Bridge collapses at Florida International University in Miami

[Solomon2]

They were actually conducting a stress test on it earlier in the morning prior to the collapse.
It's supposed to withstand the effects of a category 5 hurricane so whatever happened is definitely a major failure which is extremely rare in the US. Safety standards in the US are of the highest order and money is never a consideration when it comes to the safety of the public.
This type of bridge had been built over 800 times prior to this one.
They built it on the side of the road for safety and logistical reasons and it only took 3 hours to turn it and move it in place. So for this to happen is very unusual and was probably either a defective portion of the poured concrete or a weight miscalculation. It could've also been an error in the stress testing process. Either of those are extremely rare.

I suspect systemic assembly error. In this type of construction the bolts have to be torqued exactly right otherwise when the bridge is moved into position the assembly jiggles and the load isn't distributed properly. Bolts over-stress and eventually break from concentrated loading and soon the whole structure falls down.

 

[takeitwithyou]

True. The bridge just finished 5 days ago . If America is willing to spend some money on infrastructure . they should look to China to help them with building infrastructure.

ROFL. do you want us to put up pics of your handy work and results? so yeah- these guys F_- up big time. This is an outlier and not the norm for us. probably used Chinese steel

China - the country that can make the world's largest armchair (but where the motorways collapse just TEN MONTHS after being built)

A pedestrian overpass example in Shanghai of China, with similar amount of budget and construction time: $20 million + 2 years.

Construction business in the US must be super profitable. Feel envy.

View attachment 459598 View attachment 459599

We don't pay slave wages so it costs us more. We also have to guarantee worker insurance etc etc. there are several regulations and it mostly gets done while not impeding traffic flow as much (hence longer time). I agree it's not on the cheap. This incident is an outlier for us.

 

[Gomig-21]

I suspect systemic assembly error. In this type of construction the bolts have to be torqued exactly right otherwise when the bridge is moved into position the assembly jiggles and the load isn't distributed properly. Bolts over-stress and eventually break from concentrated loading and soon the whole structure falls down.

Honestly, it's hard to believe they didn't appropriately torque whatever bolts were needed.
It looked like they only had the end columns supporting it and the bridge was supposed to bear its own weight and live/dead load through the arch of it's shape, with the help of the staggered bracing in between. It didn't look to me like there was a center support in between the two lanes, so that dead load in the center span might've been too much, or a crack that resulted from a wrong mixture of the concrete that might've developed during the stress test earlier that morning started the process.

I'm sure those bolts have some type of absorbing washers or cushions of some type if it's designed to withstand a cat-5 hurricane. There needs to be some give for movement. So it would be a bit weird if the tensions were all wrong on all the bolts at one end since they would all have to give out at once in order for there to be a failure of this magnitude. But certainly nothing is impossible.

 

[Solomon2]

Honestly, it's hard to believe they didn't appropriately torque whatever bolts were needed...I'm sure those bolts have some type of absorbing washers or cushions of some type if it's designed to withstand a cat-5 hurricane. There needs to be some give for movement...

Oh yes. But unlike a hurricane, during the assembly and deployment some parts of the structure that are normally loaded in tension or compression even in a storm experience complete reversal; that's when the damaging "jiggling" can happen. Result: instead of loading the entire spread of a moment plate the load could rest only on part of it and a few bolts.

(I'd be very surprised if a design fault could pass review but sometimes these things do happen.)

There's a video of the collapse. You can see construction workers on top as the bridge fails. May they rest in peace. http://www.miamiherald.com/news/local/community/miami-dade/article205443304.html.

 

[Jlaw]

ROFL. do you want us to put up pics of your handy work and results? so yeah- these guys F_- up big time. This is an outlier and not the norm for us. probably used Chinese steel

Bhai, why so emotional. You're Indian this event doesn't concern you so you can stop the ghada chaat.

 

[takeitwithyou]

Bhai, why so emotional. You're Indian this event doesn't concern you so you can stop the ghada chaat.

 

[Hamartia Antidote]

They were actually conducting a stress test on it earlier in the morning prior to the collapse.
It's supposed to withstand the effects of a category 5 hurricane so whatever happened is definitely a major failure which is extremely rare in the US. Safety standards in the US are of the highest order and money is never a consideration when it comes to the safety of the public.
This type of bridge had been built over 800 times prior to this one.
They built it on the side of the road for safety and logistical reasons and it only took 3 hours to turn it and move it in place. So for this to happen is very unusual and was probably either a defective portion of the poured concrete or a weight miscalculation. It could've also been an error in the stress testing process. Either of those are extremely rare.

Contrary to popular belief by the Chinese here the bridge was not finished. They still hadn’t put up the center tower with the wires and the half of the bridge that goes over the water.

There’s a video here showing what it is supposed to look like when finished. Note the tower in the middle which hadn’t been built yet.

The half on the far side of the tower was installed. The near side not yet.

https://www.roadsbridges.com/fiu-pedestrian-bridge-florida

This is the install a few days ago. This is only half the bridge length. The haven't built the part that goes over the river yet.

 

[Dungeness]

Contrary to popular belief by the Chinese here the bridge was not finished. They still hadn’t put up the center tower with the wires.

There’s a video here showing what it is supposed to look like when finished. Note the tower in the middle which hadn’t been built yet.m

https://www.roadsbridges.com/fiu-pedestrian-bridge-florida

then they've got building procedure backwards. The tower was supposed to be the main load bearing structure, but we don't see it anywhere on the scene. It is like building a house first, pour the foundation later.

