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'[OT]: Structural Collapse - Engineering Debacle ??'
2001\09\12@194221 by Dan Michaels

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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.

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2001\09\12@201009 by Jim

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   "One would think that adding heavy cross
    members every 20 floors or so might
    prevent the entire structure from
    pancaking like that"

I wonder what the 'load' of oh, say, what? ten
stories is as it collapses down upon the next
story ... isn't that **the new load** that
that the floor space *then* needs to support -
- the full ten stories that just came down? Not
to mention the inertial effects that the mass
of ten stories has gained in ten feet (or more)
of distance ...

As it was, I am assuming that the vertical support
steel structural members (both external, along
the external walls and internal) *failed* on
one story initially -

- now there is no means of providing support to the
above vertical steel structural beams and hence the
stories above - you have lost your tie-in to those
supporting steel beams that were holding the above
stories over your current floor and head ... the floor
above will pancake down, overload the current floor
(and each succeeding floor), probably sheering lateral
tie-ins (each time) to the vertical steel structure
supports by overload and quite likely bowing-out
those steel vertical members as well ... floor after
floor ... till ground is reached ...

I too watched that ghastly sight - many times yesterday ...

Jim




{Original Message removed}

2001\09\12@212008 by David P. Harris

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This is my interpretation too.  The first tower to fail had one-third of it
above the crash site, while the second had one-quarter above it.  That's why
the first failed faster - more stress.
D

Jim wrote:

{Quote hidden}

> {Original Message removed}

2001\09\12@214315 by Jinx

face picon face
> This is my interpretation too.  The first tower to fail had one-
> third of it above the crash site, while the second had one-
> quarter above it.  That's why the first failed faster - more stress.
> D

In an excellent TV series called "Why Buildings Fall Down" it
was shown how the failure of one bolt can be the undoing of
a whole building. Once the loading becomes unbalanced then
that's it for the structure. Each floor is design to support its
own weight and share some load of the one above, but not
when it's falling down. As the WTC was built around corner
beams and not a robust internal lattice, once the planes took
out one of those corner ribs it was inevitable. The building was
reckoned to be able to withstand a light plane up to a 707
but nothing larger. The terrorists appear to have done their
homework in this regard, knowing that a 737/767 would be
enough to take the buildings down. And particularly as the
planes were banked as they hit, causing damage to as many
floors as possible. It looks as though some lessons were
learned after the failure of the basement explosion. If the WTC
buildings had been hit lower down I think they would have
collapsed very quickly

By contrast the Empire State Building is constructed very
solidly and could sustain severe damage without collapsing,
as evidenced by the plane that hit it in the 40's

They apparently had a 747 for the White House or Capitol, as
these would need a more explosive impact to demolish them
rather than bank on letting them collapse of their own accord.
I'd imagine though that both would have burned very well, being
older structures

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2001\09\12@223649 by Charles Anderson
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They interviewed the architect last night.  He said the towers were never
designed for having a plane full of jet fuel to crash and burn inside.
The towers withstood the impact just fine.  They said eventually the steel
supports would melt and then it comes down.  The paper said that there was
13000 gallons of jet fuel in each of the planes that hit the towers.
(Boeings site says the capacity of a 767 is 23,980 gal.)

They interviewed demolition experts that said that there is a tremendous
amount of potential energy in a build like that, and once the release of
energy starts, you can't stop it.  They said that is basically what they
do with the imploding of buildings.  Some small charges start the release,
and the rest just continues.

On Wed, Sep 12, 2001 at 07:42:21PM -0400, Dan Michaels wrote:
{Quote hidden}

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2001\09\12@233803 by Ray Gardiner

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The buildings were, tube in tube construction, with cross strcutures between
the tubes, in the case of the first collapse, the fire weakened inner
tube structure collapsed, and the collapse was inwards. Sort of looked
more like an implosion. The other tower appeared to collapse differently.

I heard the fire cladding around the steel structures was 50mm concrete
can anyone confirm this?  Obviously the fire rating was not sufficient
to handle the heat from the burning fuel, but would have been more
than adequate for "normal" fires.

Either way, it's a tradgedy, I don't think you can blame the engineers
in the 70's who designed it for not forseeing this kind of situation.

{Quote hidden}

Ray Gardiner rayspamspam_OUTdsp.com.au
[ 2001 ]

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2001\09\13@012218 by Dan Michaels

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Ray Gardiner wrote:
>The buildings were, tube in tube construction, with cross strcutures between
>the tubes, in the case of the first collapse, the fire weakened inner
>tube structure collapsed, and the collapse was inwards. Sort of looked
>more like an implosion. The other tower appeared to collapse differently.
>

This was my whole point. Tube within a tube, and they said there
were essentially no "structural" members "connecting" the tubes. The
whole thing came down like an elevator falling down a shaft, and blowing
out the outer tube as it fell. Nothing structural in the entire 110
floors to even slow it down. Just makes me wonder .....

