Nowadays, the development of modern buildings and infrastructures demands best performing material in terms of high strength, high toughness, and energy absorption ability. For these reasons the mechanical and structural behavior of Fiber Reinforced Concrete (FRC) and High Performance Fiber Reinforced Concrete (HPFRC) is investigated in this work. In particular, the thesis is focused on the shear behaviour of beams without conventional shear reinforcement. FRC shear failure domain is related both to its tension and compression properties, characterized by a high level of non-linearity of the problem due to the ductility fibers resource. Consequently, in order to assess the shear structural behaviour of fiber reinforced elements a nonlinear finite element analysis (NFEA) was conducted.