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9/11: From 'Kiss' To Collapse

In the first of a two-part series, CBSNews.com's David Kohn reports on an Iranian engineer who's trying to reconstruct exactly how the twin towers collapsed.

At just after 6 a.m., on September 11, the telephone rang at Hassan Astaneh's house in Berkeley. Astaneh was asleep, and his son got to the phone first. It was a friend, calling from San Francisco airport, where he had been due to take an early flight. "Daddy, he says that you should turn on the TV," his son told him. "There has been an accident." Astaneh went into the living room and switched on the television, which showed the twin towers burning.

He saw right away that with the intense fire, the buildings were in trouble. He knew the towers were made of steel, and that steel loses its rigidity at temperatures above 1000 degrees Fahrenheit. "It becomes, not melted, but mushy, like wet clay," says Astaneh. When the buildings collapsed, he was not surprised.

A professor of Civil and Environmental engineering at Cal Berkeley, Astaneh testified on Capitol Hill last week before a congressional committee looking into the trade center collapse. He believes that the intense fire softened the steel columns to the point that they could no longer bear the weight of the floors above. When the columns buckled, the 20 or so unsupported stories – more than 28 million pounds of steel and concrete – plummeted, crushing whatever was below.

"It's like taking a 20-story building and dropping it on a 90-story building," says Astaneh. "That 90-story building will go down like a pancake. Gravity was the cause of the collapse, not the airplanes. It was basic physics. It was gravity doing its job."

But for Astaneh, this explanation is just the beginning. For 30 years, he has studied the behavior of steel under stress. "It just happens that I have been watching for decades how steel bends and buckles," he says. For the past five months, he has been consumed with reconstructing the last 100 minutes of the towers' existence. In January, he began a year's sabbatical so he could focus solely on that work.

"I want to know what happened from the moment when the nose of that plane touched the building, that point, as we call it, when the plane kissed the building," he says. "From then until everything was stationary. It is not enough to say 'Oh, fire went on and killed the building.'"

He compares himself to an AIDS researcher 20 years ago. By that point, scientists knew that a virus was the culprit. But that knowledge was only a small step toward a cure. "We need the details," he says.

To discover these details, he is examining the remains of the buildings, looking for the telltale clues that will reveal the precise sequence of collapse. He has become an archaeologist of destruction. It is an enormously complex task, one that depends on knowledge, intuition and luck.

The research is more than an autopsy. By studying how the towers fell, engineers hope to learn how to make tall buildings that are less vulnerable to terrorism. "This was the most important structural failure in the history of structural engineering," he says. "It will change how we make buildings." According to Astaneh, the United States alone has around 50 "major" skyscrapers, defined as over 50 stories, with at least 5,000 occupancy.

A lanky man with a droll sense of humor, Astaneh, 54, came to the U.S. from Iran in 1978 to study engineering. He flew into LaGuardia Airport on Thanksgiving night.

"I really didn't know much English. We saw that there was a big table and these people are giving out free sandwiches. It was for Thanksgiving, but we didn't know that. I saw that this is a country that gives you free sandwiches when you arrive. I always say that that was the time I decided to stay." In truth, he planned to return to Tehran, where he was already an established engineer. But after the Khomeini revolution and the hostage crisis, he decided to stay, convinced that the U.S. would provide a better opportunity to do cutting-edge research and make a living.

"He's a very sharp guy," says researcher David McCallen of the Lawrence Livermore National Laboratory. McCallen and Astaneh have collaborated on a number of projects over the past five years. "He came to this country and could hardly speak English. Anybody that can go to grad school and learn English at the same time is not chopped liver in my book. He's very intense and focused, and he has a very good intuition about the behavior of structures."

Since Sept. 11, Astaneh's ethnicity has brought him extra scrutiny, especially when combined with his fervent interest in how explosions affect buildings. When he first came to New York the week after the attack, two FBI agents came to his hotel minutes after he had checked in. They questioned him for an hour before deciding that he was not a terrorist. (Unbeknownst to Astaneh, the hotel, the Tribeca Grand, was also being used by many of the law enforcement agents who swarmed to the scene after the attacks. Suspicious that a solitary traveler with a Middle Eastern name had chosen to stay in a hotel full of federal agents, hotel staff had alerted the FBI as soon as he checked in.)

Astaneh, who is a practicing Muslim, takes these suspicions in stride. He usually wins over the wary with his humor and enthusiasm; by the end of the interrogation he was giving the FBI agents a short course on the behavior of steel structures under stress. "This country has given me enough that I should look at half full side of the glass," he says. "For me it is more than half full."

He feels a deep gratitude to his adopted country. "Imagine, you come from Iran, you have nothing but yourself and your brain. You come to this country and they recognize that your brain is valuable. I didn't have any connections. My name is not easily spelled, I don't have money, I don't have anything. You come here and they give you citizenship, they give you permanent job. They take you in with just one luggage and yourself and your family. I am enjoying all the freedom I have. I can go to Iran, I can come back. I have health coverage, I have shelter, I have food, I have best job. I always feel 'What can I give back now?'"

Until 1995, Astaneh studied only how steel structures were affected by earthquakes. Then Tim McVeigh blew up the Murrah Federal Building in Oklahoma City. The bombing had special resonance for Astaneh. In 1987, while on the faculty of the University of Oklahoma, he had become a U.S. citizen on the fourth floor of that building. "It was my Ellis Island, the Ellis Island of my family," he says. "When I saw that building collapsed, I felt something."

He decided to focus on blast resistance, a field that then barely existed, and one about which he knew nothing. He began reading everything he could find on the subject; within three years, he had become an expert. He played a key role in developing an innovation known as the "self-anchoring floor," which keeps buildings from immediately pancaking when supporting columns are destroyed. (Most of the casualties at the Murrah Building were not caused by the explosion itself but by the ensuing collapse, which would likely have been prevented by self-anchoring floors.)

Despite his expertise, Astaneh initially had no idea how to go about studying the twin towers' collapse. "We haven't studied a building hit by a plane," he says. "We have to invent the tools as we go along." The week after the attack, he flew to New York, paying his own way. He didn't know what he would find. He learned that the steel from the buildings was being taken to a Jersey City scrap yard, where it was being chopped up and recycled. He made his way there and began examining the wreckage.

Throughout the fall, Astaneh went to the yard. For weeks at a time, he visited daily, examining the steel as it arrived. While welders cut the steel into smaller pieces, he prowled around, looking for key "members," as the beams and columns are known.

It is a search for mangled needles in a haystack of twisted steel. "My job is to figure out which member was damaged when it was up there, not when it fell down," he says. "That percentage is much less than one percent. Of course everything was damaged when it fell. The total steel in the buildings was 300,000 tons. I am looking for 300 tons, at the most. These are members that were hit by the plane. Those are critical. Also, I want to get hold of the members that were from floors where the planes went in and the fire went on; they were in the fire, and they are the reasons why this whole collapse started."

He has catalogued and photographed a few dozen members and set aside about ten key pieces for further study. He has also kept assorted smaller fragments, which he took back to Berkeley for chemical analysis. Fearing that airport security might look askance at an Iranian whose suitcase was filled with chunks of charred steel from the World Trade Center, he Fed-Exed these to California.

Part II: Culling Through Mangled Steel

Written by David Kohn;