Effect of Roll Forming Process Imperfections on the Buckling Capacity of Racked Beams

Abstract

Ensuring the stability and safety of steel storage racks is essential to withstand applied loads over time. Rack columns are typically produced through a cold roll-forming, enabling high productivity and open-section profiles, known as uprights. However, roll-forming imperfections can adversely affect buckling capacity. Stub column compression tests, as defined by the EN 15512 standard, experimentally determine the buckling capacity, while numerical methods further analyze it. A common way to introduce geometric imperfections in FEM models is by superposing scaled eigenmodes obtained from an elastic buckling analysis. Although standards specify imperfection types (local, distortional, global) and magnitudes, combining them remains unclear, often requiring multiple scenarios that may overly penalize capacity, as some imperfections rarely occur simultaneously.

This work determines imperfection values from predefined roll-forming imperfections and identifies which combination most significantly affects open-section column buckling capacity. The initial roll-forming imperfections were measured and each amplitude established. A FEM model incorporating these imperfections was developed and validated against experimental data. Finally, the effects of these errors and their most critical combination on buckling capacity were determined, contributing to improved design procedures and a more reliable assessment of structural performance.