Performance of mono-symmetric upright pallet racks under slab deflections

Goods and products are often stored in framed systems, such as pallet racks, which are used for industrial and commercial activities. Recently, pallet rack provisions have been significantly improved but there are still relevant aspects that need urgent attention for guaranteeing safe structural design. Among them, the interaction between the rack and the supporting surface (i.e. concrete foundation or floor slab) plays a non-negligible influence in routine design, owing to the high degree of redundancy of the skeleton frames. In addition, rack design is usually carried out using analysis packages unable to capture the behaviour of mono-symmetric cross-section members and hence all the warping effects are generally ignored. This paper summarizes a study on the influence of floor displacements on the performance of medium-rise steel storage pallet racks. In order to obtain a reasonably wide range of data of practical interest for routine design, numerical analyses have been carried out by varying several key parameters such as the position of the rack on the floor slab, the rack geometry, the floor span length and the degree of rotational stiffness of both beam-to-column and base-plate connections. Moreover, attention has been focused on the influence of the accuracy of the structural model used in the design and two commercial analysis packages, differing for the degree of refinement of the implemented finite element beam formulation, have been considered. Finally, a suitable equation is presented to estimate the reduction of performance with respect to the ideal case of racks supported by rigid floor slab.