الفهرس 
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Abstract
In this thesis, the behavior of composite cold formed built up columns under the cyclic loads is discussed. The behavior study is divided into three parts. The first part is a study of the behavior of composite cold-formed built up columns under lateral cyclic loads. The second part is based on behavior studying of it under torsional cyclic loads. The third part works on a conclusion of a mathematical equation in which the factors that are influential in improving cohesion between steel and concrete in composite columns. This study was carried out in two stages, the first stage is the experimental program and the second stage is numerical analysis. In this study, twelve composite cold-formed built up columns were used. The columns were divided into two main groups according to the height of columns. The first group consists of six composite cold-formed built up columns, and these columns are studied under lateral cyclic loads. The second group consists of other six columns, and these columns are studied under torsional cyclic loads. Columns used in this study are two lipped sigma channels. The dimensions of one lipped sigma channel are 250 * 80 * 25 * 4 mm. The dimension of the column cross section is 250 * 160 mm. The height of the columns is 1200 and 1600 mm. The study was carried out on some variables, which consist of the column height and the stiffener (lipped) length, which are divided into fully stiffened, 100 mm length, and 200 mm length. The numerical analysis was carried out through the ABAQUS program. The experimental results were compared with the results of the numerical analysis, and the results were acceptable. The results were studied and analyzed. On the other hand, the third part works on a conclusion of a mathematical equation in which the factors that are influential in improving cohesion between steel and concrete in composite columns.