Possible Failure Point Emerges in Miami-Area Building Collapse
https://www.nytimes.com/2021/06/27/us/miami-building-investigation-clues.html?smid=tw-nytimes&smtyp=curThe investigation into what may be the deadliest accidental building collapse in American history has just begun, but experts who have examined video footage of the disaster outside Miami are focusing on a spot in the lowest part of the condominium complex — possibly in or below the underground parking garage — where an initial failure could have set off a structural avalanche.
Called “progressive collapse,” the gradual spread of failures could have occurred for a variety of reasons, including design flaws or the less robust construction allowed under the building codes of four decades ago, when the complex was built. But that progression could not have occurred without some critical first failure, and close inspections of a grainy surveillance video that emerged in the initial hours after the disaster have given the first hints of where that might have been.
“It does appear to start either at or very near the bottom of the structure,” said Donald O. Dusenberry, a consulting engineer who has investigated many structural collapses. “It’s not like there’s a failure high and it pancaked down.”...
...But three years before the deadly collapse, a consultant found alarming evidence of “major structural damage” to the concrete slab below the pool deck and “abundant” cracking and crumbling of the columns, beams and walls of the parking garage under the building.
While no definitive conclusions could be drawn from the surveillance video, which was shot from a distance and reveals only one perspective of the disaster, some of the engineers reviewing it last week said it seemed to suggest that the failure began at a specific point near the bottom of the structure — perhaps as far down as the parking garage beneath the building, or on the first few floors....
