- Visual and Data Journalism Team
As rescue efforts continue, experts analyze what may have caused the collapse of a 12-story apartment complex 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 building collapse.
The images taken by a surveillance camera in a neighboring condominium show that the building did not fall at once, but rather its crash was in stages.
First, the central sector facing south collapsed. Only three seconds later it was the turn of the central sector facing north. Five seconds later, the department section 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 south-facing central sector.
Aerial footage from after the collapse shows that the area around the pool collapsed into the underground parking lot.
Although it is too early to be sure of the cause (s), the pool area was identified as an area of great concern in a structural report carried out in 2018.
That inspection alerted to a “A big mistake” in the original design of the apartment block.
Engineer Frank Morabito noted there that the ground floor pool deck was not tilted to drain, so the water “stayed in the waterproofing until it evaporated.”
The report stated that the state of this waterproofing was “beyond its useful life” and caused “significant structural damage to the concrete slab below these areas.”
Failure to replace 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 carried out “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, roof repairs were underway, but concrete restoration had not yet begun.
How could these damages have affected the building?
Structural engineer Greg Batista, who has conducted thousands of building inspections in Florida, said the concrete damage 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 within the concrete rusts and expands up to seven times its volume. The surrounding concrete cracks and that causes significant deterioration in the structural integrity of either a beam or a column. Everything What is needed is for a beam or column to fail for a Domino effect“, 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 1990s.
Movement under buildings can cause cracks and contribute to structural problems.
Professor Shimon Wdowinski claimed 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 much, but as the study was more than 20 years ago “we do not know what happened after 1999, at what level it continued to sink, if it continued to sink and how this may have affected its foundations.”
“Perhaps a point was reached where the structure could not support the load and it 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 from recent construction from an adjacent 18-story building, the Eighty Seven Park.
Residents of Champlain Towers South expressed concern in 2019 that they had felt movement and tremors during construction, but were informed that they were monitoring the situation.
Are there other buildings at risk of collapse?
Champlain Towers South was built on a reclaimed wetland in 1981.
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 checks.
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Eddie is an Australian news reporter with over 9 years in the industry and has published on Forbes and tech crunch.