NIST Testing Controversial Theory of WTC Collapse!

[Bolo Boffin]

In an effort to leave no stone unturned, the National Institute of Standards and Technology is examining whether the amount of fireproofing on the WTC structural steel was adequate. This article is actually from February of last year, but I don't recall seeing it around here...

http://www.newscientist.com/news/news.jsp?id=ns99993354

The US National Institute of Standards and Technology will soon be testing a controversial theory about the collapse of the World Trade Center towers.

According to an analysis by a leading fire-safety expert, had the fire-proofing insulation on the towers' steel structures been thicker, the towers would have survived longer and might even have remained standing after they were hit by the hijacked planes. The work is being seized on by lawyers representing victims' families and insurance companies.

If confirmed, it could also lead to changes in building codes. NIST is responsible for drawing up the final report on the towers' collapses and recommending if any changes are needed.

We interrupt this post for another exciting episode of...

Did You Know?

The fireproofing on the burning floors of the south tower was only 19 mm thick. In the north tower, the fireproofing was 38 mm thick.

Now You Know.

The north tower had twice the thickness of fireproofing, and the north tower took twice as long to collapse as the south tower.

From the famous NIST .pdf file, soon to be ignored by a conspiracy theorist near you:

On an interim basis, NIST has determined the following exact times for the major events of September 11, 2001:

• WTC 1 Plane Strike: 8:46:31 a.m.
• WTC 2 Plane Strike: 9:02:59 a.m.
• WTC 2 Collapse Initiation: 9:58:59 a.m.
• WTC 1 Collapse Initiation: 10:28:25 a.m.
• WTC 7 Collapse Initiation: 5:20:52 p.m.

WTC 2 collapsed in 56 minutes. WTC 1 collapsed in 103 minutes.

Twice the fireproofing. Twice the time. You do the math.

[GAspnes]

1. NIST is THE experts on fire effects

I think that was their original charter. My son wants to work there one day, when he's tired of doing the firefighter/civil engineer thing.

[Old and In the Way]

2. That is interesting.

I wonder if Tower 2 was to spec? Might be a real nasty civil suit there. If the insulation had been to the same spec, I wonder how many more people would be alive?

[Bolo Boffin]

3. Port Authority was exempt from code, apparently.

The article talks about this and about a plan to increase fireproofing in the buildings - which could only occur as floors became vacant.

There's definitely some kind of "real nasty civil suit" shaping up. Everything coming out of NIST right now seems to have a disclaimer about not using the material in court cases.

On whether more people would be alive, there's no doubt of that. If I'm correct about the direct corelation between fireproofing thickness and time between impact and collapse, then the North Tower would have fallen first.

This would have given the emergency response to the attack 30 more minutes to organize and evacuate the buildings. There's no counting how many would be alive today if the police and fire department had had 30 more uninterrupted minutes.

[Lavachequirit]

4. Herring fillets (make mine light red)

As one of the architects in the NOVA documentary remarks, without the spray-on insulation on the trusses the building would have no "fire rating." But that is a completely different question than to ask if, in these particular fires, with or without fireproofing, there was enough fuel and oxygen for a long enough time to raise a major part of the structure to a high enough temperature to soften steel. Given the limited supply of reasonable fuels in a modern office - chairs, carpets, drapes, the occasional pile of paper - and the poor air supply with oxygen mostly available at the outer walls, it's very hard to imagine that much of the structure could be heated to the >950°C temperature needed to even begin to soften the metal.

This problem becomes even worse in the north tower collapse, which had been smoldering along for about 100 minutes. Most of the fuel for the fires (the jet fuel of course burned off in the first few minutes, as per FEMA) had already burned off, and black smoke indicates an inefficient, oxygen-poor fire. You can't have it both ways: if it's a raging inferno it will consume its limited fuel quickly. If it's a smoldering, slow burning office fire as the firefighters described on the 78th floor of WTC-2, it won't reach the temperatures needed to soften steel. And in the WTC-1 collapse the antenna on the roof, directly over the core, was the first thing to begin to fall. No floor trusses to blame here, somehow we are asked to believe that the entire core at roof level gets so hot that it loses all strength and drops straight down, and despite the almost complete lack of fuel within the core itself.

[LARED]

6. Different Questions

But that is a completely different question than to ask if, in these particular fires, with or without fireproofing, there was enough fuel and oxygen for a long enough time to raise a major part of the structure to a high enough temperature to soften steel.

Since jumbo jets don't crash into high rise building on a regular basis, why bother installing fireproofing at all if there is no fuel that could cause a structural problem?


it's very hard to imagine that much of the structure could be heated to the >950°C temperature needed to even begin to soften the metal.

At what temperature does steel lose ---say 50% -- of its strength? Also, exactly how do you define soften?

[DeadBroke]

9. Heat and steel

Winter months, like those we're now experiencing in NYC, are a terrible time for ironworkers. There's that cold, damp, windy weather that will sometimes shut down a job - yuck! But, on the bright side it's also the time of year when the structural steel framing members of a building, unless it's very bady fabricated, will usually fit up and go together nicely.

It's the summer weather; when steel expands, when beams elongate and when steel twists and gives that makes headaches. That hazy, hot and humid weather of the dog days of summer will give an ironworker fits. The steel, just from exposure to heat of the prolonged sunlight can, just during lunch, often go from straight as an arrow to wavey and twisted.

That summer weather, sometimes just 50 or 60 degrees higher than winter, makes a big difference in how steel behaves and how an ironworker will tackle fit and finish problems.

Fit and finish of steel framing members is just as important to the structural integrity of a building as is the fireproofing. During the construction phase of a structural steel framed building ironworkers give a tremendous amount of attention to "plumbing and racking" the columns - making sure they are, vertically speaking perfectly straight.

Long before all the connecting bolts are tightened to the specified torque, long before the welding crews can run their passes, and weeks before fireproofing can be applied, a "bull gang" will string cables and turnbuckles from the top of one column to the base of the one next to it forming Xs.

The turnbuckles are twisted and tightened until the columns are straight - plumbed and racked. Backbreaking dirty work, (especially in summer heat with wavy steel that would rather twist than move) but crucial to the structural integrity of the building. Any deviations in the columns from floor to floor upsets the load bearing capacities of the structure. Inspectors will reject and mark columns that are off by as little as one-eigth of an inch. It's not a "make work" situation to prolong the job, it's a critical issue; all columns, in order to perform properly and carry their weight must be plumb.

Plumbing and racking those stiff brittle columns in winter - easy. Plumbing and racking those wavy twisty columns in summer - rough.

Heat and steel, if the 50 to 60 degree difference between summer and winter is a factor to steel a few hundred degrees from fires should matter.

[Bolo Boffin]

11. Thank you for this, DeadBroke

Who knew that prolonged exposure to sunlight could deform a piece of structural steel? You did, and you told us.

Now we know. :-)

[DeadBroke]

13. For boloboffin: true story about fire

Back in 1980-81 I was a super for a structural steel erector that was awarded a contract for the granite, aluminum and glass curtain wall on a 54 story building on Madison Avenue near 53rd Street. I had two shanties on the third floor; one served as my office and tool room, and the other was for the crew.

