- The Washington Times - Tuesday, April 5, 2005

NEW YORK — The World Trade Center towers could have survived the terrorist strike by two hijacked jetliners on September 11 and the resulting fuel-spawned inferno if the impact had not shaken critical fireproofing off steel supports, government investigators said yesterday.

A report by the Commerce Department’s National Institute of Standards and Technology said the towers’ size and their strong and innovative design prevented a larger and faster collapse immediately after the attack, giving thousands of people time to escape.

“The buildings would likely not have collapsed had it not been for the fireproofing dislodged,” said Shyam Sunder, the study’s lead investigator.

The report is the result of two years of work by about 200 federal investigators tasked by Congress to study how the towers’ design and materials withstood the attack, the reason for the collapse and the effectiveness of rescue and evacuation procedures.

The investigation’s goal is to recommend improvements to building design, construction and maintenance, especially for skyscrapers. The agency plans to issue recommendations for public comment in June.

While the report said the condition and thickness of fireproofing before the attack did not significantly contribute to the collapse, preliminary recommendations for future building design include using steel more resistant to extreme heat and fireproofing less likely to be stripped off by an impact.

However, Mr. Sunder said, “designing buildings for airplane impacts is not part of building codes and probably will not be done, because it’s more cost-effective to keep terrorists away from planes and planes away from buildings than to design a building to do this.”

The agency’s research and testing, including detailed computer simulations of the attacks, produced more than 10,000 pages of data. Much of it concerns a step-by-step analysis of how the towers fell.

First, the jets sliced through outer columns, damaged interior supports and shook off fireproofing. Then fires started by jet fuel and fed mostly by office furniture and paper weakened the building cores and floors. The collapse ensued when the floors sagged, pulling in outer columns that buckled after being weakened by fire.

Blaming heat from intense fires as a central cause agrees with earlier research into the collapse.

NIST investigators said their likely collapse sequence is supported by photos, videos, recovered steel, eyewitness accounts and records of emergency communications.

At the time of the attack, about 8,900 people were in the first tower and 8,500 in the second. About 87 percent of occupants got out, including 99 percent of those on floors below the impact of the planes, the report said.

Improvements made to the World Trade Center after the 1993 bombing, including better sprinkler and fire-alarm systems and command centers for police and firefighters, did help rescuers respond.

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