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 benefts ofered by the structural applications of fbre-reinforced concrete. In this framework, it is important to highlight how the ductility of fbre-reinforced concrete structures is strongly dependent on the fbre volume fraction together with the structural size. This crucial coupling induces two reverse ductile-to-brittle transitions in the mechanical response of fbre-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 efects can be taken into account by an efective fracture mechanics approach represented by the Updated Bridged Crack Model (UBCM), which can provide signifcant improvements in current Standards and regulations on fbre-reinforced concrete structures.