In between my shanties the general contractor placed a hoist motor, a diesel powered winch, that was used for raising and lowering the always busy temporary outside freight elevator. The cable from the winch of the hoist motor runs to the outside of the building and then via blocks, or pulleys if you will, run up through temporary pipe scaffolding that serves as an elevator shaft. The cable is painted with hash marks so that the engineer, in this case a hard of hearing man named Lenny, can see what floor the elevator is on. A "bell ringer" travels up and down with the freight car and communicates via portable radios, but also signals the engineer, Lenny by pulling on a rope which sounds a bell. One bell stop, etc. (I used to hear bells in my sleep).

The hoist motor is held in position with long u-bolts. The bolts go through holes in the concrete floor and decking and lock around a steel beam below. There are also cables installed from the hoist motor to nearby columns. Without the u-bolts and cables the hoist motor would slide and drag across the floor whenever the winch was engaged.

Lenny was, even on the most mild winter days always cold and kept a fire burning nearby, in an old 55 gallon drum. Every morning he lit up old pallets, crates, and broken planks and kept that fire going all day long, usually making the drum glow. After a few days all the fireproofing on the beam and decking directly above his fire dried out, and due to the vibrations of the hoist motor it all fell down in one huge sheet. Everyday after that I used to joke and warn him that his fire was bending my beam. The spray-on fireproofing that fell was eventually replaced towards the end of the project with some that was hand mixed in a wheelbarrow and troweled on.

Then, in 1996 I returned to the same building to install extra support beams needed to carry the weight of large, very heavy motorized rotary power files that were going to be installed. Surprisingly I had to attach the new beams to the existing ones EXACTLY where I had my shanty and right where Lenny had his fire each day.

After scraping away the fireproofing for some layout work, layout meaning measuring and marking, I checked the existing beams for level by using a water level; and sure enough, the beam that Lenny had his fire under had bowed over seven-sixteenths of an inch!

Steel + heat = problems.

[Flightful]

12. Thank the asbestos scaremongers

Asbestos was banned during the construction of the WTC, tower 1 was further along so had more of the asbestos fireproofing. I've heard that the replacement for asbestos was nowhere near as effective, so if I had family there I'd be inclined to sue Ralph Nader and his pals.

[DulceDecorum]

21. I have one word for you: Mesothelioma

THAT is what the building crews got, along with a life expectancy measured in weeks.
But I guess that just doesn't matter to anyone besides Ralph Nader and his pals.

An estimated 1.3 million employees in construction and general industry face significant asbestos exposure on the job.
http://www.osha-slc.gov/SLTC/asbestos/

http://www.atsdr.cdc.gov/tfacts61.html

[LARED]

23. Mesothelioma

Exposure to asbestos does not reduce your life expectancy to a few weeks. If you are exposed and if your body is sensitive to the fibers it usually takes a few decades to get Mesothelioma. (ie an exposure does not nearly equate to getting heath problems) Also even if you are diagnosed with asbestos related cancer most victims live quite a few years.

I'm not trying to downplay the dangers of asbestos, as it is a dangerous material if handled incorrectly. But lets deal with facts.

[DulceDecorum]

33. The White House

appears to agree with you.

CBS/AP) The Environmental Protection Agency's internal watchdog says White House officials pressured the agency to prematurely assure the public that the air was safe to breathe a week after the World Trade Center collapse.
<snip>
The White House directed EPA to add and delete information, Connaughton said, based on whether it should be released through press statements, information on the Web or other means.
http://www.cbsnews.com/stories/2003/08/09/national/main567489.shtml

"EPA considers asbestos hazardous in this situation."
Draft EPA notice
"Short-term, low-level exposure…is unlikely to cause significant health effects."
Final EPA notice

Let us look at what our colleagues at the Faux News have to say:

The use of asbestos ceased in the 1970s following reports of asbestos workers becoming ill from high exposures to asbestos fibers. The Mt. Sinai School of Medicine’s Irving Selikoff had reported that asbestos workers had higher rates of lung cancer and other diseases. Selikoff then played a key role in the campaign to halt the use of asbestos in construction.
<snip>
Selikoff was certainly right to point out that some workers heavily exposed to certain types of asbestos fibers were at increased risk of disease. But Selikoff was wrong to press the panic button about any use of or exposure to asbestos. For example, no adverse health effect has ever been attributed to Levine’s technique of spraying wet asbestos, according to Harvard’s Wilson.
We may now be paying a horrible price for junk science-fueled asbestos hysteria.
http://www.foxnews.com/story/0,2933,34342,00.html

That article was written by one Steve Milloy.
Lared, you simply MUST STOP getting your information from rabid rightwingnuts before people start getting the impression that you are a DINO.

Steven Milloy, the Cato Institute's self-proclaimed critic of "junk science," took the attacks on the World Trade Center as a cue to speak up for asbestos, which is still a product liability concern for manufacturers even though it was pulled off the market years ago due to its link with lung cancer.
<snip>
Like Milloy, the industry-funded American Council on Science and Health (ACSH) went to pains to downplay the hazard. "Some activists are raising concerns about very low levels of asbestos in the air in Downtown Manhattan since the WTC tragedy," commented an ACSH news release.
<snip>
"The study, by the Virginia firm HP Environmental, found that the force of the explosions apparently shattered the asbestos into fibers so small that they evade the EPA's ordinary testing methods," reported Newsweek on October 5. "The EPA tests for asbestos particles greater than a half micron in size.... But the study concluded that there is such an overwhelming concentration of those ultrasmall particles that many are being missed by standard microscopy techniques. 'This stuff was just crushed, just pulverized,' says lead author Hugh Granger. 'As it turns out, when we now measure and look for these very small fibers in the air and buildings, we find them, and we find them in uniquely elevated concentrations.'"
Some evidence suggests that ultrasmall asbestos particles may actually pose a worse health threat than larger particles. Smaller particles tend to remain suspended in the air where they can be inhaled, and they may penetrate more easily into the depths of the lungs. "We probably will find out a lot more about the health aspects of asbestos from this event, unfortunately," said Dr. Alan Fein, chief of pulmonary and critical-care medicine at North Shore-Long Island Jewish Health System, who has treated several patients for "World Trade Center syndrome": respiratory distress stemming from relatively brief exposures of a day or two near the collapsed buildings.
http://www.prwatch.org/prwissues/2001Q4/junkman.html

