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Thursday, September 11, 2008

From Steel in Failing Towers to Steel in Functioning Fusion Reactors

posted by on September 11 at 13:51 PM

Via the BBC:

Scientists say an understanding of how the Twin Towers collapsed will help them develop the materials needed to build fusion reactors.

New research shows how steel will fail at high temperatures because of the magnetic properties of the metal

The key advance is the understanding that, at high temperatures, tiny irregularities in a steel’s structure can disrupt its internal magnetic fields, making the rigid metal soft.

“Steels melt at about 1,150C (2,102F), but lose strength at much lower temperatures,” explained Dr Sergei Dudarev, principal scientist at the United Kingdom Atomic Energy Authority (UKAEA).

At room temperature, the magnetic fields between iron atoms remain regular, but when heated, these fields are altered allowing the atoms to slide past each other, weakening the steel….

The peak in this pliability is at 911.5C, but begins at much lower temperatures, at around 500C (932F) - a temperature often reached during building fires.

The steel backbone of the Twin Towers was probably exposed to temperatures close to this, when insulating panels - meant to protect the buildings’ structural frame - were dislodged by the impacts of the hijacked planes.

Part of the mysteries of the falling towers has to do with the extremity of the situation. Steel really hadn’t been placed into such a situation—with both intense heat and enormous stress and strain—before the towers fell. We learned something about our world that we can now apply to the future.

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Posted by Looserman | September 11, 2008 2:05 PM

there is no "mystery of the falling towers". there is a reason that steel structure is insulated from fire. this is it.

Posted by max solomon | September 11, 2008 2:10 PM

Max Solomon--

Of course. Like the article I linked to noted, it's been known for centuries that steel becomes much more pliable at temperatures well below its melting point. (Or, as the engineers would say, the Young's modulus of steel rapidly drops above 500c.)

Why this happened was not clear, until this recent research.

Posted by Jonathan Golob | September 11, 2008 2:16 PM

high temperatures are also useful for making pancakes.

Posted by uncle baggy | September 11, 2008 2:27 PM

September 11 can be useful for something other than the dismantling of civil liberties? Right. I'll make sure I visit you in the federal pen for that statement, Science.

Posted by P to the J | September 11, 2008 2:47 PM

What about the other steel buildings that withstood fires without collapsing?

If fires didn't melt the steel, why was there molten steel at ground zero?

Posted by skeptic | September 11, 2008 3:48 PM

Skeptic --

You know, I've wanted to write a post translating the ASCE (American Society of Civil Engineer) report about what happened on 9/11 to plain English.

My concern is, no matter what or how I wrote such a post, there would be a surprising number of people who would ask me questions like "why was there molten steel at ground zero?" Or, I would have my integrity questioned.

Part of thinking scientifically is accepting and interpreting the best available evidence, even when there are holes or inadequacies. Rarely do we get definitive observations; most of the time we have to muddle through with what we have, rather than the perfect proof we'd want.

But, I'll take your questions seriously, skeptic.

Why did the towers collapse, when other fires in steel framed buildings didn't cause collapses?
1. The WTC towers were among the tallest ever built.

2. The WTC has a very unusual structural design. Unlike almost any other skyscraper, the cladding of the WTC was integral to the structural integrity of the towers. There was far less steel and far fewer supports than in almost any other building. This meant the steel that was there was under greater stresses than is typical in a skyscraper, particularly after the exterior cladding was damaged by the aircraft.

Why was there molten steel? The energy released by the falling towers--the gravity potential energy--was on the order of a small atomic bomb. So, before the towers collapsed--during those 102 minutes between the first plane striking and the second tower falling--the fires got the heat up high enough to make the steel pliable. Once the building started the cascading failure, the heat was generated by the falling itself. The energy released when a tower of that height and mass is dropped to ground is what melted the steel, and kept the collapse going.

Posted by Jonathan Golob | September 11, 2008 4:17 PM


Seriously though, Charles Pellegrino's book Ghosts of Vesuvius, which I plug shamelessly in pretty much every 9/11 related post, has an excellent description of the downblasts and surge clouds created by the towers' collapse, and the similarities between the physics of that disaster and the destruction of Herculaneum.

Posted by Greg | September 11, 2008 4:34 PM

Jonathan, wouldn't you expect the lower floors to provide some resistance to those above, slowing the collapse? The timing of the falls suggest they didn't -- these things fell at near-freefall speed.

Note that as reported by Peter Tatchell of The Guardian on September 12, 2007, chair and vice chair of the 9/11 Commission, Thomas Kean and Lee Hamilton, have since stated that they were "set up to fail" and were starved of funds to do a proper investigation. They also confirm that they were denied access to the truth and misled by senior officials in the Pentagon and the federal aviation authority; and that this obstruction and deception led them to contemplate slapping officials with criminal charges. Also note that despite the many public statements by 9/11 commissioners and staff members acknowledging they were repeatedly lied to, not a single person has ever been charged, tried, or even reprimanded, for lying to the 9/11 Commission.

The final report did not examine key evidence, and neglected serious anomalies in the various accounts of what happened. The commissioners admit their report was incomplete and flawed, and that many questions about the disaster remain unanswered. Despite these unanswered questions, the 9/11 Commission was closed down on August 21, 2004.

Do you think we should find out what happened?

Posted by Phil M | September 11, 2008 4:41 PM

Phil M, I think you should find out what happened. Then tell everybody you can find.

Remember, the fastest way to disseminate information is via sandwich board and megaphone.

Posted by Chris in Tampa | September 11, 2008 4:48 PM

Phil M--

"Do you think we should find out what happened?"

Sure. The ASCE reports on the subject are compelling, comprehensive and do a decent job of working around the holes in the available information. That model for the collapse of the WTC towers seems to best fit our available knowledge.

Until a complete, sensible, fact-based model that better fits the available information comes along, I'm sticking with the ASCE's model.

Do you have such a complete model? Not a bunch of things you don't like about the ASCE's, but an actual, empirically-verified model, up to the level of a structural engineer's rigor?

Science is about ideas being proven with evidence. The ASCE report assembled the available evidence in an unbiased manner and came up with a model explanation that encompassed this available information.

A rational critique isn't a list of questions, but rather a comprehensive model that is supported by evidence. Do you have a rational critique? An alternative model that better fits the available data?

Posted by Jonathan Golob | September 11, 2008 5:05 PM

For those of you who are rational, check out the NIST report on the WTC collapse(PDF).

It's well written and really presents the collected data in a very honest and open manner.

If you want a bit more of a human-focused, rather than engineering-focused, report, check out the book 102 Minutes.

Posted by Jonathan Golob | September 11, 2008 5:27 PM

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