TRIAXIAL STRESS STATE OF CONCRETE UNDER LONGITUDINAL DEFORMATION OF TUBE-CONCRETE SAMPLES

Abstract

The effects that occur during the transition of concrete to a complex stress state, resulting from the limitation of transverse deformations due to the steel shell, are considered using experimental modeling. The studies were carried out on CFST samples of three standard sizes, as well as on differentiated samples of pure concrete and steel tube. Diagrams of work of samples under longitudinal compression and their comparison are given. The use of CFST structures turns out to be very effective not only as a result of saturation of the supporting structure with material, but due to the mutual influence of the components of the structure on each other. A quantitative assessment and a qualitative justification for increasing the efficiency of the concrete core as part of a CFST element are given. It is shown that the increase in the bearing capacity of the sample due to the reinforcement of a simple tube with concrete is several times higher than the differentiated bearing capacity of the concrete core. This fact makes it possible to consider CFST structures as composite ones with a non-linear increase in strength due to the joint work of the system components. The transition of specimens to the plastic state of tube-concrete specimens occurs at the same values of longitudinal deformation as for hollow steel tubes, but at high load values. The effects that occur in concrete under the influence of a steel shell create a triaxial stress state, which makes it possible to multiply the bearing capacity of any brittle material. It is shown that concrete under conditions of such a stressed state behaves rather like an amorphous material, does not collapse at all stages of deformation, and there are practically no processes of crack initiation and its propagation in concrete.