THE INFLUENCE OF STRUCTURE AND TECHNOLOGICAL DAMAGE OF CONCRETE FOR THE FULL DEFORMATION DIAGRAM

Abstract

In this work models of the stress-strain state of reinforced concrete elements are considered, depending on the structure, the initial composition of concrete, and the technological means of processing materials into the final product. The research results showed that the σс – εс diagrams change depending on the concrete strength, initial composition and its technological damage. In the work of Vakhnenko P.F. it was determined that the actual value of εсR and εси depends on the strength of the concrete. Bamburа A.N. analyzed the results of experimental studies, developed analytical expressions for determining the main parameters of the diagram σс – εс depending on the strength of concrete. Recently, the direction of development of the general theory of reinforced concrete, built on the use of complete diagrams of deformation of concrete and reinforcement, has been developed. This allows the most accurate determination of the stress state at all stages of the work of the reinforced concrete element. An important feature of complete concrete deformation diagrams is the presence of descending sections, which allow the most complete determination of the performance of concrete in the stage of destruction. The diagram does not have a stable character, because the magnitude of inelastic deformations of concrete depends on many factors: technological, speed and nature of loading, composition of concrete, technological damage and others. Based on experimental justifications, the authors derived the dependence between the strength and deformation characteristics of concrete on the ascending branch of the σс – εс diagram. Using the Heaviside function, a universal formula for concrete deformation in the form of a biquadratic dependence is proposed. The resulting law of concrete deformation over the entire loading range in the form of a biquadratic law includes deformation constants Е0, Е1 and Е2. To determine the constants, a series of experiments was conducted by means of axial compression with a single short-term load. The diagrams σс – εс for all three cases of the value of the E2 coefficient are given. A table of mechanical characteristics of concrete with the biquadratic law of deformation in compression, depending on the classes of concrete, is compiled.