I have a street light pole that happens to be too close to some powerlines, it is only too close by a small distance (but you know rules are rules!).
I just happen to have some other poles on site that are 5ft shorter and I want to swap them, but the problem is they also have different base plates.
I have been working on the calculations for the amount of force applied to the base in a 100mph wind gust, all was going well until I started working on the exact nature of the forces at the base. I am not confident that I have modeled the problem accurately.
I averaged the pole width at 6in and with a 25ft length giving an area of 13.5ft2 and the density of air at 0.07967lb/ft3 I get the following equation:
Fdrag = 1/2 ρ v2 Cd A == 1/2(.07967lb/(ft^3))((100mph)^2).47*13.5ft^2
(wolfram alpha link: http://www.wolframalpha.com/input/?i=1%2F2%28.07967lb%2F%28ft%5E3%29%29%28%28100mph%29%5E2%29.47*13.5ft%5E2)
Yeilding a force of 169 lbF.
Doing the moment equation gives 2281.5 lbF ft of torque.
The bolts are 7 1/16 in apart. I could calculate it as if the pole pivots in the center and use half the distance between the bolts to calculate the counter torque, but if the base plate doesn't yeild then my pivot point would be the farthest edge of the plate.
I am certain that the critical failure point is the bolts, either witha pull out of the concrete pad or the bolts will pull through the plate or the bolt will shear.
Ideas?
Drew K
Street Light Pole Swap
Re: Street Light Pole Swap
