In a message dated 96-10-15 16:10:01 EDT, you write:
> I'm curious as to what is meant by the tower "collapsing". I
>would have envisioned a severed guy wire to have caused the tower to bend
>over at the next lower guyed section, and all sections below that one to
>remain in place. Perhaps that idea has no engineering data to back it up?
> Several years ago during a gale, a 75 foot pine tree broke (10 feet
>up from the ground) and fall across a set of guys holding up 85 feet of Rohn
>tower. The tower folded up at each guyed section (3 total) and hit the
>ground with such force that the schedule 80 water pipe was bent at about
>a 30 degree angle where it came out of the thrust bearing. This, of
>course, is not the same case as above because of the downward force
>applied by a few tons worth of pine tree. (Needless to say, I was
>thankful that God allowed it to happen a couple hours after my children
>had finished feeding the pigs and chickens. The whole thing made so much
>noise that my wife thought something had hit the house, which was about
>60 feet away from all the action.)
Hi, Dave --
Thank goodness no one was hurt. A tree hitting the guy wires causes a
different scenario and your damage is probably typical. A big alder tree
landed on the guys of W7XR's 40M tower (55G with star bracket on top with 2
guys per guy point) and just stretched the guy wires. I don't think 45G
would have come through as unscathed. See how handy over-engineering
something can be?
> I currently have two towers, each having three sets of guy
>wires. I put the high set of guys on one anchor, and the lower two sets
>on a separate anchor. This I feel is safer in case an anchor lets go.
>(Incidently, what let go in the tree accident was the guy wire clamps and
>the tower sections which bent but not the anchors.)
> If I should ever lose a top guy wire or its anchor, should I expect
>to have the tower collapse instead of bending?
Interesting question. According to the information that I've seen, a
guyed tower will fall typically within a circle around its base approximately
30% of its height. It doesn't "fall over" because it is constrained, or
tethered, by the remaining guy wires. Talk about a pile of scrap...
BTW, this probably shoots the heck out of tower building set-back
73, Steve K7LXC
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