| Clarifying Results
ENR’s recent
editorial and significant aspects of its other coverage suggest
a need for clarification on the role and value of the World
Trade Center investigation conducted by the Commerce Dept.’s
National Institute of Standards and Technology (ENR 7/4 p.
64).
The NIST-led investigation and
concurrent research and development program addressed specific
recommendations for further study contained in the earlier
building performance assessment, conducted by the American
Society of Civil Engineers and the Federal Emergency Management
Agency. Congress directed NIST to carry out the investigation
based on input from professionals, the public and families
of victims.
The investigation, which was carried
out by a large, qualified team of NIST experts and contractors,
has addressed controversial issues related to the outcome
of the terrorist attacks, including the role of the design
of the WTC towers and fire safety features on the collapses;
egress design, emergency communications, evacuation procedures,
and preparedness on occupant life safety; radio communication
systems, roof rescue policies, physiological factors, and
command and control on emergency response operations and life
safety of first responders.
NIST has issued 30 recommendations
that address issues related to building performance, evacuation
procedures and emergency response. The recommendations were
developed with the consensus advice provided by the National
Construction Safety Team Advisory Committee, the statutorily
created and balanced group of private sector professionals
and experts that advises NIST on building failure investigations.
The NIST recommendations, for the
most part, deal with recognized hazards or common procedures
used in current design practice under normal conditions for
many building types. Recommendations do not deal with designing
a building to withstand aircraft impacts. Such design is not
required by building codes and it is better to keep terrorists
away from airplanes and airplanes away from buildings. But
public officials and building owners must determine appropriate
performance requirements for buildings at higher risk and
the cost-effectiveness of the needed safety enhancements.
Only a few recommendations call
for new requirements in standards and codes. Most deal with
improving standards for an existing practice, establishing
the technical basis for an existing requirement, making a
current requirement risk-consistent, ensuring adoption and
enforcement of an existing requirement, or developing a performance-based
alternative to an existing prescriptive requirement (without
replacing it).
The majority of the recommendations
do not apply solely to the fire hazard. They apply to several
other hazards, either alone or in a multi-hazard context.
Most buildings don’t experience–and
shouldn’t expect to experience–rare design events.
Design fire scenarios should properly anticipate rare events
that most buildings would not expect to experience over their
life cycle. Fire loss data associated with such events would
not be captured in past statistics spanning several decades.
Nor can past statistics capture new hazards.
The importance of anticipating
rare design events–and their consequences–is best
exemplified by the 1994 Northridge earthquake, which revealed
a concern with connections in steel moment frame buildings.
Readers may submit comments to NIST by the Aug. 4, 2005, closing
date at http://wtc.nist.gov.
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