On the identification of SFRC tensile constitutive behaviour

A cr-8 approach proposed by RILEM Technical Commission to design steel fibre reinforced concrete (SFRC) structures is herein discussed. The method is based on the identification of equivalent tensile strengths related to the energy dissipated up to certain kinematic thresholds in a third point bending test with an assigned geometry. This approach extends usual RIC computations based on plane-section assumption without an explicit definition of a strnctural or material characteristic length, though a softening constitutive law was introduced. On the basis of two experimental programmes investigating beams with different depth, a check of this approach is attempted. Only hooked steel fibres were considered with 80 kg/m 3 maximum fibre amount, since this limit can be regarded as an economical upper bound for the majority of concrete structures. The results confom a quite satisfactory prediction for beam up to 150 mm deep, but sometimes a dangerous overestimation of the maximum load is observed for deeper strnctures. A comparison with a F.E. smeared­ crack approach highlights the limits of the simplified approach proposed for design.