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

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Read the FEMA 403. and
Ron Hamburger's "Structural Performance of the World Trade Center and
Surrounding Buildings on September 11, 2001".

You will find that indeed the 707 is not that much different than the 767
(see FEMA 403, Fig. 1-10), but the analysis technology to do impact analysis
was greatly limited in the 1960's when the design and analysis for the WTC
was done.  Local impact nonlinear effects were almost impossible to do back
then.  This was a time of slide rules and giant main frame computers with
less power than what you now carry in a brief case.  

What the engineers did was to look at the impact energy on the structure as
a whole, and wind dominated.  The 707 was perceived to be an aircraft at
landing speed lost in fog (similar to the B-25 that hit the Empire State
Building).  The high velocity of the 767 and fuel fire ignition over a large
floor plate were not design considerations.

The plane fuel load was the source of multiple fire ignitions, and the fuel
/ air explosion, and impact removed a lot of fireproofing from the trusses.
The fuel itself flashed off in about 6 to 8 minutes.  From that point on,
office furnishings were the source of the fire.  The fire was NOT hot enough
to melt the steel, but it was hot enough to significantly reduce the steel
strength for the unprotected steel trusses.  

Ultimately the collapse of WTC 1 and WTC 2 was due to:
1.	A severely damaged structural system directly due to the plane
2.	Yield strength degradation due to fire at multiple locations in the

I have seen many collapses including telecommunication towers with all of
the guys on one side cut.  Even with that, the tower leaned over some before
it spiraled down on the base.  It does not fall over like a felled tree.  

Yes, I have been to the site.  There was no conspiracy other than with the
terrorists, there was no "gasoline", and no steel "melted".  There were no
construction corners cut.  There were no errors in the design or design
assumptions.  Aside from the terrorists, there were only issues of material
science, the ignition effects of Jet A fuel, and basic laws of physics that
caused one of the worst tragedies we have ever witnessed.  

Are there lessons to be learned?  Yes, but the issues you have raised are
not germane.  Whether or not your questions are "reasonable" or not will
only be determined AFTER you have done real research.  The research starts
with reading the FEMA 403.  There has been recent analysis that corroborates
the scenario of events.  Watching TV reports is not a good source of

Run your ANSYS and NASTRAN nonlinear dynamic modeling to predict the
airliner impact damage, then select truss members and start dropping the
yield strength to initiate the collapse mode.  Then your model will go to a
dynamic impact model.  

Harold O. Sprague

> -----Original Message-----
> From: Min Young Park [mailto:pmy1970(--nospam--at)] 
> Sent: Monday, November 11, 2002 10:16 AM
> To: seaint(--nospam--at)
> Subject: Re: Questions About the Events of September 11th (off topic)
> 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)> 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)>
> > writes:
> > > As a structural engineer, have you ever wondered
> > how
> > > the World Trade Center collaped by the airplanes?
> > 

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