الفهرس 
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Abstract
The techniques of external confinement of existing reinforced concrete columns to improve their strength and ductility has attracted many researchers in the last few decades. Several methods have been proposed for the external confinement of columns such as the conventional methods of using external reinforced concrete jacket or grout-injected steel jacket. Recently the application of wrapping with Fiber Reinforced Polymers (FRP) as a new technique for external confinement of reinforced concrete columns has been widely used.
The overall objective of this study was to investigate the behavior of axially loaded short columns strengthened with carbon fiber-reinforced polymer (CFRP) wrap. The: specific goals were to address the factors affecting the confined strength for the CFRP jacketed columns, and to propose a design approach for computing the axial load capacity for the strengthened columns. In order to achieve these objectives, an experimental program consisting of testing fourteen specimens was carried out under quasi-static axial compression load. The columns specimen involved five circular columns, six square columns, and three rectangular columns with 1.5 aspects ratio. Variables considered were the amounts of CFRP (one ply, and two plies), column ’cross-section (circle, square, and rectangle), wrapping scheme of CFRP (continuous wrap, and strips), and the presence of reinforcing steel.
Based on experimental evidences, the use of <;:FRP improves both concrete strength and ductility but to different extents. Circular columns showed superior behavior when compared to rectangular and square columns. The use of one layer of CFRP may improve the column axial capacity by 106%, 55%, and 17% for circular, square and rectangular columns, respectively. This beneficial effect was tremendous with respect to concrete ductility that improved by up to 310%, 180%, and 123% in the same columns, respectively. This finding emphasizes the use of CFRP to improve the seismic resistance of building columns as well as its strength. In this thesis, the proposed analytical approach for computing the axiaLJoad carrying capacity of the strengthened columns is presented. An incremental iterative approach was proposed to find an actual value of the ultimate strain for the confined concrete; this iteration imitates the continuous interaction between the axial applied load and transverse strain of the confined column. The relationship between the dilation rate of confined concrete and the stiffness of the FRP material is also taken into consideration. This relationship is implicitly derived though the iterative process. The analytical ultimate load capacity for the confined R.e. columns showed very good agreement with the experimental results conducted on FRP jackets.