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Surfside condo collapse: Engineers search for the cause



Many answers at this stage are speculation, but signs seem to point to some manner of failure in the lower reaches of the 13-story building, perhaps in its foundation or underground parking garage.

Those findings seem to be supported by a report that Michael Stratton was on the phone with his wife, Cassondra, who told him their building was shaking just before the collapse. She was looking out from a condo at Champlain Towers South when she told him she saw “a sinkhole where the pool out her window used to be,” he told the Miami Herald.

Engineers who viewed surveillance footage of the collapse told The New York Times the failure likely began at the bottom of the structure, in the parking garage or along the first few floors of the structure.

The footage shows a center section of the building crumble to the ground, before the easternmost portion of the building falls seconds later. Donald Dusenberry, a consulting engineer who has investigated structural collapses, told the newspaper it appeared to be “a foundation-related matter — potentially corrosion or other damage at a lower level,” though he did not rule out design or construction errors.

Ultimately forensic engineers will need to examine the columns on the ground floor for indications of the cause of the collapse, Sinisa Kolar, a Miami-based executive with the engineering firm The Falcon Group, tells CNN. They will need to test samples of concrete to examine its condition and cross-reference that with structural drawings.

“The key element to this investigation, in my opinion, lies in that rubble, in those columns and condition of the structural elements,” Kolar said. “And potentially that’s what (will) give us some sense of why this has collapsed.”

Peter Dyga, president and CEO of a Florida chapter of Associated Builders and Contractors, told CNN he’d begin any investigation in the middle portion of the wing that collapsed first.

“I’ve also seen some videos looking at the side of the building that’s still standing where it appears like the ground is creviced,” he said.

The failure may be in the support mechanism, said Kit Miyamoto, a structural engineer and California Seismic Safety Commission chairman.

“This collapse is a classic column failure, which means the building itself was supported by a series of pillars. If the pillars fail, everything fails,” Miyamoto said.

The building’s proximity to the Atlantic Ocean, with its corrosive seawater, increases the chances for spalling, wherein reinforced steel within the concrete begins to rust, said Miyamoto and Greg Batista, a specialist in concrete repair projects.

“I’ve seen up and down the coast hundreds of buildings where you have concrete problems,” Batista said. “If not maintained, whether it’s a concrete problem or a settling problem — it could be a bridge, it could be a building, it could be a dam or a sea wall — these kind of things happen if not tended to.”

A report and a lawsuit cited cracks

A 2018 report, which Surfside has released among other public records, noted problems with the building’s concrete, but an engineer who inspected Champlain Towers South last year said the report mentioned nothing alarming.
“Abundant cracking and spalling of various degrees was observed in the concrete columns, beams and walls,” the survey found. “Several sizeable spalls were noted in both the topside of the entrance drive ramp and underside of the pool/entrance drive/planter slabs, which included instances with exposed, deteriorating rebar. Though some of this damage is minor, most of the concrete deterioration needs to be repaired in a timely fashion.”

The waterproofing below the pool deck and entrance drive was failing and causing “major structural damage,” according to the report by Morabito Consultants.

The report didn’t indicate the structure was at risk of collapse.

Morabito Consultants “provided the condominium association with an estimate of the probable costs to make the extensive and necessary repairs. Among other things, our report detailed significant cracks and breaks in the concrete, which required repairs to ensure the safety of the residents and the public,” it said in a statement.

In 2015, attorney Daniel Wagner filled a lawsuit alleging “cracks in the outside wall of the building” had allowed water into one of the condominiums. The case was settled.

Still, the issues flagged in the 2018 report would not be sufficient to cause a collapse, Kolar said he believes.

“When somebody shows us damages and corrosion and exposed rebar on the underside of the balcony, that’s a horizontal element that basically supports only that floor. So, if there is a collapse of a balcony, that most likely would not cause any additional damage to the rest of the building except for that particular balcony.

