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Resilience /Disaster & failure studies


WORLD TRADE CENTER INVESTIGATION


OVERVIEW

The collapse of the WTC buildings following the terrorist attacks on September
11, 2001, was one of the worst building disasters in US history, killing 2,749
people, including 400 emergency responders.

NIST responded to calls from Congress and the public to carry out a federal
investigation of why the buildings collapsed, the evacuation of building
occupants and the emergency response. NIST was given this authority when
Congress passed, and the President signed into law, the National Construction
Safety Team Act of 2002. 

More than 200 professionals and technical subject matter experts, including 85
NIST staff members, answered the call and participated in the investigation.

As part of the investigation, the NIST team gathered every bit of evidence they
could find. Activities included:

 * Interviews with 1,056 surviving occupants of the WTC buildings and 116
   emergency responders.
 * Extensive reviews of design, construction, maintenance and inspection
   documents for the buildings 
 * Examination of hundreds of structural steel components from WTC buildings
 * Gathering and analyzing thousands of pieces of video, photographic, and audio
   evidence from professional sources and the public

NIST's World Trade Center Investigations
Learn more about NIST's work on the World Trade Center investigations, from how
it conducted the study to the recommendations and their lasting legacy.


FEATURED CONTENT

About the Investigation
Study FAQs
Investigation Meetings
News Archive
Photos, Videos and Simulations
Publications and Reports
Recommendations
Disaster and Failure Studies Repository


THE REPORTS

Throughout the process, NIST held 23 public meetings and provided multiple
opportunities for the public to review and comment on drafts of the reports. In
addition, all of the reports were reviewed by an external, non-NIST NCST
advisory committee.

In the end, NIST released final versions of the 43 reports on the WTC towers,
totaling some 10,000 pages, on October 26, 2005. NIST released final versions of
the three reports on WTC 7, totaling about 1,000 pages, on November 25, 2008.

NIST is aware of other studies related to the WTC collapse and stands by its
original findings. 


20 YEARS LATER: NIST'S WORLD TRADE CENTER INVESTIGATION AND ITS LEGACY

Read first-hand accounts of what it was like to work on the WTC investigation in
our blog series. 

Start with Shyam Sunder's reflections on the investigation and its legacy, and
then keep reading for insights on everything from what it was like to catalogue
the images and video to how 9-11 changed one researcher... and first responder
communications.

Read the blog post from Shyam Sunder


THE LEGACY


BUILDING AND FIRE CODES, STANDARDS AND PRACTICES

The WTC investigation has had a significant legacy. In the reports, NIST made 31
recommendations for improvements to building and fire codes, standards, and
practices based on the WTC investigation. While the federal government has no
regulatory authority for building and fire codes, many U.S. codes and standards
were subsequently updated to improve areas such as structural integrity, fire
resistance, occupant evacuation and emergency responder communications. NIST’s
recommendations have had a significant impact on design and construction
practices for high-rise buildings worldwide, including the new buildings at the
rebuilt World Trade Center site. 

In addition, NIST scientists conducted tests of steel from the WTC buildings to
measure their mechanical properties at normal and elevated temperatures. These
tests led to the development and validation of performance criteria for fire
resistive steel. This type of steel, which was not available at the time the WTC
was built, would not necessarily prevent a building from collapsing during a
fire, but it would give occupants more time to escape. 

Read Jason Averill's story about investigating the WTC evacuation and Steve
Kirkpatrick's work analyzing the aftermath of the Twin Towers aircraft impacts.


DNA IDENTIFICATION

NIST also played a role in the effort to identify the victims of the 9/11
attack. This effort was at the time — and still is — the largest forensic
identification effort ever undertaken. This effort was particularly challenging
because in many cases the DNA of the victims was severely degraded by exposure
to intense heat from burning jet fuel, as well as moisture and decay in the
weeks and months following the attack. To make an identification, experts
analyzed segments of DNA called forensic markers. When DNA degrades, these
forensic markers break apart, which makes them difficult to analyze.

