Buckling of multiple outside geometry (MOG) hollow sections

The loading of structures made of Circular Hollow Sections (CHS) are either limited by the design resistances of the joints or by the buckling resistances of the sections. For structures loaded by alternating loads, the fatigue design resistances of the joints have to be considered additionally. To increase the static and the fatigue resistance of joints, sections with higher chord slenderness d₀/t₀ or a higher wall-thickness ratio t_i/t₀ can be used. Since these sections are only required for increase the joint resistances but not for the resistances of the members, expensive weldments are necessary to connect sections with different dimensions. In this paper the buckling resistances of forged columns with a constant inner but varying outer diameter (MOG) in steel grades S355 and S690 with transitions at the middle as well as the accordant CHS columns are numerically determined. Appropriate initial imperfections of the columns are investigated beforehand.