Will Your Rack Design Require A Seismic Force Review?
It’s a common misconception that seismically designed rack is only found west of the continental divide. In fact, earthquake activity has been documented in multiple regions throughout the U.S., including the Midwest and Southeast. That’s why, depending on where within the U.S. a facility is located, a seismic force review may need to be taken into account by the rack manufacturer when engineering, manufacturing and installing a pallet rack system.
So how can you tell if your rack design requires one?
One of the fastest ways to determine the projected intensity of a potential earthquake in a new rack’s geographic location is to consult the Seismic Maps website (www.seismicmaps.org). By inputting the facility address (or latitude and longitude coordinates), the site will share the seismic parameters of a given location. These are two separate numbers that represent the ground acceleration at the site as a percentage of gravity: Ss, the short period (0.2 second) acceleration, and S1, the 1-second period acceleration. Your rack design engineer will use that information as part of the determination of the facility’s seismic design category and design the rack to withstand those anticipated forces accordingly.
Subsequent design decisions—all intended to increase the safety of any persons in proximity to a rack by reducing the risk of its collapse should an earthquake occur—are a result of a series of engineering calculations.
Section 2.6, “Earthquake Loads,” of the recently updated ANSI MH16.1-2012 (R2019): Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks, published by RMI, includes a complete listing of the calculations to be performed by a qualified rack design engineer. Considerations include:
- Geographic region, denoted by what is referred to by building codes as Seismic Design Categories (SDCs), which range from A to F.
- Specific site location contours and subsequent design parameters.
- Soil classification
- Supporting concrete slab thickness
Want to learn more about seismic design and rack safety? RMI includes a section on Seismicity in its list of Frequently Asked Questions.