In the biographical sketch that accompanies "The Fear Profiteers" (see cover story of this issue), Steven Milloy describes himself as the publisher of the Junk Science Home Page and an adjunct scholar at the Cato Institute. "Milloy appears frequently on radio and television; has testified on risk assessment and Superfund before the U.S. Congress; and has lectured before numerous organizations," it adds, noting that he has also "written articles that have appeared in the New York Post, USA Today, Washington Times, The Chicago Sun-Times, and the Investors' Business Daily."
These facts are all accurate as far they go, but they say nothing about how Milloy came to be a prominent debunker of "junk science." This omission is undoubtedly by design, because it would certainly be embarrassing to admit that a self-proclaimed scientific reformer got his start as a behind-the-scenes lobbyist for the tobacco industry, which has arguably done more to corrupt science than any other industry in history.
<snip>
Milloy was also active in defense of the tobacco industry, particularly in regard to the issue of environmental tobacco smoke. He dismissed the EPA's 1993 report linking secondhand smoke to cancer as "a joke," and when the British Medical Journal published its own study with similar results in 1997, he scoffed that "it remains a joke today." After one researcher published a study linking secondhand smoke to cancer, Milloy wrote that she "must have pictures of journal editors in compromising positions with farm animals. How else can you explain her studies seeing the light of day?"
<snip>
In August 1997, the New York Times reported that Milloy was one of the paid speakers at a Miami briefing for foreign reporters sponsored by the British-American Tobacco Company, whose Brown & Williamson unit makes popular cigarettes like Kool, Carlton and Lucky Strike. At the briefing, which was off-limits to U.S. journalists, the company flew in dozens of reporters from countries including Brazil, Argentina, Chile and Peru and paid for their hotel rooms and expensive meals while the reporters sat through presentations that ridiculed "lawsuit-driven societies like the United States" for using "unsound science" to raise questions about "infinitesimal, if not hypothetical, risks" related to inhaling a "whiff" of tobacco smoke.
<snip>
Casual visitors to Milloy's Junk Science Home Page might be tempted to dismiss him as merely an obnoxious adolescent with a website. They would be surprised to discover that he is a well-connected fixture in conservative Washington policy circles. He currently holds the title of "adjunct scholar" at the libertarian Cato Institute, which was rated the fourth most influential think tank in Washington, DC in a 1999 survey of congressional staffers and journalists.
Milloy is also highly visible on the internet. In addition to publishing the Junk Science Home Page and a website for the No More Scares campaign, Milloy also operates a "Consumer Distorts" website devoted to attacking Consumers Union, the publisher of Consumer Reports magazine, which Milloy accuses of socialism, sensationalism, and "scaring consumers away from products."
http://www.prwatch.org/prwissues/2000Q3/junkman.html

More from Milloy:
But data from the National Center for Health Statistics indicate these predictions were way off-base. ASBESTOS RELATED DEATHS IN THE US APPEAR TO HAVE PEAKED IN THE LATE-1990s AT ABOUT A FEW THOUSAND PER YEAR.
Yes, long-term exposures to high levels of certain types of asbestos have increased the rates of disease among former asbestos workers, particularly among those who smoked. BUT THIS IS NOT THE SITUATION AT THE WORLD TRADE CENTER SITE.
http://www.foxnews.com/story/0,2933,34756,00.html

Appeal to authority.
Milloy's main source for the claim that the non-asbestos insulation was inferior is Herbert Levine, the man who invented the process for applying asbestos insulation. Since both types of insulation presumably passed the same tests, it is hard to see what this claim is based on. Levine is quoted as saying that "if a fire breaks out above the 64th floor, that building will fall down." Did he really think that a trash can fire would bring one of these buildings down?
http://info-pollution.com/wtc.htm

Correcting myths from Steven Milloy
http://info-pollution.com/milloy.htm

Steve Milloy is TOXIC and he is NOT truthful.
Quoting him as an authority identifies one as either gullible, or wicked.

[LARED]

34. Nice try, but no cigar

I was merely pointing out that your claim that an exposure to asbestos will reduce your life expectancy to a few week was not factual. It's hyperbole, just like your implication that the White house agrees with me.

Asbestos is a serious health concern. (I know, I was trained and certified to remove it) But people need facts to deal with the hazard, not ill informed scare tactics.

[DulceDecorum]

40. Long live

Steven Milloy.
:smoke:

[Flightful]

50. Question for you

I have seen a lot of asbestos removal projects lately and it looked like the removal job created a greater risk than leaving it where it was- they did one job for a section of the Toronto subway where casual exposure was close to nil. Wouldn't the removal work stir up the fibres all over the place no matter how many precautions you take?

[LARED]

57. For the most part

I agree that as long as the asbestos is stable and not friable it should be left in place. Removing it creates a far greater exposure potential than just leaving it alone.

On the other hand the permissible exposure level of 0.1 fiber/cc is quite a lot of material. I ran a job years ago where spray on asbestos was scrapped off a concrete slab roof and we never got a reading close to 0.1 f/cc. At times it looked very dusty in the work area.

So I think each abatement project really needs a good deal of assessment to determine go or no go.

[Name removed]

5. Deleted message

Message removed by moderator. Click here to review the message board rules.

[gandalf]

7. "You do the math" assumes a lot of hypotheses

e.g. that there is a linear relationship between the thickness of the fireproofing and the time it can withstand a fire. This linear relationship might exist, and it might not. Only experts can know.

You imply that the thickness is the only factor that influences the time the building could withstand the fires (as you suggest that the double thickness led to a doubled time). That is an implausible hypotheses, not justified without further explanation.

Probably there are several factors determining the time, e.g. the impact position, impact angle of the plane. They are not identical for the two buildings, therefore cause different damages.

[Bolo Boffin]

10. You only list two...

...and what a dandy verbal argument it makes. Appeals to the common sense, simple and easy to understand, and it doesn't fly in the face of the bulk of the evidence.

Plus, it's testable. NIST is testing this theory. They're taking actual WTC structural steel and testing it for failure time of the different fireproofing. The experts will tell us if there's direct correlation.

Saying the thickness is the only factor is overstating my argument. Definitely I'm using the article to imply that it's the major factor. Displaced load was important, as was the wind stress.

As DeadBroke pointed out, however, there's good reason to believe that the fireproofing was blown off at impact. Then the steel was completely at the mercy of the fire, and the displaced load, and the wind. NIST is examining both possibilities for the most probable collapse sequence.

When NIST is done, they'll have the most probable answer that science can back, the kind of answer that may improve building codes and emergency protocol.

[Robb]

8. Mildly interesting to note

that these event times are 5 or 6 seconds off the LDEO at Columbia's calculations. Only interesting in that this would imply they didn't get their numbers from them, but worked it out independently. :shrug:

[HarryLime]

14. a very disturbing thread

"In an effort to leave no stone unturned, the National Institute of Standards and Technology is examining whether the amount of fireproofing on the WTC structural steel was adequate."

This sentence is very disturbing. It begins with "In an effort to leave no stone unturned..." Meanwhile, the author (Boloboffin) has already admitted that NIST isn't even considering the possibility that the Twin Towers were demolished, despite the overwhelming circumstantial evidence supporting the claim.

The author also seems content that NIST is focused on the "amount of fireproofing" protecting the WTC steel. However, there still remains no explanation for how jet fuel (i.e., refined kerosene) which burns at an estimated 650 Farenheit in the open air managed to melt steel. Steel can't be forged until it reaches 2000 degrees F. It doesn't melt until about 2500 F.

Nor is NIST inquiring how black fires managed to reach the temperature to melt steel.

There's also the energy deficit that hasn't been addressed. (If gravity is the only source of energy input, and the towers fall almost as quickly as they would in a free fall, there's no energy to eject large quantities of material; to pulverize everything into dust; to provide heat sources that lasted weeks after the events.)

Every indication is that NIST is providing an enormous disservice to the public by focusing on red herrings like "fireproofing". The collapses of the North and South towers cannot be explained by the burning jet fuel model. Considering the severity of the crime, any effort to distract attention on trivialities like fireproofing is a form of disinformation. For NIST it is a coverup instead of what should be a legitimate investigation.

[Bolo Boffin]

15. Are you reading the thread?

As DeadBroke has shared with us, exposure to sunlight can warp a structural beam. Sunlight can generate the required temperatures to move a piece of steel from elastic deformation into plastic deformation. Any constant source of heat - sunlight, a drum fire situated below a beam - can affect steel, even fireproofed steel, adversely.

