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Re: Questions About the Events of September 11th (off topic)

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Mr. Park,

There are a few things that you seem to have been misinformed on...

1) a 707 is NOT the same size as a 767.  A 767 (if I recall correctly) is
about 4 times heavier than a 707 and has a significantly larger wingspan
than a 707.  There is also significantly more fuel capacity on a 767 than
a 707 and since all the flights were trans-continental flights they had a
lot of fuel left at impact.

2) There were no shearwalls in the core of the WTC Towers.  There were
only columns that took vertical loads only.  The lateral system was a
"tube" system...basically the exterior framing consisted of tightly spaced
girders and columns that were rigidily connected together.  This caused
the outside walls (around the whole perimeter) to essentially act like a
moment frame, but due to the close spacing of the columns and girders the
system also was stiff enough to almost have a shearwall behavior.  The end
result is that the exterior wall/framing made the whole building behave
like a big 200'+ by 200'+ vertical tube.  The only walls in the core area
was "shaft wall" construction, which is basically specialized systems of
gypsum sheets.  This "shaft wall" provided the fire protection for the
core area, but really provided no structural intergrity.

If you want a summary of the thoughts on the mechanism of the collapse,
then take a look at Gerard's post.  I will note that depending on where
you get your information, there is still some slight desipute (as I
understand it) as to whether the core columns went first due to impact
eliminating some columns and fire weakening others OR if the floor
trusses/joists went first due to fire weakening them and then causing the
interior columns to go due to fire weakening them plus longer unbraced
lengths due to the floor going first.  If you want more detailed
information, then I would suggest taking a look at the FEMA/ASCE report
that someelse mentioned and give a web address for.

HTH,

Scott
Ypsilanti, MI

On Mon, 11 Nov 2002, Min Young Park wrote:

> I think you get me wrong.
> I don't buy what they say. It's too much to take.
> What I am interested in is how the building collapsed
> structually. That's why I put this issue on this
> board.
> Did you really visit the site and read what they say?
> After 911, I have been asked about how the building
> collapsed in that manner.
> But whenever I tried to answer the question, I came
> short. I believe the 'melt-down by airplane fuel'
> theory is a popular answer for that question. But it
> doesn't make any sense to me.
>
> Do you think the gasolin ran down to the bottom and
> melt whole columns in that short period of time? As
> you can see in many pictures, there was fire only in
> local area not in whole building. To achieve the
> building collapse in that manner, the columns should
> be melt evenly otherwise some columns fail first then
> part of the building will tip over into other
> buildings.
>
> After 911, I saw an interview on TV. A civil engineer
> who was involved in the construction of WTC said the
> building had been designed for Boeing 707. But I've
> heard that Boeing 767, which is the one hit the WTC,
> has simillar weight, size and speed. So, if the
> building had been designed for Boeing 707, it should
> have been Ok with Boeing 767 also. As you know,
> strcutural engineers allow some severe demage for that
> kind of large load but not the collapse. If it
> collapsed only by the airplane, the engineer can not
> avoid the blame.
>
> As you may know, the WTC has shear walls in the middle
> of the building continuous from the bottom to the top.
> These walls are mainly for lateral loads.(Of course
> they also take some vertical loads) And some of the
> walls take only a little of vertical loads. If we take
> this shear wall as a cantilever beam, how come this
> collapse in that manner under the lateral load at the
> tip?
>
> Let's suppose we have a 100 storey higerise building
> to be demolished in the middle of other buildings. It
> must not tip over into other buildings during the
> demolition. It would be perfect if it collapse in the
> same manner shown in WTC collapse.
> How much money & time do you think you have to spend
> on the engineering to achieve this kind of perfect
> demolition?
> What is the possibility of getting this kind of
> perfection with a random load? not just once but
> twice. I would say "mission impossible".
>
> Whenever people hear "WTC fake collapse", their
> response is " shut up you moron" even though they are
> approching with reasonable questions. As a structural
> engineer you can not say like them because you are the
> one who is supposed to answer with reasonable theory.
> As I said I don't believe this fake story. I am just
> looking for more reasonable answer by engineer.
>
>  --- richard lewis <rlewistx(--nospam--at)juno.com> wrote: > This
> email message reminds me how blessed we are to
> > live in a free
> > society.  We take so much for granted.  I can only
> > assume Mr. Ming has
> > grown up in a society where he must distrust
> > everything the government
> > does and must be constantly looking over his
> > shoulder.  It is sad that
> > all over the world human nature can do the evil
> > atrocities that he
> > insinuates here.  I am so glad we are blessed with
> > our free society that
> > makes it almost impossible for the scenario that he
> > suggests to happen.
> >
> > Lets look at this logically.  If Mr. Ming is correct
> > in his assertions
> > there would have to be hundreds of people who would
> > know the truth and
> > not speak up.  Our free press allows anyone who
> > knows something to go
> > public with it, even anonymously.  How could the
> > government hide all this
> > information from the press.  I think that would be
> > impossible.  Just ask
> > Richard Nixon.  Sooner or later someone will speak.
> > Do you really think
> > an airforce pilot and all his support staff could
> > keep it secret that he
> > took off with a load of missiles and landed with at
> > least one less on the
> > day of the plane crashed near Pittsburg and NOBODY
> > let it slip to the
> > press?  Do you really think a similar situation
> > could happen with a
> > similar air force jet that was flying near the
> > Pentagon?  Do you really
> > think that a team of construction demolition people
> > could rig a building
> > for collapse and NOBODY on the team would mention it
> > after it happens?
> > Do you really think a 767 jet with passengers never
> > flown into the tower,
> > but some other military weapon was used, and the
> > government is still
> > hiding the passengers or has killed them secretly
> > somewhere else?  Do you
> > really think that the dust at the WTC was something
> > else other than
> > concrete and fire proofing?  Do you really think it
> > was planned for one
> > tower to fall before the other?  Do you really think
> > you would find human
> > remains of a collision accident of several hundred
> > miles per hour
> > combined with an explosion?
> >
> > Now if I was living in Iraq, Pakistan or one of many
> > other dictator
> > countries around the world I would think the
> > scenario of Mr. Ming would
> > be plausible.  But just ask the Russians, how long
> > can you keep a secret
> > from the public?  Sooner or later someone creditable
> > talks.  We have not
> > seen that yet, just Mr. Ming
> >
> > Again, we are so blessed with are freedom, the envy
> > of the world!  God
> > bless America!
> >
> >
> > Rich
> >
> > On Sat, 9 Nov 2002 09:48:37 -0500 (EST) Min Young
> > Park <pmy1970(--nospam--at)yahoo.ca>
> > writes:
> > > As a structural engineer, have you ever wondered
> > how
> > > the World Trade Center collaped by the airplanes?
> >
> >
> >
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