## 1 Introduction  
There is considerable interest among engineers in the subject of strengthening timber structures. Wood is a natural material with a long history of use in construction. However, it is susceptible to a number of destructive biological processes and fire [1]. There are ways to protect wood from these threats [2]. These measures contribute to improving the durability of timber structures but do not result in an overall increase in their strength parameters. Consequently, researchers are exploring methods to reinforce timber structures. Fiber-reinforced polymer (FRP) composite materials are becoming an increasingly popular choice for this purpose. The key benefits of these materials are their low dead weight, corrosion resistance, ease of material processing, high tensile strength and fatigue resistance. These characteristics are crucial when it comes to reinforcing the structural elements of a historic building or any other building in which it is important to preserve the naturalness of the wood and the aesthetics of the building. The most commonly used composite reinforcement materials are sheets, strips, and rods. Further details on the use of composites for reinforcement can be found in the following works [3; 4; 5]. [PERSON] and [PERSON] used 12 mm diameter basalt bars for reinforcement [6]. Test results proved the reinforcement effectiveness. A 10% and 23% increase in stiffness and moment capacity in comparison to unreinforced beams was obtained, respectively. The authors concluded that basalt bars (BFRP) as reinforcement gave better results than glass bars (glass fiber-reinforced polymer). [PERSON] and [PERSON] [7] conducted a four-point bending test on small-scale glue-laminated timber beams reinforced with BFRP bars. The bar diameters were 7 and 9 mm. The study authors applied reinforcement in the compression and tension zones in a variety of configurations. In sections in which the diameter of the bars in the two zones differed, the beams demonstrated the most favorable performance. Paper [8] outlines a method of poststressing with glass fiber-reinforced plastic rods and reinforcing with carbon sheets. To simulate biological failure, holes were drilled inside the element. Tests were conducted on softwood beams made from Japanese cedar. A comparison of the results for the reinforced elements in relation to the beams in the control group shows an increase in the bending moments for the three tested groups of 4.3%, 3.5%, and 9.5%. [PERSON] and [PERSON] [9] used fiberglass for reinforcement purposes. They noted a 20-30% increase in the load-carrying capacity. The GFRP-reinforced beams demonstrated an improvement in stiffness of between 24% and 60%. The results include beams reinforced using the following two methods: one bar (three elements) and two bars (three elements). Article [10] presents a comparative analysis of the performance of poststressed composite bars and steel bars. The use of poststressed basalt bars to reinforce gluam beams proved to be a successful technique. The load capacity of the elements increased by 31.12%, the stiffness increased by 9.91%, and the ductility increased by 9.87%. [PERSON] et al. conducted tests on basalt- and carbon-reinforced pine timber beams [11]. The reinforcement was provided in the form of fabrics bonded to the external faces. Increases in both the load-bearing capacity and stiffness in comparison to unreinforced beams were obtained. [PERSON] et al. [12; 13] analyzed the behavior of timber beams reinforced with fiberglass rods. One study demonstrated an increase in bending capacity of between 18% and 46%. The degree of reinforcement of the beams ranged from 0.27% to 0.82%. A study published by [PERSON] et al. [14] indicates that composite sheets are a more beneficial solution than composite bars. However, the author highlights that the reinforcing bars placed inside the beam section are not visible, which is a significant benefit. The reinforcement of solid timber beams made of basalt bars is not studied as often as glass or carbon bars.