Análise experimental do efeito de fadiga em vergalhões de 8mm em barras isoladas e telas soldadas para aplicação em concreto armado

Abstract

This research presents a comparative study of the behavior of CA-60 rebar used in reinforced concrete structures in civil construction. The steels that are incorporated in concrete in Structural Engineering can be presented in two formats, during their execution: in isolated rebars, fixed by means of wire with heat treatment; and in steel mesh, with their meetings welded for its consolidation. Certain structural systems, such as bridges and garage buildings, are constantly subjected to the fatigue actions generated by high loads, which can cause their elements to break with requests well below the limit of resistance to static actions, which are generally calculated to the last limit state of the material. Thus, it is essential to verify the strength of the steel, used in structures with these characteristics, to guarantee the safety of the user during the useful life of these constructions. This research was carried out with the experimental analysis of test specimens of CA-60 rebars, in an isolated form and with welded connections, with the realization of fatigue tests with bars in the air in rebars of diameter 8 mm. The Wöhler Curve was generated with the results of the tests of 36 test specimens, after several tests to the choice of the adopted variations, comparing the behavior of the steel bars CA-60 with the variation of the number of cycles, generating to the end the analysis of three levels of resistance fluctuations, for each one of two forms of execution of the bars. Studies with this type of steel in relation to this resistance to fluctuations are still scarce. It should be noted that CA-60 steel is produced by cold treatment, with mechanical compaction of the grain, resulting in a higher resistance to stress and hardness, and a lower resistance to aggression of the medium (which can generate corrosion ) and ductility. Thus, this work will contribute to an improvement of the normative considerations for the last limit state design of reinforced concrete structures in CA- 60 steels.