## 1 Introduction  
The presence of masonry infill walls (MIW) in reinforced concrete buildings is quite widespread. The MIW are widely used for partition purposes and to provide thermal and acoustic insulation to the structures. Recent and past earthquakes showed that the MIW out-of-plane (OOP) collapse called into question the life-safety and near collapse limit states of many building structures [1; 2]. The MIW collapse has been responsible for human severe injuries, casualties and high economic losses [3]. Therefore, the adequate knowledge of the MIW flexural capacity is fundamental to guide the designers to develop strengthening efficient strategies to reduce their vulnerability. The MIW retrofitting need to be a priority by the national and international authorities. Application of appropriate strengthening solutions, well designed, need to be mandatory in future standards for new constructions and rehabilitation of existing ones. Currently, there is not any design procedure for prevention of the infills OOP collapse available in the codes. Due to the high non-linearity and fragility of the MIW, the retrofitting and strengthening becomes quite complicated. The experimental testing needs to address the effect of the MIW in the global response of the building structure and to identify the variables that increase the OOP collapse vulnerability. Different retrofitting and strengthening strategies can be found over the literature [4], namely the use of fiber reinforced polymers (FRP) [5; 6; 7], engineered cementitious composites (ECC) [8; 9; 10], textile reinforced mortars (TRM) and bed joints' reinforcement [11]. Concerning the last technique, it is more usual in the case of new constructions. The definition of the appropriate solution depends on different issues, being the most relevant ones the costs (material and workmanship), complexity (design methodology, interpretation of the problem) and appropriate knowledge to apply the technique. From the literature review, it is possible to observe that the most prevalent techniques are the use of FRP and TRM. Most of the studies carried out using FRP to strengthen MIW is related to their in-plane behaviour. The first application of FRP to improve the MIW OOP behaviour was carried out by [PERSON] and [PERSON] [12]. Later, [PERSON] and [PERSON] [13] tested MIW built with concrete blocks strengthened with FRP applied with two different approaches, namely: (i) application of externally bonded glass FRP laminates, and (ii) near surface mounted glass FRP rods. The walls were subjected to OOP flexural strength tests until its rupture. The most prevalent failure mode observed was de FRP delamination, and masonry units cracking near to the FRP strips. It was observed an improvement of the OOP strength and energy dissipation capacity up to 200%. Later, [PERSON] and [PERSON] [6] tested a series of MIW made of solid clay bricks subjected to distributed OOP loadings. Glass FRP was applied assuming different strategies concerning the overlapping in the frame-panel interfaces. From the results, the authors found an improvement of the panel strength up to 200% and the most common failure mode was again the delamination of the FRP strips. The authors pointed out the significant contribution of the anchorage of the strengthening material to prevent the strengthening failure for lower OOP loading demands. The TRM strengthening is a very attractive solution since it involves a composite made of reinforcing meshes such as textile meshes (made of different materials such as glass, carbon, or polypropylene) embedded in an inorganic mortar. The mortar can have standard properties or high strength and/or ductility characteristics. The TRM has the potential to integrate thermal energy insulation material, which proved to be a new trend in the strengthening of buildings' envelopes [14]. The MIW retrofitting is considered mandatory since the reduction of the out-of-plane vulnerability is a priority nowadays.