In this work different steel elements have been modeled and analyzed, both under monotonic and cyclic conditions: a cantilever column, several beam-to-column connections and finally a plane frame. The aim has been put on the different results that can derive from include, or neglect, deterioration in modeling. Degradation effect, typical of semi-compact and slender steel section, has been considered both in strength and stiffness. A sophisticated model, characterized by general validity, has been implemented in order to be used with all steel cross-section, including semi-compact and slender.