This text provides a review of relevant knowledge in the area of constitutive modelling of concrete steel bonds and their interaction. It discusses the problems encountered in assembling the various elements with the purpose of constructing the model of an element made of reinforced concrete. Whether physically or empirically based, very simple or sophisticated, long-established or brand new, the models presented in this book are produced in as rational a framework as possible, and are accompanied by comments on their advantages and limitations.