Buildings
Columns
Likely Failed First in Terrorist-Triggered WTC Fires
(enr.construction.com - 06/28/04 issue)
By Nadine M. Post
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EXTRA
LOADS Debris is on northeast corner of Two WTC
at floors 80, 81 and on 79 at right.
(Image courtesy of NIST) |
The lead investigator
of the $16-million Federal Building and Fire Safety Investigation
of the World Trade Center’s destruction says the team’s
working hypothesis is that columns, weakened by fires ignited
by jet fuel, failed and triggered the collapse of the twin 110-story
towers.
The June 18 announcement in New
York City, made by Shyam Sunder of the National Institute
of Standards and Technology, Gaithersburg, Md., implies that
floor trusses, under close scrutiny since 9/11, did not fail
first.
This “seems to confirm the
findings of the team of consultants working for Silverstein
Properties,” the WTC leaseholder, says Richard L. Tomasetti,
co-chairman of Thornton-Tomasetti Group, New York City, and
a member of Silverstein’s team (ENR 11/04/02 p. 12).
In December, a draft of the final
NIST report will be issued for public comment. The final report,
with recommendations, will be issued next spring, said Sunder,
who presented the 1,054-page progress report. The two-year
study, authorized by the National Construction Safety Team
Act (NCSTA) of October 2002, is late. The delay is mostly
due to the “complexity and scope” of the investigation,
said Sunder. He stressed it is a fact-finding, not a fault-finding,
exercise intended to result in recommen-dations to help make
buildings perform better in extreme events.
The report also offers updates
on NIST’s separate WTC research and development program,
so far costing $3 million in fiscal 2003 and $5 million in
fiscal 2004. The Safety of Threatened Buildings Program is
designed to help implement recommendations of the WTC study
and provide the technical basis for “cost-effective”
improvements to building and fire codes, standards and practices.
From the research, NIST reports it will
publish in several months a best-practices guide for mitigating
progressive collapse of buildings. Next, NIST will create
a “national R&D road map” for fire safety design
and retrofit of structures. The research also will develop
a methodology for determining the performance of partitions
in fires and guidelines and simulation tools for mitigation
of chemical, biological and radiological aerosol attacks.
>>Click
here to view image
NIST’s progress report, available
at wtc.nist. gov, also includes a working hypothesis for the
collapse of Seven WTC, before burnout but after seven hours
of burning unattended. The 47-story steel-framed building
was hit by structure and debris...
(continued...)
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