A unified approach for the ductility assessment of lightly-reinforced and fiber-reinforced concrete beams

Lightly Reinforced Concrete (LRC) and Fiber-Reinforced Concrete (FRC) beams behave similarly under bending actions. In both the cases, the transition from the softening to the hardening response during the post-cracking stage defines the minimum reinforcement of LRC and FRC beams, respectively made with rebars and fibers. Accordingly, a unified and simple approach to assess the brittle/ductile behavior of concrete beams is presented in this paper. It is based on the introduction of a non-dimensional Ductility Index ( DI ), which is positive when the ductile behavior occurs. Both theoretical and experimental analyses demonstrate the linear dependence of DI with the reinforcement of LRC and FRC beams. Regardless of the geometry and of the material properties, the definition of the minimum amount of rebars or fibers, is carried out by imposing DI = 0 . Moreover, if a bending test is combined with the linear relationship proposed, a new design-by-testing procedure for the definition of the minimum reinforcement can also be introduced. Such a procedure is a sort of compromise between complex theoretical methods and experimental campaigns on LRC or FRC beams.