I also watched the program on PBS about construction of the "super
bridge" over the Mississippi, and shuttered thru the entire show.
Now sooner had they built and strung the "first" cables, but that
they discovered the cables had already corroded inside the epoxy
coating, and the expoxy coating frayed during stringing. Just do
it over, no problem.
=============


>I heard the fire cladding around the steel structures was 50mm concrete
>can anyone confirm this?  Obviously the fire rating was not sufficient
>to handle the heat from the burning fuel, but would have been more
>than adequate for "normal" fires.
>

One engineer said he assumes the force of the plane crashing probably
destroyed a lot of the fire cladding, and then the heat eventually
melted the steel members..... plus of course, once you recognize this
scenario, you also see there is nothing below for 110 stories to
stop or even slow the first couple of floors dropping.

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2001\09\13@013453 by Dan Michaels

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Charles Anderson wrote:
.......
>They interviewed demolition experts that said that there is a tremendous
>amount of potential energy in a build like that, and once the release of
>energy starts, you can't stop it.  They said that is basically what they
>do with the imploding of buildings.  Some small charges start the release,
>and the rest just continues.
>

Of course, this is "after" they spend months cutting all of the
cross members that hold the building secure in the first place,
and/or placing the explosives in strategic places which in effect
perform this cross-cutting.

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2001\09\13@013520 by Dan Michaels

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jvpoll wrote:
>    "One would think that adding heavy cross
>     members every 20 floors or so might
>     prevent the entire structure from
>     pancaking like that"
>
>I wonder what the 'load' of oh, say, what? ten
>stories is as it collapses down upon the next
>story ... isn't that **the new load** that
>that the floor space *then* needs to support -
>- the full ten stories that just came down? Not
>to mention the inertial effects that the mass
>of ten stories has gained in ten feet (or more)
>of distance ...
>
>As it was, I am assuming that the vertical support
>steel structural members (both external, along
>the external walls and internal) *failed* on
>one story initially -
>

This ????
+----------------+
|                |
|                |
|     +----+     |
|     |    |     |
|     |    |     |
|     +----+     |
|                |
|                |
+----------------+

or this ????
+-----+----+-----+
| \   |    |   / |
|   \ |    | /   |
+-----+----+-----+
|     |    |     |
|     |    |     |
+-----+----+-----+
|   / |    | \   |
| /   |    |   \ |
+-----+----+-----+

Which is gonna do better? Which is more likely to
have the broken part crash "outwards", sparing
the floors below? Which is more likely to come down
110 stories like an elevator down an empty shaft?

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2001\09\13@124143 by Dan Michaels

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Jinx wrote:

>In an excellent TV series called "Why Buildings Fall Down" it
>was shown how the failure of one bolt can be the undoing of
>a whole building. Once the loading becomes unbalanced then
>that's it for the structure. Each floor is design to support its
>own weight and share some load of the one above, but not
>when it's falling down. As the WTC was built around corner
>beams and not a robust internal lattice, once the planes took
>out one of those corner ribs it was inevitable.
.............
>By contrast the Empire State Building is constructed very
>solidly and could sustain severe damage without collapsing,
>as evidenced by the plane that hit it in the 40's
.............


Compare WTC construction to the Empire State Bldg:

WTC:
".... Each tower is 208 x 208 ft with a column-free interior between
the outer walls and the 79-ft x 139-ft core ..."

http://www.enr.com/new/A0816.asp
http://news.bbc.co.uk/low/english/world/americas/newsid_1540000/1540044.stm

Empire:
http://www.nypl.org/research/chss/spe/art/photo/hinex/empire/interior.html

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2001\09\13@130321 by Jim

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How structurally sound is an egg carton?
Does it fulfill it's function?


> >As the WTC was built around corner
> >beams and not a robust internal lattice,
> >once the planes took out one of those
> >corner ribs it was inevitable.
> .............

A naive view that completely overlooks the effects
of the fire which serves to weaken the structural
steel with time ...

I don't think that 'corner rib thing' is anywheres
near being accurate either - someone is just
'throwing stuff out there' IMNSHO.

