analysis of the WTC building collapse

I didn't know there was a forum here for September 11. Since I saw it yesterday for the first time, I have been surprised at the lack of links to reputable sources of info. Here is one I found that is worth posting:

http://www.tms.org/pubs/journals/JOM/0112/Eagar/Eagar-0112.html

Show me steel from WTC 1 or 2 that shows fire damage? Show me steel that has melted and bent due to fire. Show me the trusses that failed. Good luck finding them.

BTW: There is a lot of good info down here, you just have to shift through the distractors and thread hijackers. It might be nice of you to get to know some of us before you pass judgement about the quality of the information presented.

The fire is the most misunderstood part of the WTC collapse. Even today, the media report (and many scientists believe) that the steel melted. It is argued that the jet fuel burns very hot, especially with so much fuel present. This is not true.
...

that steel will fail at much lower temperatures then is commonly accepted. However, the steel still had to fail at some point, whether it was at 500 degrees or 2000 degrees. There would still have to be fire damaged steel. Where is it? Did the author have access to the steel to test it?

holding the joists that was the weakest point and therefore failed first. Also that the structure was designed to withstand 3 hours of a common fire scenario, but not when the fire was initiated in such a rapid way over many floors at once.

Once a floor failed the falling weight of the floors above initiated the total collapse.

This is a very plausible explanation to me.

:hi:

I too found the Eagar zipper/pancake theory quite plausible when I read about it in
Why Buildings Fall Down.

Apparently a lot of engineers found it plausible too--it stood as the conventional
wisdom on the subject for three years, and was adopted by FEMA's $600,000 study of
the towers' collapses.

One suspects that Dr. Eagar's hypothesis of weak truss "clips" was developed without
the benefit of access to the blueprints, though. NIST,s $20 million study would
now have us believe that these "clips" were so freaking strong that saggy heat-weakened
floors pulled the perimeter columns inward, buckling them.

Unfortunately, since the steel was so hastily destroyed and photographs at the site
were prohibited, it would appear that NIST can not produce these buckled columns or
any photographs of them. NIST also can not produce any core steel samples showing
heating above 250 degrees Centigrade.

you would have had a bigger debris pile. Every floor was separated by steel pans filed with concrete. Steel doesn't pulverize like concrete can. Neither do people and the content of buildings. I have looked at 100's of pictures of the debris pile. I have see very little in it except for dust and neatly cut sections of steel. Everything else is gone. The people, the desks, the computers, the toilet bowls, everything else is gone. That's not pancaking.

really.

You know - the seventy feet depth that was excavated to get to bedrock. An awful lot of the building ended up compressed in the underground levels.

debunk anything?

In addition to the welded joint at the top, was another connection at the bottom with two bolts. In addition to that steel straps were embedded in the concrete. That should debunk the idea that all the trusses were held together by two little bolts and that these bolts failed causing the total collapse of two towers. According to the Structural Engineers Association of New York the trusses did not contribute to the collapse of the buildings.

accepting that it wasn't the clips. The engineers clearly have their work cut out for them to reconstruct what damage was done by the planes, and how the remaining structure was affected. (That doesn't mean there was a bomb).

since most of the evidence has been destroyed and the 'crime' scene was trashed.

Anyone can come up with a theory and prove and that is all the NIST report is. They refuse to look at any other alternative other then the official story and then they worked from there. If you start out with a flawed premise, then your results are going to be flawed. Also, they deliberately avoid evidence that explosives may have been used. It's hard to prove explosives were used if you refuse to even consider it.

Unfortunately, at this point the rest of the world is left with scrapes and pieces of evidence to try to figure out what happened, at least those of us who care about finding out what really happened. Skyscapers don't just turn to dust and piles of steel, not even if planes fly into them.

is that the visual recorded images of the collapse more than justifies connecting it directly to the airplane crashes and discounts explosives. Why do you not want to listen to actual experts? Do you think they were paid off? Or their families are under death threats?

Have you not read about how buildings such as these destroy themselves once a collapse begins. Whether it begins from explosives or massive structural damage from a jumbo jet, there is little difference.

the results would have looked the same?

sure.

I couldn't agree if you say the bombs effects would be invisible and inaudible at detonation.

that recorded distinctive booms before each tower collapsed.

http://video.google.com/videoplay?docid=-3498980438587461603&q=911+eyewitness

were not right before the collapse, something was exploding probably related to the fire or the planes. If it was controlled demolition the building would have been going down immediately.

don't ya?

You seem to be a OCT devotee? Do you really believe that a jet can take down a 110 story tall steel skyscaper? If jets can just cut through steel columns, then why are we using DU in Iraq? Why do we need bunker busters? Why don't we just fly old jets into targets?

