There are many reinforced concrete buildings that need to be strengthened. The philosophy of rehabilitation existing buildings is an attempt to strengthen the safety of these buildings against earthquakes by strengthening the structure. Various methods have been proposed to seismic retrofit concrete structures but in some cases due to the lack of economics, performance problems and functional defects of these designs, it is not practically possible to use them. In this study, two methods of seismic retrofit the construction of reinforced concrete structures are as follows: 1. Adding reinforced concrete shear walls; 2. Using CFRP sheets. first try to compare the technical between the two methods and the advantages of each will be mentioned. In the next stage, the economic analysis and cost comparison of both methods are expressed and finally, using the cost-benefit analysis, the most appropriate method for seismic retrofit will be selected. The models studied in this study are 3 frame reinforced concrete 5,8 and 15 stories. These frames are once designed only for the effects of gravity loads and a percentage of seismic loads (proportional to acceleration 0.1g) and are again designed and evaluated by gravity and lateral forces. Finally, due to the results of this study, it can be said that for short RC buildings, use of CFRP sheets is more suitable and for high-rise RC building, the use of shear walls is desirable to seismic retrofit. Keywords Retrofit, fragility curve, life cost assesment, cost-benefit analysis, CFRP sheets, Concrete Shear Wall.
