Engineers Set the Record Straight

Engineers Set the Record Straight on Trade Center Study Results 11/04/02

By Nadine M. Post

Engineers have bombarded several media outlets with letters recently in an effort to correct errors in coverage of the aftermath of the World Trade Center collapse. The issue is exceptionally sensitive, they say, because of pending lawsuits against the developer-owner, the Port Authority of New York and New Jersey.

The first incident involved an Oct. 22 New York Times article and its front-page summary comparing a recent engineering report on the collapse to an earlier one. It called the findings contradictory and implied there was controversy and dispute between the two study teams. W. Gene Corley, senior vice president of Construction Technologies Laboratory Inc., Skokie, Ill., and the leader of the first engineering study team, says there is no contradiction between the two reports and no dispute or controversy. "We did not say there was any flaw in the design of the twin towers or that the trusses contributed to the collapse. We said more study was needed." The second report followed up on that recommendation.

The first investigation was a building performance assessment organized by the Structural Engineering Institute of the American Society of Civil Engineers. The second report was a private study of the destruction carried out for Silverstein Properties Inc., the New York City leaseholder of the trade center.

The other incident concerns an Oct. 27 article in the New York Post that was picked up by the Associated Press, which disseminated the story nationally. The story claimed single-bolt connections in the framework of the World Trade Center's twin towers contributed to their collapse in the Sept. 11 attacks, and attributed the statement to the findings of a team of top engineers from the Massachusetts Institute of Technology.

Corley clarifies that there were "no single-bolt connections." The connection of the exterior columns to the floor trusses was welded, not bolted, directly to the exterior columns through gusset plates at the top chord of the trusses. A damper and two bolts connected the bottom chord to the exterior column. In addition, steel straps at exterior columns were embedded in the concrete topping of the floors, says Corley. The two bolts at the top and bottom chords, used for erection purposes, remained in the final assembly. The truss top chord to core-column connection consisted of a seat with a stiffener plate that contained two bolts, connected to a channel welded to the core column.

Eduardo Kausel, an MIT professor of civil and environmental engineering and the source for the Post story, says the phone interview was about a 160-page unpublished book on the World Trade Center that he and his colleagues wrote that was finished last spring. When the reporter asked Kausel how the towers failed, Kausel discussed the theory that the floor trusses failed first. "I never said one bolt or two bolts," says Kausel. The book's future is uncertain, and it has become out of date because it does not consider the more recent studies of the collapse sequence.

At least two newspapers, including The Times and the Boston Globe, have carried or have expressed plans to print corrections of various errors.

Engineers from the Structural Engineers Association of New York say that errors, innuendo and quotes out of context in the media do a disservice to the public and the engineering profession. They are concerned about the possible impact on a lawsuit filed against the port authority that alleges that design flaws in the trade center led to the deaths of the trapped occupants and firefighters.