A macro-modeling strategy for masonry elements strengthened by using the Composite Reinforced Mortar (CRM) system is presented in the paper. The CRM system consists in the application, on the wall surfaces, of a mortar coating reinforced with pre-formed composite meshes, based on long fibers, and in the installation of connectors through the masonry thickness. The numerical strategy, developed by using of the free, open-source, finite elements code OOFEM, is based on multi-layer elements, composed of layers oriented along the wall thickness, representing the masonry, the plaster and fiber-based reinforcement.

Non-linear static analyses are performed; a "Concrete Damage Plasticity" material model is adopted for both the masonry and mortar coating, while, for the equivalent layer representing the composite mesh, an elastic-brittle behavior in tension is considered. The characteristics of the materials are calibrated on the basis of the results of experimental tests performed on unstrengthened masonry, on mortar samples, on composite yarns and on CRM coupons.

The model is applied to the simulation of the in-plane and out-of-plane behavior of CRM strengthened piers; the results are compared with experimental outcomes coming from in-plane shear-compression tests and out-of-plane three-point bending tests performed on rubble stone samples (350 mm thick). The comparison shows that the model is able to realistically reproduce the experimental results both in terms of resistance and displacement capacities and in terms of failure modes.