The tensile behaviour of Ultra-High Performance Fibre Reinforced Cementitious Composites (UHPFRC) is decisive in many structural applications. A non-destructive test method (NDT) based on the magnetic properties of the steel fibres is used to determine suitable fibre content and orientation parameters. These parameters are employed in a constitutive model providing the corresponding directional dependent tensile response, which varies throughout the structure. This information is then provided to the mechanical model of the beams used to simulate the four point bending tests (FPBT). The resulting numerical F-d curves and crack patterns are confronted with those from experimental tests with a good match being generally attained.