Various retrofit techniques for reinforced concrete frame with infill wall have been steadily developed. Among those techniques, strengthening methodology based on diagonal FRP strips (FRP bracings) has numerous advantages such as feasibility of implementing without interrupting the building under operation, reduction of cost and time, and easy application. Considering the safety of structure and retrofit cost, the most appropriate retrofit solution is needed. Thus, the objective of this study is to suggest pareto-optimal solution for existing building using FRP bracings. To find pareto-optimal solution analysis, NSGA-II is applied. Moreover, the seismic performance of retrofit building is evaluated. The example building is 5-storey, 3-bay RC frames with infill wall. Nonlinear static pushover analyses are performed with FEMA 356. The criterion of performance evaluation is inter-story drift ratio at the performance level IO, LS, CP. Optimal retrofit solutions is obtained for 32 individuals and 200 generations. Through the proposed optimal solutions

reinforced concrete (RC) buildings with infill wall designed based on pre-1970s codes are vulnerable to earthquake ground motion since seismic design code was not established in that time. To resolve this problem, various seismic retrofit methods for pre-1970s RC structures with infill wall have been studied. However, conventional retrofit methods such as adding shear wall are difficult to apply and increase the weight of the structure. As a compression strut, infill wall resists lateral force such as earthquake load. If an irregular seismic wave occurs continuously, infill wall will be separated from RC frame in the corner region and involves the failure. Therefore, fiber-reinforced polymer (FRP) was proposed as a new retrofit method [1], [2]. It is a remarkable composite material having a high tensile strength and efficiency. Furthermore, it is possible to apply to the occupied