# Concrete Beams Reinforced with High Strength Rebar in Combination with External Steel Tape
## 3 Results and Discussion
### Destruction Stages of Research Beams
In the beams without reliable bonding between the tape and the concrete the yielding of the tape occurred at 0.83 \(\div\) 0.90 M\({}_{\rm dr2}\) for samples with a different percentage of high-strength rebar (40.3 \(\div\) 59.9%), respectively. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Notation of the Beams** & **0.7 M\({}_{\rm dr2}\)**, & \(\varepsilon_{\rm s}\)\(\times\)10\({}^{\rm 5}\) & \(\varepsilon_{\rm s\, tape}\)\(\times\)10\({}^{\rm 5}\) & \(\varepsilon_{\rm B\,t}\)\(\times\)10\({}^{\rm 5}\) & \(\varepsilon_{\rm B}\)\(\times\)10\({}^{\rm 5}\) & **Deflection f\({}_{\rm dr2}\), mm** \\  & \(\kappa\)H & & & & & \\ \hline B-I-1 & 44.93 & 105 & 127 & 124 & 94 & 4.55 \\ B-I-2 & 46.06 & 117 & 144 & 139 & 102 & 5.08 \\ B-II-1 & 48.10 & 259 & 304 & 298 & 147 & 9.44 \\ B-II-2 & 47.90 & 251 & 292 & 287 & 135 & 9.56 \\ B-III-1 & 49.38 & 439 & - & 498 & 221 & 20.32 \\ B-III-2 & 49.25 & 445 & - & 517 & 227 & 21.57 \\ B-IV-1 & 42.18 & - & 92 & 90 & 90 & 4.15 \\ B-IV-2 & 42.18 & - & 98 & 94 & 93 & 4.55 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The strain values in the cross-sections of the beams under loading of 0.7 M\({}_{\rm dr2}\) in zone of maximum bending moment. Comparison of the experimental results for different samples is given below. Beams B-I-1, B-I-2 (concrete compressive strength was \(\mathrm{f_{ck,cube}}\) = 48.7 MPa, ratio (\(\mathrm{f_{yk}}\),\(\mathrm{A^{1000}A_{s_{i}}}\)A\({}^{1000})/(\mathrm{f_{yk}}\)\(\mathrm{{}^{\mathrm{tape}}\)\(\mathrm{A_{s}}\)\(\mathrm{{}^{\mathrm{tape}}}\)) = 31.2%/68.8%; reinforcement percentage of the beam was 2.77%). Yielding of tape reinforcement was reached at \(\mathrm{M_{dr1}}\) = 42.7 kNm and 43.6 kNm, respectively, which accounted about 0.83 \(\mathrm{M_{dr2}}\). Yield point of high-strength rebar was reached at bending moment \(\mathrm{M_{dr2}}\) = 51.52 kNm for beam B-I-1 and 52.64 kNm for B-I-2. The value of the destructive moment, predicted by the theoretical calculation, was equal to \(\mathrm{M_{DBN}}\) = 51.38 kNm. For beams B-II-1, B-II-2, the following was observed: \(\mathrm{f_{ck,cube}}\) = 46.3 MPa, ratio (\(\mathrm{f_{yk}}\),\(\mathrm{A^{1000}A_{s_{i}}}\)A\({}^{1000})/(\mathrm{f_{yk}}\)\(\mathrm{{}^{\mathrm{tape}}\)\(\mathrm{A_{s}}\)\(\mathrm{{}^{\mathrm{tape}}}\)) = 61.9%/38.1%; reinforcement percentage was 1.97%. The yielding of the tape reinforcement was reached at \(\mathrm{M_{dr1}}\) = 31.1 kNm, which is equal to 0.57 \(\mathrm{M_{dr2}}\). The yield point of high-strength rebar was reached at bending moment \(\mathrm{M_{dr2}}\) = 55.2 kNm for beam B-II-1 and 52.4 kNm for B-II-2. The value of the destructive moment, according to the theoretical calculation, was equal to \(\mathrm{M_{DBN}}\) = 52.10 kNm. Figure 8: Graphs of stress development in the working reinforcement: (**a**) the development of stresses in stretched rebars 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 stress values \(\sigma\) (MPa). Before the beginning of the experimental investigation, the beams’ strength was calculated with the use of real \(\sigma\)-\(\varepsilon\) strain diagrams of reinforcement and concrete, which were used for the manufacturing of test samples. This made it possible to predict the operation of reinforced concrete beams under load with high accuracy. For beams B-III-1 and B-III-2, the following was observed: f\({}_{\text{ck,cube}}\) = 46.3 MPa, high-strength A1000 rebar without tape reinforcement; reinforcement percentage 0.89%. The yielding of teh high-strength rebar was reached at M\({}_{\text{dr1}}\) = 55.36 kNm for beam B-III-1 and 57.04 kNm for B-III-2. The value of the destructive moment, predicted by the theoretical calculation, was equal to M\({}_{\text{DBN}}\) = 52.85 kNm.