PSI - Issue 72

Oleksandr Chapiuk et al. / Procedia Structural Integrity 72 (2025) 308–314

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(2024), Iasnii et al. (2023); Abendroth and Soltysiak (2016)). Reinforced concrete structures are more frequently used as load-bearing structures (Kos et al. (2022), Babych et al. (2019), Mel'nyk (2019), Kovalchuk et al. (2022)) than others (Gomon et al. (2024), Bosak et al. (2021), Homon et al. (2023)), as they are strong, possess a fairly high elastic modulus, exhibit small deflections, and are capable of withstanding high temperatures. There is a substantial amount of research on the performance of reinforced concrete structures under various types of loads (Korniychuck et al. (2024), Filipchuck et al. (2024)).

Nomenclature f cube

cubic strength of concrete prismatic strength of concrete temporary tensile strength of rods

f prism

 u E s A s

initial modulus of elasticity of reinforcement

area of rods

reinforcement diameter

d P

Load

slip (displacement) of the free end of the rod relative to the end of the prisms

δ u

stress in the rod at δ u =0,2 mm conditional yield strength of rods

σ s 0 m σ 0,2 η cyc

loading level

stress in the rod (beginning of slippage)

σ s

coefficient of variability

υ

tangential stresses

τ um l an

length of rod anchoring in concrete empirical coefficient (16.5 MPa/cm) standard tensile strength of reinforcement calculated tensile strength of reinforcement level of repeated low-cycle loading

k

R sn

R s P s

Reinforcement bonding with concrete is crucial for the effective operation of reinforced concrete structures. However, there is a lack of experimental studies on this issue for A500C rebar, which complicates the calculations for its anchorage in concrete (DSTU 3760:2019, DBN B.1.2-14-2018, Eurocode 2 (2004)). This article aims to experimentally determine how the length of rod anchoring affects the maximum adhesion values to concrete and to establish the minimum length of rod insertion required. The influence of both single and repeated low-cycle loads on the adhesion of this reinforcement to concrete is also examined. 2. Methods of experimental research As part of the study on the adhesion of sickle-shaped reinforcement to concrete, the research involved examining specimens in the form of concrete prisms with a square cross-section measuring 15 cm on each side. The height of these prisms was determined based on the accepted lengths of the anchoring rods, which were 5d, 10d, and 15d. The reinforcing rods were positioned within the prisms to ensure that their longitudinal axes aligned. The protruding parts of the rods enabled them to be fixed in a press grip on one side while allowing for measurement of displacement (slippage) relative to the free end of the prisms on the other side. For this study, rods with a diameter of 16 mm (Ø16A500C) were selected. The mechanical characteristics of the rods were determined by tensile testing according to standard methods. The ultimate tensile strength of the rods was σu=672.2 MPa; the yield strength was σ0.2=497.3 MPa, and the elastic modulus was Es=199000 MPa. Concrete of design class B25 was utilized. The mechanical characteristics of the concrete were assessed by testing concrete cubes with a rib size of 15 cm and prisms with a cross-section of 15 × 15 cm and a height of 60 cm, made simultaneously with the primary samples. The concrete characteristics indicated a cubic strength at 28 days of age of