Beam design for steel storage racks

Thin-walled cold-formed steel members are used worldwide in industrial systems for the storage of goods and materials, such as drive-in, drive-through and selective pallet racks. A relevant difference with respect to the more traditional civil and industrial steel structures consists in the extensive use of thin-walled cold-formed members having non-bisymmetric cross-sections. This choice allows for the best possible structural performance while minimizing weight, and hence, achieving a very low cost of the skeleton frames. The design is influenced by the typical problems associated with the use of slender cross-section members and by the warping effects. Therefore, design of these industrial structures appears quite complex, because in engineering offices the most commonly used finite element (FE) software analysis packages offer beam formulations that are only capable of modeling the behavior of members having two axes of symmetry. The paper deals with the design of beams used in industrial storage systems. Refined parametric analyses have been carried out by means of an open source FE software package able to simulate the behavior of non-symmetric cross-section members. With reference to lipped channel and zed beams, the contribution of warping effects has been investigated with regard to not only the in-service displacements and rotations, but also focusing on its influence in the distribution of stresses at the ultimate limit state. Furthermore, in order to investigate the differences associated with the use of 6DOF and 7DOF FE beam formulations, Appendix A proposes two design examples, which are also reproduced in Appendix B by hand calculations.