European design approaches for isolated cold-formed thin-walled beam-columns with mono-symmetric cross-section

In this paper attention is focused on the uprights, i.e. on the vertical elements of the steel storage pallet and drive-in racks. Their response is quite difficult to predict because of the significant influence of the interaction between local, distortional and overall buckling phenomena, owing to the presence of open mono-symmetric thin-walled cold-formed cross-sections. As a consequence, very high engineering competences are necessarily required to guarantee relevant load carrying capacities with structural systems of extremely limited weight and of very modest costs. Design provisions admit few alternatives, leading to different sizes and weight of the racks and, a consequence, to different degrees of economical competitiveness on the market. In the framework of a more general research project on steel storage rack structures, three options to design in Europe uprights (beam-column members) have been investigated in the present paper. Several cases from practice have been selected, which comprise of uprights differing for cross-section geometry, slenderness and load conditions. A suitable finite element program for academic use characterized by a refined beam formulation capable of capturing key features of uprights has been used to model the elastic buckling interaction between the axial load and the bending moment. Non negligible differences have been observed related to the admitted approaches in terms of beam-column load carrying capacity and the direct comparison of the research outcomes offers practical indications for an optimal use of the material in accordance with the required safety standards.