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A Potentially Uneven Playing Field?
by Bill Bonekemper
Publisher & Editor-in-Chief
August 15, 2012
A Potentially Uneven Playing Field has been Created for the Helical Pile Industry by the International Code Council Evaluation Services (ICC-ES™)
On May 1 this year, ICC-ES™ staff issued ESR-2794 (read here) to Hubbell Power Systems® - the parent company of A.B. Chance® (Chance®). ESR-2794 certifies two Chance® products – SS5 and SS175 helical foundation systems. After studying ESR-2794 and comparing it to the only other two ESR’s issued by ICC-ES for helical pile products - Ram Jack Manufacturing (Ram Jack) ESR-1854 (read here) and Maclean Dixie® ESR-3032 (read here) – it becomes apparent there are significant differences in 1) the data presented for system components in the Chance® ESR, and 2) the method that Chance® selected to present capacities of helical pile system components (shaft, helix plates, caps and brackets). While Chance® should be congratulated for receiving certification for its two products; we must question how the same staff at ICC-ES™ could issue ESR-2794 in its current form assuming a strict interpretation of the mandatory requirements defined in AC358.
The following are some concerning examples and questions:
First – ICC-ES™’s AC358, the acceptance criteria for helical piles and systems, is very specific in defining what capacity verification methods are to be used to determine a helical pile and system capacity. Helical manufacturers have the option of using engineering calculations as defined by either LRFD or ASD to determine the capacities. However in section 188.8.131.52, AC358 requires an additional 30% reduction to be taken if the LRFD method is used. Based on the capacities listed in ESR-2794, it doesn’t appear that this additional reduction was applied. Additionally, it is very difficult for a reader to determine if there are any helical pile or system capacities at all that have been derived from full scale load tests.
Second – In Table 6, Chance® lists their product number C1500160, an SS5, 1.5” RCS shaft with 8” and 10” helix bearing plates, and the “Fixed Design” capacity is listed as 80.8 KIPS. With an established torque limit for the SS5 shaft listed at 5700 ft. lbs. based on a Kt factor of 10, 80.8 KIPS would require over 8000 ft. lbs. of torque. So why would ICC-ES™ staff approve the listing of misleading capacity numbers when the maximum allowable capacity for this product is 28.5 KIPS as defined by the equation in Section 3.13.2, and AC358 requires the lowest capacity must be used in the ESR? Similarly, Section 3.8 of AC358 sets the capacity limits of the foundation “system and devices” as 60 KIPS in tension and compression and 6 KIPS in lateral resistance. Capacities greater than these, which ESR-2794 contains, require special analysis with additional verification testing as prescribed in Sections 3.10 to 3.13. It appears that Chance® elected not to have their products evaluated for lateral resistance, and it is unclear if ICC-ES™ staff required additional verification testing to be performed to justify the many capacities listed that are greater than 60 KIPS.
Third – in AC358, section 3.6 clearly states that (P3) Helix Plates capacities must be verified through load testing only, yet ICC-ES staff allowed Chance® to present Table 5 - “Nominal, LRFD Design and ASD Allowable Strength’s of Helical Plates for Shaft Axial Tension and Compression”. The stated objective of AC358 is to determine and define helical system capacities with the lowest component’s capacity dictating overall system capacity. At a minimum, Table 5 adds nothing but confusion for the reader.
Lastly – As stated previously, the primary purpose of AC358 is to determine the capacities of helical pile systems – piles by themselves, piles with new construction caps, piles with brackets, etc. In ESR-2794, Section 4.1.2, a reader quickly sees that limit states have not been evaluated in this report, but rather depending upon the type of application and the products used as a complete helical pile system, limit state calculations should be done by engineers. This leaves the reader with incomplete information as to the true capacity of a Chance® helical pile connected to a bracket or a pile cap. Why would ICC-ES™ staff not require Chance® to submit load test data for systems that utilize caps or brackets?
Surely two of the most important objectives of ICC-ES™ staff include accuracy of data and consistency as it pertains to truly having a level playing field for manufacturers wanting to obtain code certifications. HPW urges ICC-ES™ staff to re-examine ESR-2794 and to address this important issue as quickly as possible to get all parties involved on a consistently accurate and level playing field for the good of our industry.
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