The stock of existing buildings across most of the European earthquake-prone countries has been built before the enforcement of modern seismic design codes. In order to assure uniform levels of safety and reduce the social and economic impact of medium to high earthquakes costly seismic intervention plans have been proposed. But their application, in order to define which building should primarily be retrofitted, requires adequate vulnerability assessment methodologies, able to model the effective non-linear response and to identify the relevant failure modes of the structure. In the case of reinforced concrete (RC) buildings, due to the lack of application of capacity design principles and the aging effects due to exposition to an aggressive environment, existing structures can exhibit premature failures with a reduction of available strength and ductility. In the last couple of decades some state-of-the-art simplified models aiming at capturing the complex interaction between shear and flexural damage mechanisms as well as behavior of rebar corrosion have been proposed in specialized literature and, in some cases, implemented in regulatory building codes and guidelines. The present paper presents how those phenomena that have a significant impact in reducing the element capacity in term of strength and energy dissipation can be implemented in the assessment of the structures.