As first responders frantically search the rubble for survivors of a collapsed residential tower in Surfside, Fla., the investigation has already begun—and it is likely to focus on multiple causes, says Mehrdad Sasani, a professor of civil and environmental engineering at Northeastern. An engineering report conducted on the building in 2018 and released Friday pinpointed structural damage issues that could have contributed to the catastrophic collapse.

Other clues have emerged as well about Champlain Towers South, says Sasani. “Usually, when there is a collapse, there are several factors involved,” said Sasani, who has researched the progressive collapse of structures, earthquake engineering, and structural integrity and reliability.

Two sections of the 12-story tower gave way without warning, one after the other, at 2 a.m. Thursday.

As of Sunday night, at least nine people were dead and 152 people were unaccounted for, according to Miami-Dade County officials.

Sasani notes that U.S. building requirements changed in 1989—eight years after the construction of the Surfside building.

“There were [new] structural integrity requirements that would help the structure to be better integrated,” he says.

In the meantime, says Sasani, this should be viewed as a rare event. People should not be anticipating other buildings to crumble in the United States, he says.

“The general concept of design is such that if failure is going to happen, it is going to happen gracefully with enough warnings,” Sasani says. “The taller the building, the more checks and balances are there, the better design is there, the better construction is there—in most cases.”

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