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.

S. SHYAM SUNDER
Lead Investigator, NIST World Trade Center Investigation
Gaithersburg, Md.