In the present work, macro-mechanical modelling of reinforced concrete structures under corrosion is performed. A traction based damage model is adopted. A discrete crack approach is used to model the fracture behaviour of concrete. The bond-slip relation between reinforcement steel and concrete is continuously evolving under corrosion, as a function of corrosion level and stress state. This is a non trivial issue, which is dealt with taking into account a total approach. Other corrosion aspects considered in this work are the reduction of the sane cross section of the reinforcement steel as well as spalling of the concrete cover. Bending tests are performed to evaluate the influence of corrosion at structural level, namely the increase of deformation as well as the decrease of the strength of the structure, leading to premature failure. Furthermore, stirrup confinement, in association with spalling, and slippage of the anchorage zone are analyzed.

In this work, a new damage model for cohesive fracture is presented. The concept of damage driving mechanism is introduced, from which the damage evolution law is derived. Special attention is paid to non pure mode-I and mode-II fracture modes, such as mixed-mode fracture and mode-II fracture under compression. Conversely to the previous traction-based damage model (Alfaiate et al. 2023), where the damage variables are derived from uniaxial tensile and shear relationships, the damage variables are now obtained explicitly from reference traction-jump displacement relationships, leading to an integration of fracture mechanics concepts with a damage mechanics approach. In this way, it is possible to explicitly control the dissipation of energy. The model is aimed at the simulation of the behaviour of reinforced concrete structures under corrosion. Corrosion affects i) cracking, which is modelled with a discrete crack approach, ii) bond-slip degradation between steel and concrete, iii) the reduction of the sane cross section of the reinforcement steel and iv) spalling of the concrete cover. In this work some illustrative examples of the performance of the model are shown. In part II, examples of reinforced concrete structures with and without corrosion are presented.

Corrosion in reinforced concrete is an important feature which can lead to increased deformation and cracking, as well as to premature failure. In the present work, macro-mechanical modelling of corrosion is performed, namely the degradation of bond–slip between concrete and steel. A mixed-mode damage model is adopted, in which the interaction between the bond–slip law and the stress acting in the neighbourhood of the concrete–steel bar interface is taken into account. Bond–slip degradation is modelled using an evolutionary bond–slip relationship, which depends on the level of corrosion. Different relevant loading cases are studied. Special attention is given to the evolution of corrosion in time, under constant load. This is done by adopting a Total Iterative Approach, in which the structure is reevaluated each time step, upon damage increase due to corrosion. Pullout tests are presented to illustrate the performance of the model. Bending tests are also performed to evaluate the influence of corrosion at structural level.

In quasi-brittle materials, such as reinforced concrete, localisation of initially diffuse cracking evolving in localised cracking patterns consists of a numerically challenging task. With conventional iterative methods, convergence of the numerical solution scheme to model crack localisation is often difficult to obtain. On the other hand, conventional total approaches, such as the Sequentially Linear Approach, although robust, fail to approximate properly the underlying material law. In the present work, a new model is introduced, designated the Total Iterative Approach, in which the internal damage variables are updated iteratively. It is found that this approach is robust, allows for the correct approximation of the material law and is a powerful tool for the analysis of softening behaviour. Some examples are presented to illustrate the performance of the model.

In this manuscript mixed-mode fracture in quasi-brittle materials is studied. A damage model is first introduced in the framework of the discrete crack approach, in which the limit surface is defined in the traction space. Dilatancy is included in this model as an additional compliance. Some experimental results are simulated, which give rise to further refinement of the model due to the effect of dilatancy. One new model is introduced, based on a nonlinear fracture mechanics approach. This is a purely incremental hypoelastic model, which cannot be derived in the framework of the damage mechanics theory. The numerical results of the two models are compared. In particular, it is found that the fracture mechanics model can better meet the requirements needed for the simulation of the experimental results.