Construction sustainability through reusability: Establishing reuse design rules for CFS channel columns subjected to local buckling

This study investigates the reusability of cold-formed steel (CFS) stub columns subjected to local buckling. The reusability is determined by repeatedly loading each column specimen eight times, including the first use, as well as final loading after accelerated corrosion equivalent to 10 years. The CFS channel columns tested are largely locally slender with varying slenderness, thicknesses, and embossments, but with the same length and fixed ends. A total of 231 tests are carried out on 24 CFS channel columns, including 192 reuse tests and 39 post-corrosion tests. The structural response, in terms of stiffness and strength, of the column during each reuse testing is assessed in detail in order to determine the reuse resistance factor (ϕ_R) to predict the reusable strength (P_n-R) for each reuse. This research establishes future reuse limits for such structural members in terms of applied load levels and number of reuses. Based on the results, the following design rules are suggested for the reuse of CFS short columns subjected to local buckling: (i) CFS sections with 0.5 mm thickness or lower, corresponding to normalised slenderness (λ_l) larger than 6.27 should not be reused; (ii) 1 mm and thicker CFS sections with normalized slenderness (λ_l) within a range of 2.16-3.21 can be reused up to two times in addition to the original use; (iii) a new relationship is proposed for determining the safe reuse resistance factor (ϕ_R) for each reuse; (iv) the reusable strength (P_n-R) can be predicted using the original material characteristics for application in practice.