Reliability of Rack Columns Designed by the Direct Strength Method

Cold-formed rack profiles are produced mainly for use in industrial storage systems. Their complex geometry and the presence of hole patterns along their length make the strength prevision of these structural elements difficult. This article evaluates the safety presented in the design of rack columns by adaptations of the Direct Strength Method (DSM), the original formulation of which does not address perforations. The safety parameters used here are the reliability indexes, calculated by the First Order Second Moment (FOSM) method, used in the calibration of the AISI S100 current standard, the First Order Reliability Method (FORM) and Monte Carlo Simulation. Only methodologies that applied the reduced thickness method in cross-section modelling produce results close to the target reliability indexes suggested for cold-formed columns. The target indexes are met for all load combinations when only distortional buckling failure is considered. However, the DSM adaptations are still imprecise when considering failure with local buckling. New professional factors were calibrated for these cases, as the design using the current $\phi {\rm }={\rm 0} .85$phi=0.85 does not meet the safety requirements.

Automated summary

This study evaluates the safety of rack column design using adaptations of the Direct Strength Method, indicating that only the reduced thickness method in cross-section modeling can meet the safety requirements for cold-formed columns.