Abstarct: The current building codes such as Iranian seismic code (STANDARD NO. 2800) permit linear elastic analysis to predict the structural response and estimate seismic demands, since the actual response of most structures under the design earthquake loading results in inelastic behavior, linear elastic procedures are cleary inaccurate and inadequate.In recent technical notes that use performance–baxsed design philosophy, such as FEMA356 and SEISMIC REHABILITATION CODE, nonlinear analysis procedures has gained importance to the extend that use of linear analysis is now very limited and designers have to use non–linear procedures. Since the IRANIAN SEISMIC CODE (STANDARD NO 2800) and SEISMIC REHABILITATION CODE are different in loading, analysis method and acceptance criteria, therefore seismic evaluation of buildings that design with standard no–2800 with SEISMIC REHABILITATION CODE can be useful. Therefore for this purpose six buildings with dual system (intermediate moment frxame + concentric braced frxame) with 5, 10 and 15 stories have been chosen and designed with IRANIAN SEISMIC CODE and then evaluated by using of static nonlinear procedure (pushover) according to SEISMIC REHABILITATION CODE and degree of weakness for each type of elements have been discussed.