Smart construction of fibre-reinforced concrete structures: size-scale effects on minimum reinforcement and plastic rotation capacity

Advanced structural design approaches should consider the economic and technological benefits offered by the structural applications of fibre-reinforced concrete. In this framework, it is important to highlight how the ductility of fibre-reinforced concrete structures is strongly dependent on the fibre volume fraction together with the structural size. This crucial coupling induces two reverse ductile-to-brittle transitions in the mechanical response of fibre-reinforced and hybrid-reinforced concrete elements: by increasing the characteristic size of the structure, an increase in its load-bearing capacity can be observed together with a decrease in its plastic rotation capacity. These size-scale effects can be taken into account by an effective fracture mechanics approach represented by the Updated Bridged Crack Model (UBCM), which can provide significant improvements in current Standards and regulations on fibre-reinforced concrete structures.