As building designers and owners last month awaited the release of an engineering analysis of last fall’s collapse of the World Trade Center towers, preliminary indications were that it would not suggest changes in building codes. The report was expected to be issued in late April or early May.
Prepared by the American Society of Civil Engineers (ASCE), a draft copy of the report was obtained by The New York Times.
According to the Times, the report concludes that failures of sprinkler systems and sprayed-on fireproofing are likely to have contributed to the collapse of the towers. The impact of the jetliners that crashed into the towers undoubtedly severed piping that supplied water for the sprinklers, and may have jarred loose fireproofing applied to their steel frames. The fires that erupted produced temperatures as high as 2000 degrees, the Times reported.
“Clearly, it was the fire that brought about the collapse,” Robert Ratay, chairman of the technical activities division of ASCE’s Structural Engineering Institute (SEI), told BD&C. Ratay assembled a committee of structural engineers to review a draft of the report, which was submitted to ASCE and to the Federal Emergency Management Agency.
Asked to comment on the report’s apparent absence of recommended changes in building codes, Ratay says his opinion isthat the investigation to date has not beenadequate enough to produce specific recommendations. But he adds that the collapses raise many important questions that may subsequently result in code changes.
Ratay believes that the buildings adjacent to the World Trade Center &m> both those that collapsed and especially those that did not &m> represent a more valuable investigative focus than the towers themselves. Identifying the source of the reserve strength demonstrated by some neighboring structures could provide useful information for building designers, he says.
Meanwhile, last September’s attacks have prompted SEI to organize a committee that will study the performance of damaged structures. Its long-term evaluations may lead to recommendations for changes in structural design practices, Ratay says. Another new SEI committee will focus on how investigations of damaged structures should be conducted, with a particular focus on the safety of the investigators.