 

[Gomig-21]

then they've got building procedure backwards. The tower was supposed to be the main load bearing structure, but we don't see it anywhere on the scene. It is like building a house first, pour the foundation later.

Hard to do that because the bridge itself was a single piece and had to be swung into place and then the center tower was to be erected and the wires installed. This is actually typical of the way most of these bridges are built since the wires have to go in last. So until then, the process is precarious and the bridge needs to be well supported and stabilized until it's permanently secured.

 

[Dungeness]

Hard to do that because the bridge itself was a single piece and had to be swung into place and then the center tower was to be erected and the wires installed. This is actually typical of the way most of these bridges are built since the wires have to go in last. So until then, the process is precarious and the bridge needs to be well supported and stabilized until it's permanently secured.

The center tower was supposed to be built on one of two piers (to the right in photo) that this section of bridge rested on, and there was supposed to be another section extended from right pier (center tower) to further right.

IMO, they should have built the tower first, then installed the "right section" bridge with temporary support. This section of bridge should be installed last. Before the installation of cables, there should be temporary supports under both sections of bridge.

 

[Actuary]

Diversity kills.

 

[Jlaw]

Contrary to popular belief by the Chinese here the bridge was not finished. They still hadn’t put up the center tower with the wires and the half of the bridge that goes over the water.

There’s a video here showing what it is supposed to look like when finished. Note the tower in the middle which hadn’t been built yet.

View attachment 459859
The half on the far side of the tower was installed. The near side not yet.

https://www.roadsbridges.com/fiu-pedestrian-bridge-florida

View attachment 459888
This is the install a few days ago. This is only half the bridge length. The haven't built the part that goes over the river yet.

It's finished. It took 5 years to build and 5 days to collapsed. The Florida governor stated it is looking into this as a serious matter. No stones will he left unturned.

 

[Davos]

The center tower was supposed to be built on one of two piers (to the right in photo) that this section of bridge rested on, and there was supposed to be another section extended from right pier (center tower) to further right.

IMO, they should have built the tower first, then installed the "right section" bridge with temporary support. This section of bridge should be installed last. Before the installation of cables, there should be temporary supports under both sections of bridge.

G'day Mate

There are more than one way to build a bridge, in this case that bridge is build using Rapid Bridge Replacement (RBR) method, or what they called Accelerated Bridge Construction in the US. Which mean the whole bridge, or a section of a bridge is delivered as a whole to replace the existing structure, it is not possible to have the central tower remain in place or else it would be blocking the automatic loader which tries to deliver the bridge on site.

What you are referring to is the traditional building over pier method, to which you build both ends of the bridge first, then the pier, then the bridge itself and finally run the cable, that method is not generally use today and usually reserved for long/sectioned bridge, for a pedestrian bridge, it is usually preferred the RBR method, because that way you could have less obstruction to traffic flow and the bridge would be finished quicker.

As much as I understand, there is a column in place to hold both end of the bridge, either the column or the bridge failed or the bridge is not secured to the column, it collapsed before the central tower and the cable can be put in place.

Regards

Davos

 

[Dungeness]

G'day Mate

There are more than one way to build a bridge, in this case that bridge is build using Rapid Bridge Replacement (RBR) method, or what they called Accelerated Bridge Construction in the US. Which mean the whole bridge, or a section of a bridge is delivered as a whole to replace the existing structure, it is not possible to have the central tower remain in place or else it would be blocking the automatic loader which tries to deliver the bridge on site.

What you are referring to is the traditional building over pier method, to which you build both ends of the bridge first, then the pier, then the bridge itself and finally run the cable, that method is not generally use today and usually reserved for long/sectioned bridge, for a pedestrian bridge, it is usually preferred the RBR method, because that way you could have less obstruction to traffic flow and the bridge would be finished quicker.

As much as I understand, there is a column in place to hold both end of the bridge, either the column or the bridge failed or the bridge is not secured to the column, it collapsed before the central tower and the cable can be put in place.

Regards

Davos

Based on the photo I attached in my previous post, there are two sections of bridge connected at the pier where the center tower should be built on. So in theory, the center tower is out of way of the loader and the bridge section that collapsed.

What I don't understand is, since the cable system is the main load bearing support for the bridge (there was no beam under the bridge to hold it up), why they would even install the bridge section without any temporary support at the absence of cables.

 

[Davos]

Based on the photo I attached in my previous post, there are two sections of bridge connected at the pier where the center tower should be built on. So in theory, the center tower is out of way of the loader and the bridge section that collapsed.

What I don't understand is, since the cable system is the main load bearing support for the bridge (there was no beam under the bridge to hold it up), why they would even install the bridge section without any temporary support at the absence of cables.

G'day Mate

You probably not familiar with the RBR method, the reason why the middle tower is an obstruction is because the Auto-Loader would need to slide the bridge horizontally in place of the old structure. Thus making anything above the old bridge or the new bridge were obstacles. Its very hard to explain the process by word, so instead I will just post a youtube video, it's a time-lapse video on a bridge built using the RBR method.

On another note, I think you mislabelled the term "center-tower" maybe what you meant is the central pier(s), which is the pier the bridge sat on. If that is what you mean, then judging from the photo, the central pier(s) is in place, but I cannot say for sure whether or not it was a temporary structure or the left over from previous structure, or even, permanent structure

The piers are circled in black

Another thing is, the bridge is a truss bridge as per the original specification, that mean the whole load bearing issue is on the whole cable structure instead of using cable tension in place to hold up the bridge, as in cable stayed bridge, the cable would have to insert until the whole bridge is completely erected, and we all know the second part of the bridge is never installed, which mean the cable would not be installed prior to collapse.

Regards
Davos