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Twin Towers toppled by weakened steel columns -

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Twin Towers toppled by weakened steel columns

At high temperature, the strength of steel is controlled by magnetic properties. It is a quantum
effect, and explains why the Twin Towers in New York collapsed in 2001. The thermal insulation
panels on the columns were knocked off by the impact from the aircraft, exposing the steel to the
high temperatures of the fire. The solution is applying the insulation in a different way, or using
new steels with additives, allowing them to maintain strength at high temperatures.


Robyn Williams: You may have noticed that we're around the time of the anniversary of September
11th and the crash into the Twin Towers. One of the most interesting papers at the conference in
Liverpool was presented by Dr Sergei Dudarev of the United Kingdom Atomic Energy Authority. This
was about the ways in which steel is deformed by high temperatures in a way that hadn't been
appreciated before and could well account for the reasons that they collapsed. What in fact have
you found about what takes place with steel over temperatures of 500 degrees Celsius?

Sergei Dudarev: The most interesting aspect of steels at high temperature is that their strength
turns out to be controlled by their magnetic properties, and you would not normally associated
quantum mechanics with such large-scale events as building collapse. But it turns out (and this is
the result of the most recent research) that the properties of steels and their mechanical strength
is controlled fundamentally by their magnetic properties, and this offers an explanation for the
loss of strength of construction steels in the Twin Towers, but also offers a very positive way
forward because we now understand what happened in designing steels that would be resistant to this

Robyn Williams: In fact they thought that the steel should be okay up to about 1,500 degrees C.

Sergei Dudarev: Fifteen-hundred degrees centigrade is the temperature at which iron or steel melts.
In the case of the Twin Towers, temperatures rarely go above 500 or 600 degrees centigrade. What
actually happened in the Twin Towers is unfortunately the thermal insulation panels were knocked
off by the impact. Had they stayed in place the buildings would have survived and nothing would
have happened. It was just an unfortunate direct exposure of steel structures to temperatures of
500 or 600 degrees centigrade that caused the collapse.

Robyn Williams: Is it surprising that people hadn't realised this before? A material like steel is
very, very common, it's been used for thousands of years and blacksmiths had taken advantage of the
fact that it's malleable at certain temperatures, that's how they fashion it. Why wasn't it known
that this catastrophic change could occur?

Sergei Dudarev: In fact it was known to engineers that if you raise temperature above, say, 600
degrees centigrade that it is not good news for the structural steels, and this is why the thermal
insulation panels were installed to protect the building from events like normal fire in the office
where somebody dropped a cigarette in a paper basket. But from the perspective of fusion research
which looks at the possibility of using steels at temperatures as high as 1,000 degrees centigrade,
there is no possibility of installing the thermal insulation panels.

Robyn Williams: This is fusion research like nuclear reactors and so on.

Sergei Dudarev: Indeed, it is very similar, and what is really a new aspect is the identification
of the microscopic cause of the collapse. Now, knowing this, we can design new chemically different
steels where we deliberately control the behaviour of magnetic moments at high temperatures and
hence control the mechanical properties.

Robyn Williams: I must say, the live pictures you've got of those wobbling molecules are quite
compelling. But what do you have to do add...which chemicals, and do you know yet how to make this
super steel?

Sergei Dudarev: Well, it is a large European project, colleagues from Germany, Switzerland, France,
ourselves, where we do experiments on various steel compositions, but what we learned from the
research we've just accomplished is we definitely need to take a broader view at what we call
steels. Most likely quite common elements could be used in order to control the magnetic properties
and hence the mechanical properties.

Robyn Williams: Does this scotch some of those many conspiracy theories (I'm sure you're familiar
with them) and explain actually what happened?

Sergei Dudarev: The answer to the terrible tragedy is had the thermal insulating panels been glued
better to the steel structures, nothing would have happened, or at least the buildings could have
been evacuated before they collapsed. It is a predictable outcome of very strong fire in a building
where a conventional steel proved to be unsuitable for the purpose, so partially the answer might
be in the use of different steel that remains mechanically stable at high temperatures, or
partially in the design of better protected structures using thermal insulation materials.

Robyn Williams: Dr Sergei Dudarev from the United Kingdom Atomic Energy Authority, thank you very
much indeed.

Sergei Dudarev: Thank you very much.