Features of the stress-strain state of normal sections of reinforced concrete beams with concrete of frame structure in a compressed zone
Abstract
Features of the stress-strain state of normal sections of reinforced concrete beams with concrete of frame structure in a compressed zone
Incoming article date: 29.04.2023The results of studies of two-layer reinforced concrete beams with a layer of various thicknesses of high-modulus concrete of the frame structure in the compressed zone and traditional heavy concrete in the rest of the section are presented. The stress-strain state of normal cross sections along the height of the beam was estimated by the values of relative deformations at the level of stretched and compressed reinforcement using the hypothesis of flat sections and actual compression and calculated tensile deformation diagrams of concrete. The influence of the thickness of a layer of high-modulus concrete on the nature of the stress-strain state between the layers is shown. The possibility of destruction of the beam on the concrete of the compressed zone was revealed due to the abrupt decrease in the actual height of the compressed zone due to the "shooting" of a layer of high-modulus concrete with its thickness less than 0.1 h0. The dependence of the relative actual thickness of the compressed concrete, i.e. the distance from the edge fiber of the compressed concrete to the neutral axis, in the studied beams on the magnitude of the bending moment is obtained. It is established that for single-layer beams, with a difference in the elastic modulus of concrete up to 20%, the dependences of the relative actual thickness of the compressed concrete layer on the bending moment are almost identical. In the studied beams, the limiting state of which is caused by the fluidity of the reinforcement, the thickness of the compressed concrete layer was 0.37 ...0.4 with a relative moment value of 0.5, and 0.33 ...0.36 with a maximum bending moment value.
Keywords: double-layer reinforced concrete beams, normal cross-sections, nonlinear deformation model, high-modulus concrete, neutral axis coordinate