Seismic Vulnerability of Pallet Storage Systems

In the last decade, increasing attention has been paid to the seismic vulnerability of steel pallet racks, mainly due to the catastrophic effects recorded in recent earthquakes and the increased use of these systems in the production and e-commerce sectors. For example, in May 2012 the Italian region of Emilia-Romagna was hit by a seismic swarm that affected many industrial buildings, causing significant damage to the structures as well as to the storage systems inside. In this paper, a parametric analysis to assess the vulnerability of these systems is presented. First, a small stock of 6-levels 7-spans pallet racks is generated by varying the upright section’s properties and considering the unbraced and braced configurations. Then, the seismic vulnerability of this stock of structure is evaluated through nonlinear time history analyses and a Cloud-like approach. For this purpose, a specific code was developed in the OpenSees framework. The rack modelling includes the main geometric and material non-linearities, both for elements and connections, as well as the pallet-to-beam friction. Fragility curves are derived as a function of the spectral acceleration (Sa) for two engineering demand parameters, significant in representing the damage condition of these structures. Finally, fragility results are presented, discussed, and compared, in order to provide useful information on the vulnerability of these structural systems.