Design procedures for cold-formed columns


To outline the design procedures required for cold-formed (thin-walled) columns.


The procedures for the design of thin-walled sections in compression are outlined [1, 2, 3]. This involves the calculation of the effective section properties, determination of related slenderness values, and calculation of the design buckling load. For unsymmetric sections, the effective section centroid will not be in the same position as that of the gross section. Bending will also have to be considered.


In the design of compression members, two phenomena must be distinguished: global buckling which depends on the slenderness of the member and local buckling which may occur if the b/t ratios of elements of the section are relatively large. The latter occurs in cold-formed members at a loading level lower than the global buckling level. In such a case, an interaction of local and global buckling gives a reduced global buckling load compared to that of a compact section.

The interaction can be simulated by replacing the cross-section with an effective section, taking into account the stress redistribution at each element of the section (see Lecture Thin-walled members and sheeting). This method allows for the calculation of the load-bearing resistance of thin-walled members (Class IV - sections) in the same way as for compact sections. Axial loading may be assumed if the compressive force is acting at the centroid of the effective cross-section.

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