الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Composite columns systems have become popular especially in tall building constructions. It is combining the rigidity of reinforced concrete with the ductility of structural steel sections. Composite columns may be concrete encased steel columns or concrete-filled steel tube columns. In this report, the codes design methods of slender concrete encased steel composite columns are presented and compared with various available experiments and numerical analysis methods. Also, investigation of the behavior of frames with concrete encased composite columns using finite element method is conducted. The nonlinearities due to materials and geometry are considered for determining the second order moment for 2-D frame multistory buildings.The main objectives of this study are to understand the behavior of slender concrete encased steel composite columns; to evaluate the ultimate load of concrete encased steel composite columns under concentric and eccentric loading; to conduct a comparison study of the second order moment values obtained using various codes methods with these obtained from the finite element program SeimoStruct for frames with composite columns and to define the factors affecting the second order moment. The major variables that influence frames with slender composite columns are investigated in this study. It is shown that the increase of number of stories and axial load of composite columns lead to the increase the ratio of the second order moment to the first order moment. The increase of steel sections, steel beams sections and overall cross sections dimensions lead to the decrease the ratio of the second order moment to the first order moment. Also the change of different of pattern of lateral loads is studied. This proves that it has a slight effect of the ratio of the second order moment to the first order moment.By comparing second order moment obtained from SeismoStruct program results to those obtained from various codes, it is shown that the1994 results are generally very close to those obtained by the second order analysis, then followed by the American Institute of Steel Construction2010(&)code and then followed by the Egyptian code of practice for Steel Construction (Load and Resistance Factor design- 2007code . The Egyptian code of practice for design of concrete Construction, (ECP203-2007 gives the highest second order moment in all cases .The (ECP203-2007code predictions are the most conservative and may not be suitable for this kind of columns.