Fiber reinforced polymer confined concrete exhibits different stress-strain behavior under different confinement levels. Therefore, classification of confinement levels is often the first step of jacketing design. Currently, the classification criteria are empirical and strength-based. In this paper, a plasticity-based criterion for classification of confinement levels is developed in the framework of Drucker-Prager plasticity. The theoretically derived criterion is simple and can be conveniently used for engineering design. In addition, explicit relationships for calculating the strength and ductility ratios of FRP confined concrete columns are developed as functions of the confinement stiffness ratio and FRP rupture strain. These relationships can be conveniently used in the performance-based design of FRP jackets for concrete columns.
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