Structural Modelling of FRC in Serviceability States: Simplified and Numerical Approaches

In recent decades, the advancements of building codes favoured the spread of fibre-reinforced concrete (FRC) in common design practice. The unified rules for the material classification and the simplified constitutive laws introduced by the CNR-DT 204 and the fib Model Code 2010, in fact, allow to effectively evaluate the ultimate capacity of FRC members, ensuring adequate safety levels. With reference to the crack openings typical of serviceability limit states, however, the predictions based upon the available simplified approaches are often characterized by a worse approximation. In this paper, starting from the experimental flexural behaviour, we propose alternative procedures for the back-calculation of the uniaxial tensile behaviour of FRC, built on the enforcement of sectional equilibrium at crack openings ranging between 0 and 0.5 mm. The experimental responses of 12 notched beams are finally compared with simplified plane-section analyses and numerical simulations based on non-linear material models available in commercial software.