Circumstantial evidence for a controlled demolition is the only evidence that you have, and it is far from overwhelming. If there were some convincing evidence that a controlled demolition took place, NIST would be examining it.

For God's sake: if WTC 1 & 2 were controlled demolitions, why the hell didn't they evacuate everyone they could and pull the firefighters out of the building before denotating? This hypothesis isn't worth the pixels it's being displayed on.

[HarryLime]

16. Blind Faith

"exposure to sunlight can warp a structural beam."

That's irrelevant to the discussion of why the Twin Towers collapsed. We know they didn't collapse from sunlight.

"Any constant source of heat - sunlight, a drum fire situated below a beam - can affect steel, even fireproofed steel, adversely."

The word "affect" isn't appropriate for the complete destruction of these steel towers.

Note also that your statements actually contradict the Official Story. If very little energy is needed to alter these steel buildings then they should have altered. They should have bent over before falling straight in their footprints.

"Circumstantial evidence for a controlled demolition is the only evidence that you have..."

That is because there has been no meaningful official investigation by the Bush regime.

"If there were some convincing evidence that a controlled demolition took place, NIST would be examining it."

Because?

"For God's sake: if WTC 1 & 2 were controlled demolitions, why the hell didn't they evacuate everyone they could and pull the firefighters out of the building before denotating?"

They wanted to achieve a collossal deception.

[Bolo Boffin]

17. That's an appropriate warning label for your post, Harry.

Thanks for providing it.

Note also that your statements actually contradict the Official Story.: Imagine that.

We are constantly being reminded here of the temperature at which steel melts or steel softens or at which point steel can be forged. It is waved like a banner to show that the fires of the WTC could never have affected the structural steel.

And now it is shown that a piece of structural steel can warp at the temperatures induced by a constant source of sunlight. I'd say that this fact completely refutes the "melting point" argument decisively. It's not irrelevant at all - it's vital to understanding how the WTC buildings collapsed.

a collossal deception: I'm struck with how apt an translation that phrase can be for Thierry Meyssan's dunderheaded "cash cow" titled L'effroyable imposture, 11 septembre 2001. Is this an endorsement, Harry? It's not a official translation, is it? :-)

[NecessaryOnslaught]

18. Sounds like a conspiracy to me

All this talk of fireproofing irrelevant to the collapse sequence. It is quite clear (as stated in post 4) that the antenna begins to drop first and remains vertical while falling. Only the systematic failure of all 48 core columns at exactly the same time can explain this. That is the point of a controlled demolition, to cut the structure out from under itself to allow for the building to fall into its own footprint (that is happened to 3-high rise buildings that day, isnt it?). To think that an asymmetrical heat source (like a liquid hydrocarbon fire) can heat differently sized columns to the point of failure at the same exact time is ridiculous. A partial collapse on one side of the building, maybe, but a building turned to dust and molten steel?? Please. The NIST makes no mention of the molten sub-level steel either. Was the fireproofing blown off in the sub-levels as well? No. So in the sub-levels we have fireproofed steel (steel that was thicker than at the crash floors) which remains molten to the point where it is fluid at least a month(and a tropical depression and a few rain storms)after the collapse. The temperature to achive this would have to be greater than 3000 F. What is the source of energy to not only turn but to keep this steel molten? I guess since the NIST isnt asking we will never know.

[HarryLime]

19. Great post. (n/t)

[RH]

24. I've heard tell that

the core of the Earth also stayed molten for some considerable time.

Before the days of refrigeration they used to keep ice all through the summer simply by piling up enough of it in one place.

I've no degree in physics, so better advice is welcome, but in the mean time it is not so much of a surprise to me that a considerable accumulation of heat may stay that way for some considerable time.

[LARED]

25. Quite clear????

It is quite clear (as stated in post 4) that the antenna begins to drop first and remains vertical while falling.

That is clearly seen in the video

Only the systematic failure of all 48 core columns at exactly the same time can explain this.

Well that might be true if all 48 core columns are used to support the antenna. Are they?


To think that an asymmetrical heat source (like a liquid hydrocarbon fire) can heat differently sized columns to the point of failure at the same exact time is ridiculous.

I would agree. Is anyone saying that happened?

but a building turned to dust and molten steel

What building did that? None of the WTC building did.

The NIST makes no mention of the molten sub-level steel either

Could it be because molten steel is an internet myth? Or could it be the NIST is doing an investigation into why the WTC collapsed and doesn't think finding molten metal in the basement unusual or pertinent after the underground fires burned for a over a month. You know every outer column was covered with aluminum. It has a pretty low melting point - around 1200 Deg F. If I recall surface imaging was performed right after the collapse to determine underground temperatures in order to help firefighters locate hot spots. I memory serves me correctly they saw temps over 1500 def F.

So in the sub-levels we have fireproofed steel (steel that was thicker than at the crash floors) which remains molten to the point where it is fluid at least a month(and a tropical depression and a few rain storms)after the collapse.

The sub floor, 7 of them, were filled with building debris as a result of the collapse. Office material burns quite nicely and hot (see above). Also if the fires are contained (as in being underground) it can get quite hot as the heat has no where to go. A few rain drops in relation to the size of the fuel source is like throwing a thimble of water into the camp fire. Even if it did get into the ruble the heat above the fires would vaporize it long before it got to the fires.

[Name removed]

37. Deleted message

Message removed by moderator. Click here to review the message board rules.

[AZCat]

39. You are right

Here is an article about the Citcorp building. I read about this first in the New Yorker, then it came up in an Engineering Ethics lecture. While it is about the weakness of bolted joints relative to welded ones, it is good material for realizing how vital these are to a building.

Link is here: http://www.crosscurrents.org/kremer2002.htm

[FredrickDouglass]

72. For God's Sake, boloboffin?

That a controlled demolition destroyed the towers has been talked about by many. It was being discussed the day it happened. Newscaster went on record saying that's what it looked like happened. So when this aganecy says that they are leaving no stone unturned, that implies it is at least investigating all the angles.

Why is his pointing out that they really aren't doing that, "not worth the pixels" used to express the view.

He's right. They aren't leaving "no stone unturned". That's not controversial. He's not saying they aren't right in investigating what they are investigating but to say that we're looking at every possible angle when you so obvouisly are not is just to define the range of discussion. So what was so obtuse about his post to warrant your calling out to God? That he presents a view you disagree with?

[Bolo Boffin]

73. Would you have NIST look into ray beams shot from Mars?

Or how about checking if a genie turned all the structural steel into lime jello? Because there's just as much evidence for either of those "stones" as there is for a controlled demolition.

They are examining all angles of the actual evidence. There is no physical evidence AT ALL for a controlled demolition. Controlled demolition isn't on the table because there's no reason for it to be examined. That's how much the scientists and engineers at NIST discount this notion.

[DulceDecorum]

74. And THAT is precisely why

we discount the scientists and engineers at NIST
and their "examinations."

[impe]

75. Well then

When the National Institute of Standards and Technology speaks..... Didn't they term it a "theory".

This theory btw is just as laughable as the solar degradation one concerning leaving "no stone unturned". First of all, NIST should try to grasp what happen to all the pulvarized stones....before trying to sell theories.

