Experimental Investigation on the Seismic Behavior of Palletized Merchandise in Steel Storage Racks

The seismic hazard associated with failure of storage racks in retail facilities open to public depends on the behavior of the rack frames and the response of stored merchandise. In this study, the seismic behavior of palletized merchandise stored on shelves of pallet-type steel storage racks is investigated and the concept of incorporating slightly inclined shelving is proposed as a measure for mitigating merchandise shedding. Pull tests and shake table tests are conducted. The main objective of the pull tests is to investigate the frictional behavior at the interface between loaded pallets and rack shelves. The major objective of the shake table tests is to characterize the dynamic response of the palletized merchandise under earthquake excitation imposed at the base of rack structures, and determine experimentally the pallet shedding fragility under an ensemble of ground excitations representative of the seismicity of the Western United States. The combination of wooden pallets and shelves with wire decking of waterfall type, typical of many rack installations, is considered. The results of the pull tests indicate that the frictional coefficient at the pallet-to-shelf interface varies between 0.37 and 0.45 for a range of loads between 0.55 kN and 13.00 kN. From the results of the shake table tests, the concept of inclined shelving appears to be very effective. An inclination of only 3.5° reduced the observed seismic merchandise shedding fragility to zero for the ground excitations considered.