<p>This chapter provides an introduction to the constitutive models commonly specified in design guidelines to describe the time-dependent behaviour of concrete and that can be used for the time-dependent analysis of composite structures. These formulations range from the simplest algebraic methods, such as the Effective Modulus Method that is widely recommended in design guidelines, to more sophisticated approaches that can account for creep and shrinkage effects in advanced modelling. The last part of the chapter provides a brief overview of multi-physics modelling that could be useful in predicting the concrete time-dependent response for composite construction.</p>