Prof. Ing. Carlo Andrea Castiglioni Seismic Behaviour of Steel ...

Seismic behaviour of steel storage pallet racking systems . 5recognized that a significant life-safety hazard could be associated with storageracks behaviour during earthquakes.FEMA was aware that current storage rack requirements were somewhat out of date.For example, the latest edition of the storage rack design specification developed inthe U.S. by the Rack Manufacturers Institute (RMI) references the obsolete 1994NEHRP Recommended Provisions, even though the Provisions document has beenupdated three times since then (i.e., in 1997, 2000, and 2003). Furthermore, duringthe 1994 Northridge earthquake (magnitude = 6.7), serious storage rack collapsesoccurred in several warehouse retail stores that would likely have resulted in injuriesand possibly deaths if the earthquake had occurred during a time when the stores hadsignificant public presence rather than at 4:30 a.m. on a federal holiday.Many existing racks have been since voluntarily strengthened or replaced andstricter quality assurance programs for rack loading and reconfiguration have beenimplemented by some owners, in order to prevent a reoccurrence of the Northridgeproblems. In addition, the 1994 NEHRP Recommended Provisions included a 50percent increase of seismic loads for storage racks in areas accessible to the public.FEMA also recognized that the design process must take into account earthquakeslarger than those recently experienced.As already mentioned, in Europe, no official document is currently available for theseismic design of pallet racks and the designers are compelled to operate withoutreferences to commonly accepted European design rules.Present Eurocodes 1, 3 and 8 give insufficient information on many design issues.Recently, rack manufacturers defined a set of conventional design criteria, based onengineering experience, and drafted a “code of good practice” for users, a strictapplication of which is intended to achieve a safe working environment (FEM2001b). This Code gives insufficient information to some design aspects.Very often designers make reference to the Rack Manufacturers Institute (R.M.I.)Specifications (R.M.I. a and b, 2002). In the meanwhile, the Industry in Europe,under the guidance of the European Federation of Maintenance (F.E.M.) issued aManufacturers’ Design Recommendations called FEM 10.2.02. (FEM, 2001a).These recommended the way in which components are brought together to providethe optimum strength and stability required to store specified pallet load size andmaximum weight. An increasing number of European manufacturers are presentlyable to design according to these recommendations, if required by their customers.Furthermore, CEN has recently activated a Technical Committee (CEN-TC344),with the aim of developing a set of Eurocodes dedicated to racking and shelving.Overview of damage to steel pallet storage racks and content spillage