Can anyone debunk the claim that the fires at the WTC weren’t hot enough to melt/alter steel?
Well, I’d say that the fact that both towers collapsed is a pretty good debunking in itself.
However, getting more technical…
[(PDF file) from the mechanical engineering department at the University of Illinois discusses the factors that brought down the WTC. It gives figures of 1727°C for the flame temperature of kerosene (jet fuel) and 1570°C for the melting point of steel.
[url=http://www.efunda.com/materials/alloys/alloy_home/steels_properties.cfm]This site](http://www.asse.org/prac_spec_analysis_wtc.pdfThis paper[/url) gives the m.p. of steel as 1371-1454°C, but this may not apply to structural grades of steel.
:smack: Repeat after me… “Preview before posting, preview before posting…”
This should have fixed the links…
This paper (PDF file) from the mechanical engineering department at the University of Illinois discusses the factors that brought down the WTC. It gives figures of 1727°C for the flame temperature of kerosene (jet fuel) and 1570°C for the melting point of steel.
This site gives the m.p. of steel as 1371-1454°C, but this may not apply to structural grades of steel.
It should be noted that the fire did not cause any of the steel beams to completely melt, but rather get so hot that they began to bend, which eventually caused the collapses.
I heard somewhere (good cite eh?) that the fires did not reach the melting temperature of steel, but were sufficiently hot as to soften some of the structural elements; as these started to fail, greater load was transferred to other elements, causing them to fail until the whole structure finally gave way.
I think we’re talking about steel beams buckling under excessive stress and heat, rather than melting to a liquid state.
I remember recently reading an article by one of the rescue workers who was involved in the clearup at Ground Zero, and he definitely mentioned seeing “rivers of molten steel”. Whether this was a bit of poetic licence or not, I don’t know.
I don’t have an online cite for this, I’m afraid, but I think it was in the September 11 anniversary issue of The Sunday Times Magazine (supplement with UK newspaper, would have been either Sept 8 or 15).
Certainly the UoI paper I cited says that the flame fronts were capable of melting steel. I think it’s been fairly well established that the collapse was triggered by beams buckling on the upper floors, thus dropping the weight onto the floors below, causing those beams to fail too, and so on, as Mangetout stated.
They may well have seen molten aluminum but steel is very doubtful.
Steel becomes very plastic with heat well below the melting point. With the remaining overstressed floor trusses deforming and stretching out of shape they quickly broke the relatively small bolts holding them to the vertical members.
Who the hell is claiming that the fire didn’t cause the collapse? Some conspircy nut who maintains the plane crash was a hoax and the towers were brought down by Jewish sabotage?
Whose bunk are we debunking?
Conspiracy nuts? On the internet? Naah…
http://www.afrocentricnews.com/html/911_firehouse_documentary.html
Apparently a bomb had already been detonated in the lobby when the first plane hit. Also:
Yes, thats obviously the only explanation. A major fire in a building supplied with mains gas wouldn’t trigger any explosions.
Conspiracy nut checklist:
Excessive use of CAPITAL LETTERS to pick out the supposedly SALIENT points? Check.
Plenty of exclamation marks?!! Check!
Bald statements of DEFINITE FACT? DEFINITELY!!!
Yeah, but Bush new the steel would melt ahead of time!
This site contains info on the heat resistance of steel.
Heat resistance can’t be specified by a single number, but for a start, steel retains about 60% of its “room temperature” strength at 550[sup]o[/sup]C.
So the WTC steel beams didn’t need to melt in order to lead to collapse. Basically what happens is that the outside of a thick beam heats up and loses strength which means that the so-far unheated portion has to carry more load. As the beam cross section heats, more and more material loses strength until eventually the reamaining, relatively unheated portion can no longer carry the load. In effect, the heating gradually reduces the size of the beam.
In addition, the strength of a beam is related to shape. An I-beam, for example, has a lot of material at the extreme outer part where the maximum stress is. These flanges are also rather thin and will heat through pretty quickly. When that happens, the beam essentially has no strength.
Crazier and crazier – like the “where’s the plane?” crowd on the Pentagon. There are members of this very message board who can testify that there was no explosion in the WTC lobby prior to the plane’s impact.
Actually, these “explosions” were the impact noises of people falling or jumping from the tower, which the documentary did cover in real time.
But I suppose we can’t ask these whackos to actually watch the stuff they criticize – else the Pentagon crowd would have seen the pictures with pieces of the plane in the foreground.
I remember seeing a picture – in a couple places – possibly in a book called “How Structures Fail”, which I can’t find at this minute, that showed a couple story building gutted and destroyed by fire. The huge steel girders were limp like spaghetti. The not-quite-so thick wooden beams were blackened, but holding the building up. Implication: it doesn’t take any unusual heat to soften steel.
Also, a lot of the floor supports on WTC were made not of solid-piece I-beams, but of much thinner triangular-truss members. Under normal conditions great, as all they need to do is direct force towards the big main structural members. Flame them to loss of tensile strength and you get trouble faster. All you really need is to reach a threshold – past it, failures will begin cascading fast.
OK - two things here. First of all, the heat generated by the impacts and the collapse was enormous- a week after the collapse you could still feel the heat coming from the site as they pulled glowing iron beams from the wreckage. The heat from fires was definitely part of Al-Qaeda’s plan: shortly after the attacks I remember reading (!) that they thought that the WTC would collapse, but they weren’t sure. They were counting on burning jet fuel to weaken the structure.
Since then, I have also read that during the WTC construction some sort of EPA regulation was enacted that forced the builders to stop using asbestos or some other fire-resistant material. The most paranoid in the world say that the hijackers knew when this happened (ie at what floor asbestos stopped being used) and purposely aimed above those floors in order to cause the most damage.
Any reliable sources for the actual construction issue? Did the WTC change materials 3/4 of the way up?
The documentary I saw on PBS said that the floor beams were fire protected by spray-on fire retardant and the center columns by drywall. The mechanical impact of the planes blew off the spray-on and dislodged the drywall so that burning fuel could run down the center columns. The steel was then directly exposed to the flame temperature. As has been pointed out, a structure is a system and failure of one part increases the load on another part and can lead to progressive collapse.
There are several web sites on the investigation. Take your pick.
The PBS show stated that the jet fuel burned off in the first 90-120 seconds, after it spread down the elevators. However, every floor contained tons of paperwork, paper-based acoustic ceiling tile, wooden furniture, foam-filled upholstery, etc. All of that stuff burns hot enough to weaken steel. The core- and-shell structure of the WTC’s plan may not have been as sound as originally believed.
I have an idea that the melting point of aluminium is higher than its ignition point. That is, if molten aluminium is in contact with air it will catch fire and burn. Isn’t that the reason you need an argon arc welder to weld aluminium?
Regards,
Agback
:eek: There aren’t words to decribe that sort of wilful ignorance. I was going to attempt a systematic debunking (none of the points are particularly difficult to address), but it would involve quoting nearly the whole article.
I don’t think so (or it may be true, but only if there is sufficient oxygen (i.e. the aluminium is powdered or something)); I remember casting items of aluminium in metalwork class with no special considerations to the stuff burning.