“Some of these damages as depicted in 2018 report — although problematic and definitely should have been addressed — in my opinion were unlikely to cause the collapse of the entire building,” he said. “It’s a giant leap from the damage depicted in that report to the collapse of the building and there are a bunch of dots missing to connect the two.”

Nothing alarming on the roof, an engineer says

Jason Borden, a structural engineer who examined the 40-year-old building last year, saw cracks in the facade and plaza level. While he was on site only for an hour, “what I did see while I was there did not alarm me at all,” he told CNN on Monday.

The 2018 report’s conclusions were “very typical of what we see in buildings of this age and condition,” he said.

The building was amid a milestone safety certification and was undergoing work on its concrete roof. Had the failure begun on the roof, Borden said, the collapse “would have looked very different.” If, as suspected, the collapse began somewhere in the bottom of the building, it’s likely something compromised a support column, he said.

Perhaps a slab fell and hit the column or a column’s braces failed or shifted, Borden speculated.

Several other experts have suggested a combination of factors could be behind the collapse.

“Usually it’s like a perfect storm,” said Atorod Azizinamini, a structural engineering professor at Florida International University.

A month after the report citing “major structural damage” was released, Rosendo Prieto, the Surfside building official at the time, told the building’s condo association that the tower was in “very good shape,” according to minutes from the November 15, 2018, meeting.

Two days before that meeting, a member of the condo board forwarded Prieto a copy of the October 2018 report, according to an email released by Surfside on Saturday.

The report’s findings were alarming, said Abieyuwa Aghayere, a Drexel University professor of structural engineering who reviewed the report. The findings should have spurred further review of the building’s integrity, the professor told CNN.

“Structural engineer report was reviewed by Mr. Prieto,” the meeting minutes state. “It appears the building is in very good shape.”

Condo resident Susana Alvarez recalled a Surfside representative say at the meeting, “The building was not in bad shape,” she told NPR.

Prieto now works for CAP Government Inc., to which CNN has reached out for comment. Prieto has not responded to requests for comment.

The building was sinking at one point

Another report that emerged last week indicates the condo tower — unlike surrounding structures — was sinking at a rate of 2 millimeters per year between 1993 and 1999. It’s unclear if the building continued to sink at that rate following the study.

More information is needed before determining if the sinking played a role in last week’s collapse, said Shimon Wdowinski, a coauthor of the study and professor with Florida International University’s Institute of Environment.

“If everything moves downward at the same level, then not so much,” he told CNN, but “if one part of the building moves with respect to the other, that could cause some tension and cracks.”

Residents would’ve noticed if the building’s “settlement” was uneven, Kobi Karp, a member of the American Institute of Architects, said last week. They would’ve seen cracks in their floors, walls and ceilings.

“The table would not be flat. Things would roll off,” he said.

It’s unclear if complaints of that nature were lodged with the tower’s management.

Buildings in nearby western Miami Beach, which was built on reclaimed wetlands, were moving at higher rates, “so we didn’t think it was something unusual,” Wdowinski said.

The building had undergone a series of inspections as part of its 40-year certification — a stringent process for updates and improvements enacted after Hurricane Andrew in 1992. The only recent repairs had been to the roof, said Kenneth Direktor, an attorney for the condominium association.

“Nothing like this was foreseeable,” Direktor said. “At least it wasn’t seen by the engineers who were looking at the building from a structural perspective.”

Surfside Mayor Charles Burkett has echoed that assertion, saying, “There’s no reason for this building to go down like that unless someone literally pulls out the supports from underneath, or they get washed out, or there’s a sinkhole or something like that.”

Surfside building official Jim McGuinness was on the roof 14 hours before the building collapsed and saw nothing unusual, he said. The building’s ongoing roofing permit was going well, he said.

“I have two words for the cause of this: under investigation,” McGuinness said.

CNN’s Curt Devine, Casey Tolan, Rosa Flores, Gregory Lemos and Gregory Krieg contributed to this report.



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