PSI - Issue 72

Serhii Drobyshynets et al. / Procedia Structural Integrity 72 (2025) 210–215

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et al. (2024); Gomon et al. (2024); Roshchuk et al. (2024)), and other composites (Mikulich (2023); Kovalchuk et al. (2022); Iasnii et al. (2023); Homon et al. (2024); Imbirovych et al. (2024)) are widely used in construction practice. The most commonly used elements a nd structures are based on concrete (Famulyak et al. (2019); Mel’nyk (2019); Borysiuk (2019); Kos et al. (2022); Babych et al. (2019)), which, compared to other materials (Datsiuk et al. (2024); Homon et al. (2024)), offers many advantages. It is well known that during operation, building structures may be subjected to various types of loads (Filipchuk et al. (2024); Kovalchuk et al. (2022); Bosak et al. (2021)), including low-cycle loading (Drobyshynets et al. (2024); Korniychuk et al. (2024)).

Nomenclature f cube

cubic strength of steel fiber reinforced concrete prism strength of steel fiber reinforced concrete

f prism E sfb  sfb,R  0,2

initial modulus of elasticity of steel fiber reinforced concrete ultimate strain of steel fiber reinforced concrete under central compression

conditional yield strength of reinforcement initial modulus of elasticity of reinforcement ultimate tensile strain of reinforcement

E s  sR

effective span of the beam

L P

load on the beam

ultimate load-bearing capacity of the beam ultimate bending moment of the beam

P u M u

η

loading level

relative strain of steel fiber reinforced concrete

 sfb

relative strain of reinforcement

 s

deflection of the beam

f

moment

M

Under repeated high-level loads, low-cycle fatigue (material continuity failure) of structures may occur. Low-cycle loading affects the deformation processes and crack formation in concrete. Reinforced concrete structures made of conventional heavy concrete have been studied to some extent under this type of loading. However, the behavior of beams made of steel fiber reinforced concrete (Drobyshynets et al. (2024)) has not been sufficiently explored. Therefore, experimental studies of steel fiber reinforced concrete beams under low-cycle loading remain a highly relevant research challenge. 2. Methods of experimental research For the research, three steel fiber reinforced concrete beams measuring 10×20×220 cm were fabricated in the LNTU laboratory. The test specimens were made of fine-grained concrete and reinforced with steel fibers (1.5% of the volume). The beams were reinforced with longitudinal and transverse reinforcement of Ø12 A-III and Ø5 Vr-I, respectively. In the pure bending zone, no upper mounting or transverse bars were installed. Along with the beams, three prisms measuring 15×15×60 cm and three cubes measuring 15×15×15 cm were also fabricated. Based on the testing of cubes and prisms, the main mechanical characteristics of steel fiber reinforced concrete were determined: cubic strength fcube = 42.1 MPa; prism strength fprism = 31.0 MPa, initial modulus of elasticity Esfb = 30430 MPa, and ultimate strain under central compression  sfb,R =0.001428. The conditional yield strength of reinforcement was  0,2 = 614.8 MPa, the modulus of elasticity of reinforcement was Es=200000 MPa, and the ultimate tensile strain was  sR=0.003175. The beams were tested in a hydraulic press equipped with special traverses, acting as simply supported single-span beams with an effective span of L = 200 cm (Fig. 1a,b), following current regulatory documents (DBN B.1.2-14-2018; DSTU B V.2.6-156:2010; Eurocode 2 (2004)). The load was applied in steps as two concentrated forces at a distance of 30 cm from the geometric center of the beam via a traverse using a hydraulic jack, with a 5-minute hold at each