EXPERIMENTAL RESEARCHES OF THE STRESS-STRAIN STATE OF HEAVY CONCRETE UNDER SMALL CYCLE LOADING OF HIGH LEVELS

Abstract

Structural elements are exposed to cyclic loads, the effect of which on the strength and deformation properties of the material has not been studied sufficiently. The impact of such loads can cause special destruction in structures, in which deformations will increase significantly under cyclic loads, not exceeding the single limit load. The purpose of the work is an experimental and theoretical study of the stress-strain state of heavy concrete prism specimens under the action of high-level cyclic loads. The methodology and results of experimental studies of the stress-strain state of heavy concrete prism specimens under high-level cyclic loading are presented. The upper level of low-cycle loading affects the performance of concrete. The dependences of the change in relative longitudinal and transverse deformations and the diagrams of linear correlation dependences of the secant moduli of longitudinal and transverse deformations of concrete prisms under low-cycle loads of high levels were obtained. A sequential three-stage deformation of concrete has been established: Stage I - gradual decrease in the increase in deformations and the width of hysteresis loops; Stage II - stabilization of the increase in deformations, hysteresis loops at the loading stages repeat each other; Stage III - increase in the increase in deformations, the width of hysteresis loops. The constructed volumetric deformation diagrams allow us to trace the trend of concrete deformation with increasing number of load application cycles. The low-cycle fatigue limit of the studied concrete was established at ncyc → ∞, the value of η_cyc = 0.747. Repeated high-level compressive loads lead to gradual decompression of the structure from cycle to cycle, "grinding" of the material, and its destruction occurs.