Structural reliability of the design of pallet-rack columns via Direct Strength Method

Rack columns are among the various structural components that compose pallet-rack storage systems. These columns possess complex geometries and hole patterns, making strength prediction challenging. Most design codes for pallet-rack structures rely on experimental tests to support strength prediction for the columns, while semi-analytical methods, such as the Direct Strength Method (DSM), have become predominant in the design of cold-formed steel members in compression. This paper evaluates the safety of rack column designs using adaptations of the DSM. The reliability analysis was based on reliability indices calculated through first order reliability analysis and Monte Carlo simulation (MCS). Load combinations were selected from the ANSI MH16.1 (LRFD), AISI S100/NBCC (LSD), and NBR 15524–2 standards to assess whether the design using the selected adaptations meets the target reliability indices across a selected range of product-to-dead load ratios. The seven pure semi-analytical adaptations did not achieve the target reliability values. Only methodologies employing the Reduced Thickness Method met the target for certain limit state. These methodologies were still imprecise for the local-global buckling limit state, necessitating the calibration of new resistance factors for potential future adoption in standards such as ANSI MH16.1 and NBR 15524–2.