Computer simulation of Champlain Towers collapse

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Deflection and steel stress patterns from the LS Dyna model of Champlain Towers South built by engineering professor Dawn Lehman and her team at the University of Washington.

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Seven minutes to collapse

Witness accounts, visible damage and a computer model offer insights into how a pool deck cave-in spread, resulting in the catastrophic failure at Champlain Towers.


The grainy security footage released hours after Champlain Towers South crashed to the ground left many assuming the tower went down without warning in mere seconds. But a recent Miami Herald investigation based on 10 key eyewitness accounts found the collapse began somewhere on the pool deck seven minutes before the northern wing of the residential tower fell.

The Herald partnered with University of Washington engineering professor Dawn Lehman to build a computer model and explore the following critical questions raised by their experiences: Where exactly could this collapse have started and how did it spread across the pool deck and into the tower to become one of the deadliest collapses in modern history?

The witnesses described the collapse sequence as a three-part failure, each with distinct sounds that engineers can use as clues when they try to piece together what happened. First, there was a series of intermittent but distinct — and increasingly loud — booms from just before 1 a.m. The loudest and final booms in the series came at 1:14 a.m. People heard the sounds on the first floor and in the basement but saw nothing, likely indicative of an initial rebar failure.

At 1:15 a.m. the western half of the pool deck and part of the valet parking area collapsed in one loud cascade of concrete. Witnesses described the collapsed region as initiating from the southern perimeter wall and extending to the northern edge of the pool deck, where a video shows the debris from the deck collapse at Column Line 9.1 near the southern edge of the 12-story tower. (That portion of the building was covered with debris after the tower fell and therefore the exact boundary is unknown.)

For seven minutes, the building creaked and

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