DSM-based design proposal for CFS columns failing in local-distortional interactive modes

This work proposes an efficient and rational approach, based on the Direct Strength Method (DSM), for the design of CFS columns failing in local-distortional (L-D) interactive modes. The development, calibration and validation of this design proposal, which is intended for codification in the near future, is based mostly on available experimental failure load data (i.e., keeping in line with the DSM “tradition”), but benefits also from significant numerical failure load data involving columns with several cross-section shapes (plain, web-stiffened and web-flange-stiffened lipped channels, hat, zed and rack-sections). Three types of L-D interactive failures are covered, namely those due to “true L-D interaction”, “secondary-distortional bifurcation L-D interaction” and “secondary-local bifurcation L-D interaction” – naturally, the current DSM local and distortional strength curves are also linked to the current proposal. The merits (accuracy and safety) and reliability of the proposed DSM-based design approach are assessed the latter following the procedure prescribed by the current North American Specification for the Design of Cold-Formed Steel Structural Members and are also compared with those exhibited by the existing methodologies to design CFS columns against L-D interactive failures.