tower wind load calculation

Hello guest

If you're just trying to get a safe ballpark estimate, velocity pressure in Pa = 0.5*ρ*V², where ρ = air density, 1.2 kg/m³, V = wind speed m/s. Multiply by the projected area of each member for the force. The full calculation gives factors less than 1 for shape of members, so above is on high side.

I assume you know how to use above to work out total bending moment at tower base, which is usually what's needed.

Appropriate wind speed depends on location but for normal purposes in UK I use 50 m/s (= 112 mph)

Cheers.......Codey

Codey,

Thanks for your information, but my problem is not how to calculate the wind pressure. My problem is the area at which the wind pressure is acting. Is there any factor to be used to multiply the overall projected area of the tower to get the bending moment of the space frame?

George.

Hello Guest

No, I don't think so, as the BM depends on the height of each member, and the distribution of member areas and heights isn't constant in general (though for a particular style of tower it might be possible to come up with a formula).

Also I'm not familiar with BS8100. I have an old (1972) copy of CP3 : Chapter V : Part 2 which covers this (I don't know what the other Chapters and Parts cover). I assume this has been superseded by BS8100. CP3 is pretty heavy going, sounds like you need to get stuck into BS8100 to find what you're after. Good luck!

Cheers..........Codey

Codey,

Thank you for your help. I can use projected hieght and area of each member, though I am thniking that there might be an easyer way to go about it. I have a copy of CP3, but it did not see any thing about wind load on space frames in the code.I understand from a journal that BS8100 covers this.

Thanks,

George.

George

Had another look at CP3 and sections 8.3 to 8.5 cover frames. Is this applicable to your problem? From a quick perusal it only seems to give forces, not moments, so as your tower probably tapers towards the top you still have some work to do.

Sections 8.2.1 and 8.2.2 give forces on individual members for a different approach, needing rather more work.

Cheers.......Codey

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Hello.

Wind Load calculation is with BS6399-2 "Wind Loads" and not with BS8110. Wind pressure calculation is clearly shown on BS6399 with respect to all particular criteria that your structure might require. ASCE Wind Load calculation is more comprehensive but carries similarities.

Anyway, back when I was designing communication tower it is always better to make an excel spreadsheet to calculate the wind pressure because it will vary according to the elevation. At the same time you can add columns on this spreadsheet for the member area, I mean the surface area of your proposed members (angle, double angle, I-Section, Circular Section, and alike). This area is impotant in determining the wind pressure distribution on the tower, specifically on the members. What comes next will be analysis using a particular software, in my case, STAAD.

It is important to remember that the main frame is moment stiff and the webs are not. The type of antenna that the communication will carry will also succeptible to huge amount of wind load.

That's all I can recall right now and I hope that it helped you a bit.

Good day...

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dear fellow

to determine wind loads on towers ,u must follow the requirement of the EIA/TIA 222F SPECIFICATIONS.

1-ADOPT A WIND SPEED ACOORDING TO REGION

1-CALCULATE CALCULATE SOLIDITY RATIO

3 CALCULATE GUST RESPONSE FACTOR

4 CALCULATE STRUCTURE FORCE COEFICIENTS

5 CALCULATE WIND PRESSURE

6 CALCULATE WIND LOADS

7 ADOPT LOAD COMBINATION AS FOLLOWS

7-A D.L +W.L

7-B D.L+W.L+ICE LOAD

8-MAKE THE ANALYSIS THE DESIGN ACCORDING TO THE SAME STANDARDS

IF YOU NEED HELPS CONTACT ME

ENGINEER FAYEZ MOUNAYER -SYRIA

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Dear colleagues,

I need guidance on the calculation of wind load on communication towers.

1. As the surface area reduces from bottom-up, do I consider pressure load per panel, by multiplying the trapezoidal area with the wind speed, or I will convert to a concentrated load at the surface nodes?

2. My dissertation is on the uplift capacity of transmission towers with case studies of communication tower foundations in my country.

3. A guide on how to apply the wind load manually will be appreciated so I can create a spreadsheet for it.

http://www.va3cco.com/towersheight.pdf