الفهرس 
ACKNOWLEDGMENT
TEST RESULT AND DISCUSSIONSOnly 14 pages are availabe for public view
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Abstract
eccentricity on the hybrid section of columns consist of steel tubes filled with concrete wrapped with fiber reinforced polymers (FRP). So the study is divided to three main sections.
Section I: Study of the behavior of concrete filled-steel tubes columns under concentric and eccentric loading.
This part specialized in studying the effect of eccentricity on the behavior of concrete-filled steel tube columns (CFST) with different tube thicknesses. So that fifteen 15 steel tubes filled with concrete were fabricated and tested. This fifteen columns were divided into three groups each group consist of five 5 columns with the same tube thickness and the same concrete grade. One of the five columns of each group was loaded concentrically, the second column was loaded with eccentricity 20mm, the third was loaded with eccentricity 50mm, the fourth column was loaded with eccentricity 80mm, and the last column was tested as beam. The results showed that the behavior of the column was affected significantly by the tube thickness and eccentricity.
Section П: Study of the behavior of concrete-filled CFRP Tubes.
This part specialized in studying the effect of eccentricity on the behavior of concrete wrapped CFRP tubes (CFFT). So that five columns of concrete wrapped CFRP tubes were fabricated and tested to failure. These five columns were listed as one group. This group of columns were casted without reinforcement steel bars then each specimen wrapped with four layers of CFRP, the first layer was horizontal, the second and the third layers were vertical, and the last one was horizontal. Each column of this group is loaded by different
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eccentricity as discribed in Section I. The first column of this group was tested concentrically, the second was subjected to load with eccentricity 20mm, the third was loaded with eccentricity 50mm, the fourth column was eccentrically loaded with 80mm, and the last specimen was tested as beam. These columns showed a brittle failure with low ductility but with high strength. The results of this group were compared with the concrete filled -steel tube columns and Concrete-filled steel tube wrapped with CFRP outer jackets.
Section Ш: Proposed New Hybrid Cross Section Consists of Concrete-Filled Steel Tubes Wrapped With CFRP Sheets.
This part is the main part of the research. The behavior of hybrid concrete filled steel tubes wrapped with CFRP (CFCFST) has been studied. Five columns were fabricated and tested to achieve the purpose of the research. Steel tubes with 2mm thickness were filled with concrete and wrapped with two layer of CFRP externally, one of these layers was applied in the longitudinal direction and the second layer was wrapped on the hoop direction. Carbon fiber reinforced polymers (CFRP) sheets were used to enhance the strength of the cross section. Interested advantages for the new hybrid section have been presented and an improvement in the structural performance of the concrete filled steel tubes were achieved. Finally, some important conclusions and recommendations were presented.