Jim



{Original Message removed}

2001\09\13@153555 by Dan Michaels

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Hopefully, you at least took the time to look at the
links shown below.


jvpoll wrote:
{Quote hidden}

>{Original Message removed}

2001\09\13@190427 by M. Adam Davis

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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:

{Quote hidden}

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2001\09\13@192537 by Jim

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----- Original Message -----
From: "Dan Michaels" <EraseMEoricomspamUSWEST.NET>
To: <RemoveMEPICLISTEraseMEspamEraseMEMITVMA.MIT.EDU>
Sent: Thursday, September 13, 2001 2:35 PM
Subject: Re: [OT]: Structural Collapse - Engineering Debacle ???


> Hopefully, you at least took the time to look at the
> links shown below.
>

I studied them intently.

You'll also find I posted the rather lengthy
treatise on:

"TUBULAR SYSTEMS/Vierendeel tube system"

Jim

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2001\09\13@224359 by Dan Michaels

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At 06:20 PM 9/13/01 -0500, you wrote:
>----- Original Message -----
>From: "Dan Michaels" <RemoveMEoricomTakeThisOuTspamspamUSWEST.NET>
>To: <EraseMEPICLISTspamspamspamBeGoneMITVMA.MIT.EDU>
>Sent: Thursday, September 13, 2001 2:35 PM
>Subject: Re: [OT]: Structural Collapse - Engineering Debacle ???
>
>
>> Hopefully, you at least took the time to look at the
>> links shown below.
>>
>
>I studied them intently.
>
>You'll also find I posted the rather lengthy
>treatise on:
>
>"TUBULAR SYSTEMS/Vierendeel tube system"
>


Well then, any comments about WTC versus ESB construction?
[outside of engineering efficiencies].

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2001\09\13@232520 by Dan Michaels

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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:
{Quote hidden}

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2001\09\14@094857 by M. Adam Davis

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I wouldn't be surprised if the empire state building were better able to
stand an airplane of that size, but it wouldn't surprise me if it
collapsed instantly either.

There is truth in the saying that they don't build 'em like they used
to.  The empire state building, IIRC, was built during the depression
when labor and steel were both cheap.  The WTC was built in the 70s.

Chances are the empire state building is more expensive to keep up with
in terms of maintenance, and were it to fall it certianly wouldn't
implode, it would fall over.

I would be interested in knowing how many beams could be bent/broken on
one side of the building before it tipped, though.  I suspect that a
large plane flying right into it would have much the same result as with
the wtc.

But changes will come.  Our architects will now put on their list of
things to design for a heading 'terrorist threats' for any building with
a carrying capacity of 5,000 people or more.  Upgrades will include
better fire exits, better fire repression systems, more redundant fire
repression systems.

Who knows, maybe someone will come up with some innovative solutions
which will eliminate the problems of pumping water at high pressure 110
stories.  This is a big reason we don't have mile high towers yet...

-Adam

Dan Michaels wrote:

{Quote hidden}

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2001\09\14@100527 by D Lloyd

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Hi,

"They" obviously thought that it was, not unlike the Titanic, invunerable
to being destroyed as reports suggest that only one tower was insured. From
what I read, the entire complex was worth 3.3bn but only insured for 1bn.

Also, if they built a building to withstand n aircraft impacts, n+1
aircraft impacts would be sufficient to bring it down. I guess the real
solution is to build them to withstand a value of n that is highly unlikely
to be achieved. However, even n=1 (or n=2 if you count both) was deemed
unlikely before Tuesday.

On a different note, I am quite surprised that there were no anti-aircraft
systems/weapons surrounding the Pentagon. Obviously, it is a very unlikely
target and a massive amount of destruction would result from shooting down
an aircraft over Washington, anyway, but the same likelihood of being
targetted could be said about Air Force 1 while it is over US soil, which
presumably gets fighter escort.

Dan

To: .....PICLISTspam_OUTspamMITVMA.MIT.EDU
cc:
From: "M. Adam Davis" <TakeThisOuTadampic.....spamTakeThisOuTUBASICS.COM>
Subject: Re: [OT]: Structural Collapse - Engineering Debacle ???



I wouldn't be surprised if the empire state building were better able to
stand an airplane of that size, but it wouldn't surprise me if it
collapsed instantly either.

There is truth in the saying that they don't build 'em like they used
to.  The empire state building, IIRC, was built during the depression
when labor and steel were both cheap.  The WTC was built in the 70s.

Chances are the empire state building is more expensive to keep up with
in terms of maintenance, and were it to fall it certianly wouldn't
implode, it would fall over.

I would be interested in knowing how many beams could be bent/broken on
one side of the building before it tipped, though.  I suspect that a
large plane flying right into it would have much the same result as with
the wtc.

