Global Buckling Behaviour of Intermittently Fastened Cold-Formed Steel Built-Up Columns

In the load-bearing wall frame system, built-up sections are utilized over single sections to enhance the performance of cold-formed steel (CFS) structural systems. Built-up CFS sections can be formed in different shapes by the use of intermittently connected fasteners in the longitudinal direction. The spacings of these intermittent fasteners can alter the global buckling behavior of built-up CFS columns, and hence, they are investigated in the present study. The change of global buckling load from a single section CFS column to a built-up section CFS column is studied with different fastener spacing. In this paper, a numerical methodology using a compound spline finite strip method is developed to compute the elastic critical buckling load of CFS built-up columns. The results of buckling analysis are compared with FE based software ABAQUS and results are found to be in good agreement. Parametric studies on back-to-back connected I section with different web to flange ratios have been carried out, and it is found that global buckling behavior of open built-up sections will move towards fully composite section buckling behavior with the reduction in the fastener spacing