## 5 Conclusions  
The experimental, theoretical, and numerical studies conducted in this work shows that the use of prestressed steel and prestressed composite bars can be a reliable way of improving the efficiency of timber beams. The following conclusions were drawn from the experimental and numerical studies:  
1. In the experimental studies, the increased load capacity of reinforced gullam beams were improved between 27.4% and 58.2% compared to unreinforced beams. In addition, the experimental study also showed improved stiffness of the timber beams by approximately 7.8%, 10.1%, and 10.7% compared to unreinforced beams. A number of factors, including the type of reinforcement used, may influence the improved load-bearing capacity and stiffness of the beams. Thus, beams using prestressed steel bars had the highest strengthening effect. In addition, they showed a tendency towards pseudo-rigidity compared to the elastic linear behavior of unreinforced beams. The damage that occurred during the experimental tests was mainly in the tension zone. Basalt BFRP, glass GFRP, and prestressed steel bars were found to be suitable for reinforcing timber elements of even the highest grade, achieving a significant increase in load capacity and stiffness.
2. For the adopted computational and numerical models of bending beams reinforced with prestressed GFRP, BFRP, and steel bars, the effectiveness of the strengthening in terms of stiffness was confirmed; in the numerical models, the values were a little higher than in the laboratory tests. Moreover, it should be noted that numerical analysis is generally used in the design of various reinforcement schemes, with particular emphasis on the configuration of wood quality classes. The slight difference of only 3.1% to 5.7% was due to the fact that all numerical data were obtained from laboratory tests. The [PERSON]'s modulus, Young's modulus, and shear modulus were determined for each quality class of structural timber. Moreover, these tests used beams of the highest quality class with significant homogeneity.
3. The above research results can be used for numerical calculations in the field of repairs or reinforcements of various degrees, patterns, and types of reinforcement in existing wooden structures as well as for technologies using the tested types of reinforcements in conservation practice. In addition, the use of FRP or steel rods can be an effective and common method for repairing glued beams or trusses in the field. Similarly, the successive development of structures reinforced with FRP rods is related to the improvement of the properties of the composite rods themselves. The greater durability of structures reinforced with FRP rods or the avoidance of costs associated with the operation of steel-reinforced structures justifies the advisability of using these composites.  
Conceptualization, A.W.-P.; methodology, A.W.-P., J.G., F.B. and J.P.; software, A.W.-P., J.G., F.B. and J.P.; validation, A.W.-P., J.G., F.B. and J.P.; formal analysis, A.W.-P., [PERSON], [PERSON] and J.P.; investigation, [PERSON]-P., [PERSON], F.B. and J.P.; resources, [PERSON]-P., [PERSON], F.B. and J.P.; data curation, [PERSON]-P., J.G., F.B. and J.P.; writing--original draft preparation, [PERSON]-P., [PERSON], F.B. and J.P.; writing--review and editing, [PERSON]-P., [PERSON], F.B. and J.P.; visualization, [PERSON]-P., [PERSON], F.B. and J.P.; supervision, [PERSON]-P.; project administration, [PERSON], F.B. and J.P.; funding acquisition, [PERSON], F.B. and J.P. All authors have read and agreed to the published version of the manuscript.  
This research was supported by Research Projects No. 1/0306/21 of the Slovak Grant Agency and by Research Projects No. 1/0623/21 and No. 1/0630/21.  
Not applicable.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to file size limitations.  
The authors declare no conflict of interest.