Unified design-oriented model for the shear strengthening of masonry walls with Inorganic Mortar Composite systems

Masonry structures may exhibit fragile behavior in seismic-prone zones. In fact, most of the energy dissipation is achieved by means of shear cracking. Consequently, in-plane retrofitting is recommended. Among the different techniques, the use of Inorganic Mortar Composite (IMC) systems is nowadays under the magnifying glass due to the appreciable advantages related to the mechanical and chemical compatibility with existing masonry substrates and, at the same time, to the possible removability of the intervention itself. Nonetheless, the available design formulae are often inadequate for predicting the additional strength provided by the dry fabric-based systems (namely Fabric Reinforced Cementitious Matrix/Mortar – FRCM) because of the plurality of options in the side-by-side placing the masonry, mortar-matrix and the reinforcement (i.e. fiber mesh/fabric). The main lacks consist in neglecting the specific contribution of the FRCM-matrix, as well as the matrix-to-fabric bond interaction. Furthermore, in case of pre-impregnated fabric (namely Composite Reinforced Mortar – CRM), an analytical model is currently missed in design Codes. In the light of this, the present paper aims to propose a novel empirical set of equations (for both FRCM and CRM cases) based on large and critical data collection, clustering, cleaning, and processing. The goal is to meet high accuracy of the foreseen using simple formulations in the perspective of design Code targeted to practitioners. Innovation is stated in providing a unified approach - first - able to account both countable (i.e. geometrical and mechanical properties of the substrate and the strengthening) and categorical (i.e. type of IMC-system, use of connectors and symmetry/asymmetry of the strengthening) variables - second. In such a way, an exploitation ratio of the matrix-to-fabric bond interaction is proposed and validated for both the FRCM- and CRM-systems. Lastly, the theoretical versus experimental comparison, associated with parametric analysis, demonstrated the reliability of the proposal, as well as the improved accuracy against other existing models.