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At the scene of the collapse of a residential building near Miami in the United States, search and rescue personnel found the bodies of four victims on Wednesday (30th), which means that the number of deaths in the incident rose to 16.
Search and rescue personnel continue to search for survivors in the rubble, and more than 140 people are still missing. US President Biden will visit the local area this Thursday.
The South Block of the Champlain Building, a 12-story high-end residential building, suddenly collapsed last week, and there are endless questions surrounding the accident.
Experts pointed out that there are many possible reasons for the collapse of this 40-year-old building, including environmental impacts and structural issues.
The moment of the collapse of the Miami building captured by surveillance video
A surveillance video was released recently, which recorded the collapse of this residential building. The video was taken from a nearby building. It can be seen that the Champlain Building did not collapse all at once, but fell in stages.
After the south-facing part collapsed, three seconds later, the north-facing part of the building immediately tilted down, and after another five seconds, the east-facing part also collapsed.
Some experts who have watched the video believe that the first to collapse may be the south-facing swimming pool area.
According to media reports, a resident talked with her husband on the phone a few seconds before the building collapsed. She looked out the window and said to him: “My dear, the swimming pool is about to collapse.”
Although the cause of the collapse cannot be determined at present, a structural inspection report of the building three years ago pointed out that the swimming pool of the building has a safety hazard.
The report pointed out at the time that the waterproofing facilities and coatings under the swimming pool had “exceeded the service life” and “caused structural damage” to the concrete layer under the swimming pool. If the waterproofing facilities cannot be replaced as soon as possible, the damage to the concrete will “expand extremely quickly.” The report also said that there have been many cracks in the beams and walls of the underground parking lot.
However, this report published in 2018 did not believe that the building would be at risk of collapsing, but suggested that the damaged part of the concrete should be repaired as soon as possible. But this restoration project did not start until the building collapsed.
Earlier this year, the chairman of the Champlain House Housing Committee warned residents that the damage to the parking lot area had “significantly worsened” and the cost of repairing the building rose from US$9 million to US$15 million.
Structural engineer Greg Batista told the BBC that damage to building concrete is one of the possible causes of the collapse.
“These houses in the coastal zone are very susceptible to peeling,” he said. Batista has conducted thousands of building inspections in Florida.
He explained that moisture will erode the steel in the concrete, and the corresponding pressure will cause the concrete to burst and peel off, which will have a huge impact on the stability of the structure. “It only takes one beam or column to collapse and it will trigger the domino effect.”
Some researchers believe that settlement also affects the stability of buildings.
Florida International University published a study last year that pointed out that the Champlain Building sank by 2 millimeters per year in the 1990s. The settlement of the land under the building can cause cracks and even structural problems in the building.
The study also included other buildings, but the sinking of the South Tower of the Champlain Building was particularly significant.
Professor Shimon Wdowinski, who led the research, said that research on the South Tower of the Champlain Building was stopped in 1999. It is unknown whether the building continued to sink and at what rate during the next 20 years.
He claimed that the fact that the building was sinking does not in itself fully explain its collapse.
Some people also believe that the vibration caused by the construction of the 18-storey “Eighty Seven Park” near the new building may have caused the foundation to loosen.
Residents of the South Block of Champlain Building reported in 2019 that they felt that the building would shake when construction was carried out nearby.
Experts pointed out that it may take longer to investigate the real cause of the collapse of the Champlain Building South Tower. Structural engineers need to study the design drawings, sample the steel and concrete on site, and study the signs of damage to the building before the collapse.
And just a few tens of meters away, the North Tower, which has exactly the same design as the Champlain Tower South Tower, still stands, but the residents are panicked, hoping to ensure that the same problem will not repeat itself. The local government has ordered an inspection of the structural stability of the North Tower.