The fire was hot enough to melt the steel!

BTW, I wonder what happened to the numerous oxygen genenerators that were carried on board the airplane?

Originally posted by HowardRoark

So if the fireproofing was knocked off the truses by the shock of the airplane impact, then it would only take about 15 to 20 minutes of exposure to a full developed fire before the trusses buckled and failed.

How did the plane impact knock the fire proofing off enough of the trusses for all of them to fail?

At most maybe 5 floors and maybe at most 50% of the fireproofing on each floor.
Again how did that allow the fire to heat up enough of the trusses to bring the whole building down?

Your fireproofing theory just does not hold up, however you look at it.

Since the Madrid Windsor Tower fire has been mentioned in this thread I would like to follow it through.

Firstly no plane flew into this building.

Secondly it was 32 stories high, slightly smaller than any of the WTC's.

Thirdly and most import it had a concrete core.

This concrete core supported the steel super stucture ......any idea what happend to the steel super stucture? .....it collapsed

That's correct it failed.

www.concretecentre.com...

Dr. Pal Chana of the British Cement Association demonstrated the relative likelihood of floor collapse in a steel versus concrete framed building, using the vivid example of the Madrid Windsor Tower fire which raged over 26 hours on 14-15 February 2005. This former landmark office block of 30 storeys featured a concrete core throughout, but with concrete columns up to the 21st floor and steel columns between the 22nd and 30th floors. Remarkably, despite the intensity and duration of the fire, the concrete floors and columns remained intact however, the steel supported floors above the 21st floor collapsed, leaving the concrete core in-situ and exposed

An investigation is underway between Spanish technical agency Intemac and UK authorities including Arup Fire, the University of Edinburgh and the concrete industry including Cembureau, BCA and The Concrete Centre. Preliminary findings suggest that a combination of the upper technical floor and the excellent passive fire resistance of the tower's concrete columns and core prevented total building collapse

www.concretecentre.com...


Of course no steel stucture has ever collapsed before due to fire but it was only the concrete core that stopped this one.

[edit on 30-3-2006 by Stateofgrace]

[edit on 30-3-2006 by Stateofgrace]

Even if the fireproofing thing did make sense as far as making trusses collapse (which would probably mean the trusses would have to be 3" and placed directly into the heat given how Howard likes to source things), it wouldn't explain why the core collapsed, or any other floor systems besides one or two, or any perimeter columns.

Trying to explain how the collapses initiated is only half the problem, if that, anyway. The initiations were nothing compared to the miraculous global collapses. Yet oddly enough, the initiations are the only things organizations such as NIST, and people such as Howard, focus on. Everything beyond that was just "inevitable."

Originally posted by Stateofgrace
This concrete core supported the steel super stucture ......any idea what happend to the steel super stucture? .....it collapsed

Ok, man, the plane impacts knocked out less than 15% of the columns in either tower, alright?

So if you want to raise that point in the case of the Windsor Tower, you should also be aware that the steel "columns" used in that building looked as though they were about 3" thick. Do some image searches and you'll see that the exterior "columns" (more like pipes if you ask me) aren't in the least comparable to the thick beams that made up both Twin Towers.

Not to mention the Windsor Tower Fire was a lot more intense and lasted a lot longer. When you couple that with the puny steel beams, you come up with happens to steel when it's too small to conduct heat very well. And even then, only some of the steel failed in that building.

Originally posted by ANOK

Originally posted by HowardRoark

So if the fireproofing was knocked off the truses by the shock of the airplane impact, then it would only take about 15 to 20 minutes of exposure to a full developed fire before the trusses buckled and failed.

How did the plane impact knock the fire proofing off enough of the trusses for all of them to fail?

At most maybe 5 floors and maybe at most 50% of the fireproofing on each floor.
Again how did that allow the fire to heat up enough of the trusses to bring the whole building down?

Your fireproofing theory just does not hold up, however you look at it.

Even under optimum conditions, sprayed on fireproofing is a fairly friable material. it is simply not designed to withstand that degree of impact.

Besides for the physical impact of the plane with the building, you also had the massive fuel air explosions that blew out windows on numerous floors.

Going back to the truss paper,




It only takes between 10 to 20 minutes for an unprotected truss to heat up in a standard fire scenario. Lets say it take 30 minutes.





The truss is still going to fail.

Even if only 50% of the trusses for a given floor slab failed, are you that confident in your knowlege of structural engineering to blindly state that that would not be enough to cause the floor slab to fail?

The floor slabs provided a critical function in the structural design of the WTC towers. They served to stabilize the exterior walls from buckling.

The critical load at which a slender column will buckle is given by Euler's formula:



Where

P-Crit is the critical load at which the column will buckle,

E = Modulus of elasticity of the material

I = Area moment of inertia

and L is the length of the column between supports (or the unpinned length).

Thus, if one floor slab fails to provide the required lateral resistance (i.e. it starts to sag), then the effective length of the column between supports is doubled. Since the above formula is an example of an inverse square law, doubling the length cuts the value for P-Crit to one quarter of the original value.


If two adjacent floors fail, then your down to 11% of your original value.



