Clues In The Twisted Steel

(CBS)  One of the twisted pieces of structural steel pulled from the World Trade Center debris could become an important clue to why the twin towers collapsed, a civil engineer says.

The legend stenciled on the metal — PONYA, 103-100, 41 — told Edward DePaola that the section of recently excavated beam came from Tower One, floors 100 to 103, and that the original, whole piece weighed 41 tons.

That puts it above the point at which a hijacked airliner struck the tower, in floors 94 to 99.

"This is incredibly important," DePaola told reporters Monday during a tour of the Metal Management Northeast scrap yard.

He pointed to a wavy section, where the steel buckled. "The metallurgist will be able to tell how hot it got," he said.

DePaola, a member of the American Society of Civil Engineers, looks for clues in the scrapyard that will shed light on why the twin towers collapsed after they were struck by the airliners. The report by his group and the Federal Emergency Management Agency is due by the end of the month.

"We need to be able to technically describe the sequence of events, minute by minute," DePaola said. "This piece bent, this piece broke, then this one gave way."

The warped piece he found will join about 100 other beams and other samples sent to a lab at Gaithersburg, Md., where they will be studied by engineers. Some of their conclusions were to be presented during a public television special, "Why The Towers Fell," airing on April 30.

The scrap yard has recycled 100,000 tons of World Trade Center steel, brought across the Hudson River from lower Manhattan by barge. The steel is cut into 4- to 5-foot sections and shipped to steel mills, mostly overseas, to be recycled.

"This stuff could come back as refrigerators, cars, appliances," said Warren Jennings, general manager of Metal Management Northeast.