PSI - Issue 81

Yuriy Panchuk et al. / Procedia Structural Integrity 81 (2026) 509–513

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Table 2 presents the averaged results of the experimental investigations. During the experimental studies of reinforced concrete beams with mixed reinforcement subjected to a single short-term load, the following characteristic features of their behaviour were identified:  prior to crack initiation (η < 0.5), only a minor development of concrete and tensile reinforcement strains was observed. The concrete in both the compressed and tensile zones, as well as the working reinforcement of the rectangular reinforced concrete beams, deformed in a compatible manner;  the formation of normal cracks at η > 0.5 caused a redistribution of internal forces from the cracked tensile concrete zone to the working reinforcement, which led to a rapid increase in strains and beam deflections, as well as a reduction in the height of the compressed concrete zone;  within the stress range of 0.5 ≤ η ≤ 0.7, a slowed growth of concrete strains and a further decrease in the height of the compressed zone were observed;  at stress levels of η > 0.7, an accelerated development of conc rete and tensile reinforcement strains and beam deflections occurred, accompanied by a sharp reduction in the height of the compressed concrete zone. This behaviour indicates the onset of the failure process and reinforcement yielding. The failure developed gradually, while the stress in the extreme compressed concrete fibre at the moment of failure exceeded its prism compressive strength;  no slippage of the prestressed reinforcement was observed during beam testing. 4. Conclusions 1. Experimental investigations of rectangular reinforced concrete beams with mixed reinforcement subjected to a single short term load were carried out. 2. The characteristic features of the structural behaviour of these flexural elements were identified. 3. Prior to crac k initiation (η < 0.5), only a minor development of concrete and tensile reinforcement strains was observed. The concrete in both the compressed and tensile zones, together with the working reinforcement of the rectangular reinforced concrete beams deformed in a compatible manner. 4. The formation of normal cracks at η > 0.5 caused a redistribution of internal forces from the cracked tensile concrete zone t o the working reinforcement, which resulted in a rapid increase in strains and beam deflections, as well as a reduction in the height of the compressed concrete zone. 5. Within the stress range of 0.5 ≤ η ≤ 0.7, a slowed growth of concrete strains and a further decrease in the height of the compressed zone were observed. 6. At stress levels of η > 0.7, an accelerated development of concrete and tensile reinforcement strains and beam deflections occurred, accompanied by a sharp reduction in the height of the compressed concrete zone. This behaviour indicates the onset of the failure process and reinforcement yielding. The failure developed gradually, while the stress in the extreme compressed concrete fibre at the moment of failure exceeded its prism compressive strength. 7. 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