Festival of Science:RESEARCHERS HOPE to develop new types of construction steel that will be able to withstand the kind of high temperatures that were caused by two hijacked airplanes crashing into the World Trade Center's twin towers on September 11th. The researchers' work has been aided after discovering what actually happened to cause the buildings to collapse.
The twin towers would not have fallen were it not for the loss of thermal insulation panels installed to protect their high-strength steel, stated Dr Sergai Dudarev of the UK Atomic Energy Authority. These protect the steel from ordinary fires where temperatures can rise to 500 - 600 degrees, he said.
Similar temperatures were reached as aviation fuel started to burn. "The problem with the collapse of the twin towers was not the fire in the building. The impact of the plane knocked off the thermal insulation panels on the steel," he said. Asked whether the buildings would have survived had the panels remained in place, Dr Dudarev stated: "Absolutely, yes."
He was speaking yesterday at the University of Liverpool during a session at the British Association for the Advancement of Science's annual Festival of Science.
Support steel in buildings is clad with thermal insulation to protect it against fire because it loses its strength as the temperature rises, Dr Dudarev said. While this has been known for centuries, scientists were unclear what actually caused this change. The degree of weakening was detailed in research that followed the collapse of the twin towers, he said.
An initial report showed steel strength falls by 20 per cent at 400 degrees and by 90 per cent at 650 degrees. "It is very surprising that steels collapse at 500 degrees," he said.
Dr Dudarev studies steels exposed to high-temperature environments such as nuclear reactors where some locations are exposed to up to 400 degrees. "It is a problem of how to make steels for applications where high temperatures are involved," he said.
Yet these temperatures and those reached in the twin towers are much less than the 1,538 degrees at which steel melts. He began studying the internal structure of steel to understand how it could turn into something with the consistency of plasticine long before reaching melting point.
The answer proved to be a surprise: "magnetic dislocations" or magnetised iron atoms, distributed throughout the steel lattice.
"The origin of the twin towers collapse was related to magnetism within the steel," he concluded. "Through that steels lose strength and buildings collapse."
Understanding this phenomenon should allow the development of new steels that do not contain magnetic dislocations. "This research shows us where we should look. You have to alter the chemical structure in a coherent way to eliminate the dislocations."
The result should be steel that retains its strength beyond the 500 - 600 degrees experienced in a building fire.
