# Concrete Beams Reinforced with High Strength Rebar in Combination with External Steel Tape
## 3 Results and Discussion
### Destruction Stages of Research Beams  
As the load increases, strain in the tape reinforcement reaches limit values that correspond to yield point. It should be noted that yielding in tape reinforcement occurred when deformations reached the value of \(\varepsilon_{\text{s,tape}}\) = 137 \(\times\) 10\({}^{-5}\). After that, during further loading, there was a significant increase in the strain of high-strength rebar and in the deflections of the beam while tensile stress in the tape reinforcement remained the same at level f\({}_{\text{yk}}\)A\({}_{\text{s,tape}}\). All subsequent load increments were perceived by the high-strength rebar until its yield strength was reached. Even after the beginning of yielding, the tape reinforcement continued to perceive the part of the load that corresponded to  
Figure 7: Specifics of beam destruction. its yield point. Yield strength in high-strength rebar was reached at relative elongation \(\varepsilon_{\rm s,rebar1000}\) = 564 \(\times\) 10\({}^{-5}\) for reinforcement of A1000 class. The largest values of concrete strain in the stretched and compressed zones, strains of stretched reinforcement and deflections up to the moment of the limit cracks' opening at load level of 0.7 M\({}_{\rm dr2}\) are given in Table 5.  
The yield point in tape reinforcement was reached earlier than in high strength rebar. At this stage, the sharp increase in strains and deformations were recorded. It was noted that after the yield point of steel tape, the beam continued to perceive the increasing load. However, after the yielding in the high-strength rebar, the additional load on the beam cannot be perceived. Therefore, further loading caused significant growth in the reinforcement strains, sharp opening of cracks, and increase in deflections. The ultimate load bearing capacity was reached after the physical destruction of the compressed concrete as a result of its fragmentation. The beams were designed in such a way that the conditional yield of the high-strength rebar occurred earlier than the failure of the compressed concrete. The destruction of the compressed concrete zone of the samples had a plastic character and began after reaching yield point in the high-strength reinforcement. After further growth of concrete strain its destruction occurred. The bending moment that corresponds to the yield stress in the tape reinforcement is denoted as M\({}_{\rm dr1}\), and the moment that corresponds to the yielding of high-strength rebar is called the ultimate bending moment M\({}_{\rm dr2}\). The values of the stresses in the working reinforcement depending on the bending moment values are shown in the graphs in Figure 8.  
Determination of the limit state of beams in terms of strength was carried out according to strain diagrams of beam reinforcement samples received from the experimental data. During the experiment, an analysis of the stress-strain state of the reinforcement and concrete was carried out and corresponding stress graphs were built. Thus, it became possible to predict the behavior of the test samples under subsequent loads and to determine the moment, corresponding to yield point in the tape reinforcement. Graphs of the development of stresses in tape and high-strength rebar depending on the loading stage are given in Figure 8.  
Theoretical values of the test samples' load-bearing capacity were determined according to methods presented in DBN V.2.6-98:2009 [46], DSTU B. V 2.6-156:2010 [43], and Eurocode 2 [44]. Experimental and theoretical values of ultimate bending moments were compared and presented in Table 6.  
From the tabular data it could be seen that in all beams where tape reinforcement had adhesion to concrete, its yielding occurred at (0.49 \(\div\) 0.83) M\({}_{\rm dr2}\) for samples with a different amount of high-strength rebar (31.2 \(\div\) 61.9%), respectively.