CALCULATED RELIABILITY OF DISTINCTIVE REINFORCED CONCRETE BEAMS SUBJECTED TO LOW-CYCLE REPEATED AND SIGNIFICANTLY VARIABLE LOADS

Abstract

On the basis of experimental and theoretical studies of the operation of continuous reinforced concrete beams under the action of low-cycle repeated and sign-changing loads, an analysis of their reliability was performed. In the course of experimental studies, it was found that short-cycle loads with variable signs significantly affect the change in the parameters of the stress-strain state, namely, they increase the width of the opening of cracks and deflections and reduce the load-bearing capacity. The method of limit states laid down in the current regulatory documents allows to ensure the necessary load-bearing capacity of the specified structures due to the use of various coefficients of reliability and responsibility. However, sufficient bearing capacity does not guarantee its sufficient reliability during operation, the quantitative assessment of which remains unknown at the project development stage. Moreover, with a change in the original design factors adopted in the calculation (classes of concrete, reinforcement and reinforcement coefficient), the directions of change of these two characteristics may turn out to be different in general, since the value of reliability is random in nature. Using the experimental results of research, a numerical example of calculating the reliability of uncut reinforced concrete beams, which tested the actions of low-cycle repeated and sign-changing loads, was performed.