But changes will come.  Our architects will now put on their list of
things to design for a heading 'terrorist threats' for any building with
a carrying capacity of 5,000 people or more.  Upgrades will include
better fire exits, better fire repression systems, more redundant fire
repression systems.

Who knows, maybe someone will come up with some innovative solutions
which will eliminate the problems of pumping water at high pressure 110
stories.  This is a big reason we don't have mile high towers yet...

-Adam

Dan Michaels wrote:

{Quote hidden}

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
{Quote hidden}

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2001\09\14@101641 by myke predko

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M. Adam Davis wrote:
> I wouldn't be surprised if the empire state building were better able to
> stand an airplane of that size, but it wouldn't surprise me if it
> collapsed instantly either.

Just as an interesting bit of trivia, the Empire State building has been hit
by an airplane.  In 1945, a B-25 "Mitchell" bomber hit the building while
turning on final after doing some sight seeing of Manhattan.

I believe about a dozen people were killed.  There was no significant fire
and the aircraft wasn't armed.  The accident resulted in a change to the
approaches to the airport (sorry I can't remember which one - I think it was
in New Jersey).


As for the WTC taking the hit, it seemed to be able to take it without any
problem.  The news reports are indicating that the problem was with the
steel softening after being exposed to high heat for an hour.  On this
basis, I doubt the Empire State Building would fair much better.

myke

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2001\09\14@110016 by Alice Campbell

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>
> Who knows, maybe someone will come up with some innovative solutions
> which will eliminate the problems of pumping water at high pressure 110
> stories.  This is a big reason we don't have mile high towers yet...
>

Well, that's not the main reason skyscrapers top out.  The main reason is the ultimate strength of the rock beneath.

The taller a building is, the more it weighs.  Calculate the weight of the building materials, furnitrure, and occupants in tons per square foot.  Now get a sample of the rock, put it in a sort of a vice and squeeze it till it breaks.  When the load on the rock exceeds the breaking strength of the rock, you have to stop adding layers.

I was once witness to a discussion in the coffee room at a former employer where the vice-president, a foundation engineer who had designed foundations for nearly all the high-rises in downtown Los Angeles, was shouting, "because the Puente Shale will only carry 80 stories, that's why."

The WTC was where it was because of the Manhattan Schist, which is a metamorphic rock that is very strong.  It stopped at 110 stories because that is where the weight of the building was pushing the strength of the rock.

Alice
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2001\09\14@122809 by goflo

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Hi Myke -

My mother was a few blocks away when that happened, re-
members it vividly.
Casualties likely would have been worse if the building
had been fully occupied, but it was a day off for many.
Anyway, B-25s displace 15 tons fully loaded - This one
was possibly 12 tons (no munitions, low on fuel) about
5% of a fully loaded 767.

regards, Jack

myke predko wrote:

> Just as an interesting bit of trivia, the Empire State building has been hit
> by an airplane.  In 1945, a B-25 "Mitchell" bomber hit the building while
> turning on final after doing some sight seeing of Manhattan.

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2001\09\14@124546 by Jim

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----- Original Message -----
From: "Dan Michaels" <spamBeGoneoricom@spam@spamspam_OUTUSWEST.NET>
To: <TakeThisOuTPICLISTspamspamMITVMA.MIT.EDU>
Sent: Thursday, September 13, 2001 9:43 PM
Subject: Re: [OT]: Structural Collapse - Engineering Debacle ???


{Quote hidden}

This is like comparing a Collins R390 to a Kenwood R200.
Each built at the time using materials and techniques
that were state-of-the-art at the time, yet one far
surpasses the other in terms of usability the performance
of her structure in terms of strength per pound ... and
each will also exhibit it's own unique mode-of-failure when stressed.

Jim

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2001\09\14@124555 by Jim

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What's the relative cost? Will the extra
material balloon the costs?

What about labor the labor/time, cumulative
for 110 stories worth -

- or was this for just to locations/floors,
as proposed earlier - which I don't think
that's practical to stop a series of floors cascading/pancaking down on each
other?

Does the extra material *really* contribute
anything except when *deep* into a failure
scenario?

The original design (as freely quoted here)
called for 2 hours worth of fire exposure/duration -
giving enough time to evacuate - should the specs
be rewritten to now mandate that the building
*NOT* collaspse due to fire - in light of all
the collateral damage that occurred?

Will the extra material contribute excessively
to weight?

Jim



{Original Message removed}

2001\09\14@124635 by Jim

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   "The terrorists appear to have done
    their homework in this regard,
    knowing that a 737/767 would be
    enough to take the buildings down."


Plowing a plane capable of carrying over 30 tons
(11,490 U.S. gallon) tons of jet fuel required
engineering skills? (The smaller 757 only carries
over 30 tons - the 767 carries more.)

