PSI - Issue 78

Annalisa Franco et al. / Procedia Structural Integrity 78 (2026) 1245–1252

1246

1. Introduction Inorganic Matrix Composites (IMC) systems have recently been introduced as a sustainable solution for masonry reinforcement, due to their greater compatibility with substrates, lower costs and better performance at high temperatures in comparison with epoxy based Fibre Reinforced Polymer (FRP) materials; moreover, permeability is improved and reversibility of the reinforcement solution can be achieved (Bonati et al., 2019). IMC systems are generally composed of fabrics of various types of fibres incorporated into an inorganic matrix (lime or cement-based mortars) and are also known as FRCM (Fabric Reinforced Cementitious Matrix); extensive research has been conducted until now to study their mechanical behaviour and durability issues (Al-Lami et al., 2020; Arboleda et al., 2016; de Felice et al., 2020; Simeone et al., 2022). Currently, Italian guidelines for the design of FRCM systems were published in 2019 (High Council of Public Works, 2019) and are mainly based on the document issued by the Italian National Research Council published in 2018 (CNR-DT 215, 2018). The development of such design documents took advantage of a fruitful cooperation with the RILEM 250-CSM (Composites for the Sustainable Strengthening of Masonry) Technical Committee, which developed, together with the ACI 549 Committee, the ACI 549.6R guide issued in 2020. The design of structural elements strengthened with FRCM systems is based on design values of the mechanical properties of these materials and, thus, having common rules for qualification procedures becomes a need. At the European level, an important step forward was the publication in the Official Journal of the European Union of the European Assessment Document (EAD 340275-00-0104, 2020) concerning the assessment of externally bonded IMC systems made of fibres and matrix of various nature. Indeed, the document provides specific assessment methods for the characterization of the tensile properties of the IMC systems under standard and modified environmental conditions (freeze-thaw, water, saltwater, alkali, alkali soil, dry heat, fuel), but also the bond behaviour to various types of substrates (concrete, clay, tuff and natural stone masonry), in addition to other properties, for totally 22 essential characteristics. It is worth noting that in Italy, guidelines for the qualification of FRCM systems are also available since 2018 (High Council of Public Works, 2018). In both cases, tests allow to determine the main mechanical properties of the strengthening system and of its components, as well as to derive specific parameters which are needed to evaluate design values for calculations. The paper presents the results of a statistical analysis based on a large experimental activity for the qualification of several IMC systems made of different fibres (glass, basalt, PBO, steel) and matrices (lime- or cement-based), produced by several manufacturers and tested in different laboratories. In particular, the results of tensile tests carried out under standard environmental conditions are herein used to calibrate the partial safety factors of both the IMC material (i.e., fabric plus mortar) and the dry fabric. The analysis herein shown is just a small part of a larger analysis that is being conducted for the calibrations of partial factors used for design, which necessarily has to take into account also the bond behaviour to fully characterize the design of IMC systems. Nomenclature d design values of geometrical property D MAX maximum absolute difference between the experimental and theoretical CDF F Ed design values of actions R d design value of resistance k characteristic values of material or product properties X d design values of material or product properties α R FORM sensitivity factor β target reliability index γ skewness of the distribution m partial factor for a material property M global material partial factor Rd partial factor associated with the resistance model and geometrical uncertainties conversion factor μ scale parameter of the fitting distribution