[DulceDecorum]

20. It TOTALLY amazes me

to see the interest given to the steel.
NOBODY ever wants to talk about the cement.
Nobody ever wants to discuss the manner high strength concrete behaves when exposed to fire.
http://fire.nist.gov/bfrlpubs/build96/art075.html
NOBODY ever wants to talk about the DURABILITY of concrete buildings.
http://www.ags.uci.edu/~colettem/clin/paper.html
NOBODY ever wants to examine the way in which the structure was reduced to superfine powder.
No, attention is always deflected away towards the steel.
The concrete building codes are just fine the way they are.
No problems in New York with acid rain.
http://www.oag.state.ny.us/press/2003/oct/oct27b_03.html
No reason for SANDIA to get involved.
http://www.sandia.gov/media/statues.htm
No interaction between high alumina concrete and rusted steel beams.
No, nothing to see here, keep your eyes on the steel.
http://www.google.com/search?hl=en&ie=ISO-8859-1&q=Non+Explosive+rock+%26+concrete+fracturing&btnG=Google+Search

WHY do you think the WTC complex HAD TO to fall-down-go-boom in the first place?
Do you honestly believe it was because of the flipping steel?
http://www.indiaconstruction.com/ConstructionWorld/may2001/guestcolumn.htm

NO.
It was because of bad Muslims and their SLOPPY REPORTING.
Nothing to see here, keep moving.
And DON'T look at the concrete, whatever you do.

[DeadBroke]

22. DulceDecorum

raises a very valid point: it's not just about the steel.

But I really don't see any effort being made to willfully divert or manipulate the focus away from other issues and towards the steel. My comments for example about steel and fireproofing were made in response to other posts about steel and fireproofing. In all honesty, being an ironworker limits my knowledge to steel. I wish I could participate and contribute in other ways, and in other threads, but my experiences have been limited.

A few weeks back there was a thread whose central theme was about the dust cloud and some analysis that had been performed on a few samples that had been collected. That thread included some info on the Trade Center concrete; it's thickness, composition and collateral concrete issues such as the rebar used and Nelson studs.

There was also a thread during the Summer that discussed the concrete, and before that there was a VERY intresting thread about the pulverized concrete and sheetrock; especially the very informative exchanges between LARED and plaguepuppy about air compression during collapse. Perhaps these threads were below everyone's radar or happened before some members joined.

Thank you DulceDecorum for posting those links. I appreciate your time and efforts.

[LARED]

26. A few points about the concrete

1. There is very little concrete in the office areas of WTC 1&2. The majority would be underground or near grade. Putting concrete in the air is very costly, hence you get the innovative steel construction of the WTC's

2. The majority of concrete that is in the office areas is used for the floors. It was a lightweight low strength concrete.

3. Concrete when exposed to fire is usually badly damaged. It spalls and tends to lose it strength. If exposed to heat long enough, it chemically changes to something else. (I think)

4. The WTC were not considered concrete buildings to my knowledge. They are steel buildings.

5. The small amount of concrete in the office areas is INSIDE the building so acid rain maybe doesn't effect it much.

6. These are distinct possibilities why no one gives a rats rear end about the concrete.

[HarryLime]

32. Pseudo-intellectualism

"It was a lightweight low strength concrete."

So by his merely stating it was "low strength" we're supposed to think it was natural that the concrete for both towers pulverized into fine powder. That happens...all the time, doesn't it?

[LARED]

35. Well Harry

if you read the post I was responding to, you may have noticed that the poster was talking about high strength concrete. I was trying to set the record straight.

BTW, there are large differences in the properties of high strength concrete and the type used in the floor of the WTC towers.

Regarding my pseudo-intellectualism. I find it necessary to point out that there is no apparent reason I can see that anyone with normal intellectual capacity would jump to the conclusion that because I pointed out lightweight concrete was used, I was trying to convince people it would be natural that the concrete for both towers pulverized into fine powder

In fact I have no reason to do that because I believe the amount of concrete that was pulverized is far less than the CT crowd believes.

Have a nice day Harry. :)

[DulceDecorum]

38. Number two

Lared claims:
The majority of concrete that is in the office areas is used for the floors. It was a lightweight low strength concrete."
Proof?

[LARED]

42. You want proof?

What have you been doing for the last 2 years? Haven't you read any of the WTC report that go into construction details???????

Tell you what, since you are sleuthing the concrete element of the investigation, why don't you prove (forget proof, how about provide evidence) where and what type of concrete was used in the office areas.

[DulceDecorum]

44. Dodging, ducking, bobbing and weaving.

Can't prove diddly, can you?

YOU are the one who made the claim of low strength concrete.
Now DEFEND it.
Or admit that you have no proof WHATSOEVER and
NO EVIDENCE to back up that statement.
Go on then.
Demonstrate the YOU did SOME reading in the last two years concerning the constuction details of the WTC.
Your bluff has been called, Lared.
The gauntlet has been thrown.
Prove yourself.

[LARED]

46. DD pay attention

http://www.house.gov/science/hot/wtc/wtc-report/WTC_apndxA.pdf

Traditionally, the compressive strength of concrete used to be around 20-50 MPa, which is referred to as normal-strength concrete . Depending on the density, concretes are usually subdivided into two major groups: (1) normal-weight concrete, made with normal-weight aggregate, with densities in the 2,200 to 2,400 kg/m3 range, and (2) lightweight concrete, made with lightweight aggregate, with densities between 1,300 and 1,900 kg/m3.

The floor slabs at WTC 1 and WTC 2 (as well as in most of the WTC buildings and vicinity) were made of concrete made of metal deck. The floor construction typically consisted of 4 inches of lightweight concrete fill on corrugated metal deck. Hence, the discussion here is focused on lightweight concrete.

If you bother to read the above link, there is a wealth of information about the properties of lightweight concrete verses other grades.

[DeadBroke]

47. Videotapes say lightweight

Back in the early to mid 1980s the EEOC, Equal Employment Opportunity Commission took several NYC area building trade unions to court for discrimination against minorities. The EEOC claimed that union membership did not reflect the mosaic of peoples making up the communities, and that union halls did not fairly give work assignments to minority members.

In response, some unions actively recruited, some fought, some went halfway. (Many cases are still unresolved, under appeal, or are in compliance litigation). Out of these battles emerged a set of recruitment videos that were produced and distributed by the Allied Building Trades Council, titled "A Career In The Construction Trades." Each video focused on a trade; carpenters, bricklayers, painters, ironworkers, concrete finishers, electrician, and etc. These recruitment videos were produced in several languages, and distributed to libraries, Vo-Tech schools, regular middle and high schools, adult learning centers, night schools, church centers, unemployment and welfare offices, and shown on NYC PBS stations.

Quickly following the recruitment videos were a second set, produced in partnership with the Department of Education for training the newly recruited union members in apprenticeship programs. Those training volumes became VERY popular and were requested by public libraries, and by vo-tech and regular public schools everywhere. Segments of some of these videos sometimes appeared on the 'Mister Rogers' TV show. I personally used the ones on blueprints and rigging (hand signals for cranes) while I was a substitute instructor the Ironworker Apprenticeship Program.

The concrete volume, "All About Concrete" was intended for classroom use. It has two videotapes, each having six 30 minute segements with review questions. The segements cover topics ranging from the history and origins of concrete, production, mixing, delivery, application, testing, pre-stressed and post-stressed concrete, and other things up to the newer specially formulated concretes, alternative aggregates, high strengths concrete and grouts, and air entrained lightweight concrete.

