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Tower Loading

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Subject: Tower Loading
From: (Bryan Sparrowhawk)
Date: Fri, 07 Feb 1997 16:27:26 -0800
I'd like to pump this thread for more information ... but first a comment on
what's transpired.

Calculations certainly help to take the guesswork out of tower installation
design.  However, the 'comfort numbers' you get when you are done
with the 'calculations' are no better than the model used.  The specs we
get from Rohn support a very simple model.  No doubt  they fudge with
lots of safety factor to account for other things such as resonances,
imperfectly placed guys etc..   This leaves us second guessing them
which i think is the underlying issue of this thread.

The other extreme in 'calculations' would be a finite element analysis, a
kind of mechanical ELNEC but more messy since it would have to
combine aerodynamics, soils engineering, and classical physics... and
other stuff i haven't thought of.  The result would be wonderful.   We
probably aren't going to see any practical info. from something like that
for awhile!

So... what i want to hear are the stories of tower failures.  Not bent
masts and crinkled yagi elements... but the real juicy ones where, for
example, a well guyed 120'  25G tower with two or three big beams on
top came down as a result of the tower sections themselves crumpling. 
I want to know what kind of storm and loading abuses were put on the
tower to make it fall.  Now that's practical information!

I bet there arent' too many failures that fit into this category.  Guy and
anchor failures.. or skimping and not guying every 30' or nearby trees
falling over a guywire are the causes i would expect to see.  I also
wouldn't think many towers fail because of a bad tower base.

Load us up with your tower post mortems.  I hear there's 1000 people on
this reflector, assuming each one knows about 5 tower installations,
that's 5000 towers... certainly a couple of them fell under interesting and
NON-OBVIOUS  circumstances that we could all learn from.

de KD7LS, bryan

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