عنوان مقاله [English]
Concrete has the lowest ratio of cost with respect to strength compared to other materials, so it is widely used in construction industry. However, it has some disadvantages, such as low tensile strength and high brittleness, which limit its application in some cases. To improve these negative properties of concrete, adding short discontinuous randomly oriented fibers to the concrete mix is an effective way. Among different types of fiber, steel fibers are used in practice more than others. Steel fibers and concrete form a composite, known as steel fiber-reinforced concrete (SFRC), which has an improved post-cracking behavior compared to plain concrete. In this study, the effect of hooked-end steel fibers on the shear behavior of simply supported concrete beams without stirrups is investigated. Nonlinear finite element method is used to analyze the behavior of specimens under shear. In numerical simulation, the effects of fibers on the tensile strength, compressive strength, compressive and tensile post-peak behavior, and bond between concrete and longitudinal reinforcement are considered. At first, finite element model is validated with experimental data. Then, the effects of adding steel fibers (0, 0.5, 0.75, and 1 percent) and of beam's height (350, 675 and 915 millimeters) on the average ultimate shear stress are studied. The results demonstrates the considerable effect of fibers on the shear strength. It was observed that adding the maximum amount of \% 1 percent of fibers can increase the shear strength about 77, 91, and 131 percent in beam having 350, 675, and 915 millimeters height, respectively. On the other hand, the efficiency of fibers depends on the height of the beam. The deeper the beam is, the more efficient the fibers are. Moreover, using fibrous concrete results in more ductile failure having ultimate deflection 3 to 4 times larger than that of plain concrete. Finally, it was understood that using fibers can mitigate well-known size effect on ultimate shear stress in beams without stirrups.