## Wind pressure on octogonal POLE for a transmission line

## Wind pressure on octogonal POLE for a transmission line

(OP)

Hi,

I did a research in internet looking for the wind pressure you have to apply in a transmission line pole. I have found that the formula is qz=0,00256 (psf) * Vw^2. 25,6 psf for 100 mph Is this right?

My pole has octogonal shape. Have I apply a coefficient for the shape? Here in Spain we have formulas to calculate the force of the wind against flat surfaces or cilindrical surfaces. Our standard don't say anything about 8-side, 12-side, 16-side poles.

Thanks.

I did a research in internet looking for the wind pressure you have to apply in a transmission line pole. I have found that the formula is qz=0,00256 (psf) * Vw^2. 25,6 psf for 100 mph Is this right?

My pole has octogonal shape. Have I apply a coefficient for the shape? Here in Spain we have formulas to calculate the force of the wind against flat surfaces or cilindrical surfaces. Our standard don't say anything about 8-side, 12-side, 16-side poles.

Thanks.

## RE: Wind pressure on octogonal POLE for a transmission line

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I have been called "A storehouse of worthless information" many times.

## RE: Wind pressure on octogonal POLE for a transmission line

My problem is that we have a family of old poles. More or less from 90's. They were tested in a full scale test and I was comparing the values We used for the test with the values I obtain now. The formulas to calculate are the same. But when the force due to wind they used 117 Kg (1170 N aprox.), with my calculation I have around 200 Kg (2000 N). I think is a big difference.

I am quite sure that my calculation are right, but it's possible that in the station for the full scale test, they didn't check the values? I am quite sure that in the 90's we use the value of 700 N/m2 (according our standard is for flat surfaces) that is not correct I think.

For cylindrical shapes we have 1000 N/m2. I think that we should use 1000 N/m2 for cylindrical surface * Projected area (m2). We have the punctual force applied in the center of gravity. Am I right?

According our standard for full scale test. We have to apply this force in the top of pole. To do this correctly, I suppose I have to take moments in the base to reduce the force in the center of gravity applied in the top of the pole. Am I right?

If you want I could send my calculations. Thanks for your help.

## RE: Wind pressure on octogonal POLE for a transmission line

Unless your wire loads are very small, the wind on the pole shaft will be a minor component of the total load.

_____________________________________

I have been called "A storehouse of worthless information" many times.

## RE: Wind pressure on octogonal POLE for a transmission line

I have the problem with a small poles where the normal force is 1600 N (360 lbf) and the force due to wind is around 1300 N (292 lbf) and our standard say that the wind due to force have to be applied in the top of the pole for the full scale test. I suppose that if you apply the value of wind force directly in the top this is not correct. That you have to calculate the equivalent force in the top. Am I right?

## RE: Wind pressure on octogonal POLE for a transmission line

I would sum moments about the base from the distributed wind pressure and the point load from the flag or wire or whatever the pole is supporting then divide the moment by the pole length to find the shear load to apply at the tip. I assume you are going to do a full scale test to verify that the pole is good for.

I don't recall if you have PLS-POLE and PLS-CADD, but if you do, you can do the analysis there by modeling the pole and applying the wind as one load case and find the base moment from just the wind load.

_____________________________________

I have been called "A storehouse of worthless information" many times.

## RE: Wind pressure on octogonal POLE for a transmission line

I have calculate with sum moments about the base with an spreadsheet that we had (I only have PLS-TOWER). At this moment we don't have to do a full scale test but It will be possible in the future because this product was tested 15 years ago. The problem is I am quite sure the calculations of the wind for that test was wrong.

I have calculate and I have to strengthen the bottom of the pole.

## RE: Wind pressure on octogonal POLE for a transmission line

I have been called "A storehouse of worthless information" many times.

## RE: Wind pressure on octogonal POLE for a transmission line

I will ask POWERLINE to quote the product.

## RE: Wind pressure on octogonal POLE for a transmission line

## RE: Wind pressure on octogonal POLE for a transmission line

Regards,

Lyle