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This study aims to examine the behavior of reinforced concrete (RC) circular columns retrofitted with ultra‐high‐performance fiber‐reinforced concrete (UHPFRC) jackets and fiber‐reinforced polymer (FRP) wraps under concentric and eccentric loading. In the present study, for the first time, UHPFRC jackets containing synthetic macro fibers (barchip) were used. The results were then compared with those obtained by UHPFRC containing steel fibers. Moreover, to improve the effect of concrete jacketing on the column behavior under eccentric loading, the innovative interface treatment of the longitudinal grooving method (GM) was applied. For these purposes, 15 such circular columns, 120 mm in diameter and 500 mm in height, were subjected to load eccentricities of 0, 30, and 60 mm. Thus, six columns were retrofitted with UHPFRC jackets 15 mm in thickness that included both steel and synthetic macro fibers (barchip) while another six were strengthened with UHPFRC jackets and intermittent glass FRP (GFRP) warps. The experimental results revealed that load‐carrying capacity raised with the increase of the load eccentricity, as evidenced by enhancements of 283%, 303%, and 401% in the loading capacity of the specimens strengthened with UHPFRC jackets containing both GFRP warps and steel fibers for eccentricities of zero, 30, and 60 mm, respectively, relative to those of the control. In addition, enhancements of 198% and 530% were recorded respectively for ductility and energy dissipation under a loading eccentricity of zero mm in specimens retrofitted with UHPFRC jackets including steel fiber and GFRP warps when compared with the same parameters in the corresponding control specimens. Finally, a previous theoretical model was adopted to derive the axial loading‐bending moment (P–M) interaction diagrams whereby the results of the present study were satisfactorily verified.

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