Elastic buckling properties of thin-walled storage rack columns under compression, e.g., critical buckling loads, are often the input parameters for analytical design solutions (e.g., the direct strength method in AISI_S100 2016). This paper deals with the accurate estimation of the elastic buckling properties of Σ-shaped rack sections with patterned holes. The investigation of the elastic buckling behaviour of three different Σ-shaped rack sections (with and without patterned holes) under compression is presented. More than 4000 finite element simulations were performed on these rack sections using the finite element program, ANSYS 18.1. The influences of the holes, perforation pattern, number of buckling half-wavelengths, and boundary conditions on the section’ buckling behaviour were studied. An alternative method is proposed to generate signature curves for solid rack sections, and its effectiveness has been tested to generate signature curves for perforated rack sections. Multihalf-wavelengths method is proposed to determine the critical buckling loads and critical buckling half-wavelengths of perforated rack sections, which has been proved to be unbiased and accurate. The results show that by considering the holes, the critical buckling loads of the rack sections decreased while the critical buckling halfwavelengths increased. The alternative method failed to generate the signature curves of perforated rack sections accurately since the shape functions used for describing the shapes of buckling modes of perforated rack columns are significantly different from those used for solid rack sections.

Introduction

Rack columns are generally made of thin-walled steel sheets, and the steel sheets are cold-formed into the desired sections of the columns. The columns are used to form the upright frames of a storage system and serve as compression members. To simplify the assembly of the upright frames and make the intervals of shelf panels adjustable, holes are often made at webs or flanges of rack columns along the length uniformly. Most rack columns have open and singly symmetric cross-sections. It imposes difficulties on structural designers for designing such columns, especially for perforated rack columns. This is because multiple buckling modes need to be considered for rack columns in the design. The common buckling modes of Local (L), Distortional (D), Torsional + Flexural (TF), and Flexural (F) buckling are shown in Fig. 1, and their definitions are given in the AISI_S100 [1]. The flexural buckling mode around the strong principal axis of the rack section is not available since the flexural buckling modes around the strong principal axis are always accompanied by torsional buckling mode due to the singly symmetric cross-section. TF and F buckling usually jointly termed as Global (G) buckling.