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An effective NLFE method for the analysis up to failure of slabs on grade is presented herein. In order to better evaluate the role played by the fibres with respect to conventional reinforcement, previous experiments on full-scale slabs on grade have been numerically simulated to reproduce the actual slab behaviour up to failure and to provide some useful information for design purposes. The adopted numerical procedure is based on the implementation of the PARC stiffness matrix into a multipurpose FE Code (ABAQUS), which allows for the definition of specific material’s constitutive relationship by compiling users’ subroutines. The adopted constitutive model includes a micro-mechanics based constitutive model for the FRC material, which takes separately into account the bridging action due to fibres and aggregates and allows for the formation of a secondary cracking, not necessary perpendicular to primary cracking, in the concrete strut between two consecutive cracks. This last important extension of the PARC model allows for more realistic numerical simulations of the slab behaviour, especially for the ultimate limit state. Finally, some design considerations could also be introduced by comparing the numerical response of slabs characterised by the same geometry and loading conditions but a different reinforcement arrangement. In particular, the behaviour of concrete slabs reinforced by steel fibres only, by steel bars only or by steel bars and fibres together was investigated.