Severe earthquake ground motions can cause various levels of damage to reinforced concrete structures. Among others, damage index (DI) is a reliable means to quantitatively measure the extent of damage that can be endured by a structure in such circumstances. This paper outlines available concepts with a view to propose a new concept taking into account the displacement ductility of specimens loaded under low rotation angles or subjected to low fatigue test. The proposed DI has been successfully applied to predict damage levels in several case studies.