How to calculate Wind load and Ice load of a custom equipment in PLS-POLE

[engratcorner]

Hello everyone,

I have been doing pole audit on electric distribution poles (Wooden - Southern Pine). As a part of it, I need to build poles in PLS-POLE which will be later used in PLS-CADD for structural loading and clearances. Recently I came across equipment such as capacitors, voltage regulators on poles which weigh more than 250 lbs at a height of around 25 - 30 feet from ground. I am pretty sure, this kind of equipment would impose considerable amount of moment on the pole. When I am trying to create such equipment in PLS-POLE, I was asked for Wind load & Ice load on the equipment. Does anyone have any idea or references to calculate the Wind & Ice loads on equipments with customized geometry.

Thank you in advance,
Rohit

 

[bhyde]

Rohit,
When I am creating equipment in PLS Pole, it doesn't ask me for the load, in particular, but rather for the wind and ice area. The wind area would be the cross sectional area of the equipment in the Z-Y or Z-X plane. The ice area would be the cross sectional area of the equipment in the X-Y plane (i.e. looking straight down). If it is asking for the actual ice and wind load, just multiply the wind pressure (psf) by the wind area (or the ice density by the ice area and ice thickness).

 

[engratcorner]

I apologize, I should have asked for wind and ice area instead of load, and this is what exactly I am looking for.

Thank you very much bhyde.

 

[dhengr]

Rohit63:
I would think your industry would have some standards on these matters, wind and ice loading, on wires, equipment, poles/towers, etc. And, that any good handbook on transmission system design would cover this also. Finally, the various wire (cable) and equipment suppliers will likely have info. on their own products on these matters. You should collect and read some of this so you get a fundamental understanding of the subject, rather than relying solely on some computer software. And, you should most certainly know how that computer software works and what it does to and with your input values; to give you your output, and then how that should be interpreted. The wind loading is bases on projected area to the wind (a worst elevation view/area of the item), along with some shape and size effects; and finally there can be dynamic effects due to the flexibility of the item (i.e. swinging or galloping motion of the cable, for example). The ice loading is not as simple as a load on the plan view area. It can be attached to the whole surface area to some substantial thickness. Most of these items are cantilever out from the axis of the pole or tower, so they apply bending moments; but they can also apply torsional moments on the pole. And, you better know how your software treats these. You might want to look at some Engineering Mechanics and Strength of Materials textbooks to get a fundamental understanding of how the program should treat these, or as a means of checking the output. You should also be getting or asking for help and guidance from a more experienced engineer (mentoring) right in your office, so they know what you do and don’t know, and they can help keep you out of trouble.

 

[transmissiontowers]

The equipment input into PLS-POLE can include the shape factor, wind area, ice area, and the weight. The PLS-CADD program criteria file determines the wind velocity (it is your input value). The USA electric utility industry does not include the ice weight and area on the structures. We do apply ice on the wires as required in the NESC, but the structures are not required to have it. When you put the equipment on the pole, you can specify the azimuth and the offset from the face of the pole. The program will take into account any P-Delta effects when you do a non-linear analysis.

As dhengr already said, our industry is a very specialized branch of structural engineering and it uses very specialized software and you can get into trouble quickly if you do not understand what the program is telling you.

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