The concrete videos include informative archive footage from the construction phases of many of NYC's major highways, airports; landmark buidings, bridges, and tunnels. The Trade Center makes two appearances; the first for it's time and cost saving prefabricated concrete floor sections where controlled curing eliminated cracks, crazing and edgelifting, and second for it's use of quote: 'lightweight and air entrained concrete.'

[RH]

49. Air-Entrained Concrete

"One of the greatest advances in concrete technology was the development of air-entrained concrete in the late 1930s. Today, air entrainment is recommended for nearly all concretes, principally to improve resistance to freezing when exposed to water and deicing chemicals. However, there are other important benefits of entrained air in both freshly mixed and hardened concrete. Air-entrained concrete contains billions of microscopic air cells. These relieve internal pressure on the concrete by providing tiny chambers for the expansion of water when it freezes."

http://www.cement.org/basics/concretebasics_airentrained.asp

[Bolo Boffin]

51. Also

Air-entrained concrete is lighter than regular concrete - less load on the structure of the building.

[DulceDecorum]

53. But HOW

would water get into the air-entrained concrete in the World Trade Center?
And HOW would it ever get to freeze?

The steel tubes are on the outside of the building and the air-entrained concrete you are speaking of is on the floor.
Where do the de-icing chemicals come in?
Why is freezing an issue regarding concrete in the World Trade Center?

[RH]

54. You wanted "proof",

(c.f Reply #26)

so tell us.

Why should the concrete be so much of an issue?

My message was intended to suggest it should not be so much of an issue.

[DeadBroke]

62. The questions you're raising

would only apply to the construction phase of the Trade Center, before the buildings were heated and sealed with column covers and glazing. Concrete, any kind of concrete used during the construction phase of a building must be protected from freezing and from extreme heat if it is to cure properly and acheive it's desired strengths. The link RH provided is very basic standard industry information intended for the construction phase of buildings and where concrete will be used outdoors and subject to elements, but it's not at all intended for concrete in completed and occupied buildings.

[DulceDecorum]

52. Lightweight concrete

uses WHAT type of aggregates?

Can you name them Lared?
Give us a list of lightweight aggregates.
I await your response.

[RH]

55. What type?

What, please, is the point and purpose of that enquiry?

[LARED]

56. Is there some point to this?

A partial list of lightweight aggregates used in various concrete mixes.

Clinker
Sintered pulverized ash
Foamed slag
Expanded clays and slag
Expanded slate
Pumice
Palm oil shell
Diatomite
Wood particles
Scoria
Pumice
Expanded perlite
Expanded vermiculite

There also seems to be a load of "designer" aggregates.

From; Lightweight Aggregate Concrete - Science, Technology, and Applications by Chandra, S.; Berntsson, L. © 2002; Noyes

So tel me DD, do you have anything regarding the high strength concrete used in the WTC floors? Anything?

[DeadBroke]

58. A Fire Chief's Comments

Probably one of the most respected Fire Chiefs of all time, and an author of some of the best firefighting texts ever written Vincent Dunn offers some good information about Trade Center concrete:

http://vincentdunn.com/wtc.html


+ + + + + + +

On a very personal note, Vincent Dunn's book "The Collapse Of Burning Buildings" which I read many years ago saved the lives of 6 volunteer firefighters I commanded at fire involving an auto dealership with a bow-string truss roof. Had I not read his book I would not have reconized the danger or anticipated the collapse.

[LARED]

60. Thanks

I've seen those comments before. Seems like a very knowledgeable guy.

[BassettWilliams]

63. Another FDNY Fire Chief has his say

http://ericdarton.net/afterwords/fireandair.html

[LARED]

48. Speaking of ducking dodging and dream weaving

it was you that said

Nobody ever wants to discuss the manner high strength concrete behaves when exposed to fire.

Which stated this small diversion, so I'm sure you can provide evidence, proof, something that indicates high strength concrete was exposed to fire in the WTC.

I await your response.

[DeadBroke]

59. Here's a quote:

" ... high-strength concrete holding up all of the Petronas Towers - not just the core - had not been developed when the trade center went up in the 1960's and 1970's."

from:
http://www.ce.udel.edu/news/ChajesNYtimes.html

[LARED]

61. Well??????

YOU are the one who made the claim of high strength concrete.
Now DEFEND it.
Or admit that you have no proof WHATSOEVER and
NO EVIDENCE to back up that statement.
Go on then.
Demonstrate the YOU did SOME reading in the last two years concerning the constuction details of the WTC.
Your bluff has been called, DD.
The gauntlet has been thrown.
Prove yourself.

:)

[DulceDecorum]

64. LOL

CORRECTION:
Post #20 DulceDecorum stated:
Nobody ever wants to discuss the manner high strength concrete behaves when exposed to fire.
Post #26 Lared stated:
2. The majority of concrete that is in the office areas is used for the floors. It was a lightweight low strength concrete.

Lared, you stated that for a fact hence the invitation to demonstrate the veracity of your claim.

We can talk about high strength concrete any old time, but why should we?
According to your statement it was never used.
Talking about it will only cause RH to complain even more about stupid distractions.
However, RH really seems to value your opinion and I am certain he too is eagerly anticipating reading any links you may provide demonstrating that low strength concrete was the material of choice used by the builders of the World Trade Center.
Balls in your court.
Links please?

[Bolo Boffin]

65. Psst, Dulce: Post #59.

There's your link.

[RH]

66. "... be certain

he (RH) too is eagerly anticipating?"

:shrug:

I'd thought it was all to relieve the amazement of DulceDecorum as expressed in #20.

[LARED]

67. I'm sure there is a point to this somewhere

Do you have any evidence that high strength concrete was used?

BTW, if you are counting on there being an important distinction between low strength and lightweight concrete as it relates to the WTC floors, be careful, you may be treading into waters over your head.

On the other hand if you have some pertinent information please share it. After all it was you that complained that no one was interested in discussing the behavior of high strength concrete in the fire.

[DeadBroke]

69. Some info that may help

It is generally accepted in the building trades that the pull-out strength of a fastener used in concrete, (such as: lead, fibre, or plastic shields; wedge anchors, sleeve anchors, and powder actuacted pins for example), is dependent on several factors but mostly on; a) the depth of fastener embedment, b) spacing of the fasteners, and c) the condition and tensile strength of the concrete.

Spacing has an important role. If holes for fasteners are drilled too closely in the concrete there will be stress interaction and cracks will develope when the fastener is inserted and tightened; so the allowable spacing of anchors for concrete floors at any building will reveal what type and strength concrete was used.

The acceptable spacing of fasteners for high strength concrete is usually five times (5X) the diameter of the fastener; so 1/2" diameter Dyna-Bolt wedge anchors, for example would need to be spaced at least 2 and 1/2" apart.

The acceptable spacing of fasteners for non-high strength concrete is usually ten times (10X) the diameter of the fastener; so the same 1/2" Dyna-Bolt wedge anchor would need to be spaced at least 5" apart. I also should add that 10X the diameter is also an old "rule of thumb" that has been around for generations.

If one were to look at the blueprints and notes of a building they would find engineering notations for the required spacing of anchors. (Engineering notes spell everything out; from the number of screws for each piece of sheetrock, to the type of grout on tiles, to the diameter and length of fasteners).

