Richard Hill wrote:
> Jim, I think it is relevant in that a well known bridge system would
> have been less likely to fail = follow the manufacturer's
> recomendations. An un-tried design is more likely to fail--and the
> failure is often due to a compounding of errors in judgement or over
> minimizing assumptions in a favorable/hopeful direction.
>
I agree with you in that sense.
> People putting up towers from the seat of their pants (sans mfg
> directions) might be equivalnet to a new design. Trying and testing
> new designs is what moves us forward, but we have to be able to
> withstand the downside if it comes.
>
I agree.
And I think that's the key to "off-nominal" antenna and tower designs:
the cost of failure is tolerable.
> The modeling that "discovered the error"--was developed after the
> bridge was built and earned the "Galloping Gertie" nick name. The U.
> of Washington engineering school did not find a solution for
> retrofitting before the loss.
I think they figured it out just before it failed, certainly not fast
enough to actually fabricate the solution. Aeroelastic vibration was a
pretty new and unusual thing then.
It is often much more expensive to
> figure out what is going wrong, and retrofit to fix it than it is to
> do it right the first time.
>
Although there are cases (particularly with very complex systems such as
software) where one cannot exhaustively determine all possible failures
(much less analyze them). In this case, one goes for failure
mitigation. An example is having a spare battery powered radio in an
airplane. In the case of a bold antenna/tower design, one might design
for a "fail soft" or "fail contained" (I think a lot of crankup with
guys schemes fall in this category)
> Cheaper--Better--Faster. Pick two.
Ain't that the truth.
jim
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