NIST’s Investigations of Structural Disasters: What We Do and Why They Can Take Years to Complete

My Background in Disasters

It seems as though I was born to be a disaster researcher. I can vividly remember seeking shelter during tornado warnings in the basement at friends’ or relatives’ houses, or in the church at the end of our street as a young child living in Wichita, Kansas. When I was 9 years old, my family moved to Hawaii when my stepdad, an Army officer, was stationed there. While we lived there, my dad’s house back in Oklahoma was destroyed by a tornado (he was able to get to an underground shelter in time), and Hawaii was walloped by Hurricane Iniki (which was my first hurricane experience, and the first major hurricane to make landfall there since Hurricane Dot in 1959). After we left Hawaii, my stepdad was stationed at Fort Bragg, North Carolina, where we experienced all the hurricanes of the late 1990s: Bertha, Fran, Bonnie (the beginning of the Texas Tech University Hurricane Research Team) and Floyd.

I was hooked on understanding weather and disasters and pursued an atmospheric science degree, but I quickly learned that day-to-day forecasting wasn’t really for me — I cared more about how weather affected buildings, communities and people, unsurprising given all the destruction I had seen. After completing my bachelor’s degree, I received a master’s degree in engineering (both at the University of Kansas), then pursued a Ph.D. in wind science and engineering at Texas Tech University. It was there that I began doing field work observing damage to buildings and communities, and the effects on people. 

My first-ever damage assessment happened to be for the 2007 Central Florida tornadoes where the Enhanced Fujita Scale (or EF-Scale) was officially put to use for the first time. The EF-Scale was actually developed at Texas Tech following a recommendation by NIST after the Jarrell, Texas, tornado in 1997. As part of the Texas Tech University Hurricane Research Team (TTUHRT), I also studied the severe weather conditions themselves, putting dozens of weather instruments out ahead of Hurricanes Dolly, Gustav, Ike and Irene, along with Tropical Storm Ida, to collect rare and valuable data on wind, pressure and temperature throughout the storms, because other weather stations typically fail when the power goes out. I was part of a team that deployed those same instruments in front of supercell thunderstorms (see the 5:40 mark in this video) to sample data from tornadoes during the landmark Verification of the Origins of Rotation in Tornadoes Experiment 2 (VORTEX2) project.

While still a student, I interned at the Insurance Institute for Business & Home Safety (IBHS), and after graduating, I spent nearly 11 years doing field and laboratory research there, studying how natural disasters affected buildings and finding ways to reduce damage. At IBHS, we blew full-size buildings to the ground using wind data like I had collected with TTUHRT; ignited houses with flying embers; published damage studies on the 2007 Witch Creek Wildfire, the 2011 Dallas-Fort Worth hailstorms, 2017’s Hurricane Harvey, and 2018’s Hurricanes Florence and Michael; collected first-of-its-kind data on hailstone characteristics; and developed a new test standard using ice balls matching those hailstone characteristics to test roofing products.

While I was able to conduct some amazing research at IBHS, when an opportunity to join NIST as the director of the Disaster and Failure Studies Program came about, I jumped at it. NIST is the premier research institute that focuses on advocating for science-based provisions in codes and standards. Through its long history of disaster research, NIST has made a huge impact in improving disaster resiliency and safety of buildings — a perfect fit for my areas of interest. I came on board in early June 2021, just a few weeks before the tragic collapse of Champlain Towers South.

NIST’s Disaster and Failure Studies Program

NIST has been investigating disasters since the early 1900s, including studies of buildings affected by earthquakes, fires and windstorms, as well as blast, construction and in-service failures. Following the World Trade Center terrorist attack on Sept. 11, 2001, Congress passed the National Construction Safety Team (NCST) Act in October 2002. The NCST Act gives NIST the primary federal authority to conduct technical investigations of building failures. This authority also mandates NIST to follow through on any recommendations resulting from the investigations, to help improve codes, standards and practices to prevent similar failures in the future. NIST has completed three NCST investigations: the World Trade Center collapses in 2001, the Station Nightclub Fire in 2003, and the Joplin Tornado in 2011. There are currently two active NCST investigations: Hurricane Maria in 2017, and the Champlain Towers South partial collapse in 2021.

NCST Investigations

One of the questions NIST often gets about our investigations is why they take so long. The simple answer is that our engineers and scientists feel a great responsibility to get them right because this work often leads directly to changes in codes and standards that are used when constructing new buildings or renovating existing buildings. Changes to these codes and standards often help save lives. 

Finding the technical cause of a building failure in an investigation can be quite complex and involve many steps, as buildings themselves are complex systems and key evidence may be damaged or destroyed. Our goal is not just to establish the likely technical cause or causes of failure, but also to justify changes to codes, standards and practices based on our findings. Other organizations, like FEMA, may do related and complementary work, but our specific focus is to generalize what we learn so that changes can be implemented to all areas and related building types throughout the country.

