Engineer: Towers collapsed from fires


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

buildings bomb-resistant.