The design and planning of these structures
*actually* requires just enough material and
technology to make it stand for the conditions
which it is designed ... and no more!

Simply knowing the fire withstanding capability
of a tall structure coupled with the knowledge
of what it was designed for in the way of an
aircraft hit was all that was required - exceed
that and the 'limits' of 2 hour fire endurance
is shortened - perhaps considerably - as it seems
to have been with the south tower - where it only
held for 55 minutes.


Jim


{Original Message removed}

2001\09\14@133911 by Dan Michaels

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Adam Davis wrote:
>I wouldn't be surprised if the empire state building were better able to
>stand an airplane of that size, but it wouldn't surprise me if it
>collapsed instantly either.
>
>There is truth in the saying that they don't build 'em like they used
>to.  The empire state building, IIRC, was built during the depression
>when labor and steel were both cheap.  The WTC was built in the 70s.
>
>Chances are the empire state building is more expensive to keep up with
>in terms of maintenance, and were it to fall it certianly wouldn't
>implode, it would fall over.
........
>


Finally - this, of course, was my point. With WTC construction,
once the upper floors were breached, the entire structure came down
like an elevator falling down an empty shaft. Cascading effect,
nothing to stop it. "This" form of failure could not occur with
the ESB.

Not sure what it might take to destroy the ESB, but my guess is
a plane flying into the upper stories would not bring it down
- as it might when hitting low on the structure. There is just
too much internal support. It might fall over, it might not,
but it certainly would not pancake in an avalanche in 8 seconds.

Hopefully, in the near future, some architects and engineers
will actually have the balls to come forward, and address
these issues. Likely not many, however, as peer pressure will
probably silence most of their voices. [eg, ever try to get a
doctor to criticize another doctor?]

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2001\09\14@133922 by Dan Michaels

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Dan Lloyd wrote:
........
>On a different note, I am quite surprised that there were no anti-aircraft
>systems/weapons surrounding the Pentagon.


It's so close to National Airport, someone could kamikaze
into it 10 seconds after takeoff.

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2001\09\14@135831 by Dan Michaels

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Good - hopefully, these issues will all be reviewed in
public forum in coming months.

However, the ESB might fail, it certainly wouldn't
pancake 102 floors straight down in 8 seconds.



At 01:03 AM 9/13/01 -0500, you wrote:
{Quote hidden}

>{Original Message removed}

2001\09\14@140313 by goflo

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Alice Campbell wrote:

> Well, that's not the main reason skyscrapers top out.  The main reason is the ultimate strength of the rock beneath...

It's possible to construct buildings which "float" in
the surrounding geology, rather than rest upon it.
Not thought practical on the scale we're discussing.

regards, Jack

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2001\09\14@140521 by M. Adam Davis

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You're right.  It would fall over, causing other buildings to fall over,
and squishing those people who are trying to escape the area.

Personally, I doubt that many more people inside would live in one
scenariou or the other, but we can state that people outside the
building of the WTC were arguably safer with the implosion than had it
fallen over.

How tall is 110 stories?  What direction would it have to fall to hit
the highest number of buildings?  How many blocks away would the antenna
tower fall?

-Adam

Dan Michaels wrote:

{Quote hidden}

>>{Original Message removed}

2001\09\14@151029 by Jim

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----- Original Message -----
From: "Alice Campbell" <@spam@electrifriedRemoveMEspamEraseMEGEOLOGIST.COM>
To: <EraseMEPICLISTspam@spam@MITVMA.MIT.EDU>
Sent: Friday, September 14, 2001 9:59 AM
Subject: Re: [OT]: Structural Collapse - Engineering Debacle ???


> >
> > Who knows, maybe someone will come up with some innovative solutions
> > which will eliminate the problems of pumping water at high pressure 110
> > stories.  This is a big reason we don't have mile high towers yet...
> >
>
> Well, that's not the main reason skyscrapers top out.  The main reason is
the ultimate strength of the rock beneath.
>
> The taller a building is, the more it weighs.  Calculate the weight of
> the building materials, furnitrure, and occupants in tons per square
> foot.  Now get a sample of the rock, put it in a sort of a vice and
> squeeze it till it breaks.  When the load on the rock exceeds the
> breaking strength of the rock, you have to stop adding layers.


In my limited research on the WTC towers - I ran across
an article where a single 135 story building had been
considered at one point - instead they went with the
two that they did. According to the same piece (I think)
they said that the bedrock in Manhattan was "easily
accessable" (it does vary in depth from 'downtown' to
'midtown' however) and very old - provding an ideal
foundation for 'skyscrapers'.

