Flag Pole Foundation - calculations vs typical 2

[beamertaylorf]

I'm a Mechanical engineer but I was asked to look into this for a friend. So far, I've been unable to make any sense of it! I've looked around this forum a lot and haven't found a post directly aimed at this weird ground set foundation sizing.

The scenario is for a 40 ft flag pole that seems to be non-constrained at grade. The wind load on the pole and flag totals about 12,000 ft-lb from how I have understood NAAMM FP 1001. The manufacturer has told my friend that this design works and has worked, but I haven't been able to get anywhere close to this small of a foundation in my calculations. I even had a Civil friend of mine run this through EnerCalc and that wasn't able to get close either. My own Excel based calculations are coming up with about 10 ft of embedment depth required for a 24 in diameter ground set.

Does anyone have any experience with these kinds of "ground set" foundations? It seems that there are "typical" dimensions out there from an old NAAMM publication that I can't find; it seems to be retired. Any experiences or thoughts on this would be a great help to my construction manager friend!

Pole (see attached):
40 ft tall (above grade) flag pole
8 ft x 12 ft flag (max)
4 ft embedment in concrete "ground set" (tapered "plug"/drilled pier)

Foundation/Ground Set (see attached):
Top diameter: 24 in
Depth: 4 ft

Loads per NAAMM FP 1001:
122 mph max wind speed (per given specs)
Axial Load: ~350 lb (weight)
Moment: ~12,000 ft-lb

 

[beamertaylorf]

JoelTXCive - do these spec sheets/drawings need a PE stamp in your experience? Even with that note that you add, wouldn't you still have to "engineer" the foundation?

 

[JoelTXCive]

I think it is a gray area. Even using he 'installed per manufacturer' language, the EOR is probably still legally responsible for all the details on the sheet.

Another idea is to attempt to pawn the design off on the contractor and the local flagpole salesperson. In similar situations we have called out "40' XYZ Flagpole by XXX company. Contractor to submit signed & sealed drawing showing installation details...yada yada yada." We do this on other items where specialty engineers are used such as wood truss engineers, or precast concrete culvert designs etc.

 

[dauwerda]

Would a 24" x 6' concrete foundation seem fairly reasonable given the discussion that we have had so far?

If it were being installed in my front yard, I would probably be ok with 6ft.