Fatigue is a phenomenon of progressive damage occurring in a member subjected to repeated loading. It is irreversible and energy is dissipated in the process. The theory of irreversible thermodynamics provides a framework to model dissipative phenomena through a dissipation potential. Damage due to fatigue in concrete manifests itself in the form of microcracking and therefore damage mechanics is a good theory to describe it. In this work, a closed form expression for the dual of dissipation potential is derived using the concepts of dimensional analysis and self-similarity in a damage mechanics framework by choosing damage as an internal state variable. Damage in a concrete member subjected to fatigue is modeled through an evolution law, which is derived from this potential. The damage variable so obtained could be used as a damage indicator. Also, the remaining life of a member could be well predicted using the proposed law as demonstrated through a validation study using experimental results available from literature.

Keywords: Fatigue damage, Concrete, Thermodynamics, Dissipation potential, Damage mechanics.