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"Michael Press" <jack@xxxxxxxx> wrote in message
news:jack-3DAA6E.14374106122006@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> In article <UZWdnSp_49ajAevYnZ2dnUVZ8tidnZ2d@xxxxxx>,
> "Nick" <tulse04-news1@xxxxxxxxxxx> wrote:
>
>> "Lighting Rep" <lightingassociates@xxxxxxxxx> wrote in message
>> news:1165380705.236078.193910@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>> >
>> > Narasimham wrote:
>> >> Phil Carmody wrote:
>> >> > "Richard Henry" <pomerado@xxxxxxxxxxx> writes:
>> >> > > Narasimham wrote:
>> >> > >
>> >> > > > Sorry,it is not so as we gather.As Progenoskes also
>> >> > > > observed,Tacoma
>> >> > > > Narrows Bridge was a new physics/mechanics situation as a
>> >> > > > strange
>> >> > > > unsteady state aerodynamics phenomenon that had not been
>> >> > > > encountered in
>> >> > > > engineering situations up till that point of time...naturally
>> >> > > > not
>> >> > > > mathematically modeled to be handed down to practising design
>> >> > > > engineers.The failure analysis commitee also cleared them of any
>> >> > > > charges of negligence. Even in late nineties a Boeing aircraft
>> >> > > > empennage was destroyed at Japan Norita airport due to such
>> >> > > > causes.However the degree of goofitude in Hyatt Hotel is an
>> >> > > > order
>> >> > > > of
>> >> > > > magnitude higher.
>> >> > >
>> >> > > The Hyatt Hotel walkway was not built as designed, so it is hard
>> >> > > to
>> >> > > fault the designer.
>> >> >
>> >> > Not built as *originally* designed. They changed the designs because
>> >> > they were not practical from the manufacturing standpoint. It was
>> >> > built in accordance with the new designs. Designers somewhere, and
>> >> > the people who reviewed and signed off those designs, are to blame.
>> >> >
>> >> > And you *can* fault the original designer too for designing
>> >> > something
>> >> > for which the components and construction were practically
>> >> > impossible.
>> >> >
>> >> > Phil
>> >> > --
>> >>
>> >> If you build 10 stories above the foundation, the foundation has to
>> >> take the weight of 10 stories in compression.If you hang 10 stories
>> >> down from the ceiling,the ceiling has to take the weight of 10 stories
>> >> in tension.What prevented adoption of floorwise tapering I-Beams or
>> >> welded taper tubes? It is the speed needing to ignore blind
>> >> spots.Granted things are more clear in hindsight.However insistence on
>> >> routine elementary but mandatory structural checks by a second party
>> >> in
>> >>
>> >> large constructions e.g., by finite element analysis would have
>> >> routinely eliminated such loopholes when elemental modeling would be
>> >> considered.This is not maths but managerial practice of safety concern
>> >> in engineering. But"Safety does not sell."
>> >
>> >
>> > Ummm - Remember - Most everything, built, designed, engineered,...
>> > Is completed by the LOW bidder - You get what you pay for...
>> >
>>
>> My father is a retired structural engineer and he knew, for instance,
>> someone who was killed in the Melbourne bridge disaster (box girders, I
>> believe) where the bridge collapsed whilst it was in construction.
>>
>> There is the well-known Tay Bridge disaster where the bridge collapsed
>> over
>> the river Tay with a train on it, shortly after it was completed.
>>
>> But bridges don't get built by sitting on a sheet of paper or on the
>> computer.
>>
>> There is also the French cathedral (possibly Beauvais) that collapsed in
>> the
>> thirteenth century. The roof was bigger than any previous cathedral and
>> if
>> the proof was in the pudding the pudding collapsed.
>>
>> See
>> http://www.tech.plym.ac.uk/sme/FailureCases/List_Engineering_Successes_Failures.htm
>
>
> Many cathedrals collapsed during the era; mostly from
> wind load, which is why the ones still standing are all
> graced with those buttresses, flying and otherwise.
>
> The box girder fiasco is an example of
> over-engineering. By optimizing the strength to weight
> ratio in each of two dimensions as if the other
> dimension did not exist, they built in a failure mode
> that does not exist in one dimension; a failure mode
> that is complete collapse.
>
> From Catastrophe_Theory_and_its_Applications [1]
> "For an analysis of the stiffened plate, in which
> equating the loads at which a whole_plate buckling and
> between-stiffener buckling occur leads to a hyperbolic
> umbilic catastrophe see [23].
> (Such plates are a standard component in box-girder
> bridges whose wreckage was decorating the motorways of
> Britain and the rivers of Australia a few years ago:
> but so much else was found wrong by the enquiry that
> efficient cause, proximate cause, ultimate cause etc.
> are less than clear.)"
>
> [1] Poston and Stewart, 1978. Pitman.
> [23] Thompson, J.M.T and Hunt, G.W. "A bifurcation
> theory for the instabilities of optimization and
> design." In
> _Mathematical_Methods_in_the_Social_Sciences (D.
> Berlinski, ed.) Synthese, to appear.
My father has said that a well-known engineer was prepared to go to the
limits of current knowledge.
In pure maths, noone gets killed...
Nick
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