الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Cold formed channel sections (CFS) are widely used as purlins. Purlins are secondary membersthat connect the main structural frame with the outer cladding material, such as corrugated roof or wall sheeting. Choosing the optimum sections’ proportions of any cold formed section in order to acquire the most economical section is hardfor a designer. For that reason many researchers applied different optimizationtechniques in order to acquire the most suitable section dimensions. In this thesis optimization of CFS C-lipped channelbeamwas done using three optimization methods which are;Particle Swarm Optimization (PSO), Genetic Algorithm (GA) and Sequential Quadratic Programming (SQP). The optimization will be carried out with respect to their flexural strength calculated withthe Effective Width methodaccording to the Egyptian Code of Practice (ECP)and calculated according to the ultimate strength of the section by using theDirect Strength Method approach (DSM). To describe DSM in the optimization problem a new technique has been applied by obtainingfunctions that estimate the capacity of the beam in each failure mode. The same technique will be also applied for ECP. These functions were obtained byusing nonlinear regression formore than 6200moment capacitiesfor all failure modes and for both design methods. These functions will be considered as the objective function in the optimization process.In ECPthe distortional buckling strength of cold formed section is not considered.As a result in this research the new proposed method based on effective width provision introduced by Cheng Yu according to the American Iron and Steel Institute(AISI), will be applied to ECPto estimate the capacity of the section in the distortional buckling mode.Itwas found that it gave reasonable results when applied to ECP.During optimization process; the constraints used were the ratios between the elements to one another and they are not given by neither of the Egyptian code nor the American specifications. As a result they were studied in threegroups with different ratios helping to find the most optimum once.The sections obtained from optimization of the beam in the local and the distortional mode will be checked against lateral torsional buckling. AFinite Element analysis for the optimum sections obtained using ECP were modeled using linear buckling analysis to investigate the first mode of failure for those studied sections and to compare it to the results obtained using ECP.