On the reliability of the design approach for FRC structures according to fib Model Code 2010: the case of elevated slabs

The paper focuses on the reliability of the design approach proposed in Model Code 2010 for the estimation of the ultimate capacity of fibre-reinforced concrete (FRC) elevated slabs on the basis of different tests for material characterisation. The fracture properties of the material are determined through three-point bending tests on notched beams, and through double edge wedge splitting (DEWS) tests carried out on cylinders cored in the full-size test structure. As a case study, an FRC elevated flat slab is considered, consisting of 9 bays (panels) of a 6×6 m2 dimension and supported by sixteen circular concrete columns having a thickness of 0.2 m and a full-size of 18.3×18.3 m2. The ultimate bearing capacity of the slab experimentally determined is compared with the design value predicted by means of a procedure based on limit analysis following the Model Code 2010. The results show that the method proposed in the Model Code 2010 using the characteristic values and the classification is reliable. Even if the tests are affected by a significant standard deviation and the two experimental campaigns with 3-point bending tests give a significant difference from class “5c” to class “3e”, the structural test presents a bearing capacity that is always larger than the predicted one, which considers a safety coefficient for the material γF = 1.5.