The federal investigation into the calamitous collapse at Champlain Towers South in Surfside, Fla., has concluded that the condominium’s pool deck failed more than four minutes before the 12-story residential building collapsed. The fiasco, during the night of June 24, 2021, killed 98 occupants.
Researchers at the U.S. Department of Commerce’s National Institute of Standards and Technology are still working to detect the initial event, they reported at a March 7 National Construction Safety Team Advisory Committee meeting . The NIST team, made up of structural and geotechnical engineers, materials specialists, social scientists and other specialists, aims to finish its technical work this summer. The goal is to release a draft report for public comment, including recommendations, in May 2025. NIST expects to release the final report in the fall of 2025.
Analysis of videos shot in and around the 40-year-old structural concrete building, including two videos obtained in December, as well as interviews with witnesses, helped clarify the timeline of the collapse, according to Judith Mitrani-Reiser, associate chief of NIST’s Materials and Structural Systems Division and the probe team leader.
David Goodwin, a NIST research chemist specializing in forensics and team member, said a video overlooking the Champlain Towers South parking lot under the pool’s concrete deck, when enhanced with the help of from the FBI, shows fallen debris before the building. collapse Although still a preliminary analysis, the enhanced video appears to show parts of planters and patio furniture, which had been on the deck, in the garage below. Also, one column is not visible where the researchers think it should be, but Goodwin said that could be due to obstructions or poor lighting.
Social scientist Emel Ganapati, yet another member of the NIST team, said some residents of a particular apartment block in the building described hearing noises on the night of the collapse. They compared the noises to banging, hammering, or furniture being moved above them.
“The noises got louder and louder before … the collapse of the pool deck,” Ganapati said.
Other videos revealed various signs of mid-rise movement and damage, including a hallway floor that was collapsing before part of the building collapsed. And video from a nearby building shows the collapse started on part of the south face, the side facing the pool, below the third floor level and spread north from there, according to Jack Moehle , also a structural engineering researcher at NIST.
“The first two videos, along with eyewitness accounts, provide compelling evidence that the first major collapse was on the pool deck,” Moehle said.
The NIST team previously highlighted design deficiencies and construction deviations they found in the pool deck, as well as photos showing signs of distress on part of the pool deck where planters had been added . Georgette Hlepas, a member of the geotechnical engineering team, described how water was seen around some of the pool deck drains and leak damage was discovered in the roof of the garage below.
Design deficiencies
However, the pool cover is not the team’s only hypothesis of failure. Additional structural analysis also revealed deficiencies in the building’s design that did not meet building code or common standards at the time it was built, according to James Harris, another structural engineer on the team. There were also constructional deviations in the tower, such as in columns where reinforcing bars were installed with less overlap between top and bottom assemblies than the minimum allowed by the building code, which is what had been specified on the plans .
Researchers are still working through several hypotheses about what factors may have played a role in the collapse, said Glenn Bell, NIST team lead associate and forensic structural engineer.
“While there is strong evidence that the collapse was initiated in the pool deck, we have not yet ruled out that a failure was initiated somewhere in the tower that precipitated the collapse in the pool deck. pool,” Bell said.
The team has also been testing materials and simulating material degradation to better understand key points of the structure. Researchers have taken 497 concrete cores and completed hundreds of mechanical tests for compressive strength, modulus of elasticity, and splitting tensile strength. They have also extracted 369 steel reinforcing bars and completed 40 tensile property tests.
Bell said the team expects the technical work to be substantially complete by the end of July, when work on the report, including recommendations, will begin.
“Over the next six months, the main driver of our research activities will be the substantial completion of our technical work through the analysis of failure hypotheses,” Bell said. “As we are concentrating on the most likely hypotheses, thoroughness and rigor demand that we sufficiently analyze all reasonable possible scenarios.”
This article was updated on March 12.
