A growing attention has been paid to the seismic vulnerability of steel pallet racks in the last decade, mainly due to the catastrophic effects recorded in recent earthquake events. For example, in May 2012 the Italian region of Emilia-Romagna was hit by a seismic swarm that also affected many industrial buildings, causing significant damage to the structures as well as to the storage systems of goods inside. The logistic sector is nowadays asking for safer and more performing storage systems, both for the safety and protection of workers but also to reduce business risk. However, most of the pallet racks still in use today (also in seismic areas) do not comply with the recent seismic regulations. In this context, it is necessary to assess their actual vulnerability, so as to be able to define seismic retrofit solutions as well.

In this paper, a parametric analysis, useful to manage the several structural parameters that characterize storage structures, was performed in order to assess their vulnerability. To do so, homogeneous stocks of pallet racks were generated by varying the total height, the inter-story height between load levels (and so the number of levels), the upright section’s properties and the lateral-load resisting system (braced and unbraced conditions). Then, the seismic vulnerability of these stocks of structures was evaluated through nonlinear time history analyses and a Cloud analysis approach. For this purpose, a specific code was developed in the OpenSees framework. The rack modelling included the main geometric and material non-linearities, both for elements and connections, as well as the pallet-to-beam friction. Fragility curves were finally derived as a function of the spectral acceleration (Sa) for various engineering demand parameters (EDPs), significant in representing the damage condition of these structures. Fragility results were presented, discussed and compared, in order to assess the impact of the main structural parameters in the vulnerability of these structures.