MAIN PARAMETERS OF THE UNIVERSAL CONCRETE STATE DIAGRAM IN THE REINFORCED CONCRETE ELEMENTS AND STRUCTURES

Abstract

This article presents the research results on the search and methodologicaljustification of the main parametric points of the universal dependence of the concrete deformationdiagram c c in reinforced concrete elements and structures. It is shown that, unlike others, thisdependence is not empirical, but obtained analytically using the hypothesis of "stiffness nonlinearity".The using expediency this hypothesis to describe the concrete stress-strain state in reinforcedconcrete elements and structures is substantiated by the results of experimental studies by otherauthors.The most important differences between the concrete deformation standard diagram c cand its state actual diagram in reinforced concrete elements and structures are reflected. It isindicated that the descending branch of the diagram c c reproduces the stresses redistributionfrom one concrete fiber to another. It is substantiated in detail why it is impossible to obtain adescending branch of the concrete deformation diagram for centrally loaded standard samples(concrete cylinders or prisms) under standard test conditions.The nature of the change in the secant modulus of concrete deformations in standard prototypesduring their testing is investigated. It has been established that the ratio between the initial modulusof concrete deformation Ec0 and the normalized modulus of elasticity Ec depends on the concreteclass. The numerical values of the indicated ratios for different classes of heavy concrete are determined and given. It is argued in detail why the compressed concrete ultimate deformability  cumust be determined by the state diagram of the element or structure itself, and the concretedeformation descending branch should be limited by the criterion of ultimate bearing capacity(Fermat's criterion) dM / d(1/ r)  0. The reinforcement influence on the length of concretedeformation diagram descending branch of standard prism samples under axial load is estimated.