Seismic upgrade of pole barns

Asked January 29, 2018, 11:29 PM EST

I would like to improve the survivability of the pole structures on my farm. I live south of Independence OR on clay soil (which may liquefy in the expected big earthquake). Is there a source of information that will help me improve my buildings DIY? Are there engineering firms that can help me with the appropriate fix-up given my designs and soil conditions. My haybarn has a large solar panel array on its roof which would provide power if the electrical grid is down. Preserving these panels is essential. Tony

Polk County Oregon disasters small farm issues

1 Response

Thank you for being proactive in your preparations for the Cascadia Subduction Zone Earthquake. The more each of us is prepared for this event and the altered life following it, the better it is for all of us. Though we don’t know exactly when it will occur or even how strong this earthquake will be, preparations for this event should be taken seriously; which you have and I applaud you.

If I am understanding your question correctly, there are three main concerns: 1) the soil structure stability and risk of liquefaction and its relationship to the integrity of the pole barn and incorporated solar panels, 2) the structural stability of the potentially top-heavy pole barn during an earthquake, and 3) Is there anything you can do to mitigate potential issues.

Certain soil structures can be changed due to intense ground motion resulting in the soil not being able to support the built structure. One change in soil structure is called liquefaction due to the change from solid to a viscous liquid, however according to a colleague in the OSU School of Engineering, clay soils don’t usually liquefy during earthquakes but they can lose their ability to support structures if the ground shaking is strong enough.

According to the Oregon Department of Geology and Mineral Industries’ (DOGAMI) hazards map, the Independence, OR area is coded orange for liquefaction which indicates this hazard is rated moderate. However, there are areas around Independence that are rated high. You may want to explore the map yourself at: https://gis.dogami.oregon.gov/hazvu/.

You can have the soil around your pole barn tested. It is not an inexpensive proposal, but it may provide you with the information you need to determine your next steps. Look for an engineering firm that offers Geotechnical engineering services.

As far points 2 and 3, there is a lot of missing information such as the size of the barn, the footing system, and the general construction of the pole barn that prohibits giving any mitigation suggestions. I can tell you that wood constructed buildings tend to fare well in an earthquake due to their ability to sway. Also, engineering firms are available for consult for a nominal fee. That may be the best option for you.

As an FYI, the OSU School of Civil and Construction Engineering has completed research on ways to stabilize soil that has the potential to be weakened during earthquakes and on geotechnical engineering in general that you may find interesting. For instance, Dr. Armin Stuedlein has some interesting work on using timber pile for ground improvement (http://web.engr.oregonstate.edu/~stuedlea/P_LiqMit.php).