As building designers and owners last month awaited the release of an engineering analysis of the World Trade Center collapse, preliminary indications foresaw no recommendations for significant changes to building codes.
Prepared by the American Society of Civil Engineers (ASCE), the report was expected to be presented to Congress on May 1. But a draft copy was obtained last month by The New York Times.
According to the Times, the ASCE study concludes that failures of sprinkler systems and sprayed-on fireproofing are likely to have contributed to the Sept. 11 collapse of the 29-year-old Twin Towers. The impact of the hijacked 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.
"Clearly, it was the fire that brought about the collapse," says Robert Ratay, chairman of the technical activities division of ASCE's Structural Engineering Institute. Last month, he told BD&C that his group had reviewed the report before submitting it to the Federal Emergency Management Agency.
Asked to comment on the report's apparent absence of recommended revisions for building codes, Ratay says he believes that the investigation so far has not been adequate enough to yield specific changes. But he adds that the collapses raise many important questions that may yet alter existing codes.
Ratay believes that the buildings adjacent to the Twin Towers — both those that collapsed and especially those that did not — represent a more fertile investigative field than the towers themselves. Identifying the source of the reserve strength demonstrated by neighboring structures could provide useful information for designers, he says.