You don't know much about the technology behind armored defenses do you?

As for what a jet plane can do to steel columns there are both pictures and computer simulations that show the answer is plenty given enough speed and mass of the flying object.

if it was a welded connection or a bolted connection. Both design methods are suitable and one is not necessarily stronger or better than another.

You said it, not me. LOL

but failed to address my point.

but are more expensive and time-consuming (of course it depends on the actual dimensions, but I'm generalizing).

The Citicorp Tower case is a good example of the trade-offs made between the two methods (see article below).

William LeMessurier:The Fifty-Nine-Story Crisis: A Lesson in Professional Behavior

Who are you to commit such slander - a government plant?

Please take your ridiculous claims back to some other more gullible forum - we understand fizziks here.

... if welds can't fail, why did they even use pre-made columns, beams, and trusses to build the Twin Towers? Why not just fabricate the whole building on-site by using welding rods to weld the necessary structural elements? If the buildings structure is nothing but welds and welds do not fail, the building will never fail!

:) Make7

has been shut down by the drywall-steel-concrete industry. Another example of the failure of corporate America - WE AMERICANS DEMAND THE TRUTH!

The only thing better than "all-weld" would be a soylent building...


It's made of people!

SHC = Spontaneous human combustion.

I fear that soylent buildings would be bursting into flames at random on an all too frequent basis. Unless there is a genetic marker that can be used to identify the persons that are susceptible to SHC and exclude them from the "manufacturing process". If that is the case then the idea certainly has merit and should be explored further. Soylent buildings could be part of the solution to some of the most difficult problems we face as a species.

- Make7

But perhaps, with a little ingenuity, we can turn this vulnerability to our advantage. With judicious placement of SHC structural elements, removal of old soylent buildings can be simplified if we can figure out how to trigger the SHC mechanism. We can call this new method "controlled demolition". I'm sure it'll sell like hotcakes!

It'll sell like soylent green hotcakes.

Please try to stay on topic.

:) Make7

Mea culpa, mea culpa.

... which has been surpassed in many respects. Perhaps you'd like to read NIST's final report, which you can find here:
http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf

I don't agree with the idea I think you're pushing, but I can't really be bothered to argue about it today. However, I would like to point out that the hijackers were right in the centre of the FBI's counterterrorism coverage.

I only started looking at any of this yesterday in detail. I have never doubted the official story in any great respect. Small details that can't be explained, sure, but the basic story of the attack is pretty sound.

As for your statement regarding the hijackers I can't tell what you are implying.

Also, where do you stand on the question of the building collapse. Was it a result of the airplane impact and fire or not?

The best 9/11 sceptic sites are:
http://911research.wtc7.net/index.html
and
http://www.911review.com/
for explosive demolition

and
http://www.cooperativeresearch.org/project.jsp?project=911_project
for the other stuff - the whole thing is too much, just click on the various chapters to get a feel (OK, I'm biased here).

You might also want to read Steven Jones' paper, which you can find here:
http://www.physics.byu.edu/research/energy/htm7.html

As you point out in your post 9, the insulation is key to NIST's theory. NIST's testing of the insulation can be found here:
http://wtc.nist.gov/NISTNCSTAR1-6A.pdf
It begins on page 263 (p. 315 of the .pdf).

I don't buy and impact and fire collapse, for various reasons, such as the damage caused by the planes was only reduced the gravity load-bearing capacity by about 15% in each building, the planes' fuel tanks were more than half empty, the fuel burned up in the first 10 minutes anyway, the recovered steel doesn't support NIST's simulation results, the Twin Towers were combustibles-lite, etc. Plus, 7 wasn't hit by a plane, so I can't see what stripped its fireproofing.

That the hijackers were "right in the middle of the FBI's counterterrorism coverage" is a quote from the 9/11 Commission's staff director, Eleanor Hill; it was broadcast on an edition of MSNBC's Hardball on 21 July 2004. The full quote is:


By it she means that in the US the hijackers associated with 14 terrorist suspects the FBI investigated before 9/11. I mean that there are more imporant issues than why the WTC collapsed. Also, I'd like to point out that the NSA intercepted some of the hijackers' communications from/to the US.

I will look at some of that, but only as a distraction from my real responsibilities.


A snippet from your response:
"such as the damage caused by the planes was only reduced the gravity load-bearing capacity by about 15% in each building"

How do you know that? Because I think the problem you are overlooking is that no one knows exactly how how much damage was done by the planes, just that it was enough (see a link below for some decent analysis of the physics involved), and then "lets try to understand it as much as possible so we can design better buildings."

