Local–global buckling interaction procedures for the design of cold-formed columns: Effective width and direct method integrated approach

The present paper is aimed to show recent developments addressed to steel cold-formed column members affected by local–global buckling interaction. The formulations examined are not new but based on known solutions for thin-walled cold-formed columns: the effective width method (EWM), the direct strength method (DSM) and the effective area method (EAM). All of them were previously elaborated and calibrated by different authors. The main idea is to allow integrating effective width and direct methods in the design procedures, in order to make it easier to perform the computation of the resistance of steel cold-formed columns and to offer common prescriptions for both direct and effective width methods. Further a simple and easy way to access the column resistance on the basis of direct strength method avoiding the obligation to access computational programs to find the local buckling compressive load for usual cold-formed sections is proposed. For all of this the original formulations of EAM and EWM were recalibrated with the help of experimental results previously published and the resistance partial coefficients are checked.