Influence of floor deflections on the performance of steel storage pallet racks

One of the most important applications of thin-walled cold-formed elements is for the fabrication of selective steel storage pallet racks used to store goods. From the structural point of view, these systems are generally unbraced in the longitudinal direction and braced in the transversal direction. Recently, pallet rack provisions have been significantly improved, especially for what concerns design assisted by testing; however, further key aspects of relevance for structural design need urgent attention. Among them, it is worth mentioning the interaction between the racks and the supporting surfaces (i.e. foundations or floor slabs), which is expected to have a non-negligible influence in routine design, owing to the high degree of redundancy of the rack skeleton frames.This paper summarizes a study on the influence of floor displacements on the performance of medium-rise steel storage pallet racks. In order to propose a wide range of data of practical interest for routine design, the effective load-carrying capacity has been evaluated by varying the position of the rack on the floor slab, the rack geometry, the ratio between the floor span and the rack length and the degree of rotational stiffness of both beam-to-column joints and base-plate connections. Moreover, a suitable equation, which is independent of the adopted design approach, is proposed to estimate the reduction of the performance with respect to the ideal case of racks supported by a rigid floor slab. Validation of the equation is carried out using design cases that are significantly different from those used for its calibration. Finally, Appendix A proposes complete design examples detailing the main calculations necessary to predict the reduction of the load carrying capacity associated with the floor slab deflection.