Ductile-to-brittle transition in GFRP-bar reinforced concrete: bar-roughness effect on pseudo-plastic rotation capacity

The Cohesive/Overlapping Crack Model (COCM) is able to describe the transition between flexural cracking and flexural crushing failures occurring in high-performance GFRP-bar reinforced concrete (GFRP-RC) beams by increasing beam depth and/or GFRP reinforcement percentage.In this framework, tensile and compression ultimate behaviours of the concrete matrix are modeled through two different process zones that advance independently one of another.The application of this nonlinear fracture mechanics model to GFRP-RC highlights that the ductility, which is represented by the plastic rotation capacity of the beam, occurs for high-strength concrete matrix only when the internal reinforcement can slip.Thus, the slippage of the GFRP-bar inside of the concrete matrix becoming a basic new requirement for this type of reinforcement, a comprehensive preliminary campaign is devoted to optimize the surface roughness of this internal reinforcement, to obtain a suitable pull-out behaviour.In particular, the GFRP-bar roughness is varied following a geometrical progression in rib spacing, to investigate the slippage behaviour, thanks to which the pseudo-plastic rotation capacity of the composite beam is guaranteed. GFRP-RC AS A SOLUTION TO