Abstarct: Over the years, failures in buildings and bridges occurred due to earthquakes, demonstrated the essential need for strengthening structures. Fibre Reinforced Polymer (FRP) composites have received increasing attention as an appropriate material for strengthening RC frxames. This is due to their high strength, light weight (high strength-to-weight ratio), and corrosion resistance. Confining RC structural members with FRP results in the enhancement of axial load-carrying capacity and ductility. In fact, the behaviour of concrete confined with FRP is improved. Mechanical properties such as compressive strength and ultimate strain of concrete are dramatically increased. The objective of this study was to evaluate the opportunities provided by using modern strengthening schemes for seismic retrofit of existing RC frxames. In this thesis, the effects of FRP rehabilitation on the seismic performance of reinforced concrete frxames were investigated. Non-linear analysis of frxames strengthened with FRP was conducted in SAP2000 and ABAQUS softwares. Pushover analysis on three reinforced concrete frxames with 4, 8 and 12 stories (representing short, medium and high-rise buildings) was accomplished before and after retrofitting. These analyses were performed in SAP2000 software and using the results seismic performance and response modification factor of commonly reinforced concrete moment frxame structures were studied. In addition, for a more accurate understanding, a single story one-bay concrete frxame was modelled and analyzed in ABAQUS software, and the effects of FRP systems, added to structural components, on the seismic performance of the frxame were studied. The results of the analysis indicated that the use of FRP systems considerably improves the seismic performance of concrete frxames.