Dick,
> Fred, I think what this proposes is that the common failure mode for a
> tall broadcast tower is a vertical downward crushing failure from
> excessive weight and other vertical stresses. With all guy supports
> intact, it crumples about its base.
Certainly the common failure mode of commercial towers (other than
intentional sabotage) is failure of one member (either vertical or
horizontal) which will result in a crumpling or crushing fall.
> For (relatively) short guyed amateur towers under 100 feet the most
> common failure mode is that of a broken guy support from excessive
> horizontal forces. While the failure of a top guy of a multi-level
> guyed tower might constrain the debris radius by allowing top sections
> to fold around lower guy supports, this would still not be the classic
> downward crumple observed in the TV tower.
This would only happen if all they guys on a single side failed at the
same time. The only failure mode in which I could envision a multiple
simultaneous guy failure is vandalism (the anchor rod is cut) or if
the anchor block were to fail and the anchor pull out of the soil.
If an amateur tower were, for example, have a leg rust out I would
expect a crumple or crushing fall just like a commercial tower.
> I dare say if the TV tower had suffered the total loss of one of its
> upwind guy supports, it, too, would have fallen like a giant tree.
Even with a guy failure, since most large guyed towers have multiple
anchor points in each director, the failure isn't likely to be a
"topple" failure.
73,
... Joe, K4IK
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