Analytical models for structural behaviour of fibre reinforced concrete beams with steel or FRP bars

Fibre reinforced concrete (FRC) offers an improved resistance to cracking and crack propagation, which leads to increased strength and toughness in flexure. As there is a lack of understanding of structural behaviour of FRC,this paper reports a study on the influence of fibres on the behaviour of flexural members, and it focuses on a partial-interaction structural mechanics model for the deflection calculation of concrete beams reinforced with steel or FRP bars and fibres. For this, a model is developed to incorporate fibres into both tension and compression regions in generating moment-rotation response and also on crack formation and the tension-stiffening mehanism. For calibrating these models an experimental study on the bond-slip relationship between FRP bars and fibre concrete was required for the tension stiffening analysis; and an experimental study on the slip-crack width relationship between fibres and concrete required for the moment-rotation model. The moment-rotation and tension stiffening models were then used to obtain the load deflection (P-Δ) response through integration of discrete rotations at the determined crack locations throughout the member. The theoretical load-deflection responses are compared to the experimental results, showing very good correlation for the ultimate flexural capacity and the ductility of PVA fibre reinforced concrete members.M.S. Mohamed Ali, A.H. Sheikh, D.J. Oehlers and P. Visinti