The NIST organization doesn't really care about satisfying the concerns of people who really think it was possible to fake the attack in such a way that 110 story buildings collapsed exactly where the planes hit but it wasn't the plane that initiated it. The American people don't want to spend the money to try and convince you when it likely would never be enough, maybe because you would discover that a 3rd cousin of Bush works in the organization that investigated the building collapse.

Before you say, "See their plan worked!" why not spend a little time to come up with a more feasible conspiracy plan for getting us into war with the Middle East, there are some that would qualify I am sure. The attack on the Cole, the embassies that were bombed, and other terrorist attacks on Western interests where any of those faked by our government? Maybe I could sink my teeth into one of those.

The basic problem with the NIST computer modeling effort is that there are too many unknowns and the mathematical models are full of guess work. There simply is no way to model it with the kind of exactness you think they should. Take a look at these calculations I read through yesterday, it seems like an honest and time consuming effort to allay some of the fear mongering someone pervaded on you.

Perhaps you have already read it, I hope not.

http://www.911myths.com/WTCREPORT.pdf

15% is NIST's base case figure (you have to weight the columns a do a couple of calculations, but that's what it will come out to). If you know of a better study than NIST's base case, please link to it. I think it must be about right, give or take a percent or two (actually take a percent or two if you ask me).

You wrote:

Eh? That means that you think NIST's models aren't conclusive, right?

Of course I've read Frank Greening's stuff. With reference to the facts that, for example, he uses double the building's actual weight and, as far as I can tell, pulls the aircraft damage estimate out of his ear, what weight are you suggesting should be placed on it?

I'd also like to point out that the CIA conducted a major operation against 3 of the hijackers in January 2000.

On edit: made the next to the last paragraph more exact.

describe a range of scenarios that depend on the initial damage. I would not say they are proof of the exact collapse sequence in terms of what components failed, only likely sequence based on input to the model that could be less accurate than required. But the question is not whether a bomb was placed on the floor where the airplane collided with the building.

Since you strenuously dispute the weight used by Greening, how about you provide a source for your number?

CIA, hijackers? Can't we stay on one basic issue at a time? We are talking about the building collapse and analysis of that.

... for the weight of one tower. You can find it, for example, on pages 3 and 23 of his paper.

NIST says:


Greening gives the weight of the concrete in one tower as 48,000,000 kg. What on earth does he think accounted for the other 90% of each tower's weight?

You wrote:

That's nice of you. However, you can't support NIST and Greening and Eagar - they all give different explanations. In fact, Greening even called the NIST study "highly inaccurate".

Further, I would like to point out that German intelligence informed the CIA that United 175 hijacker pilot Marwan Al Shehhi was involved in terrorism as early as spring 1999.

Mass of the World Trade Center
http://hypertextbook.com/facts/2004/EricChen.shtml

Both towers were built out of steel frames, glass, and concrete slabs on steel truss joists. A single tower consists of 90,000,000 kg (100,000 tons) of steel, 160,000 cubic meters (212,500 cubic yards) of concrete and 21,800 windows. One single tower has a mass of about 450,000,000 kilograms (500,000 tons). The interior design of the World Trade Center contains 240 vertical steel columns, which were called the Vierendeel trusses. These steel columns maintained the tower's structure and helped to create an extremely "light"building.


----------------------------------------------------
When the Twin Towers Fell
One month after the attack on the World Trade Center, M.I.T. structural engineers offer their take on how and why the towers came down.

by Steven Ashley

http://www.public-action.com/911/jmcm/sciam/

Though the WTC towers stood over 1,360 feet above the street level, the structures' bases were actually set 70 feet into the ground, and one had a 100-foot-tall antenna atop it, so with 205-foot widths, they had a lot of area facing the wind," the engineer stated. He calculated that the approximate maximum wind shear force that a single face needed to withstand to be somewhere around 11,000,000 pounds. The gravity loads (weight) produced by the towers at their bases were on the order of 500,000 tons, Fowler said.

What is the cause of the different explanations. I think its a worthwhile question. After reading the conclusions from I think 4 sources with credentials in engineering, I believe that this type of building failure (resulting from severe damage) is too unusual and complex for there to be complete agreement on factors such as load bearing capability of the remaining structure and the exact role of the fire. So the debate focuses there. Its a technical engineering debate and it does not attempt to argue with people who think explosives were planted by secret agents working for the US government. The terms used and descriptions of how the building reacted may not be the best for lay people to understand. For instance, the sagging floor. I think it would make more sense to lay folks if they better explained why the floors sagged. Did the floor sagging really pull in the outer columns? This is not a good description in my opinion. There were increased forces on the remaining columns and increased forces on the floor trusses, it was a complete system that deformed under the increased loads and as a result of weakening in some areas from heat. There should not be much doubt that the fire did weaken uninsulated steel. It can be shown to happen in small scale tests, or by examining other post fire structures that were completely destroyed and the resulting difficulty of reconstructing events. THere is consensus that the fire would weaken the steel if it burned long enough in the area of unprotected or under protected steel structures.

