Steel Fibre Reinforced Concrete for Precast Structures: nonlinear F.E. analyses for reinforcement optimization

The interest of the precast industry in using Steel Fibres Reinforced Concrete (SFRC), is progressively increased in the last years due to several improvements of the industrialisation and products’; this allows a partial or total substitution of the conventional reinforcement by randomly oriented fibres. Beside that, the guidelines recently introduced have provided fundamental rules which have allowed to standardize and well-define the design process of the SFRC elements. SFRC could be successfully employed to produce roof elements, beams and facade panels but the producers are more and more disposed to use SFRC technology for the production of particular elements (small slabs, pipes, cantilever walls, tanks, road shoulders etc.) whose small dimensions or complex shapes make the use of conventional reinforcement very hard. The structural behaviour of theses particular precast elements may be investigated by using finite elements models based on non-linear fracture mechanics (NLFM); one of these models, well implemented in the F.E. programme “Diana 9.1”, is a constitutive model based on total strains called “Total Strain Rotating Crack Model”. Guidelines introduced in Italy (C.N.R. DT-204) provide tools to perform non-linear analyses in order to verify the SFRC structures both at the Ultimate Limit State and at the Serviceability Limit State. The aim of the present research work is to show the possibility of employing SFRC in some particular precast elements. The study was performed through NLFM analyses with the aim of obtaining optimised design solutions based on the use of SFRC in combination, if necessary, with conventional steel rebars. Numerical results show that SFRC allows to optimize the reinforcement and may be considered a good alternative both for cost and labour-time savings.