One of the first steps required in an investigation is collecting data and evidence. Evidence can include pieces of buildings, building design and construction documents, security camera footage, eyewitness accounts, and data submitted by the public, among other materials. In the World Trade Center (WTC) investigation, the NIST team developed a database of more than 700 evacuation accounts from the media and conducted more than 1,200 interviews with survivors and first responders. According to a blog post by my NIST colleague Jason Averill, the WTC team listened to every 911 call, and fire, police and Port Authority radio records. In the case of the Champlain Towers South collapse, there are hours of interviews and footage to review, 40 years of building design and maintenance records to closely study, and hundreds of tagged evidentiary debris (floor slabs, columns and beams) to characterize that have been collected by our team. The early stages of building investigations are like solving a massive jigsaw puzzle, where various clues are pieced together to identify the original location of every component extracted from the collapse. This is a complex process that first and foremost must not interfere with the search, rescue and recovery efforts.

For each investigation, we consider all possible failure hypotheses, sometimes dozens of them, and then gather data to support, or disprove, each hypothesis. The failure hypotheses help us prioritize any testing protocol developed in an investigation, characterize the condition of the building prior to the failure, and understand the possible role of the collected evidence in the failure. We typically use a combination of nondestructive and destructive testing and must quantify uncertainty in each step of the measurement and analysis process. In the case of the investigation of the Station Nightclub Fire — which killed 100 people in 2003 when pyrotechnics used by the performing band ignited a fire — the research team conducted dozens of tests on polyurethane foam, ceiling tiles, wood paneling and carpet collected from what remained of the building to understand the contribution of each to the ignition and fire spread. In the Hurricane Maria investigation, scale models of critical buildings (such as hospitals) and their surrounding terrain have been tested in a wind tunnel to gather data on wind pressures and forces to link these measurements to the observed building damage.

Test data are then used as input in analytical and computational models, to realistically simulate the building failure. The models themselves are extremely complex, and our teams must ensure the building components and interactions are accurately represented. A blog post by longtime NIST researcher Richard Gann described how the WTC team created fire models for each floor of the twin towers, to understand how heat from the fires affected the steel, concrete and connections, and how the fires eventually caused the towers to collapse.

Failure models must also be validated, in other words, confirming that they perform as expected, and this typically requires complex laboratory tests. In the case of the Station Nightclub Fire investigation, the team went beyond testing the individual components mentioned above and built and tested a full-scale mock-up of the raised platform where bands performed at the nightclub, to understand how a fire could spread.

At the beginning of an investigation, anything is possible, and we keep an open mind and follow a rigorous, systematic scientific process that will ultimately prove the actual, technical cause of a failure; this often means taking the extra effort to prove that dozens of alternatives were not possible. 

To establish the likely technical cause of failure, the investigative teams develop and thoroughly test hypotheses based on the evidence and data they collect. We also receive and consider many theories on failure mechanisms from other researchers, as well as from media stories and directly from the public. I keep a special folder in my email inbox that helps me log and sort through these before they are sent to our subject matter experts. Often these external theories are ones our team has already considered. When a particular theory gains traction or popularity in the public, we may directly address it in our final report so that the public will understand why we did or did not believe that theory to be consistent with the available facts and evidence.

All of these NCST investigations take a lot of time and work to do properly. The WTC investigation took four years for the twin towers and an additional three years for the collapse of WTC 7. The Joplin Tornado investigation took nearly three years to complete. The shortest NCST investigation to date was our work on the Station Nightclub Fire, which lasted about two and a half years. We know that these are all very long times for those affected by these disasters, but it is so important to get them right.

Impacts

NCST investigations are some of the most complex building engineering problems to solve, and they can have tremendous impact on the safety of Americans in the future. After the WTC investigation, more than 40 code changes were enacted across the International Building Code and International Fire Code, 10 code changes were made by the National Fire Protection Association (NFPA) in the Life Safety Code (NFPA 101), and two were made in the Uniform Fire Code (NFPA 1). 

After the Station Nightclub Fire investigation, changes were made to the Life Safety Code regarding sprinklers, restricted festival seating, crowd management, and egress inspection record-keeping. 

Most recently, the NIST staff members who led the Joplin Tornado investigation were successful in getting one of the key recommendations implemented — tornado risk maps have now been included in a key building standard that serves as the design basis for buildings throughout the U.S. This same building standard now also includes tornado-resistant design criteria, another recommendation of the Joplin NCST investigation. We’ve also seen the National Weather Service improve tornado prediction and warnings. The recent Dec. 10, 2021, tornado outbreak is a stark reminder of how important these changes are to reducing damage, injuries and loss of life.

These examples of changes to codes, standards and practices are why our engineers and scientists work so hard, and so long, on these investigations. They painstakingly go through each detail, chase down multiple possibilities, and must prove to themselves and the world that they have found the most likely technical cause of the building failure. This intense scientific work helps create positive and lasting change for our communities.