The devastating impact of the Canterbury earthquakes in September 2010 and February 2011 have demonstrated the importance of ensuring that storage racking systems and shelves are designed and maintained to withstand seismic activity.
All regions of New Zealand are liable to earthquakes, and bulk storage facilities and retail stores must consider building content restraint as part of their hazard identification and management programmes.
The standard for Seismic Restraint of Building Contents (NZS 4104:1994) requires the restraint of building contents in certain conditions. The standard provides considerable detail, and building owners and employers should make themselves aware of its requirements.
Figure 1: Suggested seismic restraint of items in storage racks
The Seismic Restraint of Building Contents standard has a variety of options for restraint of goods. As an example it suggests that items stored on shelving systems in supermarkets above 1.8 – 2.0 metres should be enclosed with sliding gates.
The Department of Labour recommends that employers or persons in control of a place of work should engage a consulting engineer to review their shelving systems’ verification and certification to ensure that they meet the requirements of NZS 4219:2009 – Seismic Performance of Engineering Systems in Buildings, which contains the current state of knowledge on the topic.
The relevant design standards for shelving/racking systems are:
Regular checks of shelving systems should be conducted to look for damage from forklifts or trolleys, missing bolts, bent steel supports or shelves, etc.
In frequently occupied areas (defined by Seismic Restraint of Building Contents), palletised goods should be restrained to prevent them from creeping and/or falling from the racking system.
The height of shrink-wrapped pallets should not exceed two times their base, in order to reduce any toppling effect. The shrink wrapping should extend around the base of the pallet so that the goods and the pallet form one unit.
Pallets should be in good condition – broken pallets should be removed from service.
Extra care needs to be taken when shelving hazardous substances. If incompatible hazardous substances fall from shelving in an earthquake and their packaging is breached, chain reactions such as the release of hazardous gases or sparks leading to a fire could occur.
For further information on hazardous substance storage, refer to documents 6, 7, and 8 listed in the References section.
Certain supplies of stock, such as shrink-wrapped canned or bottled goods, are heavy enough to cause serious injuries or death if they fall off shelves onto workers or shoppers.
Heavy or solid items should not be stacked more than 1.2m high without restraint to prevent causing injury during an earthquake. Heavy items must not be stored near frequently occupied areas or near doors/exits to prevent blockage during an earthquake.
The BRANZ Design Guide contains advice for inspecting storage racking systems after an earthquake, where racks have collapsed or have become seriously misaligned:
If an earthquake has caused stock to fall from shelves, even if there is no apparent rack damage, it is recommended that:
Note: New Zealand and joint Australian/New Zealand standards are available for purchase at Standards New Zealand. Visit them at www.standards.co.nz.
copyright: NARGON - the National Association of Retail Grocers of New Zealand