الفهرس 
Effective width method (EWM)Only 14 pages are availabe for public view
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Abstract
Cold formed steel members are slender thin-walled sections highly susceptible to instability phenomena involving local, distortion, and global (flexure or flexure torsion) buckling. The current specifications design the cold formed steel columns for their local-global interactive failure modes. However, angle columns buckle in major axis torsion and flexure torsion interaction for short and intermediate columns, as well as minor axis flexure for long columns. Thus, the results are inaccurate.
Therefore, this research investigates the behavior and load carrying capacity of cold formed steel angle columns subjected to axial compression. The studied angle columns were equal and unequal sections plain and lipped with pinned and fixed boundary conditions. The implemented parametric study covers a wide range of overall slenderness λc, width to thickness a/t, and width to lip depth a/d ratios.
Numerical models were performed using ABAQUS in two stages: linear and non-linear analysis. The linear analysis is to obtain the buckling modes that are leveled to be used as geometric imperfection in the non-linear analysis, which is used to obtain the load carrying capacity. Geometric imperfection, for short and intermediate columns, were applied by 30% of section wall thickness exhibiting torsion and flexure-torsion buckling. On the other hand, the geometric imperfection of long columns, applied by L/1000, exhibits flexure. These levels were shown to be in good agreement with the actual geometric imperfection resulted from experimental tests. The performed models were compared to experimental ultimate load results collected from the literature. Results correlate well especially to imperfection factor 30% of wall thickness. Finally, numerical results were compared with the results calculated using EWM and DSM.
This study indicates that:
- Cold formed steel angle columns buckling modes depends on length. Since short to intermediate columns buckle in torsion to flexure torsion and the flexure value increases with the length. Long columns buckle in minor flexure.
- Plain and lipped angles have different signature curve profiles, which depends on thickness.
- EWM and DSM ultimate strength prediction is either safe or unsafe with range of 10 to 40%.