Clarification of the provisions of the limit state method regarding the normalization of the "σ – ε" dependences of concrete under compression and tension. Part 1

Introduction. In two parts of the article, the conceptual and methodological issues arising in the calculations of reinforced concrete structures using the limit state method with a nonlinear deformation model (NDM) according to SP 63.13330.2018 are investigated. The first part is devoted to the formulation of the problem and the development of the conceptual framework. Aim. To improve the concepts and terms about the laws and diagrams of concrete deformation under compression and tension in terms of their normalization in calculations using the limit state method. Methods: formal logic (analysis, synthesis, induction, deduction), methods of probability theory and mathematical statistics, the method of limit states. Results. It is shown that the regulatory framework for calculations using the limit state method based on NDM contains contradictory and ambiguously understood terms, and some very important concepts about the normalization of the mechanical properties of concrete are missing. In this part of the article, it is proposed to fill in these gaps with new concepts introduced by the author and eliminate existing contradictions and inaccuracies. Conclusions. It is proposed to exclude the ambiguous terms "state diagram", "working diagram" and "diagrammatic method" from the normative and scientific circulation in calc ulations of structures according to NDM. In SP 63.13330.2018, the section "Terms and definitions" should be supplemented with currently completely missing terms and definitions related to NDM calculations, which is possible, among other things, on the basis of the 12 new concepts introduced by the author on the laws and diagrams of concrete deformation under compression and tension with strict mathematical content, which ensure the completeness, integrity and interconnectedness of the normalization of characteristics. physical and mechanical properties of concrete. The differences in concepts are related to the assignment of its fixed probability p∈[0.004;0.5] to the left-hand percentile of the normal distribution at a constant confidence level α = 0.95 to the left boundary of the confidence interval for estimating this percentile based on the t-distribution.