Jim


>
> I was once witness to a discussion in the coffee room at a former employer
where the vice-president, a foundation engineer who had designed foundations
for nearly all the high-rises in downtown Los Angeles, was shouting,
"because the Puente Shale will only carry 80 stories, that's why."
>
> The WTC was where it was because of the Manhattan Schist, which is a
metamorphic rock that is very strong.  It stopped at 110 stories because
that is where the weight of the building was pushing the strength of the
rock.
>
> Alice
> --
>
>

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2001\09\14@153346 by Kev

picon face
Remeber the airplane striking the 14th St Bridge in DC on take off?  The
Pentagon is virtually on the other side of that bridge.

Local (DC) radio had a statment from a local "offical" that we cann't
consider closing Regan National Airport since 10,000 people are employeed
there.

Personally I think we should consider closing it or exchange Regan National
for Bowling Air Force base.  I belive Congressional workers consider Regan
National to be very "handy", maybe they will rethink this.

Kev


> >On a different note, I am quite surprised that there were no
anti-aircraft
> >systems/weapons surrounding the Pentagon.
>
>
> It's so close to National Airport, someone could kamikaze
> into it 10 seconds after takeoff.

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2001\09\14@153602 by Chris Carr

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I have been following this thread with interest.
Thank you all who have contributed for your reasoned and
thoughtful submissions. This has been the one thing
that has stopped me from switching off OT.

Right, that's buttered you all up 8-)
I have a question. Does it really make economic sense to
go so high pushing all engineering disiplines to the limits
or does personal/corporate/city/state ego also come into the
equation to justify building the structure ?

Either way, in the light of recent events, I would think that
risk assesments on skyscrapers worldwide are now been revised
particularly by the Insurers and the revised insurance costs
could make some of these buildings no longer viable.

As a personal aside, I have been up a couple of these buildings
in the USA and Canary Whafe in the UK and quiet frankly they scare
Willies out of me. (Hell, even the Post Office Tower in London did that)
yet I felt safe at the bottom of a South African Gold Mine.
There is obviously something wrong with the way my brain is
constructed.

Regards

Chris Carr

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2001\09\14@154013 by Sean H. Breheny

face picon face
I find it interesting that Reagan National wasn't even the point of origin
for the plane that hit the Pentagon, was it? I think it was Dulles.

Sean

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2001\09\14@172237 by M. Adam Davis

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The realestate in packed cities is so expensive, it makes a lot of sense.

An office on the 90th floor of a skyscraper leases for as much as an
office in the third story of a five story building.  Maybe even more,
for those who value a nice view.

Ego is also a great deal, though.

It'll be interesting to see what they do with that spot.  Lots of people
want a memorial, others will settle for a memorial and building, and
another group wants an even larger building thumbing our noses at the
attackers.

-Adam

Chris Carr wrote:

{Quote hidden}

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2001\09\14@185724 by goflo

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M. Adam Davis wrote:

> It'll be interesting to see what they do with that spot.  Lots of people
> want a memorial, others will settle for a memorial and building, and
> another group wants an even larger building thumbing our noses at the
> attackers.

I vote for #3, although I had a different gesture in mind.

regards, Jack

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2001\09\14@211745 by Dale Botkin

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On Fri, 14 Sep 2001, Dan Michaels wrote:

> Finally - this, of course, was my point. With WTC construction,
> once the upper floors were breached, the entire structure came down
> like an elevator falling down an empty shaft. Cascading effect,
> nothing to stop it. "This" form of failure could not occur with
> the ESB.

With something like the WTC or ESB, a tall building in a densely populated
area, I think I would specifically design the structure to ensure that it
would *NOT* topple.  An imploding building will kill everyone in it, a
toppling one could kill everyone in several other buildings as well.  I'd
probably want to build for X hours of resistance to any given catastrophe,
then a controlled implosion like the two WTC towers did.  Imagine how many
lives were saved when they collapsed!  Sounds counter-intuitive, I know,
but better two holes full of rubble than several square blocks of carnage.
If you can't make it withstand everything short of a nuke, at least go for
a controlled, least-damage failure mode with a pretty well known survival
time.  It's just too bad not enough people realized the towers were going
to do that.

Dale
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2001\09\14@215535 by Dan Michaels

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Peter Peres wrote:
>
>> However, the ESB might fail, it certainly wouldn't
>> pancake 102 floors straight down in 8 seconds.
>
>Yes, maybe it would topple whole and crush 10-20 buildings on the way.
>Sinister as it may sound, the fact that the WTCs pancaked like they did
>was probably a feature. Do you realize how far the destruction would have
>reached, if they had not ? Besides probably killing everyone dead inside
>anyway, and spreading the burning kerosine nice and even over 3 blocks.
>These pancake collapses are a rather good idea in a densely populated area
>imho.
.................


