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news
Engineers explain
WTC collapse
By Larry Brunson
Jr.
On-line Forty-Niner
Many people have
wondered why the World Trade Center collapsed only after about
30 minutes of burning. Contractors for the twin towers said
that the towers would be able to withstand bomb damage; unfortunately
this was not the case last week.
According to Amir
H. Aryan, a civil engineering lecturer at Cal State Long Beach
and licensed civil engineer, the heat from the jet fuel was
over 1,000 degrees, which caused the steel foundations of
the towers to lose its structural integrity.
"In aerospace
engineering, what happened to the towers is known as the zipper
effect," Aryan said. "One floor fails, then another
floor fails, and the structure gets weaker and weaker causing
an accelerated collapse."
Aryan said the
towers were very safe buildings, and were designed to withstand
earthquakes, hurricanes, and strong winds, but they were not
designed to withstand the heat generated from jet fuel.
Steve Tsai, chair
of civil engineering, said it was speculated that the amount
of fuel burning from the explosion of the planes explains
why the towers collapsed.
"Engineers
suspect that the heat and fire weakened the structures, causing
them to collapse," Tsai said.
The collapse of
the towers happened at an alarming rate, according to Tsai.
This was a progressive collapse, meaning the collapse was
like a chain effect.
"Perhaps many
of the floors in the towers had already collapsed that we
couldn't see, and then all the weight and pressure caused
the structure to collapse," Tsai said.
Joseph Plecnik,
professor of civil engineering, said approximately 6,000 to
10,000 gallons of fuel from both planes that crashed into
the twin towers, causing them to burn for so long.
Since the towers
were built with steel beams, the tremendous amounts of fuel
and heat from the explosion caused the steel beams to melt
on the top floors of the towers. The melted steel weighed
the building down, causing the concrete to crack on each floor,
inducing the towers to collapse, according to Plecnik.
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