Engineer finds clues in WTC wreckage

JERSEY CITY, New Jersey (CNN) -- The jets that sliced through the twin towers of the World Trade Center were like bullets shot into people, a structural engineer said Friday.

Funded by a grant from the National Science Foundation, Abolhassan Astaneh-Asl has spent the past two weeks collecting "perishable data."

That has meant picking through debris moved from Ground Zero to a Jersey City scrap yard so that scientists can establish what failed, when and how.

The professor at the University of California at Berkeley said preliminary evidence indicates the structures withstood the impacts of the planes.

Astaneh-Asl drew that conclusion after coming across clues like a steel support 1.5 inches thick from around the elevator shaft in the center of one of the towers.

A semi-circular chunk of the support is gone. "It looks like a big bullet passed through here," he said.

Judging by the curve of the chunk, that bullet, he said, was most likely the nose of a Boeing 767.

Despite the fact that 40 percent of the steel beam was torn away, the column did not collapse, an example of redundancy built into the 1970s-vintage structure. "The impact did nothing to this building," he said with admiration.

Instead, a preliminary examination shows it was the fire with heat exceeding 1,000 degrees Fahrenheit that caused the steel to fail and the floors to drop, pancaking into mounds of debris, he said.

Astaneh-Asl came across another piece of steel with a slice through part of it, "like a knife on butter."

He suspects that the mark was left by the plane's wing. "Steel doesn't fracture like this unless it's hit by something sharp and fast," he said.

And he found a chunk of solder that had been in a toilet. He plans to send it to a lab at the University of California, where researchers will try to determine how hot it was inside the bathroom.

Much of his work, though, is mundane: Collecting pieces of glass and weighing them, so that a computer model of the building that he is creating to simulate what happened will be as accurate as possible.

Gypsum taken from steel columns will be tested to see what kind of fire protection it offers.

And steel wires, used to reinforce the floor, will be examined to determine how strong they are.

So far, he said, his work shows the building was well constructed: washers appear to have been properly bolted; the builder used top-quality materials.

Astaneh-Asl said he hopes his work might one day be used to help design a different structure perhaps using different materials that would keep a plane from piercing the core of a building and spilling its explosive cargo of jet fuel, he said.

The estimated 300,000 tons of steel from the towers will be melted and made into new steel. Hugo Neu Schnitzer East is one of several scrapyards with city contracts.

Manager Bob Kelman says he has spent more than two decades in the scrap metal business but has never before seen metal in the shape he is now getting it.

"I've seen four-inch and five-inch steel beams twisted into shapes never intended -- that many would think impossible," he said.