الفهرس 
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Abstract
Wrapping of concrete columns externally with carbon fiber-reinforced polymer (CFRP) sheets is considered as an efficient strengthening technique. The efficiency of FRP-confined strengthening system depends mainly on different encountered
parameters such as the FRP confinement ratio, shape and size of cross-section, and cross sectional aspect ratio of non-circular columns. The FRP confining system of rectangular cross section column is less effective than on a circular column and its effectiveness depends on the ratio between the sides of the cross-section. In case of FRP-confined rectangular columns, the cross-sectional aspect ratio affects significantly the efficiency of this strengthening technique, whereas the effectively confined area of FRP-confined rectangular columns is a function of the dimensions of the rectangular columns and the radius of the corners. Therefore, in the
updated version of the ACI 440.2R-08, the limitation of the aspect ratio of FRP
confined rectangular columns is extended from 1.5 to 2.0 as a limit to apply this strengthening technique, and the effect of the cross-sectional aspect ratio (h/b) was added as a shape factor for noncircular cross section columns confined by FRP Fundamental to the study of FRP-confined rectangular columns is the issue of effectiveness of FRP confinement, which may significantly decrease due to the presence of 90° corners or abrupt change of direction around the perimeter FRP tends to rupture at sharp corners square and rectangular due to the cutting effect of the concrete corner. In general, the effectiveness of confinement increases with the corner radius increases. Therefore, in the strengthening of non-circular columns, the sharp corners of the columns should be rounded to reduce the detrimental effect of the sharp corners on the tensile strength of the FRP, and to enhance the effectiveness of confinement. On other words, the cross section of rectangular shape columns (Shape modification) should be modified before applying FRP-confined strengthening
system.