The equivalent fatigue approach is a method for transforming complicated loadings into simpler ones, equivalent in terms of damage, without information about the geometry of the structure. It has been used for the design specifications of metallic structures, for the conditions of their tests trials, and finally for the characterization of customers and markets. The case of the one input equivalent fatigue approach has been thoroughly investigated at PSA. The current work treats the extension of the equivalent fatigue approach to the case of multi-input loadings. Especially the aim of this paper is to develop Markov chain models for the equivalent fatigue loadings.