# Concrete Beams Reinforced with High Strength Rebar in Combination with External Steel Tape
## 3 Results and Discussion
### Curvature and Deflections of Test Beams  
Theoretical calculations were carried out according to normative regulations for load levels of 0.4 M\({}_{\text{dr2}}\) and 0.7 M\({}_{\text{dr2}}\) in order to further conduct the comparative analysis of experimental data. Deflections development of studied beams are presented on graphs in Figure 9. From the graphs it could be seen that at loading levels, which are less than the moment of crack formation, deflections increase proportionally to the loading level. Parts of the graphs that correspond to this stage of loading are practically rectilinear. The values of deflections of twin beams until the moment of crack formation are practically the same and maintain linear relationship. After the formation of cracks in the concrete of the stretched zone, the growth in deflections increases, which is expressed by the distortion of the graphs (see Figure 9). As could be seen from the Figure 9, the beginning of yielding of tape reinforcement is accompanied with a further increase in the growth of strains and deflections. The greater the percentage of tape reinforcement, the sharper the increase in deflections can be observed after its yielding. It depends on the difference in forces perceived by tape and rebar. The maximum permissible deflection was accepted equal to the value of 1/250 of the beam span according to DSTU B V.2.6-156:2010 [43], namely 9.6 mm. Numerical experimental and theoretical values of deflections are presented in Table 7. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & & **Load Bearing Capacity (Yield Point of** & & & **Deflection** \\  & & & **High-Strength Rebar, Crashing of the** & & & **\(\mathbf{f_{dr2}}\), mm at M = 0.7 M\({}_{\text{DBN}}\),** \\ \cline{4-8}  & & & & & & \\ \cline{4-8}  & & & & & & \\ \cline{4-8}  & & & & & & \\ \hline B-I-1 & 42.70 & 6.87 & 51.52 & 51.38 & 0.3 & 4.55 & 5.5 & 20.9 \\ B-I-2 & 43.60 & 11.98 & 52.64 & 51.38 & 2.4 & 5.08 & 5.5 & 8.3 \\ B-II-1 & 31.10 & 8.01 & 55.20 & 5.6 & 9.44 & & 10.2 \\ B-II-2 & 31.10 & 7.36 & 52.40 & 52.10 & 0.6 & 9.56 & 10.4 & 8.8 \\ B-III-1 & - & - & 55.36 & 4.5 & 20.32 & 21.8 & 7.3 \\ B-III-2 & - & - & 57.04 & 52.85 & 7.3 & 21.57 & 21.8 & 1.1 \\ B-IV-1 & 51.49 & 7.91 & 51.49 & 2.4 & 4.15 & 4.4 & 6.0 \\ B-IV-2 & 50.57 & 10.72 & 50.57 & 50.25 & 0.6 & 4.55 & 4.4 & \(-\)3.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Experimental results for steel–concrete beams with combined reinforcement. The results of the study prove that when the percentage of high-strength rebar increases, the values of deflections increase. For example, the beams B-I-1, B-I-2 with ratio \((\rm f_{yk}A^{1000}A_{s}A^{1000})/(\rm f_{yk}\,^{\rm tape}\,A_{s}\,^{\rm tape})=31.2%/68.8%\), and the reinforcement percentage of 2.77% can be considered. Deflections at loading level 0.7 \(\rm M_{d,2}\) were equal to the following values: 4.55 mm for beam B-I-1 and 5.08 mm for beam B-I-2, which accounted for 47.4% and 52.9% of the limit permissible value (9.6 mm), respectively. For beams B-II-1, B-II-2, the following was observed: ratio \((\rm f_{yk}A^{1000}A_{s}A^{1000})/(\rm f_{yk}\,^{\rm tape}\,A_{s}\,^{\rm tape})=61.9%/38.1%\); reinforcement ratio--1.97%. Comparison with the beams of previous series shows that the deflections at loading level 0.7 \(\rm M_{d,2}\) increased by 2.1 times and reached value of 9.44 mm--for beam B-II-1 and 9.56 mm--for beam B-I-2. Thais values amounted about 98.3% and 99.6% from the limit permissible deflection value, respectively.