# Out-of-Plane Experimental Study of Strengthening Slender Non-Structural Masonry Walls
## 1 Introduction
The development of more advanced FRP materials with better mechanical properties in recent decades has enabled these materials to become one of the main strengthening materials nowadays. Increasingly, various composite materials are used, such as carbon fiber-reinforced polymers (CFRP) [25; 26; 27; 28], glass fiber-reinforced polymers (GFRP) [29; 30; 31; 32], basalt fiber-reinforced polymers (BFRP) [26; 33], and others. They are externally attached (e.g., [34]) or near surface mounted (e.g., [35]) to existing walls in various ways, commonly using epoxy resins. Such polymerized composites are more durable and resistant and have superior mechanical characteristics. The first research group that studied the bending behavior of masonry strengthened with FRP systems was [PERSON] et al. [36]. Additional researchers who worked on various FRP systems [26; 37; 38; 39; 40; 34] have proven that both out-of-plane flexural resistance and ductility of the wall increase with the external application of FRP composites to the wall surface. A significant increase in mid-span displacement was obtained when applying near surface-mounted CFRP strips using flexible adhesive [41]. Based on the experimental investigations involving masonry walls strengthened with glass and carbon fiber composites that adhere to their surface through an epoxy adhesive [25], it has been shown that compression crushing of the wall and the debonding of the strengthening composite from the wall represent typical failure mechanisms. The main disadvantages of FRP systems are the high cost of epoxy resins and their poor performance at high temperatures. Additionally, working with epoxy resins indoors is a potential hazard for the respiratory system. In addition to FRP systems, there are other strengthening methods to improve out-of-plane wall behavior, such as FRCM--fiber-reinforced cement matrix, which shows similar results to FRP systems [42; 43; 44; 45]. Numerous research contributions analyzing different types of FRCM-strengthening systems are available in the literature [46; 47; 48; 22; 26; 49; 50]. Three [44; 51] and four-point [26; 43; 46; 52; 53; 54; 55] bending tests have been conducted on different types of masonry walls strengthened with FRCM systems. Furthermore, an extensive review [56] of experimental studies involving various FRCM systems of out-of-plane strengthening has recently been published. However, these methods are still time consuming, as it is necessary to wait for the cement to set and harden before the surface can be further processed. Another disadvantage is the additional mass applied to the primary structure. Despite a number of existing wall-strengthening systems, there are not much data available on the strengthening of non-structural masonry walls. The only out-of-plane experimental research on non-structural masonry walls' strengthening was performed by [PERSON] et al. [57]; glass fiber composite fabric was applied to existing non-structural masonry walls with flexible polyurethane adhesive. Due to the lack of experimental studies and data on non-structural partition walls' out-of-plane behavior and possibilities for its strengthening, it was decided to conduct an experimental campaign to identify the failure mechanisms as well as the best strengthening solution. The focus was set to be on preventing an out-of-plane collapse and consequently protecting the occupants of existing buildings from life-threatening hazards.