I am glad you keep pointing out the incompetence of the CIA and the FBI and Bush. THey are certainly not the masterminds or iron hand dictators that it would take to pull off the plots many in this forum are pushing.

... depending on whether its the weight for the upper 110 floors, or for the whole building. What Greening (and Bazant and Zhou) might be doing is taking all the concrete in the basement and saying some of it was on the upper floors. Greening's figure is different to NIST's: they can't both be right. It's been discussed here before and the conclusion was that NIST is right on this one and Greening is wrong.

You wrote:

NIST say they have photograph proof of this; I don't understand what you think is wrong with their photos.

Further, I would like to point out that two of the hijackers actually lived with one of the FBI's counterterrorist informants.

on the weight that is generally agreed to be correct?

250,000 tons for the top 110 floors.

hastily put together, and is now much out of date.

NOVA flogged Dr. Eagar's speculations greatly after 9/11; it appears
they have now removed them from their 9/11 web pages.

The recent NIST study completely reversed Dr. Eagar's findings, and
AFAIK there was never a peep raised from MIT in Eagar's defense.

So while I commend your wish for respectable sources, I'd suggest you
find more up-to-date ones.

I may be behind but I catch up quickly.

I do note however that the comments on the fire temperature seem to have been born out by the NIST conclusions.

The sequence of events in the collapse do appear to be off compared to NIST findings but I would not agree that anything was completely reversed. NIST says the damage to the insulation was key.

specifically that FEMA claimed that weak truss clips unzipped, and the unbraced perimeter
columns then buckled outward. (The obvious problem with this theory is that the truss
clips on the core side were apparently strong enough to pull the core down.)

NIST says the truss clips were so strong that the perimeter columns buckled inward.

the fire temperature seem to have been born out by the NIST conclusions.

NIST has the nasty habit of assuming what it purports to prove. Their reasoning
clearly goes: The towers collapsed totally, therefore initiation of collapse anywhere in
the building necessarily leads to total collapse. Since the structural damage was insufficient
to bring the buildings down, therefore the fires must have gotten hot enough to weaken
the steel.

Their conclusion that this is so is unsupported by any physical evidence. NIST has not
one core steel sample showing heating above 250 degrees C. (And they ignore the FEMA
samples that do show high heating, because these also show unusual sulfidative evaporation
that suggests the use of thermate or explosives.)

I don't see why you must have samples of the steel that reached 500C to conclude that it did happen to some of the exposed (non-insulated) steel. A combination of their small/large scale fire tests the computer modeling, the photographic evidence and the information from studies on other fires would make it quite plain.

Also, I agree with their method of modeling the collapse to fit the photographic information.

As to explosive devices....well you don't want me to go there, do you? I will if you insist.

give us your views as to what caused the "high temperature sulfidation" of the steel. Others here have tried but failed so far. i'd like to hear your reasoning as others also would I presume.
Thanks,
Bill

is required to discredit any demolition explosion theory.

because no one has yet to draw a link between "high temperature sulfidation"
and explosives/thermite. You are basically saying that lacking any other explanation it must be explosives/thermite. That is not the case - you still have to show a direct link between the two. Care to give it a shot?

How can you with a straight face bring up sulfidation again? I'm still waiting for you to explain what it has to do with the collapse of the WTC. Do you have an answer yet?

Are these some of the threads in which others have failed to provide explanations?

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=103556&mesg_id=103556

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=105517&mesg_id=105517

You will also find some references therein:

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=125&topic_id=105517&mesg_id=105561

Regarding both WTC1 and WTC2 NIST claims: "Once the upper building section began to move downward, the weakened structure in the impact and fire zone was not able to absorb the tremendous energy of the falling building section and global collapse ensued."

This does not quite match your paraphrase. Did you have some other part of the report in mind?

http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf
pp. 145-146



Wasn't that conclusion validated in addition by plane impact simulations, global structural response simulations, and fire simulations based on fire dynamics models, validated by laboratory burning tests, voluminous photographic and video records, and first person interviews with 1,200 building occupants and emergency responders?

I thought some might be interested

Stability of the World Trade Center Twin Towers Structural Frame in Multiple Floor Fires

Structural Responses of World Trade Center under Aircraft Attacks