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ICC-ES Approves Significant Changes to AC358

by Moncef Souissi

October, 2016

On October 4th at their meeting in Los Angeles, the International Code Council Evaluation Services (ICC-ES) approved some significant changes to AC358 – the acceptance criteria for helical piles, systems and devices.  The changes had been formerly requested by the Ad Hoc Committee of Helical Pile Manufacturers after several months of meetings and conference calls required to work through the technical elements of the proposed changes.

The changes include:

  • Previously AC358 provided ICC-ES reports only for the 1.50” (38.1mm) & 1.75” (44.5mm) RCS shafts and the 2.875” (73.0mm), 3.0” (76.2mm) & 3.50” (88.9mm) O.D. round shafts
  • The new revised AC358 provides ICC-ES reports for RCS shafts with dimensions between 1.50” & 3.0” and round shafts with O.D. between 2.375” (60.3mm) & 4.50” (114.3mm)
  • The Kt values for the 1.50”, 1.75” RCS shafts and for the 2.875”, 3.0” & 3.50” O.D. round shafts will still be limited by values published in AC358, 2014.
  • For all other shafts, the Kt value will be limited by the value obtained from the following equation  Kt = 22.285 * (deff)^-0.9195 where deff is the effective shaft diameter. For round shafts, deff is the same as the O.D. for RCS shafts, deff is the diameter of a circle circumscribed around the shaft or the diagonal distance between opposite corners of the square shafts.
  • All the new shaft sizes are considered conforming. Non-conformity comes only from the other items in Table 3 in AC358.

Moncef Souissi

Project Engineer

IAS Lab Technical Manager

CTL / Thompson