It is the professional practice of construction foremen to save all blueprints, engineering notes, time sheets, change orders and revisions of the work they performed. I have checked, (spent several hours yesterday) my records of the work I performed at the Trade Center and found that the required spacing for fasteners I used in the concrete floors was ten times (10X) the diameter of my fastener, which indicates the floors were not high strength concrete.

[LARED]

70. Thanks for the info

It is quite useful. I don't do much commercial construction, but in industrial construction and design I am involved in, we now use the poured epoxy anchors for most equipment that is under stress or not constructed with "J" bolt anchors.

The expoxy is very quick, very strong easy to use and you can mount equipment on pretty "green" concrete without having to worry about over-stressing it when installing the anchors.

[DeadBroke]

71. Cool coincidence

If the weather will cooperate I have an upcoming job at a paper manufacturing plant and will be using BRUTEM AB 3 part (18.5 K 125MPa) epoxy specified by the engineering consultants for anchor bolts and wickets. Previously used CEILCOTE 648 high strength epoxy grout on crane rails there. Epoxy; love the strength, hate the limited working time.

[LARED]

68. Balls in your court. n/t

[DeadBroke]

31. About that acid rain

all I can find so far is the Port Authority's concerns about pollution and how it factored in their choice of granite for Bldg #7 instead of marble.

From the searches I've done it seems the PA had several samples of both marble and granite, in varying sizes and thicknesses, and from many quarries sitting in open fields near their airports and atop some buildings exposed to all weather conditions to test their endurance, reactions to thermal cycles, pollution and something called an L/r factor which somehow is a measure of strength against buckling.

Could you please offer more insight on the acid rain?

[DeadBroke]

76. More on acid rains & Trade Center

Yesterday I was able to speak with a retired facilities worker from the Port Authority about a variety of topics including pollution. No expert, just a guy with a lifetime of unique experiences, he stated that acid rains and other pollutants were a concern at the Trade Center and at other PA properties and were closely monitored, but explained that "nature" - specifically the weather patterns for the NYC area corrected any possible problems; damaging acid rains came from the west, but cleansing rains came with more frequency from the east and south. In his opinion the main weather concerns were high winds and extended heat waves or cold snaps. Prolonged hot or cold periods caused expansion and contraction of the exterior aluminum column covers on the facade, sometimes interfering with the window washing track and meachanism. Sometimes the track would become inundated with grain and seeds blown in from the midwestern states. Acid rains, in his opinion were of no major concern to the PA and "didn't set off any bells or buzzers."

[NecessaryOnslaught]

27. Molten Steel

http://www.democraticunderground.com/discuss/duboard.php?az=show_topic&forum=125&topic_id=6095#6143

did someone say molten steel?

[Bolo Boffin]

28. Fire Endurance Testing of the WTC Floor System

From my cherished .pdf file:

"The interim findings contained in the May 2003 progress report stated that from the documents reviewed NIST had not been able to determine the technical basis for the selection of fireproofing material for the WTC floor system or how the specified fireproofing thickness would achieve the required 2 hr fire rating.

"In addition, NIST found no documentary evidence indicating that a test based on ASTM E 119 had been conducted to determine the fire rating of the WTC floor system. The Port Authority stated that “there are no test records in our files” in response to a NIST question asking “Were tests performed on the fire resistance of the composite floor system during the design or construction phase of the project.”

"While the benefits of conducting a full-scale fire endurance test were realized, apparently no tests were conducted on the specific floor system used in the WTC towers. Such project-specific testing was and is not normal practice but may be conducted when circumstances warrant it, for example, in a new or unique application.

"A composite bar joist floor system with spray-applied fireproofing represented an innovative application in the 1960s. Four additional factors contributed to the uniqueness of the system: (1) the use of bar joists in the floor system of high-rise buildings such as the WTC towers; (2) the long unsupported span of the floor system (about 60 ft in the long direction, about 35 ft in the short direction); (3) the role of the floor system in ensuring stability of the WTC structural system; and (4) the floor diaphragm action required to transfer lateral (wind) loads to the columns.

"NIST engineers are working with experienced engineers from Underwriters’ Laboratories, Inc. ( http://wtc.nist.gov/solicitations/wtc_awardQ0281.htm ) to determine the fire endurance rating of typical WTC floor systems under both as-built and specified conditions under the fire conditions prescribed in ASTM E 119. In addition, NIST is using the tests to study the effects of fireproofing thickness, scale, or size of the tested assembly, and thermal restraint at the ends of the assemblies.

"The tested composite floor assemblies include the concrete slab on metal deck, two pairs of main joists integrated with the concrete slab to provide composite action, two bridging joists, and fireproofing applied on steel with primer paint. Four tests are being conducted:

• A 17 ft span with ends of the assembly restrained from thermal expansion in a typical furnace representing current U.S. practice. This test will use the 1/2 in. fireproofing thickness specified by the Port Authority when the towers were built.

• A 17 ft span with ends of the assembly restrained from thermal expansion in a typical furnace representing current U.S. practice. This test will use the 3/4 in. fireproofing thickness representing the as-built condition of the buildings before the process, still under way on September 11, 2001, was initiated to upgrade the thickness to 1-1/2 in.

• A 35 ft span with ends of the assembly restrained from thermal expansion in a furnace twice the typical size and representing a full-scale 35 ft assembly. This test will use the 3/4 in. fireproofing thickness representing the as-built condition in the buildings before the process, still under way on September 11, 2001, was initiated to upgrade the thickness to 1-1/2 in.

• A 35 ft span with ends of the assembly not restrained from thermal expansion in a furnace twice the typical size and representing a full-scale 35 ft assembly. This test will use the 3/4 in. fireproofing thickness representing the as-built condition in the buildings before the process, still under way on September 11, 2001, was initiated to upgrade the thickness to 1-1/2 in.

"Additional rods and double angle structural members are placed within the furnace in each test to evaluate the effect of different fireproofing thicknesses up to 1-1/2 in."

[AZCat]

29. Good Reading

I wish people would put more effort into research before popping off about things that can be answered (or debunked) by reading the information available online or by heading to the library. Thanks bolobuffin for keeping a level head.

Note: here are some quickies
"The hardness and other characteristics of many steels and some nonferrous metals can be changed by heat treatment"
(pg. 48, Machine Design- An Integrated Approach 2nd. Ed., by Robert L. Norton)
The temperatures being listed in the forums for melting steel are far higher than those necessary to modify the properties of steel. Tempering, for example, can occur as low as 400 deg. F. There are also other forms, such as "cold working" and "hot working" that can affect metals. There are thousands of case studies of bizarre failures that occurred because of something like this.

Hope all this helps.

[DulceDecorum]

41. More good reading

Summary
The effect of thermal insulation on fire safety in buildings and the resulting potential hazards may be summarized as follows:
2 Insulation can influence the rate at which a fire will grow.
* a well insulated room will retain heat with resulting potential for faster fire growth.

