## 3 Results  
The results of the tests are presented in Table 5. The results are given for each set of beams, i.e., series A, B, C, and D beams. In particular, the load carrying capacity and bending stiffness of the beams are shown below as well as the mean values and standard \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Classes of Quality for**} & \multicolumn{3}{c}{**Young’s Modulus**} & \multicolumn{3}{c}{**Poisson’s Modulus**} & \multicolumn{3}{c}{**Shear Modulus**} \\ \cline{2-13}  & \multicolumn{3}{c}{**(MPa)**} & & & & & & & & **(MPa)** & \\ \cline{2-13}  & **L** & **R** & **T** & **LR** & **LT** & **RT** & **TR** & **RL** & **TL** & **LR** & **LT** & **RT** \\ \hline Class of inferior-quality KG & 90,200 & 890 & 390 & 0.46 & 0.48 & 0.57 & 0.36 & 0.045 & 0.017 & 550 & 450 & 95 \\ Class of medium-quality KS & 11,500 & 930 & 420 & 0.47 & 0.50 & 0.59 & 0.38 & 0.047 & 0.019 & 880 & 685 & 100 \\ Quality grade of wood KW & 13,200 & 950 & 430 & 0.49 & 0.52 & 0.61 & 0.41 & 0.048 & 0.021 & 960 & 790 & 115 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The material models for wood. Figure 5: A numerical FEM model for a reinforced beam. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & \multicolumn{3}{c}{**MOE (MPa)**} & \multicolumn{3}{c}{**Poisson’s Ratio**} & \multicolumn{3}{c}{**Shear Modulus**} \\ \cline{2-13}  & **L** & **R** & **T** & **L** & **R** & **T** & **LR** & **RT** & **LT** \\ \hline Epoxy glue & 3200 & 96.59 & 96.59 & 0.3 & 0.015 & 0.3 & - & - & - \\ Steel & 205,900 & 6214.91 & 6214.91 & 0.25 & 0.0125 & 0.25 & & 8000 & 80,000 \\ BFRP & 79,200 & 2390.58 & 2390.58 & 0.19 & 0.0095 & 0.19 & - & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The material models for the reinforcing elements. deviations for each group of beams. The tests showed a percentage increase in the maximum load capacity and bending stiffness of reinforced beams of types B, C, and D compared to unreinforced beams of type A. The percentage increase in maximum load capacity ranged from 27.4% to 58.2%. Based on the study, it was found that the lowest value was achieved by type C beams, while the highest value was achieved by type D beams. At the same time, it can be seen that type D beams with a prestressed steel bar were characterized by the highest percentage increase compared to other reinforced beams. It can therefore be concluded that the maximum load-bearing capacity of wooden beams can be effectively increased using prestressed steel bars. The MR-displacement curve at mid-span for all types of test beams is shown in Figure 6. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Beam** & **Reinforcement** & **Reinforcement** & **Max. Load** & **Stiffness EI** & **Ultimate** \\  & & **Ratio (\%)** & **F/2 (kN)** & **(kN \(\times\) mm\({}^{2}\)**)** & **Displacement** \\  & & & & \(\times\) **10\({}^{9}\))** & **(mm)** \\ \hline A1 & - & - & 19.9 & 2.07 & 55.2 \\ A2 & - & - & 17.9 & 1.75 & 50.4 \\ A3 & - & - & 18.5 & 2.03 & 53.9 \\ A4 & - & - & 19.4 & 2.05 & 56.2 \\ A5 & - & - & 20.5 & 2.09 & 57.8 \\ Average & - & - & 19.2 & 2.00 & 54.7 \\ value & & & & & \\ Standard & - & - & 1.0 & 0.14 & 2.8 \\ deviation & & & & & \\ C1 & GFR & 1.8 & 24.5 & 2.75 & 44.2 \\ C2 & GFR & 1.8 & 22.3 & 2.24 & 43.1 \\ C3 & GFR & 1.8 & 25.1 & 2.67 & 44.5 \\ C4 & GFR & 1.8 & 24.4 & 2.59 & 46.8 \\ C5 & GFR & 1.8 & 26.0 & 2.62 & 41.9 \\ Average & - & - & 24.5 & 2.57 & 44.1 \\ value & & & & & \\ Standard & - & - & 1.4 & 0.20 & 1.8 \\ deviation & & & & & \\ D1 & Steel & 1.8 & 29.9 & 3.03 & 42.1 \\ D2 & Steel & 1.8 & 31.2 & 2.96 & 44.6 \\ D3 & Steel & 1.8 & 30.7 & 2.92 & 46.5 \\ D4 & Steel & 1.8 & 30.2 & 3.02 & 42.9 \\ D5 & Steel & 1.8 & 32.6 & 2.91 & 44.7 \\ Average & - & - & 30.9 & 2.97 & 44.2 \\ value & & & & & \\ Standard & - & - & 1.1 & 0.06 & 1.7 \\ deviation & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The results of experimental bending tests.