Recent earthquakes in the Midwest and East Coast point to increased need for seismic consideration in warehouse construction
While we typically associate earthquakes with areas such as California, recently Monroe, Michigan, was hit with a 3.2-magnitude earthquake. Light to weak shaking was reported as far as Bowling Green, Ohio, up through Sterling Heights, Michigan and into Canada.
Earlier this month, a magnitude 5.1 earthquake along North Carolina’s border with Virginia shook homes and businesses as far away as Atlanta, followed by at least 13 aftershocks.
The U.S. Geological Survey said the quake was the strongest to rock the region since a magnitude 5.2 quake in 1916.
Changing seismic patterns in the U.S.
According to the USGS, between 1973–2008, there was an average of 25 earthquakes of magnitude three and larger in the central and eastern part of the country. This rate ballooned to over 600 M3+ earthquakes in 2014 and over 1000 in 2015. Although this number has decreased in recent years, it is still much higher than the natural earthquake rate and affecting areas previously thought “safe.”
The USGS in recent years has been monitoring and reevaluating the hazard due to earthquakes to account for these recent changes.
Code changes for seismic areas
For those of us who plan and build warehouses and racking, it’s a reminder of how critical it is to make sure that all building and material handling structures are up-to-code for the area in which they are built.
With a better understanding of structural performance during an earthquake event, standards will continue to evolve, placing more demand on the rack design.
And this doesn’t apply only to new rack installations. One of the dangers involves rack that is repurposed or moved to areas for which it was not engineered.
“Old habits are hard to break,” says rack engineer Arlin Keck, PE. “And unfortunately, that also pertains to old perceptions. Many of us remember when the only time that seismic design was considered was for installations going into California or possibly the St. Louis – Memphis corridor.
“As this recent earthquake illustrated, that is no longer the case. When purchasing new storage racks, it behooves the end-user to choose a rack manufacturer (that) is an R-Mark certified member of the Rack Manufacturers Institute, to design your racking system to assure that the structure is seismic-compliant.”
The Rack Manufacturers Institute (RMI) Standard is the recognized U.S. specification for the design, testing, and utilization of industrial steel storage racks. Responsible rack users will want to demonstrate that their racks meet this recognized standard for seismic design. RMI created the R-Mark Certification Program as a way for storage rack users and customers to clearly identify those rack manufacturers whose components and design are in accordance with the RMI Specifications. Steel King® is one of 22 rack manufacturers that holds an active R-Mark License.
Another consideration is that one of the continuing trends within warehousing includes automation – in the form of both pick modules and automated storage and retrieval systems. Both systems raise the stakes of a potential rack collapse – in terms of expensive equipment and the lives of people working within the structure.
Some of the causes of rack failure are rack overload, non-engineered storage system design, equipment accidents, and earthquakes. Make sure you choose a material handling contractor that has experience and knowledge regarding seismic zoning.
Where indicated, all rack should be installed and used in accordance with seismic requirements for maximum safety. If you have questions, please don’t hesitate to call. Steel King specializes in seismic design for rack construction.