NIST Surfside Collapse Investigation Continues

THURSDAY, JUNE 16, 2022


Since the U.S. Department of Commerce’s National Institute of Standards and Technology launched an investigation into last year’s partial collapse of the 40-year-old Champlain Towers South in Southside, Florida, the assigned team of federal investigators has developed roughly two-dozen hypotheses.

The team is reportedly working to prove or disprove each potential cause by using compiled evidence from the collapse and various analyses.

“To determine how and why the failure occurred, we can leave no stone unturned,” said Glenn Bell, the associate lead investigator. “We have to thoroughly investigate each possibility.”

Tower Background

The complex was built in 1981 by late developers Nathan Reiber and Nattel Construction, which is listed as inactive in state records. Since the collapse, media outlets and the City of Surfside have uncovered documents surrounding the structure’s condition. According to a 2018 inspection report from Morabito Consultants, the condominium had “major structural damage” to its concrete structural slab below the pool deck that needed “extensive repairs.” These damages included descriptions of abundant cracking and spalling throughout the columns and walls, in addition to exposed and deteriorating rebar.

The report was generated in preparation for the building’s 40-year recertification.

While Morabito did not warn that the building was unsafe, it urged the condo association to make repairs soon, as the concrete problems could “expand exponentially.” At the time of this assessment, repairs would have cost an estimated $9 million. However, after dissension among board members and owners, delayed action caused the repair prices to hike up another $6 million to a total of $15 million.

At the time of the collapse, consultants acknowledged that the building was in the early stages of a three-year renovation plan, which had started with roof work about six weeks prior.

Collapse Information

Around 1:30 a.m. on June 24, 2021, part of the Champlain Towers South condominium in Surfside, Florida was reported to have collapsed. Made up of three buildings, the towers were each 12 stories tall and contained 342 units.

That same day, more than 80 rescue units were reportedly on the scene. By Sunday, 35 victims were pulled from the structure with two more pulled from the rubble. Eleven of them were treated for their injuries.

A state of emergency was also declared on the day of the collapse, which allowed the Department of Homeland Security and FEMA to coordinate relief efforts at the scene, which also involved containing a fire within the debris. The following Saturday, Gov. Ron DeSantis and Surfside Mayor Charles Burkett turned their attention to the “sister building” to the tower that fell, noting that it was built with the same team. Residents in Champlain Towers North began being aided by FEMA to find temporary housing.

Crews also reported that day that a fire had been diminished.

That Sunday, heavy equipment was sent to the scene to help manage the shifting debris after rescuers dug a 125-foot-long trench (20 feet wide and 40 feet deep) to add to the around-the-clock excavation effort.

In later reports, it was determined that the partial collapse had resulted in the death of 98 people.

NIST Launches Investigation

In August, the U.S. Department of Commerce’s NIST announced its selection of a team of technical experts to investigate the partial collapse of the Champlain Towers South.

The investigation team is headed by Judith Mitrani-Reiser, Associate Chief of the Materials and Structural Systems Division in NIST’s Engineering Laboratory. In her role, Mitrani-Reiser will lead the development and coordination of statutory processes for making buildings safer.

Glenn Bell, Co-Director of the safety organization Collaborative Reporting for Safer Structures, and Co-Founder of the American Society of Civil Engineers' Technical Council on Forensic Engineering has been assigned to serve as the team’s associate lead.

Other team leads and their projects include:

  • Jim Harris and Jonathan Weigand: Building and Code History;
  • David Goodwin and Christopher Segura: Evidence Preservation;
  • Ken Hover and Scott Jones: Materials Science;
  • Youssef Hashash and Sissy Nikolaou: Geotechnical Engineering; and
  • Jack Moehle and Fahim Sadek: Structural Engineering.

Throughout the investigation, the team is slated to provide regular updates on its progress, which will include public meetings with the National Construction Safety Team Advisory Committee, annual reports to Congress and progress reports. However, the NIST reports that it will not issue preliminary findings or conclusions before publishing a draft report for public comment.

In early investigations of the collapse, the Miami Herald brought to light that the 12-story condominium tower had had multiple, extensive structural flaws present since the beginning of the building’s life—about 40 years.

Reportedly, the plans that came from a firm that no longer exists specified structural columns that were too narrow to accommodate the necessary amount of rebar to support the building. This meant that contractors had to choose between inadequately attaching floor slabs to supports or putting extra steel into columns that were too small.

