Federal investigators released the results of their investigation into what caused the deadly 2021 collapse of the Champlain Towers South condo in Miami that killed 98 people.
Five years after the disaster, the National Institute of Standards and Technology blamed the failure of two garage column connections beneath the pool deck. The critical moment occurred roughly three weeks before the actual collapse, when the connections between the concrete slabs and columns failed, according to the investigation, crediting the findings to an “extensive technical investigation.” This caused “cracks to grow and loads to redistribute in the pool deck over the next three weeks,” NIST said.
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NIST experts determined that a “punching shear failure” occurred at the two garage columns, a type of failure where forces pushing down on a steel-reinforced concrete slab cause it to crack and bend around a supporting column, putting overwhelming pressure on the connection holding it in place.
The fracturing and warping of the pool deck’s concrete slab shifted increasing weight to the adjacent columns until it overwhelmed them, setting off a domino effect that collapsed much of the building.
Identifying the critical sequence of events failed to let anyone off the hook, however. NIST concluded the blame for the collapse lay with those who constructed the building, finding it failed to meet the safety requirements 40 years ago when it was built.
“When building structures are designed and built to required codes and standards, they have margins against failure, meaning they should be able to support much more load than they are expected to bear,” investigator Judith Mitrani-Reiser said. “In the case of Champlain Towers South, however, these margins against failure were too narrow from the start.”
NIST identified several problems beginning with the building’s inception, finding the construction itself differed from the original design. Heavy landscape planters and thick paving stone were added to the pool deck later on, adding tons of new weight to an already faulty structure. These additions were particularly damaging and, when combined with corrosion over time, proved fatal.
“The low margins against failure were primarily caused by two factors,” co-investigator Glenn Bell said. “First, severe and widespread deviations in the building’s original structural design from the codes and standards of the day, but also some limitations in those codes and standards. And second, deviations in the building’s construction from the design drawings.”
The structural deficiencies were known well before the ultimate collapse. A 2018 structural field survey released by Surfside city found “major structural damage” to the pool deck’s concrete structural slabs and failed waterproofing throughout the tower. The pool deck and garage underneath it required repairs in 1996.
Worst of all for the building’s owners, NIST found that warning signs of the building’s imminent collapse were ignored. A residential sliding glass door popped out of its frame, entry gates were jammed shut, and hours before, there was considerable water leakage through the garage ceiling.
Bell and Mitrani-Reiser presented the team’s findings in a detailed animated presentation on Monday.
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“We appreciate everyone who has helped with this work, including the survivors and the families of those who were lost,” Bell said. “With their invaluable input, this effort will help make other buildings safer, help prevent tragedies like this from happening again, and help honor the lives of the Champlain Towers South victims.”
NIST said it would now focus on putting together the final report, combining the evidence analysis, test results, and computational modeling presented on Monday.
