Confining concrete is one of the effective methods to strengthen reinforced concrete (RC) columns which enhances compressive strength and ductility of ocncrete. Moreover, it changes concrete stress-strain curve. Since stress–strain curve of concrete strengthened with FRP is different from that of normal concrete, interaction curves for axial force and bending moment (M-P) of normal concrete cannot be used as designing RC columns strengthened with FRP sheet. This research aimed to model correct behavior of concrete and FRP sheets in OPENSEES software to determine axial and bending capacity of RC columns confined with FRP sheet for rectangular sections. Verification of this works was investigated and confirmed by comparing it with experimental results. Currently, common method to design columns strengthened with FRP is based only on controlling compressive strength. This means that if wrapped FRP sheet together with concrete can provide desired compressive strength, design method is confirmed and this issue that stress- strain curve for normal concrete is different from that of confined concrete, is not considered. Thus, this research verified the design method by using modeling in OPENSEES software. Results demonstrated that the design method can be used prudently.