الفهرس 
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Abstract
In recent years, the use of externally bonded Fiber Reinforced Polymers (FRP) has become increasingly popular for civil infrastructure applications around the world. Significant research has been devoted to circular columns subjected to axial loads and retrofitted with FRP. Numerous models have been proposed by various codes and researchers all over the world throughout the past 20 years. In contrast, very limited data has been reported on the influence of concrete compressive strength on the confinement effect. Lack of clear design guidelines illustrating the influence of the concrete compressive strength on confined concrete sections subjected to combined flexural and axial loads necessitates further research. A total of fourteen FRP-wrapped reinforced concrete circular columns were tested up to failure under static loading conditions. The tested columns were compared to traditional reinforced concrete columns. The main variables in the study included concrete compressive strength, eccentricity of the applied load and confinement level. The proposed research highlights the influence of the concrete compressive strength on the behavior of circular FRP-retrofitted concrete columns subjected to combined bending and axial loads. The effectiveness/feasibility of strengthening low-grade concrete columns with carbon FRP sheets are examined both experimentally and analytically using the current available hypotheses and design guidelines. Tests results illustrated the beneficial effect of the low strength concrete in enhancing the axial load carrying capacity of retrofitted columns.