Seismic Zones and Pallet Rack

• Seismic Pallet Rack Standard Models (many others available)

Taller racks, higher density...

In recent years, higher-density storage systems such as VNA (very narrow aisle) have increased the complexity of safely designing a racking system. While building codes have gotten stricter—and safer—storage technologies have pushed the envelope.  Tolerances are tighter, and errors less tolerable, especially in seismic zones near major active faults. With an array of pallet racking solutions that ranges from selective to pallet flow, the need to carefully assess your Seismic Design Category D through F project is amplified.

When attempting new construction or renovations to existing facilities, you should always consult your local building department for the most up-to-date information on code restrictions in your area. You can also get a general overview and resources for your area at the USGS.

This guide is meant as a general reference tool, and should not replace professional consultation.

An important foundation

Another important consideration is the ground your building is built on.  It is important to know where fault lines are located, but consider this: about half of the major destructive earthquakes occur on previously unknown faults, such as Kobe-Northridge.

Soils that are subject to mass failure can result in damage occurring far from an earthquake.  In a major earthquake near San Francisco, ground failure occurred near the fault line and on land filled in, near San Francisco Bay, far from the fault line.  The land between the two zones was largely unaffected by the earthquake. If you are building a warehouse or other facility that includes pallet rack, it's worth your time to consult local officials about soil conditions, even if you aren't near a fault line.

Different rules are in play depending on your location. State, local, and county regulations vary widely from place to place in terms of building codes. In most Seismic Design Category D, E & F areas, your rack must be engineered for seismic events. In some places, that means a licensed engineer must design the system to meet code requirements.

As the table and map above illustrate, zones are categorized from SDC A (least risk) to SDC E (most risk). The higher the number, the more restrictive the requirements are for structures such as pallet rack, catwalks, mezzanines, and conveyor.

When more and more high-density storage equipment is put into smaller warehouses, the risks are amplified. This is why so much effort has gone into laws governing man made structures in seismic zones. Taller racks, packed in tighter have been the trend. Although rack collapses due to earthquakes are relatively rare, they can be devastating for business and dangerous for employees.

What causes most rack collapses?

According to OSHA, all goods, materials and equipment at work sites must be stacked, stored, and secured in such a way that they do not flow, move, roll or collapse. Workers responsible for stacking, storing, or securing goods, materials, and equipment must be trained in the safe methods for doing so (see Part 14 of the OHS Code and sections 13, 14 and 15 of the OHS Regulation).

Pallets and storage racks are commonly used in storage and warehousing applications. Pallets and storage racks may support heavy loads that have the potential to injure workers and damage equipment if the pallets and racks fail and loads fall. Storage racks in particular must remain structurally sound.

The leading causes of storage rack system failure, acting alone or in combination, are:

1. Poor storage rack design - the rack is inherently unsafe;
2. Incorrect installation and assembly;
3. Using the wrong material handling equipment to load and unload the storage system;
4. Operator error when using material handling equipment; and
5. Structural problems with the floors or walls of the storage area - supporting structures may be overloaded, floors may not be sufficiently level.

While seismic activity is not one of the primary causes, building racks to seismic specifications helps protect against some of these factors and is absolutely vital in high earthquake risk areas. Due to the proliferation of taller, denser racking systems, the need to engineer your system to withstand seismic shock is paramount.

Racks, shelving, fixtures, etc. should be regularly inspected for damage and other defects that might cause loss of strength or result in injury or damage. You should train your workers to report any damage to storage racks as soon as is practical. Keeping racks in good repair or (if needed) replaced, will yield safety dividends.

Racks for high risk seismic zones

Seismic-rated pallet racks are constructed differently than, and cost more than conventional racking. Typically, they feature more ability to resist seismic pressures because of construction and engineering differences.

Since requirements vary so widely, we advise you to contact Cisco-Eagle for more information on rack projects within a higher risk seismic zone.

• Seismic Rack Inquiry
• Seismic Pallet Rack Standard Models (many others available)