Guy:
Changes in temperature have an effect but not very much in the range you
specify. Wind speed does based on the square of the velocity. It must be
remenbered thay this Qs value is a datum and the design values are created with
factors modifing this value. Please remember that these all are approximations
of enviromental loads which tend to be highly variable. The Qs value used in
the
UBC depends on the Basic design wind speed for an region which is based on a
statistically determined wind velocity experienced in an area with a return
interval of 50 years. Trying to put accuracy beyond the decimal point is futile
and not important. The additional factors account for height above ground,
gusting, exposure criteria and shape of structure. You need to keep all this in
mind when you look at the Qs value it is just the starting point and is based
on
F=MA.
Hank
KR7X
______________________________ Reply Separator
_________________________________
any thanks all for continuing to pursue this in an open forum. Please
keep it up. I am starting to get a little bit of a grip on things.
Also am scheduling a free day to get over to the library at NC State
with my calculator, etc. The quotations of source books will be very
useful.
A question below in quoted text.
Again, thanks, & 73,
Guy
k2av@qsl.net
O
>
>
>
>Bill:
>
>The equation used in TIA/EIA 222-F which is the latest revision and the UBC
>defines the basic wind speed stagnation pressure (a datum) value as:
>
> Qs = 0.00256V*V
>
> This is base on Bernoulli's equation which can be arrainged to give
>
> Qs=1/2*RHOair*V*V8
>
> Density(air) at 59 deg F and 29.92 in Hg is 0.0765 lbs/cf
> Rho=Density/g
> RHOair=.0765/32.2
>
> To express in MPH
>
> Qs= 1/2(.0765/32.2)(1/3600)*(1/3600)(5280/1)*(5280/1)*V*V
>
> Qs= 0.00256*V*V
As temperature goes up the load would decrease. Hurricanes tend to be
70-75 degree events, very warm. Tornados and Thunderstorm microbursts
seem to be very cool, 45 degrees or 50?
Another event common enough, 30-40 mph with rain, 50-60 degrees.
Also in other parts, 30-40 mph with temps below freezing, say 20
degrees F.
What kind of variations would these place in the final figure. What
would be the worst value of these?
>
>
>I don't know of any safety factor in this derivation
>
>Hope this helps
>
>73
>
>Hank / KR7X
>
Guy L. Olinger
k2av@qsl.net
Apex, NC, USA
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From: k2av@qsl.net (Guy L. Olinger)
To: "Hank Lonberg" <Hank.Lonberg@harrisgrp.com>
Cc: "towertalk@contesting.com" <towertalk@contesting.com>
Subject: [TowerTalk] Re: Projected Area (something rotten in
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Date: Mon, 24 Aug 1998 16:24:41 GMT
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