As rescue efforts continue, experts analyze what could have caused the collapse of an apartment complex of 12 apartments in Surfside, Miami .
A wide variety of possible causes are being considered, from structural defects to environmental effects, and whether a combination of factors may have triggered the sudden collapse of the building.
The images taken by a surveillance camera in a neighboring condominium show that the building did not fall at once, but its collapse was in stages.
First, the sector south-facing central collapsed. Only three seconds later it was the turn of the central sector facing north. Five seconds later, the section of apartments facing east collapsed.
Some experts who analyzed the images believe that the initial collapse occurred at the base of the building, around the pool area, facing the central sector facing south.
Aerial images from after the collapse show that the area around the pool collapsed into the underground parking lot.
Although it is too much Soon to be sure of the cause (s), the pool area was identified as an area of great concern in a structural report conducted in 2018.
That inspection alerted about a “a big mistake” in the original design of the apartment block.
The engineer Frank Morabito warned there that the platform of the pool on the ground floor was not inclined to drain, so the water ” I stayed in the waterproofing until it evaporated. ”
The report assured that the state of that waterproofing was “beyond its useful life” and caused “significant structural damage to the concrete slab below these areas.”
If the waterproofing in the near future would cause the degree of deterioration of the concrete to “expand exponentially”, he warned.
He also listed “abundant cracks… of columns, beams and walls” in the basement parking lot below the complex. But he did not suggest that the building was in imminent risk of collapse, although he urged that concrete repairs be done “in a timely manner.”
The repair estimate for the entire building was over $ 9.1 million. Morabito Consultants said that at the time of the collapse, the roof repairs were underway, but the concrete restoration had not yet begun.
640 How could this damage have affected the building?
Structural engineer Greg Batista, who conducted thousands of building inspections in Florida, said that the damage to the concrete could be a possible explanation for the collapse.
“These buildings along the coast are susceptible to what we call spalling,” the expert told the BBC.
“Basically, the reinforcing steel inside concrete rusts and expands up to seven times its volume. The surrounding concrete breaks and this causes a significant deterioration in the structural integrity of either a beam or a column. All it takes is for a beam or column to fail for a domino effect to occur, ”he described.
A study by researchers from Florida International University published last year found that the building was being sinking at a rate of approximately 2 millimeters per year in the decade of 1990.
Movement under buildings can cause cracks and contribute to structural problems.
Professor Shimon Wdowinski stated that the study did not focus on Champlain Towers South in particular, but that the building stood out as one of the places that showed the most subsidence.
He said it was not a lot, but since the study was more than 20 years “we don’t know what p asó after 1999, at what level it continued to sink, if it continued to sink and how this could have affected its foundations. ”
“ Perhaps a point was reached where the structure could not support the load and Collapsed. But this is a structural problem. They are not things that I study, ”he told BBC Mundo.
“What we do know is that the building that collapsed in Miami has been sinking for decades, but that alone does not explain the collapse,” he emphasized.
Another factor to analyze is the vibrations of the recent construction of an adjacent building of 18 flats, the Eighty Seven Park.
The Champlain Towers South residents raised concerns at 2019 that they had felt movement and tremors during construction, but informed them that they were monitoring the situation.
Is there other buildings at risk of collapse?
Champlain Towers South was built on a reclaimed wetland in 1981.
- How Miami Beach was built by gaining ground from the sea in a swampy area (and the risks that this implies)
Most buildings along the coast and those of high rise elsewhere are built on pile foundations, using concrete and steel columns to transfer the load from the building to the ground.
A short drive away is Champlain Towers North, built to an almost identical layout.
Residents want to know if their building faces similar problems and local authorities have ordered new controls.
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