[edit on 30-3-2006 by HowardRoark]

[edit on 30-3-2006 by HowardRoark]

Ah, nvm.

I said Howard was probably basing that info off of 3" pieces of steel, but it was that >3cm stuff again. XD

And I still wonder how your typical, open-atmosphere hydrocarbon fire, with a poor fuel/air ratio, is going to heat anything to even near 800 C, especially with all the heat lost to air and smoke and concrete and etc. The fact that that chart shows steel being heated to almost 1000 C shows pretty clearly that those test conditions weren't accurately representing what would've been going on in the WTC.


And I see Howard still hasn't shown any evidence that there was sufficient buckling, and still hasn't shown any evidence that a global collapse should have resulted from the failure of a single floor.

Originally posted by bsbray11
And I still wonder how your typical, open-atmosphere hydrocarbon fire, with a poor fuel/air ratio, is going to heat anything to even near 800 C, especially with all the heat lost to air and smoke and concrete and etc. The fact that that chart shows steel being heated to almost 1000 C shows pretty clearly that those test conditions weren't accurately representing what would've been going on in the WTC.

here is an interesting case study of a real fire test. Although the test was conducted in a timber framed apartment flat, it is interesting to see how high the temperature got from the fire.

Peak temperatures in the living area of the fire flat reached approximately 1000°C and remained at this level until the test was stopped at 64 minutes having reached one of the planned termination criteria.

1000 C, huh? What were they burning in there, Thermite?

Nah,

The fire test compartment consisted of a single flat on level 3 of the building. The fire load was provided by timber cribs spread over the floor area of the flat.

Clearly wood is a much more dangerous material in a fire than jet fuel.

I also found this page which has the following chart:

The effect of ventilation and fire load on fire severity is illustrated in Figure 2. Fire tests were conducted in compartments where the fire load and the natural ventilation were varied. The well ventilated compartments experienced lower temperatures and fires of shorter duration. In Figure 2 the numbers identified with each curve indicate the fire load density in kg/m2 (ie 60, 30 or 15) and the ventilation area as a proportion of the façade area (ie ½ or ¼).

Now haven’t you been claiming that the black smoke is due to the lack of oxygen? Isn’t this the same as saying that the fires were poorly ventilated? From that chart, a poorly ventilated fire is hotter, not cooler.

Note that the fire load of a typical office space runs about 30 lg/m2. But for the WTC you would have to account for the additional fire load from the jet fuel and the aircraft cabin components.


Another study of compartment fires

As can be seen in the above table, peak measured temperatures exceeded 1300oC in five tests, this measurement being supported by the observation of total heat fluxes of up to 350 kW/m2 and velocities of over 15m/s.
These values are somewhat higher than those observed in typical full-scale compartment fire tests and can be attributed in part to the highly insulating walls, the inclusion of plastic in the fuel and the short residence times (due to high flow rates).

Plastic in the fuel, huh? I wonder if that is anything like what is found in a typical office environment?

Great explanations

What people keep thinking is that all the floors had to be weakened for the building to fall... when in fact the force from the falling top 5-whatever it was floors was greater then the floors below could support.

I think we should be thankful that the buildings didn't fall over onto nearby structures.

either way the building fell in a pancake effect...but it was a controlled demolition that caused that

Ugh hmm if a pankake affect can make a building fall like it was a controlled demolition... then all you gotta start is a pankake affect

Originally posted by ConfederacyOfUnity
either way the building fell in a pancake effect...but it was a controlled demolition that caused that

Nice circular argument.

At any rate, the collapse was the result of a buckling failure of the support systems. There is no way the building could have fallen any way other than straight down.

Gravity is king.

Originally posted by HowardRoark
Gravity is king.

Gravity is actually the weakest fundamental interaction. The force that prevents solid matter from falling through other solid matter is much stronger.

Take, as an example, when WTC2 started to lean (had angular momentum), and then this lean miraculously disappeared without opposite force being applied it. If the lean had not disappeared, the top floors would've continued to tilt because the force preventing them from falling straight down through solid matter (the exact same material, only a lot more of it) is an exponentially stronger force than gravity.

That's what should have happened, too, if any collapse at all were necessary.

Coincidentally, when matter falls onto more matter, the falling matter tends to slow from the resistance. Funny that that never bothered the WTC collapses.

[edit on 6-4-2006 by bsbray11]

Has anyone mentioned possible motives for an alleged demo job? other than to provide an excuse for more DOD spending, spying on dissident Americans and putting armed troops over the second largest oil reserves in the world?
We know that Silverstein profited immensely but what about this?........
The basements of the World Trade Centre contained vaults used by the COMEX metals trading division of the New York Mercantile Exchange.
Some 3,800 gold bars, weighing 12 tons and worth more than $100 million, lie buried under the mountains of rubble left after the attack. Has anyone found out what happened to all that gold? Sounds like there were heaps of motives for the collapse, in fact there seems to be more reasons to drop the towers than reasons to leave em alone.

[edit on 9-4-2006 by haji]

[edit on 9-4-2006 by haji]