Unbraced pallet rack design in accordance with European practice–Part 1: Selection of the method of analysis

Abstract

Industrial steel storage pallet racks are quite similar to the framed steelworks traditionally used for civil and commercial buildings: great differences are due to both the presence of boltless beam-to-column connections and to the very extensive use of thin-walled cold-formed members. Serviceability response as well as ultimate limit conditions are quite complex to predict; high engineering competences are required to guarantee significant load carrying capacities with structural systems of extremely limited weight, and, as a consequence, of very modest costs to be competitive on the market. Design standards have been recently updated worldwide; with reference to the European practice, different alternatives are now offered to designers: from the selection of the method of analysis to the approaches for the serviceability, resistance and buckling checks of the whole racks as well as of its main components. The design paths admitted by the Codes correspond to different values of the structural performances guaranteed by racks, or equivalently, to significantly different costs.A two-parts paper has been written to summarize the first research outcomes of a study on the static design rules currently adopted in Europe for steel storage pallet racks. In particular, a parametric numerical analysis has been developed on medium-rise racks of different configurations, member geometries and rotational stiffness of both beam-to-column and base-plate connections. A wide range of cases of practical interest, comprising of mono- and bi-symmetric cross-sections used for uprights, has been analyzed by means of an open source finite element program for academic use, improved by authors with a suitable beam formulation accounting for main warping effects. The present part 1 deals with the selection of the method of analysis, i.e. 1st or 2nd order elastic analysis, depending on the rack deformability to horizontal loads. Internal forces and moments on members are significantly influenced by the effects of lateral displacements as well as by the type of the beam formulation adopted in the finite element analysis program. In the following, different design alternatives are discussed: the use of the overall buckling analysis, a classical approximate method and few theoretical approaches. The rules for the resistance and stability checks of beam-column members under static loading are discussed in part 2 (“Essential Verification Checks”) of this two-parts paper, together with a critical analysis of the influence of warping effects on the serviceability limit state for lateral deflection of the whole racks.