Abstarct: Abstract Concrete and rebar are the constituent members of reinforced concrete, the result of their connection is consistent strain and stress and integrated behavior. In the field of concrete admixture, each of them causes changes in the behavior of concrete and they are used according to different uses. For example, adding fibers to concrete will reduce cracking, reduce shrinkage and increase impact resistance. In this study, the behavior of reinforced concrete reinforced with steel fibers in capped rebar is investigated, in which the change in elongation compared to reinforced concrete without fibers is investigated. In this research, 27 beam-to-column connections have been investigated in the laboratory. The target rebar in the samples is made of three grades of 12, 14 and 16 mm and 28-day compressive strength of concrete in two types of 35 and 45 MPa. Concrete samples were analyzed in three simple categories of 0.5% and 1.5% fibers. The results of the test data prove the increase of force absorption in the rebar as well as the reduction of elongation (about 25 to 50%) in fiber concrete compared to concrete without fibers.