FRC Hybrid slabs: Reliability of model code approaches

Fibre reinforced concrete (FRC) material is characterized by a high intrinsic scatter in the results when tested according to standard notched beams. However, it is observed that structures affected by a high stress redistribution show a significantly reduced scatter in their structural behaviour. Therefore, the use of the characteristic material constitutive parameters from a standard test leads to overly conservative design. The Model Code 2010 has introduced a coefficient, named structural redistribution factor, that is able to take into account a reduced variability of the structural response, when compared to that identified from a standard material test. The paper investigates the behaviour of FRC slabs to highlight the difference in structural response of FRC elements with respect to the expected response computed according to the standard specimens used for material characterization. To this aim, FRC slabs of 2×2 m, 15 cm thick, supported on four points at the mid-span of each side, are tested under a point load. Different slab solutions (R/C, FRC only and a Hybrid solution with FRC and steel rebars) are compared and discussed. The material considered can be classified as 5b according to Model Code 2010. A yield line approach is also adopted to validate the formulation proposed by Model Code 2010 for the structural redistribution factor in the cases investigated.