## 1 Introduction
Economical and efficient solutions with easy applications procedures must be developed and proposed to designers and construction companies. Before application on existing constructions, the realization of mechanical characterization tests allows to assess and discuss the efficiency of retrofitting solutions, check if there are any local or global problems related to the compatibility between the retrofitting material and the wall. These solutions aim to reduce the out-of-plane collapse vulnerability and reduce their impact on society. [PERSON], et al. [15] studied the effectiveness of TRM strengthening applied in infilled RC frames subjected to combined IP-OOP loading tests. A total of 6 specimens were tested, namely: two non-strengthened specimens; two specimens built with horizontal and vertical bed joints reinforcement; two models strengthened using a glass fibre mesh that was cast in an extra fibre-reinforced plaster layer. No detailed properties were provided concerning the strengthening material. From the test results, it was observed that a higher OOP strength of the strengthened specimens was achieved for more considerable IP prior drift. Without strengthening it was observed a substantial reduction of 23%, while the strengthened specimens reached a drop of about 6%. The strengthened specimens reached an OOP strength 54% higher than that the as-built ones. [PERSON], et al. [16] tested the TRM effectiveness to improve the MIW OOP behaviour. Full-scale specimens were tested, in which the walls were built with hollow clay brick masonry units. From the results, it was noticed that the panels OOP behaviour improved significantly, reaching 2.7 times to 3.5 times higher OOP strength. It was also concluded that the retrofitting allowed the controlled collapse of the panel. [PERSON] and [PERSON] (2019) carried out a scaled testing campaign, comprising six half-scale and single-story masonry-infilled RC frames strengthened with TRM and subjected to OOP loading demands. The strengthening improvement varied from 3.79 to 5.45 times for single-wythe wall specimens and 2.45 for double-wythe walls. On the other hand, it was reached an increase of the energy dissipation capacity from 138% to 261%. More recently, [PERSON], et al. [17] carried out a set of OOP tests in infilled RC frames strengthened with TRM. The primary goal was to prevent the OOP collapse and assess the importance of the anchorage of the strengthening materials. For this, the authors tested two different types of anchorages, namely a weak plastic connector and a more robust L-shape glass fibre connector. From the tests, the authors noticed that the maximum strength improved 77% to 122% and their energy dissipation capacity up to 93%. It was evident the prominent role of the anchorage since it guaranteed the proper position and fixation of the strengthening material during the tests. Later, [PERSON] and [PERSON] [18] tested the application of TRM in scaled infilled RC specimens with and without mesh-frame anchorages. The authors found an improvement of the maximum strength from 145% to 445% and of the energy dissipation capacity from 139% to 261%. Based on the results available in the literature it is possible to address some conclusions about the beneficial effect of using TRM to strengthen MIW; however, it has not been studied the impact of the mesh tensile strength. Additionally, a detailed characterization of MIW made of hollow clay horizontal brick units, strengthened with TRM under OOP loading demands is still missing in the literature. The principal objective of this research work is to study the effectiveness of using TRM strengthening in MIW subjected to flexural strength tests parallel to the bed joints. A total of eighteen specimens were tested, in which eight were not strengthened (two without plaster and six with plaster) plus ten strengthened specimens (five with a soft textile mesh and five with a strong one).