To cope with this challenge, researchers at NIST, Ohio University and Bode
Technology developed new forensic markers involving shorter segments of DNA,
which by virtue of their small size are more likely to remain intact as the DNA
degrades. This effort allowed forensic experts to identify thousands of remains
that otherwise would have never been returned to their families. The research
conducted at NIST in the aftermath of 9/11 led to the development of new
“mini-markers” that are now routinely used in criminal casework. These markers
have helped investigators solve countless sexual assaults, homicides and other
crimes that would otherwise have gone cold.

Read John Butler's reflections on assisting with the 9/11 World Trade Center DNA
identifications.


PUBLIC SAFETY COMMUNICATIONS

Among the victims were more than 400 first responders, including firefighters,
police officers, and Port Authority officers. These deaths revealed a huge gap
in public safety communications and fundamentally changed NIST’s research focus
in public safety communications. During the disaster, first responders struggled
to communicate due to lack of interoperability among the radio systems and
over-crowded communication channels. As a result, the 9/11 Commission made
communications research for public safety a priority, and tasked NIST with
finding solutions.

NIST established its Public Safety Communications Research division and became a
technical advisor to Congress and the White House on issues surrounding public
safety communications. This new research focus helped established FirstNet, a
nationwide broadband network dedicated to first responder communications. In the
20 years since the attacks, NIST and its partnering research organizations and
industry have resolved many of the radio interoperability issues and now focus
on modernizing communications technology for first responders.

Read Dereck Orr's reflections on how 9-11 changed him, and public safety
communications.


NATIONAL FIRE RESEARCH LABORATORY & DISASTER RESILIENCE PROGRAM

As a result of the WTC investigation, NIST established the National Fire
Research Laboratory, which has provided a unique capability to test performance
of large-scale structures under realistic conditions. NIST also established a
Disaster Resilience Program, focused on ways to improve the safety and
resilience of buildings and communities in the face of multiple threats
including wildfires, hurricanes, tornadoes and earthquakes. Improving resilience
has emerged as a major theme of the 21st century, and the NCST Act, created in
response to 9/11, has enabled NIST to conduct technical investigations of
subsequent significant disasters. including the Joplin, Missouri, tornado in May
2011; the 2003 Station nightclub fire in West Warwick, Rhode Island; the effects
of 2017’s Hurricane Maria on Puerto Rico and, most recently, the Champlain
Towers Collapse in Miami, Florida, in June 2021.


BLOGS


RECONSTRUCTING THE FIRES THAT BROUGHT DOWN WTC 1, 2 AND 7

September 8, 2021
Everyone has a story about where they were when they heard about the disaster
universally called “9/11.” Mine begins in Ottawa, Canada. As chance would have
it


INSIDE THE TOWERS ON 9/11: MY STORY OF INVESTIGATING THE WTC EVACUATION

September 3, 2021
The kickoff meeting On Nov. 1, 2002, in a small conference room on the
Gaithersburg, Maryland, campus of the National Institute of Standards and
Technology


REFLECTIONS ON ASSISTING WITH THE 9/11 WORLD TRADE CENTER DNA IDENTIFICATIONS

September 1, 2021
On Tuesday, Sept. 11, 2001, I walked to work from my home in Olde Towne
Gaithersburg, Maryland, and arrived at my office shortly before 9 a.m. I had
just


ANALYZING THE AFTERMATH OF THE TWIN TOWERS AIRCRAFT IMPACTS

August 27, 2021
I consider myself lucky to have been able to perform contract engineering
research and consulting for my entire career. The work environment has been
somewhere


PUTTING TOGETHER THE BIG PICTURE FOR THE WORLD TRADE CENTER DISASTER
INVESTIGATION

August 25, 2021
Imagine assembling a jigsaw puzzle of more than 14,000 pieces without an image
on the box showing what the final picture will look like. Imagine that important


HOW 9/11 CHANGED ME AND FIRST RESPONDER COMMUNICATIONS

August 20, 2021
If you remember Sept. 11, 2001, that day is most likely imprinted on your mind
like no other day. You remember what you were doing and who you were with. You


20 YEARS LATER: NIST'S WORLD TRADE CENTER INVESTIGATION AND ITS LEGACY

August 18, 2021
The collapse of the World Trade Center (WTC) buildings following the terrorist
attacks of Sept. 11, 2001, was one of the worst-ever building disasters in


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