PSI - Issue 81

Serhii Drobyshynets et al. / Procedia Structural Integrity 81 (2026) 406–410

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(Rybak et al. (2024); Kovalchuk et al. (2024); Babych et al. (2017); Chapiuk et al. (2023)), although alternative composite materials may also be used instead of steel. The use of reinforced concrete contributes to reduced operation and maintenance costs of structures. Experimental investigations aimed at determining the deflections of steel fiber reinforced concrete, reinforced concrete and reinforced concrete with rebar and steel fibers beams after exposure to low-cycle loading, as well as their comparative analysis, represent a relevant and timely research task.

Nomenclature L beam span a beam width b beam height η cyc

low-cycle loading level maximum deflections residual deflections

f max f min

2. Methods of research For experimental investigations under laboratory conditions, six rectangular beams with dimensions of 10×20×220 cm were manufactured. According to the type of reinforcement, the specimens were divided into three series, two beams in each series: steel fiber reinforced concrete, reinforced concrete and reinforced concrete with rebar and steel fibers. All test beams were produced from fine-grained concrete of identical composition in order to ensure comparability of the test results. Steel fiber reinforced concrete beams (series B-1) were reinforced exclusively with dispersed reinforcement in the form of steel fibers, the content of which was 1.5% of the total volume of the concrete mix. Reinforced concrete beams (series B-2) were provided with conventional rebar reinforcement: longitudinal main reinforcing bars with a diameter of Ø12 of class A-III and transverse reinforcement with a diamet er of Ø5 of class Vr -I. Reinforced concrete with rebar and steel fibers beams (series B-3) combined both types of reinforcement, rebar and dispersed, which made it possible to assess the composite action of steel fibers and reinforcing bars within the concrete matrix. The mechanical properties of the materials used are presented in (Drobyshynets et al. (2025)) and were assumed to be identical for all specimen series. Beam testing was carried out on a hydraulic press equipped with special loading frames that ensured single-span beam conditions with a calculated span length of L = 200 cm (Fig. 1). The testing procedure complied with the requirements of the applicable regulatory documents, in particular DBN B.2.6-98:2009, DBN B.1.2-14:2018, DSTU B V.2.6-156:2010, and Eurocode 2:2004.

Fig. 1. Beam testing under low-cycle loading

The load was applied in a stepwise manner in the form of two concentrated forces arranged symmetrically with respect to the midspan at a distance of 30 cm from the geometric center of the beam. Load transfer was carried out through a loading frame using