A murky video looking into the basement-level garage of the Champlain Towers South condo, recorded from the street by a tourist just minutes before the 12-story building caved in, is more than just a macabre curiosity. Experts say it’s a critical piece of evidence that shows the beginning of the deadly collapse sequence.
“It looks like the slab fell down,” said Dawn Lehman, professor of engineering at the University of Washington. “This is certainly the first place where we see structural damage before the collapse.”
Experts were already zeroing in on that part of the garage ceiling — below the pool deck at the edge of the part of the building that collapsed — as the likely point of first failure. The video was the missing piece.
According to building plans, the slab shown crumbled in the video was located beneath a large planter on the pool deck, where in 2018, engineer Frank Morabito noted “major structural damage.” The slab fell directly adjacent to the part of the garage where a pool contractor noted unusual amounts of standing water, indicating a potential problem in the area, 36 hours before the collapse. Just moments before the total collapse of the part of the building above, two eyewitnesses also described a crater opening in roughly the same area from which the debris in the video appeared to have fallen.
“It really does suggest that the initiation point is there,” Lehman said. “All of this matches up together.”
See where the ‘initiation point’ is in relation to the rest of the building
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Around 1:15 a.m. on June 24, tourist Adriana Sarmiento heard a loud noise from her hotel and headed outside to investigate. She looked south, across 88th Street, toward the Champlain Towers South condo, and was shocked by what she saw through the entrance to the underground parking garage.
“I saw the roof of the parking garage on the floor — huge chunks of concrete,” Sarmiento told the Miami Herald. She took out her phone and recorded a short video. The time stamp shows 1:18 a.m. Emergency calls about the building collapsing started coming in at 1:26 a.m., 911 records show. The whole side of the building shown in Sarmiento’s video was gone.
“Something was happening a few minutes before the building comes down,” said Abi Aghayere, a Drexel University engineering researcher. “There was something happening around this deck area [above the debris]. For this type of flat slab construction, my hypothesis is the punching shear began at this slab level.”
“Punching shear” failure is when concrete slab cracks and falls away from the column supporting it. Aghayere said that type of initial failure can cause sudden collapse.
In 2018, Frank Morabito, an engineer under contract with the condo association, surveyed the building and noted a “major error” in the design resulting in lack of proper drainage. That error was causing severe damage to the concrete slab below the pool deck and planters — some that sit directly above the part of the garage seen covered in rubble just moments prior to the catastrophic collapse.
As it turned out, the damaged conditions highlighted by Morabito only deteriorated further, as he warned they would, according to an April letter from the president of the Champlain Towers South Condominium Association first reported by USA Today.
“The observable damage such as in the garage has gotten significantly worse since the initial inspection,” the letter said. The extent of the damage could not be known without removing the immense planters and pulling up all of the tiles on the pool deck, the letter added. Meanwhile, a report from 2019 by Morabito noted something “curious” about concrete samples taken from the area but did not elaborate.
Still, deteriorated concrete does not usually break without a trigger, Lehman said. The video shows the initial collapse, but not the specific trigger, she said.
“I don’t know why the slab broke,” Lehman said. “When you’re looking at what could have caused this you want to look at multiple things. And unexpected loading is one.”
Although she cautioned against speculating too much, based on the 2018 report of structural weakness below the planter on the pool deck, Lehman offered one theory.
“If there was all this standing water, and if the planter was collecting the water and the water wasn’t evaporating because it was raining a lot and there was already deterioration there, that could be a cumulative effect,” she said.
Engineer Mohammad Ehsani said the rubble indicated the slab above was beginning to fail at the time the video was shot. He also pointed to the planter above the area as a possible reason for the strain.
“That’s a very heavy concentrated load, and if the reinforcing bar below it [was weak], just before it collapses you would see chunks of concrete falling down,” Ehsani said.
Even still, experts agree that in general a building should not fall due to a single failure of a slab. But Aghayere said a review of the building plans, inspection reports and photos from the collapse shows a lack of necessary backstops.
“It doesn’t have structural integrity reinforcement,” Aghayere said. “Because there’s no structural integrity reinforcement if it falls, it just goes.”
Structural engineer and retired building inspector Gene Santiago said the part of the building that collapsed was lacking an adequate number of structural walls called “shear walls” that would have helped the building resist caving under lateral or twisting forces from an initial failure of a slab on a single floor.
“There doesn’t seem to be enough of them in the plans,” he said. There were no shear walls in the east-west direction, he pointed out.
In general, experts agreed that the building, which was constructed in the early 1980s, was not designed with the same level of redundancy as modern-day buildings.
This story was originally published July 02, 2021 5:00 AM.