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Buildings
NIST Could Take Over Disaster Investigations
(enr.com-
5/06/02 issue)
By Nadine M. Post in Los Angeles and Sherie Winston
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| GROUND
ZERO More can be learned from behavior of nearby
buildings than from failure of towers, suggests
engineer. (Photo courtesy of FEMA) |
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Draft legislation unveiled May 1 before
the House Science Committee would give the National Institute
of Standards and Technology the lead role in disaster investigations.
The proposal instructs NIST's director to put together a team
of experts, from public and private sectors, within 48 hours
of an event.
The legislation was announced with the release of the federally
sponsored investigation of Ground Zero and nearby buildings
after the Sept. 11 plane attacks on New York City's World
Trade Center.
The NIST panel would conduct investigations
of any future building failures, whatever the cause. It would
have full authority, including to access the site, collect
and move evidence and subpoena witnesses. Though the proposal,
sponsored by Science Committee Chairman Sherwood Boehlert
(R-N.Y.), also gives NIST the same authority for any additional
investigations related to the events of Sept. 11, "the
bill is about the future," says David Goldston, committee
chief of staff.
Legislation is expected to be formally
introduced this week and considered by the full committee
by month's end. Committee staff also is in the early stages
of working with Senate staff on a companion measure.
The Federal Emergency Management Agency
sponsored the $1-million WTC study that was organized by the
Structural Engineering Institute of the American Society of
Civil Engineers, and released the report's conclusions. The
greatest implication for the engineering community is a recommendation
for "an improved level of interaction between structural
and fire protection engineers...to consider the behavior of
the structural system under fire as an integral part of the
design process."
Though there is much curiosity about
the collapse mechanism of the towers, "perhaps more interesting"
is the behavior, during unusual events such as fires, of the
surrounding buildings, said Bill Baker, chief of structural
engineering at Skidmore Owings & Merrill, Chicago, and
a core member of the study team, while speaking at a recent
meeting on tall buildings in Los Angeles.
The report states up front that despite
the "massive" structural damage sustained by the
twin 110-story towers when the planes hit, the buildings did
not collapse immediately, as most smaller buildings would.
This gave people "a false expectation" that the
buildings would not ultimately collapse, despite the fuel-triggered
fire and the defeat of six major building systems at the impact
floors, said Jon D. Magnusson, chairman and CEO of engineer
Skilling Ward Magnusson Barkshire Inc., Seattle, at the same
Los Angeles meeting. Magnusson also is a member of the SEI-ASCE
team.
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| DIVERSITY Designing buildings against plane loads is futile,
considering the variety. |
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National defense resources should be
directed to airplane and other security rather than to hardening
buildings against airplane attack, says the report. But for
buildings being evaluated or designed for extreme events,
the report's operative recommendation is redundancy in all
building systems. Fireproofing needs to be "tough"
under impact and fire conditions that deform steel members.
Also, it is important to understand frame connection performance
under impact loads and during fire conditions.
The report encourages continued development
of a system for performance-based design in fire-protection
engineering. This would involve improving existing models
that simulate fire spread in structures. The team recommends
further study for many subjects, including performance criteria
and test methods of fireproofing materials relative to durability,
adhesion and cohesion when exposed to abrasion, shock, vibration,
rapid temperature rise and high temperature.
Baker calls the study, performed mostly
by volunteers and with limited funds, more of a reconnaissance
effort than anything else. "The event was absolutely
huge," he said. "It will take a long time to come
to conclusions."
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