Most experts weighing in on the matter chose the latter, which is a recipe for air pockets that accelerate corrosion.

Among the speculation that was looking at how a partial collapse of a patio could have brought down part of a 12-story building, The Washington Post also brought together engineers, construction plans and a computer simulation to come to two main scenarios.

First, if the deck initially collapsed where it joined the building’s facade, that could have overloaded the already-thin columns, causing them to buckle. Second, if the deck remained attached to the columns as it kept collapsing, that would have caused the tugging and twisting of the columns and the surrounding beams, causing them to fall.

Regardless of the final cause, building codes and inspections are already being reformed—with some Miami engineers saying that they have been evaluating 30-50 properties a week.

The Champlain Towers South investigation is the fifth investigation NIST has conducted using authorities granted by the 2002 National Construction Safety Team (NCST) Act. The Act reportedly gives NIST and its team the primary authority to investigate the site of a building disaster; access key pieces of evidence such as records and documents; and collect and preserve evidence from the site of a failure or disaster.

In addition, the Act also calls for NIST to issue reports and make recommendations to improve building codes and standards.

Developed Hypotheses, Further Investigations

On June 9, members of the NIST team investigating the partial collapse of the Champlain Towers South gave an update on their progress during a National Construction Safety Team Advisory Committee meeting.

Although the team has reportedly developed roughly two-dozen hypotheses—both publicly highlighted and others—regarding the deadly collapse, Bell reports that they have not yet determined a clear initiating event.

NIST

On June 9, members of the NIST team investigating the partial collapse of the Champlain Towers South gave an update on their progress during a National Construction Safety Team Advisory Committee meeting.

Throughout what Bell has described as a “difficult, complex investigation,” the team has been testing each possibility through two main strategies: progressive collapse analysis and collapse evidence analysis.

With progressive collapse analysis, Bell reports that the team uses tools like computer simulations to determine an initiating point of failure and how it spread through the structure. The latter strategy is just how it sounds, where the team looks at nonquantitative evidence such as videos of the collapse, photos of the damages and specimens taken from the debris pile. It is reported that NIST has more than 600 physical specimens from the collapse pile.

While much of the materials were collected by NIST, the Institute is asking anyone with related data to share it on its data portal, where other photos, videos and documentation has been submitted.

In addition to these efforts made by NIST and the public, Bell said that probers are taking the various analyses to create a detailed timeline of the minutes before, during and after the collapse. The team is also developing 3D models, and plan to create animations demonstrating their eventual findings.

During the next steps of the investigation, NIST recently reported that the team would begin invasive testing and preparation of physical evidence collected from the collapse site. This process will involve manipulating evidence, core drilling and cutting of specimens to collect samples, which cannot be fully accomplished in the tight confines of the current NIST warehouse.

“Invasive testing will provide important information about the properties of the concrete and reinforcing steel and the potential roles those properties may have played in the collapse,” said Bell. “This is an important step in the investigation, one we are able to take only after months of careful investigation and preparation.”

This testing will include physical tests to determine the samples’ mechanical properties, chemical tests to determine material characteristics such as density and porosity, and corrosion testing.

To better prepare for these next steps, NIST brought in a board-certified industrial hygienist to conduct air sampling for asbestos fibers to ensure the safety of those accessing the materials. The preparation and moving of materials to a new location for the next round of testing is expected to take several weeks.

Since the investigation was launched, Engineering News-Record reports that the NIST broke up its efforts into six different projects to examine different aspects of the case more efficiently. Several of those aspects include building code and code history, evidence collection and preservation, materials science, geotechnical engineering and structural engineering.

The team is also looking at remote sensing and data visualization.

After the team is able to determine a cause for the partial collapse, NIST is slated to issue recommendations for changes to building codes and standards, in an effort to avoid a similar tragedy, by the end of 2024.

“Nearly a year after this terrible collapse, our dedication is stronger than ever to get to the bottom of what caused Champlain Towers South to collapse so that a tragedy like this never happens again,” said Judith Mitrani-Reiser, the lead investigator.

   

Tagged categories: Accidents; Building codes; Condominiums/High-Rise Residential; Corrosion; Design - Commercial; Fatalities; Good Technical Practice; Health & Safety; Health and safety; NA; NIST; North America; Program/Project Management; Project Management; Residential; Safety

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