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Re: Flag Drag
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- Subject: Re: Flag Drag
- From: "Robert Kazanjy" <rkazanjy(--nospam--at)gmail.com>
- Date: Mon, 11 Sep 2006 20:35:55 -0700
On 9/11/06, Neil Moore <nma(--nospam--at)omsoft.com> wrote:
Use ANSI/NAAMM FP 1001-97. I don't think that there is a later edition.
Equation 4 will give you the wind load for nylon or cotton flags.
Equation 5 will give you the wind load for polyester flags.
You certainly need to know what the height of the building is and then use the appropriate formulas for that. You also need to know what the governing wind speed is. For unknown areas we usually use 130 mph with no flag. (We consider the flag gone at that wind speed). Then we check the flag and the pole combined at 90 mph. The flag poles that we design are usually 400 feet and higher, free standing single poles.
The above mention code provides sample calculations in Appendix A. If you are concerned about buckling, we then reference Section 4 of the Standard Specification for Structural Supports for Highway Signs....ect, published by AASHTO.
Neil Moore, SE, SECBneil moore and associates
consulting structural engineers
shingle springs, california
530 677-4308
At 10:58 AM 9/11/2006, you wrote:
David,
Wouldn't it be waving in the plane of the wind?
I think that the wind blowing on the surface area of the pole would govern the design.
Sharon Robertson, P.E.
Arcon Engineers
5625 Ruffin Rd, Ste 130
San Diego, CA 92123
858/503-7854
858/503-7858 fax
Visit us on the web at www.arconengineers.com
From: David Maynard [ mailto:DMaynard(--nospam--at)kfx.com]
Sent: Monday, September 11, 2006 10:55 AM
To: seaint(--nospam--at)seaint.org
Subject: Flag Drag
Here's what I got.
A flag pole wants to be installed on top of a Structure. I want to make sure that the flag pole on hand is capable of the loading. Therefore, I need to know how to calculate the wind load on the waving banner. Is there a spec out there, or can someone point me in the right direction, as to a design procedure for this. I'd appreciate it.
David Maynard, PE
Gillette, Wyoming
Sorry I'm so late to the thread....I found this eariler today but didn't have time to post it.
Thje projected area of the flag might seem overly conservative but a flag can have much higher drag forces than a simple vane.
here is a rather geeky treatment of the phenomena
http://moretti.ceat.okstate.edu/icsv609r.pdf#search=%22%20%22drag%20force%22%20on%20flag%22
note referenece 3.....would be a great resoucre if someone could track down a copy
I also found this posting on an engineering forum
14 May 03 18:54 |
I
came across this thread like a few others who wanted more information
on the wind drag of flags and streamers - and there is not a whole lot
out there. I am pleased to report that I have found a good reference on
this subject: an article by J. M. Roehm in the Jan-Feb 1986 issue of
Building Standards Magazine, page 10. (You can obtain a
fax copy of this article by calling the nice folks at www.icbo.org, who run the magazine). The article presents drag force results from towing flags behind an airplane and they come up with the following formulae which are DIFFERENT from the Hoerner and previous estimates, and generally give lower drag force values: V = wind speed, Area = one-sided area of flag Nylon: Drag(pounds) = 0.0010 x (V,mph)^2 x Sqrt(Area, sq. ft) Polyester: Drag(pounds) = 0.0014 x (V,mph)^2 x Sqrt(Area, sq. ft) For those of you who prefer MKS units, like myself, this converts to: Drag(Newtons) = 0.073 x (V,m/s)^2 x Sqrt(Area, m^2) for nylon, with polyester flags giving a force 1.4 times greater. Note that unlike traditional formulae for aerodynamic drag, here the force is proportional to the _square-root_ of area, not area directly, so a "drag coefficient" is not really appropriate. |
cheers
Bob
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- Flag Drag
- From: David Maynard
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