# Concrete Beams Reinforced with High Strength Rebar in Combination with External Steel Tape
## 3 Results and Discussion
### Curvature and Deflections of Test Beams
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{3}{*}{
\begin{tabular}{c} **Notation of** \\ **the Beams** \\ \end{tabular} } & \multicolumn{3}{c}{**0.4 M\({}_{\rm d,2}\)**} & \multicolumn{3}{c}{**0.7 M\({}_{\rm d,2}\)**} \\ \cline{2-7}  & \multicolumn{1}{c}{**DBN**} & \multicolumn{1}{c}{**(\(\rm f^{\rm DEN}\,_{\rm 2}\)**-**f**(\(\rm f^{\rm exp}\,_{\rm 2}\)**)/**f**(\(\rm f^{\rm exp}\,_{\rm 2}\)**)/**f**(\(\rm f^{\rm exp}\,_{\rm 2}\)**) \%**} & \multicolumn{1}{c}{**Experimental**} & \multicolumn{1}{c}{**DBN**} \\  & \multicolumn{1}{c}{**f**(\(\rm f^{\rm exp}\,_{\rm 2}\)**)/**f**(\(\rm f^{\rm exp}\,_{\rm 2}\)**)/**f**(\(\rm f^{\rm exp}\,_{\rm 2}\)**)/**f**(\(\rm f^{\rm exp}\,_{\rm 2}\)**)/**f**(\(\rm f^{\rm exp}\,_{\rm 2}\)**)/**f**(\(\rm f^{\rm exp}\,_{\rm 2}\)**)/**f**(\(\rm f^{\rm exp}\,_{\rm 2}\)**) \%**} \\ \hline B-I-1 & 2.21 & 2.15 & \(-\)2.7 & 4.55 & 5.08 & 20.9 \\ B-I-2 & 2.35 & 2.15 & \(-\)8.5 & 5.08 & 5.5 & 8.3 \\ B-II-1 & 4.81 & 4.5 & \(-\)6.4 & 9.44 & 10.2 & 10.2 \\ B-II-2 & 3.98 & 4.5 & 13.1 & 9.56 & 10.4 & 8.8 \\ B-III-1 & 8.25 & 8.9 & 7.9 & 20.32 & 7.3 \\ B-III-2 & 9.64 & 8.9 & \(-\)7.7 & 21.57 & 21.8 & 1.1 \\ B-IV-1 & 1.94 & 9.3 & 4.15 & 4.0 & 6.0 \\ B-IV-2 & 2.08 & 2.12 & 1.9 & 4.55 & 4.4 & \(-\)3.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Experimental and theoretical values of deflections of test beams. Figure 9: Graphs of the deflections in beams: (**a**) the development of deflections for series B–I; (**b**) the same for series B–II; (**c**) the same for series B–III; (**d**) the same for series B–IV; X-axis indicates experimental values of bending moment M (kNm); Y-axis indicates the corresponding deflections f (mm). For beams B-III-I, B-III-2, the following was observed: concrete beams reinforced with high strength rebar of A1000 class, with reinforcement ratio of 0.89%. Comparing with the beams of first series, defection at loading level of 0.7 M\({}_{\text{dr2}}\), increased in 4.5 to 4.2 times, respectively and reached values of 20.32 mm--for beam B-III-1 and 21.57 mm--for beam B-III-2. These values exceed the maximum allowable deflection by 211.7% and 224.7%, respectively. For beams B-IV-1, B-IV-2, the following was observed: steel-concrete beams with tape reinforcement, which has adhesion to concrete (reinforcement ratio 3.45%). Compared with the beams of the first series, deflections at loading level 0.7 M\({}_{\text{dr2}}\) decreased by 10% and amounted to 4.15 mm for beam B-IV-1 and 4.55 mm for beam B-IV-2. This was equal to 43.2% and 47.4% from the maximum allowable deflection. The valid normative code DBN B.2.6-98:2009 provides full concrete strain-diagrams and the corresponding equations, which allow us to assess with sufficient accuracy the deformability of both steel-concrete elements with combined reinforcement and reinforced concrete elements. The deviation from experimental data does not exceed 20.9%. Thus, when comparing the values of moments of ultimate crack opening, maximum moments, deflections, and the percentage of high-strength rebar, it can be concluded that the combined reinforcement of steel-concrete beams using A1000 steel bars and S275 tape is sufficiently effective under the condition of transferring 25-55% of tensile forces to high-strength rebar. The use of such combined reinforcement allows us to reduce the percentage of reinforcement by 15-30% due to the higher design strength of high-strength reinforcement. In addition, such an approach enables us to ensure the requirements for strength, deformability, and crack resistance of the structure.