## 3 Results  
Uncertainty in design codes leads to the lack of a clear description of which shelf sizes (item 2 in Figure 10) should be taken into account, and which should not. The dimensions of the shelves can be significant and proportionate to the main rib of the section. Taking into account their rigidity will clarify the shear force that the section of concrete perceives. With a section of 300 \(\times\) 500 mm, a protective layer of concrete of 50 mm, and a concrete class of B25, Qb according to equation 2, is equal to:  
\[\mathrm{Q_{b}}=\frac{\mathrm{\varphi_{b2}\cdot R_{pt}\cdot b\cdot h_{0}}^{2}}{ \mathrm{C}}=\frac{1.5\cdot 1050\cdot 0.30\cdot 0.45^{2}}{0.45}=213\ \mathrm{kN} \tag{3}\]  
The hypothesis put forward in this study is as follows:  
Figure 10: Sectional areas taken into account: 1—section considered in the calculation, according to [7], 2—section ignored in the calculation. It is necessary to find out how position 2 affects the operation of the section. Figure 9: Test samples before the experiment. Whitish traces of Teflon grease are visible. Reinforcement protrusions are made to prevent errors: rods of larger diameter are laid at the lower faces. Support and cargo steel plates are located in the center of the photo between the beams. The share of the shear force perceived by the shelves in the cross-section is proportional to the ratio of the moments of inertia of the main rib to the moments of inertia of the shelves. The ratio of the shear force that the concrete of the tee section perceives to the rectangular one is equal to the ratio of the main central moments of inertia. To test this hypothesis, we perform the calculation by numerical methods. The distribution of internal shear forces depending on the design scheme obtained as the result of the calculation is summarized in Table 2 and shown in Figure 11. The difference in the character of the shear force diagrams depending on the place of application of the load is visible. When a load is applied to the shelves, the force in the central rib is stepped. When a load is applied to the rib, the diagram of the shear force in the side flanges becomes stepped. The shear force diagram on the rib is linearly uniformly variable. The observed effect was formed due to the introduction of rigid inserts. Confirmation of the most accurate result was obtained through a small-scale experiment. This experiment took into account the scale factor. The size of the coarse aggregate of the mixture is 2 mm, which is 10 times less than the coarse aggregate for conventional structures. However, the determining factor is the stress, which remains unchanged, since it is obtained by reducing the force to the area. The reliability of the results obtained in the course of small-scale experiments is achieved due to the minimum required number of samples [26]. According to the results, it can be seen that the ratio of the moments of inertia and the perceived shear forces is equal when loaded on the main rib. The ratio of forces is 85% to 15% and 86% to 14%. \begin{table}
\begin{tabular}{c} **Shear Force** \\ **Total Shear** \\ **Force, for the** \\ **Entire** \\ **Section** \\ \end{tabular} \\ \hline
1 & Rib & 312,500 & 0.85 & 2.62 & 0.78 & 2.88 & 0.86 \\
2 & Shelves & 56,250 & 0.15 & 0.74 & 0.22 & 0.48 & 0.14 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary table of calculation results. Figure 11: Shear force diagrams in the vertical rib and flanges. It can be seen that the side shelves perceive part of the shear force. The stepwise or linear character of the change in the transverse force, as well as its value, depends on the place of application of the load. Before testing, the samples were marked with \(\rm{R_{i}}\) and \(\rm{T_{i}}\), which means rectangular and tee sections, respectively. The tests were carried out in the laboratory LLC \"Donskaya Stroitelnaya Laboratoriya\" using Matest equipment (Figure 12), which allows for the fine adjustment of the load increase.