Repairing or strengthening of structural members is required in many cases to prevent damages caused by seismic loading. The application of fiber reinforced polymer (FRP) composites has been successfully promoted for external strengthening of reinforced concrete (RC) members such as RC columns. These jackets are commonly formed in a wet layup process for confinement of columns. It has been well established in recent studies that rupture strains of FRP measured in tests on such FRP-confined RC columns fall substantially below those from flat coupon tensile tests. Furthermore, this problem is more important in rectilinear columns because of premature rupture of FRP at corners due to stress concentration at these parts. Up to now, numerous studies have been conducted on FRP confined rectangular columns to improve the efficiency of composite in confinement, such as using FRP strips at corners. In this study, a new method was investigated as using CFRP strips at corners and CFRP battens at sides. In the method, FRP composites does not experiment any curvature in confining section and the behavior of FRP is very close to flat coupons in tensile tests. For this purpose, forty-two RC columns with 133x133 mm cross section for square columns and 110x160 mm cross section for rectangular columns were tested experimentally under concentric and eccentric (30, 60, 90 and 120 mm eccentricity) loading. All of column specimens were 500 mm high. The experimental results clearly demonstrate that the new method of corner strip-batten make more uniform confinement pressure distribution on section and eliminates the stress concentration at corners; so improves the performance of FRP in confinement significantly. In this case, the compressive strength and ductility of column specimens were respectively increase 11.1% and 42.8% compared to the column confined using intermittent wrap. Based on results obtained from the current study, the effectiveness of FRP confinement is reduced under axial-flexural loading. In this case, the compressive strength of column specimens under zero, 60, 90 and 120 mm eccentricity of loading, were respectively increase 42.4%, 40.4%, 31.6% and 21.8% compared to the unconfined columns. Key Words: CFRP composite, Rectilinear RC column, Confinement, Corner strip, FRP batten, Eccentric loading.