Peter, this is the essence of my conjecture in starting this thread.
I repeat conjecture - just wondering about the basic philosophy of
these designs. In my heart, I believe the guys who designed the WTC
are having nightmares after watching that collapse.

Re the WTC, in coming down, it did destroy/severely damage another
8-10 buildings as it is. Maybe if the ESB were hit near gnd level
it would topple, but I'm not so sure if hit at the top. If you missed
the link from the other day, take a look again at the internal
structure:

http://www.nypl.org/research/chss/spe/art/photo/hinex/empire/interior.html

In comparison, between the inner and outer tubes of the WTC was
only concrete [reinforced no doubt], 110 floors worth.

Hopefully, someone who knows these things will surface one of these
days and compare construction techniques - but I fear the powers that
be don't want the public at large to think about this sort of thing.

Also today's horrific factoid -

they now estimate that only 10,000-20,000 people were in the WTC
when the planes hit. "Most" of the 50,000 who work there were not
yet at work. About 4700 are known missing. Do the math, vis-a-vis
evacuation.

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2001\09\17@041037 by Jim

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----- Original Message -----
From: "Dan Michaels" <@spam@oricomspam_OUTspam.....USWEST.NET>
To: <spamBeGonePICLISTEraseMEspamMITVMA.MIT.EDU>
Sent: Friday, September 14, 2001 12:58 PM
Subject: Re: [OT]: Structural Collapse - Engineering Debacle ???


> Good - hopefully, these issues will all be reviewed in
> public forum in coming months.
>
> However, the ESB might fail, it certainly wouldn't
> pancake 102 floors straight down in 8 seconds.

... after withstanding a 11,000 gallon (assuming a fully
fueled 757, a 767 is over twice that amount) jet-fuel fire
in it's *mid-section* (HALF the building weight?) for 55
minutes ...

Tell me what spec you would like to see here?

Perhaps *twice* the amount of fire-proof cladding should be
applied to the structural steel from, say the half-way (or higher)
point down?

Perhaps new materials and a staggered application should be now
considered?

Jim

{Quote hidden}

each
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2001\09\17@114443 by Dan Michaels

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jvpoll wrote:
........
>> Good - hopefully, these issues will all be reviewed in
>> public forum in coming months.
>>
>> However, the ESB might fail, it certainly wouldn't
>> pancake 102 floors straight down in 8 seconds.
>
>... after withstanding a 11,000 gallon (assuming a fully
>fueled 757, a 767 is over twice that amount) jet-fuel fire
>in it's *mid-section* (HALF the building weight?) for 55
>minutes ...
>
>Tell me what spec you would like to see here?
.............
>


Hopefully, engineers and architects who are involved in the
construction of large buildings will come together and review
their design practices in the near future. I am sure that the
failure mode we all witnessed is giving them nitemares about
now.

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2001\09\17@234807 by mark

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Saw on TV that each tower had a 600 ton counterweight on the top.

When those weights were released due to structural failure, only

ground stopped them.


On 12 Sep 2001, at 22:35, Charles Anderson wrote:


<color><param>0000,0000,FF00</param>> They interviewed the architect last night.  He said the towers were never

{Quote hidden}

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2001\09\18@032030 by Jinx

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 Saw on TV that each tower had a 600 ton counterweight on the top.
 When those weights were released due to structural failure, only
 ground stopped them.

 And probably lift gear and aircon tanks too

 Sad that no survivors were found even way down in the subway. I thought
that
 someone may have survived that far down down, perhaps with access to food
 from concessionaries or whatever they have in subways

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2001\09\18@110443 by Jim

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  "And probably lift gear and aircon
   tanks too"

The weight of the 'lifts' was borne by a central
structure - the "inner tube" some would call it -
which was (apparently) reinforced concrete ... all
elevators (lifts) and stairs were also located in
this inner structure ... which also (apparently
again) supported each floor's weight near each floor's
center.

The outer 'Vierendeel tube system' or 'Vierendeel Truss'
structure then bore the weight of each floor's outer
perimeter and provided the entire structure's rigidity.

It will be interesting to read the post mortem analysis
by such groups as the American Society of Civil Engineers
in publications such as  "The Journal of Performance
of Constructed Facilities". It was most enlightening
reading their analysis of the structure failure of the
Murrah Building from the blast in Oklahoma City.

Jim


{Original Message removed}

2001\09\19@044904 by Peter L. Peres

picon face
> Perhaps new materials and a staggered application should be now
> considered?

