Modelling damping in a reinforced concrete structure under seismic loading is a challenging problem: damping is often introduced at the global level (for instance with the famous Rayleigh's method), which do not necessarily provides accurate results. Another ap- proach consists in introducing damping at different scales by modelling the main dissipative phenomena which occur in the structure. The behavior of concrete under cyclic loading plays an important role in the dissipation of the seismic energy imparted to a structure. Therefore we present in this paper the theoretical formulation of a constitutive model for R/C elements under cyclic loading, coupling plasticity and damage.