[TowerTalk] wind load vs Rohn specs

[Lonberg, Hank]

Al:

I'm unaware of any site that provides what you are looking for, however
someone may be aware of one.

As far as the abbreviations you refer to, I'll give you a brief definition:

Ce - this is the gust factor for wind load on a structure, varies with
     height and actual exposure of the structure to wind load. Tabulated
     in the UBC(Uniform Building Code). Part of the wind pressure equation
     p=Ce*Cq*I*Qs*A. I= importance factor (1.0 for most structures).

Qs - Design stagnation wind pressure based on a design wind speed. This
design wind speed is specified by the governing jurisdiction. The
basic formula is q=0.00256*V*V. V is the design wind speed in MPH.
This value is also tabulated in the UBC.

Cq - This is the factor that accounts for the shape of the structure. For a
     triangular tower it is 3.2 

fa - this is the acutal stress in an component

Fa - This is the allowable stress in an component. For allowable stress
design it is usually 0.6 * Fy (yield stress).

Unif. Load - loads on a structure are classified as to how they are applied 
             Uniform loads are distributed along the length of an element
like the wind load on the tower.

Conc. Load - load that are localized or are applied at a specific point on 
             an element, like the antenna or mast.

Hope this helps, this is sophmore level statics from engineering school. The
code items are a little more specialized and unless you are using the
Building Codes I wouldn't expect someone to be familiar with them.

73

Hank Lonberg P.E.(S.E.) / KR7X




-----Original Message-----
From: Al Williams
To: towertalk@contesting.com; Pete Brunet/Austin/IBM
Sent: 9/1/00 7:59 PM
Subject: Re: [TowerTalk] wind load vs Rohn specs


Please, will someone define just what is meant by projected area and
windload.  Also, what is the relationship between the two? (not in terms
of
numbers but in words).  Is there a place on the internet where this
information is available?

I am trying to follow the analysis for Triex LM470 and US Tower HDX572.
Although I have two engineering degrees,  some of the terms and
abbreviations used by the structural and civil engineers are unfamiliar
to
me.  What is Cq, Qs, Ce, fa, Fa?  Also, Triex analysis has all of the
tower
section loads stated as "Unif. Load" whereas the antennas and mast loads
are
stated as "Con. Load".

Tower Talk seems the perfect place for this topic!

k7puc

----- Original Message -----
From: "Pete Brunet/Austin/IBM" <brunet@us.ibm.com>
To: <towertalk@contesting.com>
Sent: Friday, September 01, 2000 7:26 PM
Subject: Re: [TowerTalk] wind load vs Rohn specs


>
> >Pete, You are in the wrong code. There is no .67  To get the ROHN
assumed
> EPA value you multiply their are by 1.2 for rounds and 2.0 for flats.
>
>
> According to the Force 12 brochure they start by knowing their
antenna's
> projected area.  The generate their windload number by multiplying
their
> projected area by .67 and they publish that number in their brochure.
In
> order to know what projected area they started with I would have to
> multiply their windload by 1.5.  Make sense?
>
> If I know their projected area, can I assume that since it is a round
> member antenna I can use the round member spec?
>
> The antenna is 30' of Rohn 25.  My zone is rated 70 mph.  The shortest
> tower I see in their manual is 40' so I will use those numbers.
>
> Concerning the coax, let's forget about it and say that our
configuration
> will be close to the Rohn configuration.  Besides the antenna, what
other
> top of tower items will a PE want to know about, e.g. mast and
rotator?
>
> Thanks, Pete ws4g
>
>
> --
> FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
> Submissions:              towertalk@contesting.com
> Administrative requests:  towertalk-REQUEST@contesting.com
> Problems:                 owner-towertalk@contesting.com
>
>


--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com

--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com