<p>This paper presents a theoretical analysis for a circular concrete column reinforced with longitudinal FRP bars under axial-flexural loading. The results reveal that the balanced failure state of the column typically does not occur in the first quadrant of the interaction diagram (compressive-flexural behavior). This is because the rupture strain of common FRP bars is higher than the yield strain of conventional steel bars. To meet the balanced failure state, the axial load must reverse to tension while the eccentric distance shifts to the opposite side of the cross-section. Consequently, the balanced failure state shifts to the second quadrant of the interaction diagram, which represents tensile-flexural behavior. Due to the low compressive mechanical properties of FRP bars, an increased reinforcement ratio results in only a slight increase in the compressive capacity of the columns. The effect of FRP bars in tension becomes more distinct as eccentricity increases. The interaction diagram demonstrates that the tensile properties of FRP bars significantly contribute to the load capacity of columns, particularly as the eccentricity approaches the balanced failure state and extends through the tension zone to a pure axial tension load. The analysis also shows that the concrete strength primarily affects the capacity of the columns under compression failure, while the elastic modulus of the FRP bars has an effect especially when the axial load is small. Furthermore, reduction factors for the compressive and elastic modulus of the FRP bars have an insignificant effect on the column's interaction diagram. The proposed theoretical formulas at each column behavior state are viable for evaluating circular concrete columns reinforced with FRP bars under concentric and eccentric loading.</p>