Earth Anchors / Ground Screws per Building Code?

[mustangsvo85]

I’m in solar and I’d like to use ground screws on our pipe rack PV arrays. Been talking to local jurisdictions on this and they seem lost. Does anyone have experienced with these and could you help point out anything in the CBC or IBC that would help get them on board?

 

[dauwerda]

I believe you are referring to helical piles, is that correct? If so, the 2015 IBC does mention them and provide some design requirements in section 1810. My experience is that they typically need to be load tested at each site and the manufacturer/installer does the site specific design based on the load test results.

 

[JStephen]

I've seen similar items used or sold to anchor swing sets, storage buildings, mobile homes, as anchors for guylines on utility poles. I would assume the last use is actually engineered, not so sure about any of the others.

 

[JAE]

Usually these are performance-based specifications where you provide the location and number of piling and indicate the required capacity (with a safety factor of 2 or more).
The helical piling supplier will then install and certify the pile capacity.

You can also demand load tests, as dauwerda states, to help verify if the piling capacity is indeed achieved. Typically helical piling are installed to a set torque-vs.-axial capacity relationship based on the soil types.



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[mustangsvo85]

Not helical piles. Ground screws. See this link for an example...

https://americanearthanchors.com/files/2414/3255/6630/pe46hex-specifications-installation.pdf

Does anyone here have experience with load testing these in So Cal? If you're not familiar with So Cal, it's a terrible place for engineers. Too many book smart engineers that have never held a hammer.

 

[JAE]

Whether helical pile or "ground screw" the concept here is the same - the IBC doesn't have anything direct in there about it that I'm aware of unless the latest 2018 version does.

The IBC does have a section near the beginning where it states something to the effect that "nothing in this code precludes the use of other methods, systems, materials, etc."

So you as the engineer should use engineering judgement to ensure safety/welfare of the public in specifying these things - researching where they got their load capacities (per the link you provided) and convince yourself of their veracity and perhaps use a little more safety factor if you are unsure.

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[TehMightyEngineer]

JAE, the 2015 IBC does include helical piles in the various foundation sections (see the index) as well as includes them in special inspections.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[mustangsvo85]

Yes, helical piles are covered, and familiar enough for jurisdictions. The building officials I’ve beeb encountering want these screws I’m proposing to be UL listed or something similar. I’ve tested them, they are quite strong, so I’m comfortable using them, but I should be able to just do a pull test on site for the inspector to show the screws can handle 2-3 times the load needed. These inspectors here have no clue though.