Flag Pole Footing - 180' 1

[LHiggins]

I'm designing a 180' flag pole with a 40’x80’ flag. I used NAAMM's FP1001-07 but updated loads using ASCE 7-10. My question has to do with the footing and embedding the pole. The pole base is a 42" diameter steel pipe sitting in a 52" corrugated sleeve. The manufacturer/installer insists that the sleeve be filled with sand and that no grout is necessary. The footing itself is 6’ diameter and 19’ deep concrete. I’ve agreed to the sand but am insisting on 6” of non-shrink grout at the top so that the pipe has something to bear on and transfer the force to the footing at the top. Is there either a specification or standard somewhere that would shed some light on the grout/sand installation?

 

[SAIL3]

Is it possible for a continously tapered pole/stack to develop resonant wind vibration??. The critical wind velocity that causes this is directly based on the diameter of the pole.

 

[JStephen]

I would assume so. Keep in mind that the wind velocity also varies as you go up, so it's not a perfect correspondence anyway.

 

[SAIL3]

JS..I think you may be correct, at least, on these super-tall poles where the taper is very slight. I can visualize, say a 50ft length of these poles where the combination of the small increase in diameter and the normal varying of the wind that it could set up a vortex shedding situation. I still find it difficult to accept that the driving force developed from this segment of the pole would be large enough to drive this vibration, unless these tall poles are more flexible than I anticipate. The final Acuity pole design was tapered and also has a damping system perhaps to cover that possibility.

 

[LHiggins]

I found this paper on vortex shedding and pole structures. It's taken me a hole day just get to the model shapes and their forces. I'm still doing research to figure those out. (Have been having fun converting to metric to match the equations) and trying to match the equations to the output in the examples. The good thing about my pole is the first 100' will be in pretty turbulent air as there is a high overpass that runs by it. Turbulent air means no vortex forms.

http://www.wceng-fea.com/vortex_shedding.pdf