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# what is the formula in AASHTO for the wind moment on a pole

## what is the formula in AASHTO for the wind moment on a pole

(OP)
I am designing the footing for a light pole in a part. I need to calculate the moment from the wind pressure. I found the following formula online but do not have access to the AASHTO "Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals" to check. Can someone please verify for me if this is correct:

Wind moment = (½ x circumference x wind pressure) x (pole height^2)/2

### RE: what is the formula in AASHTO for the wind moment on a pole

There isn't any formula in AASHTO for wind moment. You're assumption is correct although some people use 1/2 diameter instead of 1/2 circumference.

### RE: what is the formula in AASHTO for the wind moment on a pole

I don't do AASHTO and it's been many years since I have done hand calculations of wind on poles, but my observation is that the light poles are generally tapered columns of 8, 12, 16, 18 sides, or round shapes. I guess it depends on how tall your pole is because most of the codes I know, have height factors on wind pressure. Back in ancient history, I wrote FORTRAN programs to do pole analysis and design and we broke the pole down into pieces and calculated the shear on each segment (based on its average diameter)and summed up the moments at the base. If the pole has a big wind area at the top from the lights, the wind on the pole shaft may be comparatively small.

If you have a general purpose FE program and model the pole as a step-wise tapered series of sections, you should be able to calculate the pressure on each segment in a spreadsheet. And I agree with bridgebuster that the formula should be based on the pole diameter and not the circumference.

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