Impact of protective coatings on fire resistance and axial capacity of galvanised CFS columns

The literature on the structural performance of cold-formed steel (CFS) columns under fire conditions is limited. This study delivers critical insights into the buckling behaviour of back-to-back connected CFS columns with three different fire-resistant coatings. These columns underwent various heating and cooling procedures. Outcomes of this research offer significant implications for building codes and standards, particularly in understanding the effects of thermal exposure and cooling methods on CFS structural elements. In all specimens, the failure pattern observed was consistent, characterised primarily by significant buckling. Notably, sections coated with perlite demonstrated superior performance in fire resistance compared with other sections that were coated and heated. Among the coated specimens heated to 60 min and cooled using air, BC2AC (perlite) has the highest ultimate load at 268.93 kN, which is just 1.7% lower than the unheated section and 7.2% higher than BC1AC (gypsum) and 12.6% higher than BC3AC (vermiculite). This study contributes essential observations into the axial resistance of columns with various coatings under varying temperature and cooling conditions, potentially informing updates to standard guidelines regarding the impact of heating and cooling.