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Helical Piles and Earthquakes
by Bill Bonekemper, Publisher
Our industry has undergone and continues to undergo significant research and laboratory testing on the performance of helical piles subjected to seismic forces. However, there have been little, if any, efforts in North America to build a comprehensive database of structures that have either been (originally) constructed using helical piles or helical anchors as deep foundations or anchoring systems, or structures that have undergone seismic retrofitting for their foundations.
The time has come for the North American helical pile industry to take the next step to document the performance of helical piles and anchors used to support structures when the structures are subjected to the forces generated by a seismic event. Efforts like this have been ongoing for 10-15 years in New Zealand and Japan, and now it is time for our industry to begin documenting how our products and the structures they support survive the effects of a significant earthquake after the next big one hits in North America.
Just to bring our readers up to date, the Helical Piles and Tiebacks Committee of the Deep Foundations Institute (DFI) has sponsored significant research and testing efforts over the past three-plus years, and testing (scaled liquefaction) is continuing currently. HelicalPileWorld.com (HPW) has been deeply involved with the DFI assisting with fund raising and sponsorship efforts so the research and testing could be accomplished. Via the HPW website, there has been a significant amount of coverage of all the research and testing events and activities. Information can be found by accessing the following link and the additional links within the article - http://helicalpileworld.com/dfi_helical_pile_seismic_study_update_february2018.html
As readers will see from this article and the other supporting articles, there has been a lot of research and testing work completed by the lead researcher, Dr. Amy Cerato and her graduate students at the University of Oklahoma. The testing that has been completed to date reveals that the ability of helical piles to successfully withstand significant seismic forces is indeed very, very promising.
Helical Pile New Construction and Seismic Retrofit Database
Effective immediately, HPW will begin efforts to build and maintain a database that contains essential information about the existence and location of structures that have either been originally constructed on helical piles or anchored with helical anchors, or those that have undergone a seismic retrofit using helical products. As many people in our industry already know, the City of Los Angeles, CA passed legislation in 2015 requiring many, many structures in L.A. to undergo mandatory seismic retrofitting (click here to read ordinance). HPW recently communicated with the L.A. building department about record keeping for the retrofitting projects and learned that no records are being kept that document what kinds of products have been used to provide the required foundation augmentation to meet code requirements. Hopefully a large earthquake never again strikes the L.A. area, but it would be very unfortunate if hundreds or even thousands of structures have been retrofitted with helical piles and another earthquake strikes while no records exist to facilitate an effective post-quake analysis. It would be equally as unfortunate if no records exist that document projects where helical piles or helical anchors where installed to support new structures.
Reaching Out for Help
The geographic scope for this project is certainly not limited to the City of Los Angeles, as there are a number of geographic regions in North America where there is a history of high seismic activity. HPW needs a lot of help to accomplish this database objective – help from contractors and engineers who have already been or will continue to be directly involved with new construction and/or retrofit projects where helical piles or helical anchors have been used. HPW wants to work with these industry professionals to help document projects and gather the essential information that will be needed to conduct any post-earthquake studies that could reveal critically important information about helical pile and helical anchor performance.
Over the years, HPW has published several hundred project histories some of which were seismic retrofits. Click here to read about one such project from our archive
Persons and companies that wish to become involved with collecting and submitting project information should contact:
Bill Bonekemper, Publisher
After the next big one hits in North America, will the helical pile industry be prepared to definitively document how structures supported by helical pile products were affected?