tessellation based on the randomly placed nodes. The cross-sectional properties of these elements are obtained from the dual Voronoi tessellation of the same set of random nodes. For the interface be- tween reinforcement and concrete, the lattice nodes are not placed randomly but at special locations, such that the middle cross-sections of the lattice el- ements form the boundaries between the two phases (Bolander and Berton 2004). The nodes of the lattice elements have six degrees of freedom, namely three translations and three rotations. These degrees of free- dom are related to three displacement and three ro- tation discontinuities at the centroid of the middle cross-section of the elements. The three rotation dis- continuities are related to moments by elastic relation- ships. The three displacement discontinuities are used in interface constitutive models to determine the cor- responding tractions. In the present study, an elastic interface model is used for the reinforcement. One limitation of the present lattice approach is that it only predicts Poisson’s ratios of less than 1 / 4 for 3D and less than 1 / 3 for 2D. This is restrictive for the 3D modelling of the steel reinforcement, which has a Poisson’s ratio greater than 1 / 4 . This limitation could be overcome by combining the lattice model with continuum tetrahedra as discussed for the 2D case by Grassl et al. (2006). However, this approach is beyond the scope of the present study. The inter- face model for concrete is based on a combination of plasticity and damage, which describes the soften- ing and reduction of the unloading stiffness in ten- sion as well as the nonlinear hardening response in high confined compression (Grassl 2009). For the in- terface between concrete and reinforcement, a new cap-plasticity model is proposed which is described in more detail in the next section. plain the small number of models which are available based on this three-dimensional approach. Discrete approaches, such as lattice and particle models, might be a favourable alternative to describe this discontin- uous problem. Their potential to model corrosion in- duced cracking and its influence on bond is assessed in the present study. Lattice approaches have been used successfully in the past to model the failure of concrete, as reported by Schlangen and van Mier (1992) and Bolander and Saito (1998). The model by Bolander has been shown to accurately reproduce analytical solutions for elasticity and potential flow problems (Yip et al. 2005; Bolander and Berton 2004). Further- more, it allows for the use of constitutive models, which are formulated by means of tractions and dis- placement jumps, as commonly used in interface ap- proaches for concrete fracture (Caballero et al. 2006). These have been shown to result in an element-size independent description of crack-openings. This lat- tice approach is used in the present study to describe the mechanical response of three phases, namely rein- forcement, concrete and bond between reinforcement and concrete. In this approach, the lattice elements do not represent the meso-structure of the materi- als (Zubelewicz and Baˇzant 1987). Instead, they are used to discretise the continuum. Thus, constitutive models are required for all three phases, which are described in more detail in the following sections. 2.1 Elasto-plastic cap model for the bond between concrete and reinforcement In the lattice model, the nodal degrees of freedom are related to displacement jumps at the middle cross- section of the lattice element. This three-dimensional displacement jump u$_{c}$ = ( u$_{n}$, u$_{s}$, u$_{t}$ ) T is transformed into strains ε = ( ε$_{n}$, ε$_{s}$, ε$_{t}$ ) T by means of the interface thickness h as The three subscripts n , s and t denote the normal and two tangential directions in the local coordinate sys- tem of the interface (Figure 2a). The thickness of the interface h (Figure 2b) is chosen to be equal to the lattice elements crossing the interface between rein- forcement steel and concrete. The strains are related to the nominal stress σ = ( σ$_{n}$, σ$_{s}$, σ$_{t}$ ) T by the elasto- plastic stress-strain relationship The present lattice approach for the modelling of cor- rosion induced cracking follows the framework de- veloped by Bolander and his co-workers. The nodes of the lattice are randomly located in the domain to be analysed, subject to the constraint of a min- imum distance (Zubelewicz and Baˇzant 1987). The arrangement of the lattice elements is determined from the edges of the tetrahedra of the Delaunay 2 MODELLING APPROACH ε = u$_{c}$ h (1) Figure 1: Three-dimensional modelling of reinforced con- crete: Concrete, reinforcement and bond between concrete and reinforcement are considered as individual phases. Left: Concrete cube (light grey) with reinforcement bar (dark grey); right: detail of interface between reinforce- ment and concerte. σ = D$_{e}$ ( ε − $^{ε}$c − ε $_{p}$) (2)