The equivalent fatigue approach is a method for transformingcomplicated loadings into simpler ones, equivalent in termsof damage, without information about the geometry of thestructure. It has been used for the design specifications ofmetallic structures, for the conditions of their tests trials, andfinally for the characterization of customers and markets.The case of the one input equivalent fatigue approach hasbeen thoroughly investigated at PSA. The current work treatsthe extension of the equivalent fatigue approach to the caseof multi-input loadings. Especially the aim of this paper isto develop Markov chain models for the equivalent fatigueloadings.