Miami pedestrian bridge collapse

[CADplans]

I remember watching a show detailing the building of sections of the Chesapeake Bay Bridge–Tunnel "bridge" being built in 1960 using this technique.
so, tensioned concrete is at least 60 years old,,,

Chesapeake Bay Bridge–Tunnel - Wikipedia

 

[California]

Juan Browne's videos on the Oroville Dam Spillway collapse and repair are excellent, the best descriptions I've seen. (My home in town is an hour downstream so I followed those intently. )

Browne's video today is equally excellent. It will be interesting to follow his narratives. The guy is a genius, a renaissance man with wide interests.

The tensioning rod that seems to have popped out of the top of a chord along with its hydraulic tensioning machine, can be seen in one of his pictures.

Pipeliner over on WW posted the following video. It is a slow motion version of the Miami Herald video I linked yesterday. This time the location where the bridge first broke is more obvious.

 

[Stimw]

Looked like the workers harness failed as he was falling.

Stay tuned, they are still analyzing the Titanic and the World Trade Center.

 

[bigdeano]

Watching the surveillance video they showed on tv, it looks like the diagonal member at the north end failed in compression right near the top. I wonder how long they let the concrete cure. Pretty dumb letting traffic underneath until it was stabilized.

 

[Streetcar]

Watching the surveillance video they showed on tv, it looks like the diagonal member at the north end failed in compression right near the top. I wonder how long they let the concrete cure. Pretty dumb letting traffic underneath until it was stabilized.

The diagonals were designed as stiffener not structural member, the diagonal broke as result of the structural failure.The bridge was a post tensioned beam

 

[crazyal]

Kind of odd that the point where the bridge let go was also where a crane was set up and a manlift was located.

 

[houstonscott]

I wonder were in China the steal came from...

 

[MossRoad]

I wonder were in China the steal came from...

Where vs Were vs Wear...
Where vs. Were vs. Wear: What’s the Difference? - Writing Explained

 

[Mace Canute]

This might be of interest to some of you.

https://facilities.fiu.edu/projects/BT_904/MCM_FIGG_Proposal_for_FIU_Pedestrian_Bridge_9-30-2015.pdf

 

[MossRoad]

Juan Browne's videos on the Oroville Dam Spillway collapse and repair are excellent, the best descriptions I've seen. (My home in town is an hour downstream so I followed those intently. )

Browne's video today is equally excellent. It will be interesting to follow his narratives. The guy is a genius, a renaissance man with wide interests.

The tensioning rod that seems to have popped out of the top of a chord along with its hydraulic tensioning machine, can be seen in one of his pictures.

Pipeliner over on WW posted the following video. It is a slow motion version of the Miami Herald video I linked yesterday. This time the location where the bridge first broke is more obvious.

Not failure related.... but did anyone else notice that almost to a T, as soon as it happened, everyone left their cars and trucks and ran TOWARDS the disaster, most likely wanting to help. Puts a little faith back in humanity.

 

[Jstpssng]

Not failure related.... but did anyone else notice that almost to a T, as soon as it happened, everyone left their cars and trucks and ran TOWARDS the disaster, most likely wanting to help. Puts a little faith back in humanity.

Yes, there was no hesitation, they were out and running.

 

[MossRoad]

The diagonals were designed as stiffener not structural member, the diagonal broke as result of the structural failure.The bridge was a post tensioned beam

I think the diagonals were structural. If you look at a cross section of the bridge, the walkway was the bottom flange of the I beam, and the canopy was the top flange of the I beam. The diagonals were the web of the I beam. The cables to be added later were supposed to be stiffeners to help control the bounce of the bridge.

What's questionable is that the diagonals were not steel. They were tensioned concrete. This is kind of unique to this bridge. Everyone knows that non-tensioned concrete is weak across a span. If the tensioning rods/cables in one of those diagonals were loose, that means there was not-enough-to-no-tension in that piece of structural concrete.

As many others have said..... why was traffic allowed under it until it was done? A rush to complete it.

 

[Redbug]

As many others have said..... why was traffic allowed under it until it was done? A rush to complete it.

I think the local politics did not want to inconvenience the public with closing down a road for a few days. The engineers said it was safe so everyone went along with that. Maybe things will change after this? It seems no one was allowed to second guess the "experts", and lean on the safety side.

 

[deezler]

Not failure related.... but did anyone else notice that almost to a T, as soon as it happened, everyone left their cars and trucks and ran TOWARDS the disaster, most likely wanting to help. Puts a little faith back in humanity.

Yeah except the RAV4 (or whatever grey CUV) driver who checks out the scene, and then is like, time to GTFO and u-turns it out of there.

 

[MossRoad]

Can't say I blame him. With all the terrorist stuff going on these days, who knows how any of us would react coming upon that scene. If I had my kids in the car, I'd leave the scene as quickly as possible. Who knows why he left. It was good to see that many ran to help.

 

[Mace Canute]

Not failure related.... but did anyone else notice that almost to a T, as soon as it happened, everyone left their cars and trucks and ran TOWARDS the disaster, most likely wanting to help. Puts a little faith back in humanity.

Yeah, I saw that too. Good on them! :thumbsup:

 

[KennyG]

Yeah except the RAV4 (or whatever grey CUV) driver who checks out the scene, and then is like, time to GTFO and u-turns it out of there.

This got me thinking. If I was there, I think I would try to get my vehicle farther away if easily possible. I would assume there would be a lot of emergency vehicles arriving and I would not want to block things up for them. Maybe the guy moved 100 feet away and ran back. I always give people the benefit of doubt.

 

[John Fitzgerald]

There are lots pointing fingers and wanting to "get a rope".

 

[Streetcar]

I think the diagonals were structural. If you look at a cross section of the bridge, the walkway was the bottom flange of the I beam, and the canopy was the top flange of the I beam. The diagonals were the web of the I beam. The cables to be added later were supposed to be stiffeners to help control the bounce of the bridge.

What's questionable is that the diagonals were not steel. They were tensioned concrete. This is kind of unique to this bridge. Everyone knows that non-tensioned concrete is weak across a span. If the tensioning rods/cables in one of those diagonals were loose, that means there was not-enough-to-no-tension in that piece of structural concrete.

As many others have said..... why was traffic allowed under it until it was done? A rush to complete it.

From the articles I have seen, the bridge was a post tensioned beam. The canopy and diagonals were bracing to stiffen the beam . The cables were decorative.
It is common to tension beams that are over live traffic.
It does not appear to be any post tensioning in the canopy or diagonals

 

[buckeyefarmer]

Where vs Were vs Wear...
Where vs. Were vs. Wear: What’s the Difference? - Writing Explained

Or steel and steal

I wonder were in China the steal came from...