Design of Cold-Formed Steel Built-Up I Section Columns subjected to Interactive Buckling

Abstract

An experimental investigation into the behaviour of cold-formed steel (CFS) built-up I column assembly compressed between fixed ends is presented. To study the interactive buckling mode of failures, the built-up column assembly is designed to be doubly symmetric and locally slender. A total of forty-one columns were tested including different cross- section dimensions, lengths, intermediate connection spacing, and slendernesses. It is experimentally shown that the local buckling deformations caused the built-up cross-section assembly columns to fail predominantly in interactive local and flexural-torsional buckling. The influence of intermediate fastener spacing was also prevalent in the failure modes. The appropriateness of the AISI’s maximum intermediate connection spacing limitation is verified to prevent global instability failures. The test and design results comparison indicated that the current AISI’s DSM design curve for interactive buckling is unconservative for the CFS built-up columns with predominant interactive local-global failure mode vulnerability. Therefore, a modified design curve for interactive local-global buckling is proposed