A computational model for simulation of steel fibre reinforced concrete with explicit fibres and cracks

A new formulation is herein proposed to embed discrete fibres and cracks in finite elements. The main features of the fibre behaviour are automatically accounted for, including bond and snubbing effects. Fibres can interact with cracks and are modelled without the need for additional degrees of freedom. A comprehensive constitutive law directly models the two possible fibre failure modes: pull-out and tensile rupture. The bridging effect of fibres crossing active cracks follows a pull-out relation that depends on the current crack width, fibre orientation, relevant mechanical and geometric fibre properties, and quality of surrounding cement-based matrix. Fibres can be randomly positioned inside a structural member using a non-uniform distribution. The effect of crack openings is transmitted to the neighbouring material as rigid body movement. Numerical tests of material and structural scale are simulated to assess the performance of the technique. The model is shown to adequately simulate the complete behaviour of the members without the need for fitting material parameters to capture complex failure mechanisms. The model is also used for a rational justification about the loss of ductility when fibres are used in concrete beams flexurally reinforced with small amounts of longitudinal reinforcement. (C) 2020 Elsevier B.V. All rights reserved.