Executive Summary : | Cold-formed steel (CFs) members under compression often encounter stability issues related to local, distortional, global, or interactive buckling modes. The ability of CFs members to exhibit stable post-buckling behaviour is considered an important advantage. The methods for CFs members namely, the effective width method (EWM) and direct strength method (DsM), provide procedures for the design of compression members affected by independent buckling modes (local, distortional, and global) and their interaction [local-global (LG), local-distortional (LD), distortional-global (DG), and local-distortional-global (LDG)]. However, many researchers reported the limitations of the DsM strength curve and improvements were suggested [schafer (2002), Kumar and Kalyanaraman (2012, 2014 & 2018), Young et al., (2012), Gunalan and Mahendran (2013), Landesmann et al., (2016), Cava et al., (2016), Hancock (2018), He et al., (2020)]. One of the major limitations of DsM and its modification is that both local and distortional buckling strength equations were developed based on test or finite element analysis (FEA) results for compression members with fixed-end boundary conditions. Accounting for other boundary conditions, such as pinned or partially fixed through effective length factor for the elastic global buckling strength (PcrG) may not sufficient for CFs members having singly symmetric cross-sections due to the shift of effective centroid due to non-uniform distribution of longitudinal stress caused by local/distortional buckling. The adverse effects on column strength due to the shift of centroid under local buckling and distortional buckling in pinned-ended columns are not addressed by the present DsM. No DsM-based design method is available at present for members undergoing a shift of effective centroid. This project aims at the development of DsM-based design strength curves for the strength of CFs columns affected by independent buckling modes and their interaction. |