Back to the future!!! Build pyramids! Pyramids do not collapse either way.
You need to wait 5000 years for the top to be abraded by the weather.

Peter

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2001\09\19@071034 by Russell McMahon

picon face
> > Perhaps new materials and a staggered application should be now
> > considered?
>
> Back to the future!!! Build pyramids! Pyramids do not collapse either way.
> You need to wait 5000 years for the top to be abraded by the weather.


Yes - pyramids really rock (groan) but the packing density of the occupants
is a bit low for modern applications - a dead loss in fact.


               RM

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2001\09\19@082628 by D Lloyd

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"Yes - pyramids really rock (groan)"

- A beer mat or something similar placed under one corner should stop that
rocking....

[exp(groan)]

Dan


To: PICLISTspam_OUTspam@spam@MITVMA.MIT.EDU
cc:
From: Russell McMahon <spamBeGoneapptech@spam@spamCLEAR.NET.NZ>
Subject: Re: [OT]: Structural Collapse - Engineering Debacle ???



> > Perhaps new materials and a staggered application should be now
> > considered?
>
> Back to the future!!! Build pyramids! Pyramids do not collapse either
way.
> You need to wait 5000 years for the top to be abraded by the weather.


Yes - pyramids really rock (groan) but the packing density of the occupants
is a bit low for modern applications - a dead loss in fact.


               RM

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2001\09\20@154421 by Peter L. Peres

picon face
> >> Perhaps new materials and a staggered application should be now
> >> considered?
>
> >Back to the future!!! Build pyramids! Pyramids do not collapse either
> >way. You need to wait 5000 years for the top to be abraded by the
> >weather.
>
> Yes - pyramids really rock (groan) but the packing density of the
> occupants
> is a bit low for modern applications - a dead loss in fact.

Apparently the people who built that hotel in Las Vegas (?) didn't know
this. Anyway a pyramid wastes a lot of ground space. Maybe the sides could
be plated with solar collectors to put them to good use. Two adjacent
sides ? What's the orientation of those pyramids in Egypt again ?

Peter

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2001\09\20@191912 by Russell McMahon

picon face
> > >> Perhaps new materials and a staggered application should be now
> > >> considered?
> >
> > >Back to the future!!! Build pyramids! Pyramids do not collapse either
> > >way. You need to wait 5000 years for the top to be abraded by the
> > >weather.
> >
> > Yes - pyramids really rock (groan) but the packing density of the
> > occupants
> > is a bit low for modern applications - a dead loss in fact.
>
> Apparently the people who built that hotel in Las Vegas (?) didn't know
> this. Anyway a pyramid wastes a lot of ground space. Maybe the sides could
> be plated with solar collectors to put them to good use. Two adjacent
> sides ? What's the orientation of those pyramids in Egypt again ?


Apparently to be REALLY effective pyramids need to be built at the centre of
gravity of the visible land masses (as viewed from space) as the Great
Pyramid, apparently, is. As there is only one such spot per hemisphere and
the great Pyramid has already taken one you best hurry :-). (And I have no
idea where the apparent cofg of the Southern hemisphere land masses is but
odds on it's in water.)



       RM

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2001\09\20@204626 by Sean H. Breheny

face picon face
Hi Russell,

Huh? Are you joking? What do you mean by "really effective"?!

Sean

At 10:43 AM 9/21/01 +1200, you wrote:

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2001\09\21@024854 by Russell McMahon

picon face
> Hi Russell,
> Huh? Are you joking? What do you mean by "really effective"?!

Yes, I was joking, but the statement was based on what has been stated by
some to be fact but which I have not checked the basis of for myself.
REPORTEDLY - if you view the world's land masses from space then the Great
Pyramid at ?Giza is at the centrre of gravity.
This strikes me as a somewhat specious claim as, depending on your point of
reference when projecting your map you could find many points which would be
the c of g of the resultant flat map. I imagine that by appropriate choice
you could arrive at the Great Pyramid as the c of g  - But it was a good
start for a spurious comment. The pyramid concerned was enough only for 1
occupant in the penthouse but I understand there were a number of lesser
unfortunates in the lowe levels.


       Russell


> >Apparently to be REALLY effective pyramids need to be built at the centre
of
> >gravity of the visible land masses (as viewed from space) as the Great
> >Pyramid, apparently, is. As there is only one such spot per hemisphere
and
> >the great Pyramid has already taken one you best hurry :-). (And I have
no
> >idea where the apparent cofg of the Southern hemisphere land masses is
but
> >odds on it's in water.)
> >
> >
> >
> >         RM

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