5 Higher temperatures during fires in insulated structures may affect structural strength.
* structural steel members can lose strength when heated to high temperatures.
* higher temperatures can cause deflection and buckling of thin walls.
http://irc.nrc-cnrc.gc.ca/cbd/cbd218e.html
More about the "sloppy reporter."
http://irc.nrc-cnrc.gc.ca/irccontents.html

Myth 7: Concrete is invincible, Steel and Timber are Not.
A final myth relates to the primary structural materials of steel, concrete and timber.
It’s common to think of steel as losing its strength quickly when heated. In fact, single steel elements retain approximately 50 percent of their ambient temperature strengths at 1000ºF (550ºC). Research shows that due to load redistribution, unprotected steel structural frames may withstand significantly higher temperatures than 1000ºF (550ºC) with only localized deformation.6 In fact, reinforced concrete loses significant strength above 1400ºF (760ºC), as illustrated in the SFPE Handbook of Fire Protection Engineering.
Another common notion is that concrete does not lose strength at all in fire – that it’s “invincible.” However, the loss of concrete cover in the Channel Tunnel fire is a good example of the failure of concrete through spalling under high fire loads. Exposure of reinforcing due to spalling action can lead to the premature failure of members.
http://www.chiefengineer.org/article.cfm?seqnum1=1407
Credentials: http://www.chiefengineer.org/static/about_us.cfm

The effect of Fire
Although the massiveness and incombustability of a concrete construction seems immune to fire, the graph below shows otherwise. After an increase of temperature of 500° C the strength of a concrete structure is halved!
<snip>
Important factors causing spalling:
* Free & Chemically bound water combine to cause steam
pressure build-up
* Expansion Ratio of water-to-steam = 1 : 1700
* Temperature in excess of 500°C
* Concrete Grade dependant
* Moisture content over 3% = spalling almost 100% within 30
minutes of exposure.
http://www.promat-tunnel.com/idprt003.htm

Fire curves: Time v Temp
The RWS curve was developed by the Rijkswaterstaat, Ministry of Transport in the Netherlands. This curve is based on the assumption that in a worst case scenario, a fuel, oil or petrol tanker fire with a fire load of 300MW could occur, lasting up to 120 minutes.
http://www.promat-tunnel.com/idprt004.htm

[AZCat]

43. Thanks

Here's another link that also might be helpful.
It's about TWA Flight 800, but the info on Jet-Av fuel combustion seems to be relevant.

http://www.galcit.caltech.edu/EDL/projects/JetA/misconceptions.html

[DulceDecorum]

45. You are welcome

The Explosion Dynamics Laboratory worked with the National Transportation Safety Board on the TWA 800 crash investigation from 1996 to the present. Caltech is the lead organization in developing a 1/4-scale test facility to simulate the explosion within a 747 center wing fuel tank. Working with Caltech are Applied Research Associates (Denver), Combustion Dynamics Ltd (Medicine Hat), Christian Michelson Research Institute, University of Nevada (Reno), Desert Research Institute, and Sandia National Laboratories. We have carried out a comprehensive study on the explosion properties of aviation kerosene and the effects of the specific fuel tank geometry on explosion development.

Sponsors
US Navy (MURI)
DARPA (with GE)
US Department of Energy (ASCI ASAP Project)
http://www.galcit.caltech.edu/EDL/index.html

[DeadBroke]

30. The role of the floor system

The key line in bolo's floor system message is: "(3) the role of the floor system in ensuring stability of the WTC structural system"

Usually, in a typical high rise structural steel framed building, after the columns and beams are raised, plumbed, racked, leveled, bolted and welded; corrugated interlocking galvanized steel decking is shook out, and welded to beams with Nelson studs. Rebar is laid out across the decking, usually in a waffle pattern, tied, and then wire mesh is unrolled. Once the reinforcing steel work is complete concrete is poured, vibrated to make sure it fully encapsulates the rebar, leveled, and then troweled smooth. (Rebar is necessary because concrete, which has high compressive strength also has little tensile strength. The rebar, which are long steel bars, will take the tensile loads as the concrete takes the compressive loads). This concrete floor is a one piece monolithic form that ties all the components together. It helps assure stability, carries the floor loads, and acts as a large beam, distributing weight and load changes to the columns.

The Trade Center did NOT have this type of floor system. The concrete floors of the Trade Center were not capable of offering the same stability that a momolithic form would. They were prefabricated sections, poured atop steel trusses, trucked in to the site, and raised into position between the core and exterior walls. The floors were made of many independent sections or pieces and did not have the one piece monolithic form that would have tied everything together.

The "role" of the floor system is one of the keys to understanding the collapse.

[LARED]

36. Thanks again

for your insight.

[plaguepuppy]

77. Question about the floor trusses

So most (all?) of the floors of the towers were assembled using these pre-fab floor sections with the concrete already in place - were any at all poured and floated in place?

There's something that I've been meaning to ask you about how the corrugated steel floor pans were attached to the tops of the trusses: as I recall you indicated that each "ripple" of the corrugated steel was riveted to the top of the truss, and also spot welded. Is that actually how they were attached or am I misremembering?

And also: did the mechanical floors have a different floor system? There are some pictures of floors with something bigger than the trusses, smallish box beams maybe. These are the same pictures that the "no trusses" guy used to try to prove that the trusses were an elaborate hoax. They would seem to add quite a bit to the overall coupling of core to perimeter under normal wind-loading conditions, depending on how many such membrane floors existed.

[DeadBroke]

78. Answers

Floors: The original plan was to have the all floor sections built off site, including pouring and finishing the concrete floors. From speaking with workers employed there during the construction phase the plan worked well for most of the first tower however, the erection process often moved too quickly for the fabrication process, thanks to the availability of ironworkers, mutliple cranes, and material staging areas just outside the Holland Tunnel in NJ; so many of the floor pans of both towers were raised into place without the concrete, which had to be delivered to the site via transit mix trucks, loaded into hopper hoists (temporary high speed diesel powered winch hoists with hoppers that ran up and down on scaffolding in the core), raised to the floors being poured, poured into the floor sections, leveled and finished - but both methods, the off site prefab and on site pour did not result in one piece monolithic concrete floors.

While working at the Trade Center I encountered numerous floor joints. Most of my crew refered to them as expansion joints. They looked like expansion joints, and might have acted as expansion joints, but they were actually the joints between sections. When we cut through the floor of the contract library (as I described in a previous thread long ago) for a stairwell we had to "adjust" the plans due to a floor joint being right where they wanted the stairwell. The Trade Center did not have a one piece monolithic floor like other buildings. One engineer speaking at an ironworkers function IMHO perfectly described the floor as being like "big ice cube trays" bolted between walls. An offsite prefab floor was easy to spot - smooth, perfectly leveled and consistant. On site wasn't nearly as level and from drilling into it I sensed that all the aggregate was at the bottom indicating it was over-vibrated.

Decking: The interlocking corrugated (galvanized steel) decking was laid out across the trusses and welded to the trusses with "Nelson Studs." These are large diameter pins or dowels that fit into a welding gun that welds the stud, decking, and truss all together. Studs are normally placed in the deep ripple of the decking along each truss or beam. The rebar is later tied to these studs. I don't know for sure what diameter/length/spacing of Nelson Stud was used at the Trade Center, and I am unsure of the guage of the decking they used. I've asked guys that worked there, but got too many different answers.

Beams: Many of the photos and movies taken during the construction phases show beams spanning the distances between the core and outer columns. These beams were used on the lower floors immediatley above the multi-storied lobbies, atriums and retail areas because they offered more strength than the trusses, and because they could tie the core and outer columns together better than a truss. Beams were also used higher up at the motor room and sky lobby levels; to act as "belly bands" to stiffen the building and help dampen winds and to carry the weights of the mechanical equipment and water tanks etc. There were trusses, just a few in these areas too, along the short side - oversized to carry more weight, but beams were at every motor room and sky lobby level.