Light pole design
Light pole design
(OP)
Does anyone have any examples or know of any particular design references for analysis of a light pole?
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RE: Light pole design
good luck
RE: Light pole design
(1) I have used an excerpt from Section 6 ASCE 7-95 for wind loads on buildings to determine qz (velocity pressure and then p (wind load) on theppole and lights to come up with moment and shear at the base of the pole (top of drill shaft). It would seem to me that there should be a reduction factor to apply to the drag against the pole since it is round ands smooth, but since I am relying on a spec for buildings I have no documentation to back that up. Does ASCE 7-95 have such a factor and if so could someone lead me to it (supply a reference)?
(2) Broms Method looks at a "pile" and determines an ultimate soil reaction to the overturning forces involved (due to wind loading in my case). How do you determine the Moment capacity of a round reinforced concrete drill shaft (so I'll be able to show that the shaft is not overstressed)?
RE: Light pole design
If you need to check the concrete pier, use standard column design tables for a very small (approaching zero) vertical load and get your moment from there. Any two foot diameter reinforced concrete pier is going to be OK, but you should run the numbers.
RE: Light pole design
1. http://www.engineering-international.com/ &nb... flagpole spreadsheet
2. http://commerce.wi.gov/wps/sb/content/docs/SB-Comm...
3. http://www.usda.gov/rus/regs/bulls/1724e-205.pdf
Hope these help.
RE: Light pole design
And, regarding foundations, be conservative. The single largest reason for light and flag and similar structure failures is not wind, but deflection. Who trusts a deflected pole? And the primary reason for deflection is underestimating the effects of rocking or oscillation. One must consider vibration, natural frequency, response, etc.
Not to discourage, but to educate, and make one awares that many simple things are in fact complicated. Call a local structural/civil PE who is willing to share and educate.
Good luck......
RE: Light pole design
The California Building Code (=Uniform Building Code + amendments) has a design method for sizing the pole foundation in §1806. I recently completed a pole foundation design for moving an 85' high pole from one location on a site to another. I took the wind force on the pole and converted it to a moment at the base of the pole, then converted this moment toan eccentric load on the top of a circular column (i.e. the foundation). I have assumed that the foundation depth calculated per the CBC/UBC method created a column fixed at the bottom, and I have assumed conservatively assumed no passive resistance from the surrounding soil. Eccentrically loaded round columns are a bit of a pain by statics, but there's a neat equation in my concrete book called the Whitney-Hognestad Formula that allows you to check an eccentrically loaded column under tension control.
Fred
RE: Light pole design
But, all the codes arrive at approximately the same place anyways.