Engineer: Towers collapsed from fires
By JEFFREY GOLD
The Associated Press
JERSEY CITY — A structural engineer examining the
twisted bones of the World Trade Center said Friday he
has tentatively concluded the towers collapsed because
of intense fires fanned by jet fuel.
The interior steel remained supportive after the
crash, only buckling when the fire exceeded 1,000
degrees, Abolhassan Astaneh-Asl said.
“The impact did nothing,” Abolhassan Astaneh-Asl said,
pointing to a massive interior column from the south
tower that he believes remained standing even after
three-quarters of it was sliced away by a jet part.
He expects that research will examine whether a
tougher skin for future skyscrapers might be useful in
deterring similar assaults. A steel-concrete composite
exterior, for example, might crumple a plane and keep
more fuel outside, he suggested.
“This building could not fight. It was just innocently
standing there and somebody shot it,” said
Astaneh-Asl, a professor of structural engineering at
University of California-Berkeley.
Pieces of one of the planes — the largest the size of
a business envelope — were found imbedded in steel
facade columns of one tower on the opposite side from
where they entered, Astaneh-Asl said.
“The airplane did not do much damage,” he said,
showing bolts and fasteners that suggest to him the
towers were well designed and well constructed.
Once beams supporting the floors began to buckle in
the fire, the floors pancaked and that brought the
towers down, he said.
Astanah-Asl, under a grant from the National Science
Foundation, plans to build a computer model of the
towers from data gleaned in the mounds of steel at
ground zero and at a massive scrap yard in New Jersey.
The computer model will examine if the buckling could
have been prevented and whether additional
fireproofing would withstand even a fully fueled
airliner, he said. The steel had protection for about
three hours of an office fire, he said.
“All scenarios will be looked at,” Astaneh-Asl said.
Workers at the Hugo Neu Schnitzer East yard in Jersey
City, just a mile across the Hudson River from the
Trade Center, saw the towers fall.
They have now been trained to alert Astanah-Asl to
possible clues as they labor round-the-clock with
torches and heavy machinery, cutting into steel panels
up to 6 inches thick.
Eventually, nearly all of the estimated 310,000 tons
of Trade Center steel will be diced and sent to mills,
where it will be melted and forged again, Hugo Neu
general manager Robert A. Kelman said.
The south tower interior column with a chunk missing
was probably hit by the jet’s nose or an engine, and
was between floors 47 and 78, he said, adding that the
location will eventually be pinpointed.
The hollow rectangular column has four sides (16 and
32 inches wide), composed of steel 1.5 inches thick.
Analysis of the sheared face would help determine how
fast the jet was traveling at that time, Astaneh-Asl
Astaneh-Asl, 53, led a team that studied damage to the
San Francisco-Oakland Bay Bridge after the 1989 Bay
Area earthquake, and has investigated methods to make