NIST World Trade Center Disaster Investigation

The NIST World Trade Center Disaster Investigation was a report that the National Institute of Standards and Technology (NIST) conducted to establish the likely technical causes of the three building failures that occurred at the World Trade Center following the September 11, 2001 terrorist attacks. The report was mandated as part of the National Construction Safety Team Act (NCST Act), which was signed into law on October 1, 2002 by President George W. Bush. NIST issued its final report on the collapse of the World Trade Center's North and South towers in September 2005, and the agency issued its final report on 7 World Trade Center in November 2008. NIST concluded that the collapse of each tower resulted from the combined effects of airplane impact damage, widespread fireproofing dislodgment, and the fires that ensued. The sequence of failures that NIST concluded initiated the collapse of both towers involved the heat-induced sagging of floor trusses pulling some of the exterior columns on one side of each tower inward until they buckled, after which instability rapidly spread and the upper sections then fell onto the floors below. 7 World Trade Center, which was never directly hit by an airplane, collapsed as a result of thermal expansion of steel beams and girders that were heated by uncontrolled fires caused by the collapse of the North Tower and failure of the fire-resistive material.

Context

Collapse of the World Trade Center

During the September 11 attacks, two hijacked jet airliners struck the Twin Towers of the World Trade Center (WTC), one to each tower. As a result, the two 110 stories-tall skyscrapers collapsed, causing complete destruction to the entire WTC complex and killing 2,763 people. The South Tower collapsed at 9:59 a.m. Eastern Daylight Time after burning for approximately 56 minutes. 29 minutes later, the North Tower collapsed having burned for 102 minutes. When the North Tower collapsed, debris fell on the nearby 7 World Trade Center, damaging it and starting fires that burned for almost seven hours, compromising the building's structural integrity. 7 World Trade Center collapsed at 5:21 p.m. The collapse of the World Trade Center was unprecedented; never before had a steel-framed multi-story building suffered a complete collapse as a result of fire. In the immediate aftermath, knowledgeable structural engineers began providing a range of explanations in an attempt to help the public understand these tragic events. However, a coordinated effort would need to be organized to investigate and analyze the complex series of events that led to each collapse.

FEMA World Trade Center Building Performance Study In the aftermath of the attacks, researchers responded immediately by traveling to the World Trade Center site where they began collecting data. Among the first were members of the Federal Emergency Management Agency (FEMA) and American Society of Civil Engineers (ASCE), who together formed a Building Performance Study Team to understand how the building structures failed and why. The team produced the first official government report attempting to explain the destruction of the World Trade Center complex. They were able to make many observations and findings, including preliminary analysis of the damaged structures, analysis of the buildings' fire suppression systems, and recommendations to building codes and fire standards for including airplane impact into building design. FEMA's final report, FEMA 403 issued in May 2002, titled World Trade Center Building Performance Study: Data Collection, Preliminary Observations, and Recommendations, also provided a substantial amount of data about the event not documented elsewhere. Their findings suggested that fires, in conjunction with damage to the structural members and fire suppression systems inflicted by the jet airliners, played a key role in the collapse of the buildings. However, the team's investigation was hampered by a number of issues. The lack of authority of investigators to impound pieces of steel for examination before they were recycled led to the loss of important pieces of evidence that were destroyed early during the search and rescue effort, and much of the steel had already been recycled in the one month that had lapsed between the attack and the deployment of the team. The team was further impeded by ongoing criminal investigations by the FBI and NTSB. In a hearing to the U.S. House of Representatives' Committee on Science on March 6, 2002, a panel of witnesses and experts described the obstacles as:

No clear authority and the absence of an effective protocol for how the building performance investigators should conduct and coordinate their investigation with the concurrent search and rescue efforts, as well as any criminal investigation Difficulty obtaining documents essential to the investigation, including blueprints, design drawings, and maintenance records Uncertainty as a result of the confidential nature of the BPAT study Uncertainty as to the strategy for completing the investigation and applying the lessons learned Because of these inadequacies, the Building Performance Study team could not "definitively determine the sequence of events leading to the collapse of each tower." The report was remarkably blunt in pointing out shortcomings and missteps in the investigation and its recommendation for another, more thorough and authoritative investigation.

National Construction Safety Team act

As a result of the inconclusive FEMA Building Performance Study team's findings and concerns over missteps in its investigation, the U.S. House of Representatives drafted legislation that would give wide powers, including the right to issue subpoenas, to teams investigating building failures. The bill also mandated that the teams would be centered at the National Institute of Standards and Technology (NIST) whose building and fire research laboratory in Maryland had conducted extensive investigations of building failures in the past. The bill, cited as the National Construction Safety Team (NCST) act, passed the House and the Senate and was signed into law on Oct. 1, 2002 by President George W. Bush. The NCST act gives NIST a clear mandate to:

… excerpt ends here. Continue reading the full article.