[TowerTalk] Guying a self-supporting tower - Yes

[Jim Lux]

I think one approach to the problem is this...

1) Clearly, it's going to be somewhat design specific. The mechanism and
critical loads for failure in a free standing tower (bending) and for a
guyed tower (buckling) are different.  Bending depends on the strength of
materials.  Buckling loads depend only on the stiffness, not the material
strength. Most real guyed towers are probably some combination of the two,
and complicated by the fact that free standing towers are often tapered,
while guyed towers are not.

This is the "hire an engineer to make sure" scenario... which doesn't
provide a universal or generic answer, or resolve this long running debate.
You will get several "point design" data points.. Tower A can be guyed,
Tower B cannot, Tower C, we don't know because it hasn't been analyzed.

2) A more fundamental question would be is there any configuration (i.e.
combination of stiffness and strength) where the guyed column would fail and
the canteliever beam would not, with the same lateral load.  This would
answer the "it can't possibly happen question", since all you need is one
example where a plausible structure will fail with guys but not without.

This is a bit tricky.  There are a raft of handy formulas and rules of thumb
for things like steel tube with uniform diameter, but I suspect that a
lattice work tower is pretty far from that, and some fundamental assumption
in the rule of thumb will be violated.




----- Original Message -----
From: "Doug Renwick" <ve5ra at sasktel.net>
To: <towertalk at contesting.com>
Sent: Sunday, April 10, 2005 8:14 AM
Subject: Re: [TowerTalk] Guying a self-supporting tower - Yes


> I am willing to give the 'NO Group' a bit more time to present
> a case before coming to a conclusion.  No matter how flat a
> pancake is - there are still two sides.
>
> What do you do in the absence of your points 1 and 2?  No
> manufacturer direction and no engineering analysis.  I suppose
> one choice would be to not put up that tower.  The other choice
> is to find out what experience others have had.
>
> I think the experience factor should have more weighting than
> either points 1 or 2.  Someone here once said "experiment trumps
> theory".  If I have sensibly guyed self-supporting Delhi towers
> for 35 years without a single failure, I have enough data to
> recommend guying in my area.
>
> "A good plan today is better than a perfect plan tomorrow".
>
> Doug/VA5DX
>
> David Robbins K1TTT wrote:
>
> > The only 'sensible' conclusions to this are the following:
> >
> > 1. do what the manufacturer says for 'standard' installations
> > 2. do what a qualified mechanical engineer who has performed the
analysis on
> > the specific design says for non-standard installations
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
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