Keywords: scaled boundary finite element method, finite element method, discrete crack model, cohesive crack, fracture, reinforced concrete.

Modelling multiple crack propagation in reinforced concrete (RC) remains a challenging task as it involves a multitude of nonlinearities such as the compressive behaviour of concrete, plasticity of reinforcement, aggregate interlock mechanisms, bond slip interaction between the reinforcement and the concrete and dowel action of the reinforcement. Many studies use the finite element method (FEM) to simulate crack propagation in RC. These methodologies usually use smeared [1] or discrete crack models [2] to represent the cracks. FEM-based discrete crack models experience difficulties in modelling crack propagation in RC structures because they usually require remeshing algorithms. This is further complicated by the requirement for fine crack tip meshes or special purpose elements to accurately represent the stress singularity.

A novel hybrid finite element-scaled boundary finite element method was recently developed by Ooi and Yang [3]. It is flexible in remeshing multiple cracks and is efficient in extracting accurate stress intensity factors from semi-analytical solutions of the scaled boundary finite element method (SBFEM). These are achieved using a simple yet flexible local remeshing procedure that is solely based on the finite element method and replaces any existing crack tip elements with SBFEM rosettes after remeshing.

In this study a novel RC model is developed that is based on the hybrid finite element-scaled boundary finite element method with automatic discrete multiple cohesive crack propagation modelling capabilities. The cohesive cracks are modelled using nonlinear cohesive interface elements (CIEs) that are automatically inserted along the crack paths as they propagate. The model assumes the linear elastic behaviour of concrete and does not consider the plasticity of concrete under compression and compression cracking. Any adjacent reinforcement is lumped into a layer of four-noded quadrilateral elements that is connected to the concrete bulk using nonlinear CIEs. A bond model that incorporates two important mechanisms in RC fracture i.e. the bond stress-slip between concrete and steel and the splitting tensile cracks along the reinforcement layer is used to model concrete-steel interaction.

Fracture of a RC beam is modelled. The predicted response, crack propagation process and final crack pattern results of the RC model compare well with other experimental and numerical results available in literature.

1

Y.R. Rashid, "Analysis of prestressed concrete pressure vessels", Nuclear Engineering and Design, 7, 334-344, 1968. doi:10.1016/0029-5493(68)90066-6

2

D. Ngo, A.C. Scordelis, "Finite element analysis of reinforced concrete beams", Journal of the American Concrete Institute, 64, 154-163, 1967.

3

E.T. Ooi, Z.J. Yang, "A hybrid finite element-scaled boundary finite element method for crack propagation modelling", Computer Methods in Applied Mechanics and Engineering, 199, 1178-1192, 2010. doi:10.1016/j.cma.2009.12.005

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