Adam, you're probably correct in all you say. Now
compare to/conjecture about the construction of the
Empire State Bldg --> which is what I have been trying
to get people to consider.



At 07:02 PM 9/13/01 -0400, you wrote:
>The cross members required to support the load of 20 stories falling at
>9.8 meters per second would require exponentially stronger members below
>to support 40 stories falling at 9.8 meters, etc.  Otherwise someone
>could pick the weak spot and hit it.
>
>This would actually add tremendously to the cost of the building.
>
>Furthermore, the building held up long enough that they could have
>gotten everyone who was not hurt by the initial blast, including the
>firefighters if they understood how long they had, and had better plans
>in place.
>
>As has been said so many times before, we are learning some terrible,
>but necessary lessons because of this.
>
>The building did what it was supposed to do.  It is not necessary to
>beef every other or every future high rise up to withstand the truly
>extreme forces the WTC withstood.  You can't account for everything,
>and, like actuaries, we have to find a point where the safety systems in
>place meet the costs associated with them.
>
>Of the 50,000 people who were inside the building at the time fo the
>attack, probably less than 10% will have died.  Please don't
>misunderstand - it is an unacceptable loss for us - but financial
>backers and the engineers who must cut costs will ultimately design the
>building for the stresses placed on it 99.999% of the time, and not well
>enought for that extra one thousandth of a percent which would have
>allowed some 10k pound of jet fuel to burn on several floors for several
>hours without collapsing.  They will then say that in the one in a
>million chance that the building had undergo those stresses, and 90% of
>the population of the building escaped largely unscathed, then it would
>be good enough.
>
>I would be surprised to find many people on this list who design a GFI
>into their circuitry for the one in a million chance that it would be
>dropped into the tub, when it is not used anywhere near one.
>
>-Adam
>
>Dan Michaels wrote:
>
>>Chris Pringle wrote:
>>
>>>I was quite interested to hear from one of our structural engineers earlier
>>>today. Apparantly it wasn't the aircraft that caused the buildings to
>>>collapse. The buildings were designed to take the hit of an aircraft.
>>>
>>>What brought the buildings down was the fire. The buildings hadn't been
>>>designed to survive a fire. When the structure became warm, the steel
>>>supports were no longer strong enough to support the weight of the building
>>>and so it gave way.
>>>
>>
>>
>>While watching the towers collapse [again and again, ugh], I was
>>struck by the way the entire structures simply pancaked vertically
>>[had they fallen "over", they would have wiped out half of Manhattan],
>>picking up speed as they went, and wondered how on earth do you
>>build a building that does just that.
>>
>>I heard several interviews with structural engineers, and not one
>>had the balls to address this particular issue. They all said, "we
>>designed for hurricanes and wind loading and [small] fires ......,
>>but not for anything like this .....".
>>
>>At any rate, turns out the reason for the collapse dynamics is
>>because they build these things as a tube within a tube, with an
>>inner tube bearing most of the weight, and the outer tube a series
>>of girders up the outside wall - but there are essentially "no"
>>structural elements connecting the two. This is what the paper
>>said today.
>>
>>Take a close look at pictures of the 1st tower collapsing, and
>>one of the "obvious" things you are similar length girders flying
>>off in all directions. These are about the length of one story
>>height or so.
>>
>>Small wonder they came down the way they did. One would think
>>that adding heavy cross members every 20 floors or so might
>>prevent the entire structure from pancaking like that, and
>>might add only minimally to the overall cost.
>>
>>--
>>http://www.piclist.com#nomail Going offline? Don't AutoReply us!
>>email listserv@mitvma.mit.edu with SET PICList DIGEST in the body
>>
>>
>>
>>
>>
>
>--
>http://www.piclist.com hint: To leave the PICList
>mailto:piclist-unsubscribe-request@mitvma.mit.edu
>
>
>
>

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu