Florida International University released time-lapse videos of the installation of their pedestrian bridge that eventually collapsed on a busy road in March.
A group of men can be seen in the clips – showing three different angles – working on the 950 ton bridge, just moments before it would eventually crash on March 15 and kill six people.
Using a jack, the workers hoped to tighten the steel rods that ran through a concrete support truss that was vital for the bridge’s north section, the Miami Herald reports.
The videos were made utilizing still photos taken by FIU cameras between March 1 and March 19.
Florida International University released time-lapse videos showing the area where the bridge was from March 1 to March 19
They show the bridge being raised to go across Southwest Eight Street on March 10 and then collapsing on March 15. The following days, the videos show workers efforts to clear the rubble.
Built for what is known as the Tamiami Trail, the $14.3million bridge was made possible through the accelerated bridge construction process – preventing the need for road closures.
Two special transporters lifted the bridge into place toward the center of the span on March 10.
Videos -providing multiple angles, show the bridge’s collapse on March 15 and the days used to clean up the debris
The end of the sags, meant to rest on pylons once the structure was set, would sag under its own weight while moved.
To counteract the sag, steel support rods were added and placed in diagonal support pieces at the two span ends.
Adding further support, the rods were tightened and loosened after the span was resting on the pylons.
Workers can be seen de-tensioning the two sides of the ends on March 10. Five days later, they can seen climbing on top the bridge attaching the jack.
Large cracks were forming around the support in the days leading up to the collapse
But an engineer from bridge designer’s FIGG Bridge Group – W. Denney Pate – relayed in a voicemail to the Florida Department of Transportation that he was not worried about the cracks
But by then, they were unaware that the support was not designed for the levels of stress it was undergoing.
Large cracks were forming around the support in the days leading up to the collapse.
But an engineer from bridge designer’s FIGG Bridge Group – W. Denney Pate – relayed in a voicemail to the Florida Department of Transportation that he was not worried about the cracks.
FIGG employees met with FIU officials, Munilla Construction Management representatives and the FDOT to discuss the cracks on March 15 before the collapse.
FIGG employees met with FIU officials, Munilla Construction Management representatives and the FDOT to discuss the cracks on March 15 before the collapse
Information regarding what transpired in that meeting have not been released by the FDOT.
While the re-tensioning occurred, a few westbound lanes of traffic were closed while five eastbound lanes were left open.
And by 1.47pm, the bridge would collapse and kill five motorist and a subcontractor on the scene.
Five motorist were killed when the bridge fell. A subcontractor who was out on the bridge, also died
The reason for the re-tensioning is unknown, but it is believed to have been in an effort to ease the cracks.
‘The design was better at the south end than at the north end,’ said David Beck, a structural engineer. ‘There was clearly concern about what was happening at the north end.’
Beck explained that the de-tensioning of the north end rods potentially escalated the concrete damage and when the workers came back to work on the bridge on May 15, ‘it was like pulling a trigger and going bang.’
FIU could not be reached to a comment about the videos.