## 1 Introduction  
Masonry constructions are a large part of the worldwide existing buildings, especially in Italian city centers; they represent an important historical and cultural heritage which needs to be preserved. The recent earthquakes, especially the last large ones that hit the Central Italy with several events in 2016-2017, confirmed the high seismic vulnerability of masonry constructions ([PERSON] et al., 2020 [1]). This raised the interest of the scientific community to improve the masonry seismic capacity through the use of new techniques and innovative materials. In last decades, new strengthening and repair systems were developed and studied, based on the use of Fiber Reinforced Polymers (FRP) and Fiber Reinforced Cementitious Matrices (FRCM) materials. The first ones are based on the use of high strength fibers bonded by means of epoxy resins, mainly oriented in only one direction, on concrete, masonry, steel, or wooden substrates (Council of National Research (CNR) DT200/R1, 2013 [2]; CNR DT201, 2005 [3], CNR DT202, 2005 [4]). The use of epoxy for both impregnating and bonding the fibers allows realizing very thin strengthening systems, with no mass increase and stiffness. The FRCM materials are becoming very diffuse in the last years, especially for strengthening of masonry elements, due both to the use of cement-based matrices, which are more compatible with the masonry substrates than the epoxy, and to the \"grid\" configuration of the fibers, which are usually oriented according to two orthogonal directions and are thus more suitable to adsorb multidirectional stress distributions in masonry walls. Moreover, such a technique is less sensitive to the debonding phenomena that affect the FRP materials (CNR DT200/R1, 2013 [2]), and, in comparison with the traditional use of reinforced concrete layers, it allows to reduce the thickness of the strengthening intervention to only 10-15 mm. Due to the great interest in the application of FRCM systems, many experimental studies have been carried out by means of both tensile tests, aimed to characterize their mechanical behavior, and of bond tests, aimed to investigate the bond performance when applied on concrete or masonry substrates ([PERSON] et al., 2013 [5], [PERSON] et al., 2016 [6], [PERSON] et al., 2017a [7], [PERSON] et al., 2017b [8], [PERSON], 2018 [9]). Moreover, by means of experimental tests or analytical approaches, FRCM materials were analyzed as strengthening systems for several masonry elements subjected to in plane ([PERSON] et al., 2011 [10]) or out plane ([PERSON] et al., 2019a [11], [PERSON] et al., 2019b [12]) loading conditions. Within the numerical investigations, several studies available in literature are focused on the most suitable modeling strategies for simulating both the behavior in tension of FRCM systems and the global behavior of masonry walls strengthened with these materials ([PERSON] et al., 2014 [13], [PERSON] et al., 2016 [14], [PERSON] et al., 2019 [15], [PERSON] et al., 2020 [16]). The experimental assessment of the shear strength of masonry walls was affusinely carried out by means of \"diagonal-compression\" tests ([PERSON] et al., 2008 [17], [PERSON] et al., 2009 [18], [PERSON], 1997 [19]). This kind of test is quite simple to realize in a laboratory and has been largely diffused to also estimate the effectiveness of innovative materials ([PERSON] et al., 2013 [20], [PERSON] et al., 2013 [21], [PERSON] et al., 2016 [22], [PERSON] et al., 2019 [23]). In such a test, a square masonry wall is loaded in compression, along one diagonal, up to failure, which is usually characterized by formation of cracks along the loaded diagonal, i.e., a \"diagonal cracking shear\" failure.