METHOD OF STUDY AND WORK OF CONCRETE CONCRETE ELEMENTS BETWEEN MIXED ARMY FOR MALOCYCLE LOADS OF HIGH LEVELS

Abstract

In real conditions, reinforced concrete constructions of buildings and structures are exposed to repeated loads. The action of this type of load can cause in the design of the destruction of a special form, in which deformation of structures increases indefinitely with repeated loads that do not exceed a one-time destructive load. In order to study the influence of low-cycle static loads of high levels on the strength and deformation characteristics of reinforced concrete bending elements with mixed reinforcement, prototype samples of beams of a rectangular section measuring 200x100 mm, 2000 mm in length, were tested. According to the results of the stress-strain state of experimental beam samples, the following conclusions can be drawn:

- the work of beams with mixed reinforcement for low-cycle loads of high levels is determined by the value of the upper relative level and the number of load cycles. The work of beams can be characterized by three stages: "squeezing out" deformations - 1st stage; stabilization and elastic work - herd II; Decomposition and destruction - Stage III. For the beams tested at the upper level of loading htop = 0,98 the first two stages were not detected;

- the work of concrete consisted in accumulation of damages in the compressed zone both at loading and unloading stages, and the cyclic loading resulted in a three hundred duct deformation of the compressed zone of concrete;

- the deformation of the stretched armature was determined by the value of the upper relative load level htop, there were few signs of the three stages of deformation;

- low-cycle loads slightly influenced the change in the height of the compressed concrete zone, with the increase in the number of load cycles, its value slowly decreased;

- the main deformation changes (deflections) occurred in the first 3-5 cycles of little cyclic loading;

- low-cycle loads had a negative impact, increasing the loss of previous tension reinforcement;

- the slipping of reinforced concrete reinforcement in the ends of the beams was not detected;

- a definite boundary of low-cycle tensile beams, the value of which was 0.891;

- samples of beams were destroyed due to the achievement of low cycle fatigue, destruction occurred in the normal section at stresses in the working armature equal to the boundary of fluidity, as well as the crushing of the compressed zone of concrete.