Local and Distortional Buckling of Cold-Formed Rack Columns

This study analyzes the local buckling of the webs and the distortional buckling of the cross-section in cold-formed rack columns. The web has a rolling groove， and its effects include： the release of the Poisson effect； a larger developed width which weakens the transverse bending stiffness； and the groove acting as a one-sided stiffenerfor the web， whose bending stiffness requires specific consideration in calculation， as the stress on the groove is part of the plate stress. The total potential for buckling analysis was formulated considering these effects. The energy method was used to obtain the local buckling stress of the grooved web， enabling the determination of the local buckling capacity and the classification of the sections. Distortional buckling occurs usually for the flange of the rack column， the flange is rotationally restrained by the web， the newly derived buckling stress for the web， together with the developed width， are used to determine the rotational restraint， leading to more rational approach for distortional analysis of the rack column， examples reveals that the proposed method has smaller buckling stresses， 5.6%-10.9% smaller than neglecting the effect of the groove.