david rann wrote:
>
> > I read that the WTC buildings were welded rather than riveted.
>
> I admit that I have not hung any iron in 10 years, and in the 15 years prior
> had never seen a riveted connection. But might I also add, welded
> connections are extremely rare in structural steel. The overwhelming
> majority of structural steel connections are today performed with bolts.
Not true. Structural steel welding is still widely practiced. See my
prior email in this thread for the government overview document.
>
> The planes chosen for this task were fueled to fly across the country, thus
> supplying sufficient heat for a sustained period to cause failure of all
> supporting members in the vicinity. The engineers could play with numbers
> for months or longer to come up with no economical alternative. I doubt that
> a riveted structure could have withstood such an assault. Surely in the
> future these considerations will be considered in building design, but the
> "Capitalists" will be hard pressed to pay extra for public safety.
> Dave
Actually the designers were proud of the strength of the towers to
absorb the hit of a laden plane and remain standing. They hint that
other towers are built to a lesser standard and probably would have
buckled at impact. The WTC was really overbuilt.
I'm a little confused by your last sentence. We could build a plane the
size of a 747 that could survive the blast of a suitcase full of plastic
explosives, but it would have a payload so tiny that operation would be
uneconomical. Think 6 or 8 engines of the current size and about 50
passengers and their luggage. No lucrative air freight cargo. Who could
afford to take such a plane?
When the engineer makes a design, fitness of purpose and cost to
puchase/operate are the two primary goals. Do you want to set the
fitness goals so high that the costs make the product unusable?
The real engineering failure that I see with the WTC is a human one. The
tower has been hit. You have 20 minutes before it crumbles, how do you
evacuate the souls who survived the initial impact? Remember, you have
to factor in human behavior and multiple types of hits. That's where I
believe the lessons learned from the first WTC bombing were not applied.
And I'm not sure that they are applied to new buildings either.
Jon Rush
///
/// shop-talk@autox.team.net mailing list
/// To unsubscribe send a plain text message to majordomo@autox.team.net
/// with nothing in it but
///
/// unsubscribe shop-talk
///
///
|