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Helical Pile Manufacturers Come Together (Again) to Consider Changes to ICC-ES AC358 for Larger Diameter Helical Piles
by Bill Bonekemper
Recently a conference call took place to address the issues surrounding updating the International Code Council Evaluation Services (ICC-ES) Acceptance Criteria AC358 for Helical Piles Systems and Devices. The call was planned and hosted by Moncef Souissi, Project Engineer, IAS Lab Technical Manager for CTL/Thompson’s Fort Collins, CO office. Seven of the nine helical pile manufacturers that previously agreed to serve on the Ad Hoc Committee joined the conference call. The full list of participating manufacturers to date includes:
- Geotech Enterprises
- Hubbell Power Systems
- Ideal Manufacturing
- MacLean Power Systems
- Magnum Piering
- Patriot Foundation Systems
- Techno Metal Post
In addition to manufacturers’ representatives on the call, ICC-ES engineers David Zhao, Yamil Moya and Kevin Hoang joined the call. The call lasted over an hour, and the primary focus was on the Kt values for different helical pile shaft sizes. In the current AC358 (revised September, 2014), the 1.50“ & 1.75” Round Corner Square (RCS) shafts and the 2.875”, 3.00” and 3.50” round shafts have been assigned specific Kt values. Most manufacturers want to add additional shaft sizes to the current AC. There were two approaches discussed including:
Approach 1: Change the wording in section 188.8.131.52. The concept is to go back to AC358 that was published in 2007 where conforming and non-conforming products can both be evaluated, however non-conforming products are required to have double the number field tests. Both the ICC-ES engineers and some Ad Hoc member were against adopting this approach because non-conforming products will have many different Kt values given the soil conditions and other factors that affect Kt.
Approach 2: Statistical Analysis. This is the approach the majority of the parties seem to favor. CTL/Thompson has collected a lot of helical pile test data over the years. The CTL team is doing statistical analysis for round shaft sizes ranging from 2.375” O.D. to 4.50” O.D. For RCS piles, the group has agreed to use the effective diameter (measured diagonally – as was initially done by engineer Bob Hoyt in one of his landmark papers). This is the approach that the entire group agreed to on the conference call, and the wheels are now in motion. The CTL team committed to have a preliminary draft to present to the Ad Hoc committee by June 7th.
Souissi is also inviting Ad Hoc members to meet with him while attending the DFI SuperPile’16 conference in Chicago June 7-9. Also, if there are other helical pile manufacturers interested to become involved with the Ad Hoc Committee’s efforts, they are encouraged to contact Moncef Souissi.
Or by phone: (970) 206-9455