. REFERENCES [1] G. Bertani, L. Patruno, A. M. D’Altri, G. Castellazzi, S. de Miranda, A single-surface multi-failure strength domain for masonry, (2023) Submitted to International Journal of Solids and Structures [2] I. Rivet, N. Dialami, M. Cervera, M. Chiumenti. "Mechanism-Based damage and failure of Fused Filament Fabrication components" (2023) submitted to Composites Part B