The theoretical stress-strain model for compressed composite cement materials’ behavior without empirical coefficients was proposed by Iskhakov in 2018. This model includes the following main parameters describing concrete behavior: stresses and strains corresponding to the border between the elastic and non-elastic behavior stages of a concrete specimen, ultimate elastic strains, and stresses and strains at the end of the post-peak region. Particular attention is focused on the descending branch of the stress-strain diagram, as well as on the analysis of concrete elastic and plastic potentials. These potentials are important for assessing the dynamic response of the concrete element section, as well as for concrete creep analysis. The present research is aimed at experimental verification of the above-mentioned theoretical model. The obtained experimental results are in good agreement with the theoretical ones, which confirms the model’s accuracy and enables a significant reduction in the empirical coefficients number in compressed reinforced concrete elements design. This, in turn, represents the scientific novelty of this study.

Loading rates affect the behavior of concrete specimens from the beginning of the loading process until failure. At rather high loading rates, longitudinal deformations in concrete specimens under a compressive load are practically elastic up until the ultimate limit state. It has been previously demonstrated that transverse deformations effectively indicate high-strength concrete behavior in the entire static loading process range. A theoretical model for cylindrical concrete specimen failure under compressive load, based on a structural phenomenon, has also been proposed. The aim of the present research is experimental verification of using transverse deformations in addition to longitudinal ones for investigating high-strength concrete behavior at the non-elastic stage. This research is based on testing normal-strength concrete cylindrical specimens under compression at relatively high loading rates. The theoretical model of the cracking and failure scheme of the cylindrical specimens are experimentally confirmed. The obtained results demonstrate that it is possible to use transverse deformations for the interpretation of initiation and development of inelastic deformations in high-strength concrete up to class C90 based on the data for normal-strength concrete specimens of class C30 subjected to relatively high loading rates.

The relationship between transverse and longitudinal deformations (Poisson ratio) in the compressed zone of bending reinforced concrete elements is still not properly considered in designs. This factor is important as it is related to the formation of transverse cracks in the compressed zone of the elements. The main aim of the present research was an experimental investigation of the Poisson ratio in the compressed zone of real single- and two-layer reinforced concrete beams as well as a comparison with the theoretical model proposed in this study. The elastic and elastic–plastic stages were analyzed using experimental data for real beams with a span of 8 m. It was shown that the term “Poisson coefficient” had a limited validity for elastic longitudinal deformations up to 0.5‰. After reaching this limit, the suitable term was “Poisson ratio”. The obtained results allowed a more accurate prediction of transverse deformations and the corresponding cracks, defining a new limit state for bending reinforced concrete elements. Therefore, the authors recommend that the obtained results are considered in order to increase the design accuracy of reinforced concrete bending elements. The outcomes of this study and the proposed theoretical concept should be included in modern design provisions.