Hi Orcastraiter; Re: "It will have been the first steel building to collapse due to fire alone then."
This isn't accurate. For example:
The FEMA report further states that until the attack at the WTC, no protected steel-frame buildings had been known to collapse as a result of a fire. The key word is "protected." In Chicago, Illinois, the McCormick Place Exhibition Center collapsed as a result of a fire in 1967. In this structure, the steel-frame of the building was unprotected. The reference to McCormick Place is significant because it illustrates the fact that steel-frame buildings can collapse as a result of exposure to fire. This is true for all types of construction materials, not only steel.
iaei.org
But what really matters here is the nature of the fire.
I think you're failing to take into consideration the importance of the rate at which the fire burns. It's pretty obvious that if the fire takes, for example, a couple of days to burn through a building, the maximum temperatures in the structure will be far less than in a building where the whole thing burns in a few hours.
A normal fire gets started at one point and then slowly spreads. But the WTC fires were created by catastrophic events that set fires over a wide region of the building simultaneously, along with fuel. This sort of fire is going to get a lot hotter a lot faster, and will more likely drop a steel framed building.
As an example, there was recently a fire in a Madrid steel framed building that partially collapsed it. The conspiracy crowd say that the fact that it only partially collapsed is a clue. But the fire burned for 26 hours. The WTC6 was set on fire on multiple floors simultaneously along with a great deal of wind. Of course that's going to burn very much hotter than a fire that slowly spreads from floor to floor through the ventilation holes.
I would think that steel buildings that are set on fire at multiple points simultaneously are likely to collapse. Probably the best examples of this sort of behavior would be during the fire bombings of the Axis powers of WW2, but it's difficult to find details on the net.
There was a steel framed building in Spain that partially collapsed after a fire of 26 hours. The conspiracy crowd are claiming that since the fire lasted 26 hours and the building survived, the WTC should have survived a fire of only a few hours. But this logic is silly. It's well known in fire circles that fast fires are more dangerous for steel buildings, while slow fires are more dangerous for concrete. The reason is that steel will conduct away the heat from a slow fire and stay cool and strong, while concrete conducts heat slowly and requires a long baking time to fail.
Here's an example of a steel framed building that burned down in the US recently:
"Fire destroys aircraft hangar
California - A metal aircraft hangar containing a fixed-wing plane and a glider was destroyed when heat from a fire caused it to collapse. The fire may have been burning for some time when a passerby discovered it, since the building had no fire-detection or -suppression systems. Built on a slab foundation, the single-story, steel-frame hangar had metal walls, a metal roof, and partition walls that divided the building into several sections that could be sublet. However, the walls didn't extend to the ceiling."
www.nfpa.org/displayContent.asp?categoryID=709&itemID=19683
Re: "Can you explain how the building collapsed symmetrically in free fall time? For that to happen, every column in the entire building would have had to reach critical buckling loads simultaneously. The odds of that happening due to fire alone are astronomical."
When one member collapses, the weight it once held falls on other members which then collapse. It's near simultaneous, particularly when there is some sort of common element failing, and especially when the design was particularly balanced (like a soap bubble).
Of course an objective of architecture is to design buildings that don't fall down. But it should be noted that this is in tension with the objective of designing buildings that are inexpensive. My unprofessional opinion is that the architects were a bit light on the WTC design. The nature of any engineering is to every now and then discover, through disaster, that one has built something with a bit too little margin of safety. It's also possible that the material used to protect the steel wasn't up to par.
Things that are designed to be "just strong enough" are naturally going to fail simultaneously in multiple places. This is what modern engineering is all about, something that could only be dreamed of a century or two ago. An appropriate poem:
The Deacon's Masterpiece or The Wonderful "One-Hoss Shay": A Logical Story
Oliver Wendell Holmes
Have you heard of the wonderful one-hoss shay,
That was built in such a logical way
It ran a hundred years to a day,
And then of a sudden it -- ah, but stay,
I'll tell you what happened without delay,
Scaring the parson into fits,
Frightening people out of their wits, --
Have you ever heard of that, I say?
...
legallanguage.com
And what is this BS about how modern steel buildings are impossible to burn down because they're designed to be resistant to it. I suppose you think that modern beef can't have dangerous bacteria? That modern aircraft can't crash accidentally? That modern mining companies never pollute the environment? That modern intelligence agencies can't be wrong about WMDs? That modern oil companies can't spill oil? That modern automobile manufacturers never produce dangerous cars? That the modern military doesn't kill civilians? I mean, what kind of perfection are you assuming of the architects and engineers here? The fact is that humans are disasters waiting to happen. What the WTC showed is that some steel framed buildings are insufficiently resistant to fire.
-- Carl
P.S. Also of interest:
www.bfrl.nist.gov/pdf/GCR04_872.pdf
www.royalsoced.org.uk/events/reports/2003-2004/fire_structures.pdf |
