Application of fiber-reinforced polymer (FRP) for retrofitting and rehabilitation of concrete structures is a common method. The main role of FRP confinement for reinforced concrete (RC) columns is to increase the ultimate strength and strain of confined concrete core and therefore improve in the load carrying capacity of the columns. However, it is possible that a previously short column fails due to buckling after the application of FRP confinement. In other words, the enhanced compressive strength of a retrofitted column may go beyond its buckling load. Therefore, a design criterion to predict this condition is necessary for the designers in the preliminary and final stages of the design. In this paper, a predictive model is proposed to determine the slenderness limit of FRP confined circular RC columns. The suggested relation was derived using one of the accurate design-oriented strength models for FRP confined concrete columns as well as analytically derived buckling equations. The effect of hybrid FRP confinement is also incorporated in the suggested slenderness limit. Moreover, a parametric study was performed on the suggested model to specify most influential parameters. The accuracy of the proposed relation was evaluated using a database of experimental results collected from previous studies. The results of the evaluations demonstrated acceptable accuracy of the proposed relation in predicting behavior and failure mode of FRP confined RC columns.

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