DISASTERSNIST Releases Extensive Video Update on Champlain Towers South Investigation

The National Institute of Standards and Technology’s (NIST’s) National Construction Safety Team (NCST) has released an extensive video update on its investigation into the June 2021 partial collapse of the Champlain Towers South building in Surfside, Florida. The update reviews the investigation’s history and progress, shares preliminary findings, and highlights potential impacts that this complex investigation could have on building codes and standards.

In the video, investigative lead Judith Mitrani-Reiser and co-lead Glenn Bell explain how the team has determined that some of the hypotheses they are considering for how the failure occurred have a higher likelihood than others. The team has reviewed two dozen hypotheses, relying on extensive physical evidence, imagery, historical records, witness interviews, remote sensing data, laboratory testing, computer modeling and more.  

“As we have shared in previous updates, there were many design and construction problems that weakened the building from the start,” said Mitrani-Reiser. “These deficiencies posed many potential failure initiation possibilities both in the pool deck and the tower, and each is being carefully considered so that we can narrow our focus to the most likely ones and seek to rule out others.”

The two experts describe the extensive planning and coordination that helped the team systematically work through analyses, testing and modeling to arrive at its preliminary findings. They note that from NIST’s initial deployment of a preliminary reconnaissance team in the first 48 hours after the collapse, this investigation has relied on collaboration with local authorities and expertise from across the federal government, private industry and academia.

Higher-Likelihood Collapse Hypotheses
Bell walks viewers through three hypotheses with higher likelihood, beginning with the failure of one of the typical slab-column connections in the pool deck. He describes factors that contributed to low margins of safety in the pool deck, including understrength of the building’s original structural design relative to the requirements of the building code. Additionally, he notes that steel reinforcement was not placed where it should have been, leading to significantly diminished strength of the pool deck slab and slab-column connections. He also points to heavy planters that were not in the original design, as well as a rehabilitation of the pool deck decades earlier that added sand and pavers, increasing the load on a system that was already functionally and structurally inadequate. The team also found corrosion of the steel reinforcement in the pool deck concrete, which can weaken the slabs and slab-column connections.