Clarification of the provisions of the limit state method regarding the normalization of the "σ – ε" dependences of concrete under compression and tension. Part 2

Introduction. In two parts of the article, the conceptual and methodological issues arising in the calculations of reinforced concrete structures by the limit state method using a nonlinear deformation model according to SP 63.13330.2018 are investigated. The second part is devoted to the development of a mathematical apparatus and a computational justification of the new concepts introduced in the first part about the laws and diagrams of concrete deformation under compression and stretching conditions.

Aim. To develop and substantiate a calculation apparatus clarifying the provisions of the limit state method in terms of normalization of the "σ – ε" dependencies of concrete under compression and tension.

Materials and methods. The formal logic (analysis, synthesis, induction, deduction), methods of probability theory and mathematical statistics, the method of limit states.

Results. The inconsistency and imperfection of regulatory documents of the Russian Federation is shown: on the control of the uniformity of concrete properties; on the technical conditions of its use; on the technical conditions of cement as the main component of concrete; on the mechanical calculation of reinforced concrete structures. The coefficient of statistical transformation of the reference law of concrete deformation under compression – γ_с (for tension – γ_t) is proposed, which makes it possible to switch from the reference law to all other laws of deformation necessary in the calculations of reinforced concrete structures for two groups of limiting states.

Conclusions. To eliminate contradictions in the norms, it is necessary to introduce a single standard for the uniformity of the physical and mechanical properties of concrete, for example, to adopt V = 0.135 or another value developed and agreed upon as a result of discussion by the community of scientists and engineers. To tighten the uniformity requirements for cement, for example, to adopt V = 0.03–0.05, as it was previously regulated in Soviet standards. In order to fully normalize the strength and deformation characteristics of concrete, which are included in the dependences "σ – ε", it is necessary to normalize at least 7 parameters presented in the formulas of this article.

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