Probing Into A Miami Surfside Condo Collapse And Structure Failures A Slow Process

MIAMI (June 25, 2021)–A tower standing in the skyline alone the beach–is the site of one of the worse catastrophic structural failures in the urban cities history. Determining what went wrong reaches back to 2018 but why and how any city government could fail the people — is a slow and agonizing process.

Experts interviewed by the Miami Herald said the investigation of the Champlain Towers South, likely to be undertaken by the National Institute of Standards and Technology, will have many possible causes to explore, including:

▪ A failure in the condo tower’s foundation;

▪ Steel corrosion in the concrete structure;

▪ An explosion;

▪ Construction damage;

▪ Improper design or construction.

Six experts discussed with the Miami Herald the potential causes of Thursday morning’s calamity and which they thought most plausible based on the information currently available in photos, video and records released by the city.

While none felt certain of their answers, most seemed to agree that the way the building collapsed seemed to be triggered by a failure near the base of the structure.

“It looks similar to something that was intentionally demolished,” said Kevin DuBrey, the director of project management at Hillman Engineering, a firm that inspects high-rise buildings in South Florida for potential damage. “Usually they would do that underneath. They would set the charges on the columns and beams down below and let it collapse on itself.

Gene Santiago, a structural engineer and retired building inspector, said he “still can’t get over the way it fell down — like an implosion,” he said. “Like a demolition job.”

While experts suggested the following hypotheses were most likely to have caused the collapse, they also stressed that a combination of various factors was possible. Atorod Azizinamini, chair of the Department of Civil and Environmental Engineering at Florida International University, told the Herald that this type of collapse is usually the result of “a perfect storm of several factors coming together at the same time.”

#MDFR chaplain and firefighters take a moment to visit the memorial site near the Champlain Towers for a moment of prayer and reflection. They prayed for strength and peace for the families affected, as well as protection and endurance for the men and women commited to the rescue efforts.

HYPOTHESIS 1: STEEL CORROSION IN STRUCTURE

Structural plans from 1979 show that the Champlain Towers South Condo was built using a “flat slab” style of construction in which concrete slabs reinforced by steel rebar sit directly on top of support columns — a common method of construction for everything from parking garages to apartment buildings, experts said.

Over time, the rebar in the concrete can become corroded and crack the slab and joints, potentially weakening the structure. If one part of the structure collapses due to corrosion, it could cause a larger catastrophe.

A concrete slab that’s damaged by corrosion can be prone to a type of failure called “punching,” in which the column punctures the slab and weakens the overall structure, Abieyuwa Aghayere, a professor of forensic engineering at Drexel University. He said that could be one explanation for the building’s sudden collapse.

“Punching is usually sudden,” he said. “It doesn’t give much warning.”

A 2018 report by Frank Morabito, an engineer who inspected the condo, found that poor drainage in the pool deck caused “major structural damage” to the concrete slab below.

“If the pool is leaking and the pool slab is gradually getting destroyed, that could be a problem if it is not maintained,” Santiago said. “Again, it seems like something the residents and condo association would have noticed and corrected.”

Normally, experts said cracks indicating corrosion would be visible, but Morabito said he had limited access to assess the extent of the damage that may have been partially obscured by tiles placed on top of the slab. It’s unclear from the limited records made available by Surfside whether the damage was repaired.

Still, experts cautioned not to jump to conclusions. Investigators will go through the debris to determine the likelihood of failure due to corrosion.

“Contaminated concrete should not have been an extreme problem that would cause catastrophic failure in a 1981 building,” said Miami engineer John Pistorino.

When asked about the likelihood of this kind of damage, experts agreed context is important.

HYPOTHESIS 2: FAILURE IN THE FOUNDATION

The condo was built on a “concrete pile foundation” that appears to sit directly on top of the limestone bedrock, according to the 1979 plans.

Danger, the retired building chief for Miami-Dade County, described the Champlain towers as “conventional concrete buildings for that era, nothing fancy, nothing out of the ordinary.” Experts agreed that the type of foundation should have withstood shifts in the soil and other changes in the ground.

“There should be no issues with the foundation, period, because we design here for harsh and corrosive conditions, high winds and storm surge,” said Pistorino, an engineer with a 50-year career in Miami who has been instrumental in writing state and county building safety laws. “The only time I’ve seen whole buildings collapse because the foundation failed was when Hurricane Gilbert hit Mexico — but it’s totally different construction down there.”

To investigate foundation issues, inspectors will generally take “concrete cores to look at the actual foundation and additional borings to see how the pilings held up,” he said.

“Nothing strikes me [as a red flag],” Aghayere said after reviewing the foundation design. Still, he said, investigators will look at more than just the plan.

“Again, as part of the failure hypothesis, is to say OK, how stable is the rock at the bottom? At least to rule that in or rule that out,” he said.

HYPOTHESIS 3: CONSTRUCTION DAMAGE

Champlain Towers South was in the early stages of three years of expected construction on various aspects of the building, starting with the roof, said Jeff Rose, a contractor who has done renovations on units there and whose parents lived there — and were out of town when it collapsed.

Rose said construction on the roof had begun about six weeks ago, which involved replacing the roof, replacing the stands on which air conditioning condensers rested, and replacing electrical disconnects for air conditioning units. Rose said his parents could hear jackhammers or other demolition tools being used to remove the old roof.

“If they were storing materials and equipment on the roof in an incorrect location in the middle of the slab instead of on top of the columns, that could cause stress on the roof,” said Santiago, explaining that roofs are designed to hold 30 pounds per square foot to meet code. “If you’ve got an overloaded roof slab and it punches through, it goes down, down, down, one level pulling down the next — pom, pom, pom — and it never ends until it hits the bottom.”

Roof failure could have triggered a “perfect storm” collapse, theorized John Colby, a retired architect from Boca Raton.

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