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[3rdman]

I don't know if anyone has been watching the news or not...This happened right by my house. Apparently 5 people are dead (crushed) under the bridge after is slammed into the street.

I am not an engineer but it appears that the bridge was not being installed properly. The bridge was meant to be a suspension-type with half overhanging the street. A shorter section was to be done over an uneven plain on the FIU campus. The center was to be a tower that would "suspend" the weight of both sides...here is the kick in the balls: they appear to have installed the longest section only over the weekend without the tower in place and nothing holding the weight under the center of the bridge over the street!

I'm certain they will claim that the numbers showed no issue with this but clearly they were wrong...heads are gonna roll...what were they thinking???

 

[3rdman]

Before...

During..

After...

 

[OH-MyCar]

I'm actually taking some graduate courses at FIU, but luckily I'm always at the Biscayne Bay campus. My phone's been blowing up in the past couple of hours from every relative I've not heard from in years.

That area is cursed, though. I must've received a campus alert text every other week last year for MMC pedestrians being in hit & run accidents and now this happens.

 

[Slayer-33]

Damn the main support tower wasn't in place already?

 

[TrainedRage]

Ban all bridges! Write to your congressman and get ready to protest lack of infrastructure to save future lives.

Seriously how does this happen? Same with the I94 bridge collapse in MN. Just no one doing their job and checking structural integrity? Or shortcuts taken on the build?

 

[Jezan]

How the fuck do they instal a suspension bridge and not have anything to hold it while the suspension is not ready yet? I mean that kinda defeats the purpose of the suspension part if they didn't need supports -_-

 

[Dubloon7]

i would first look at the construction docs, speak to every worker under the contractor, freeze everything related to the contractor and their company, as well as the structural engineer. from what i see it may be poor foundation "design" and installation, connection design, and decking materials possibly poor.

from the model pictured above i do not see the tension cables, and this was opened too early and improperly installed without quality assurance.

the road that runs underneath would have to be closed off while this was being constructed. so, why they opened it up without the vertical and diagonal supports is a failure on the project engineer, contractor, and residing jurisdiction

 

[iamblades]

Someone clearly fucked up, but seeing how beefy that truss span is, it looks like it should have been fine on it's own(if it was properly engineered and/or built), which brings up the question of why the fuck are you building a ridiculously over-engineered cable stay pedestrian bridge anyway when a truss bridge should suffice just fine, but government waste is the least surprising thing about this.

ETA:

Just found the design proposal for the bridge, and the truss was supposed to exceed the load requirements on it's own, the cable stayed part of it was intended to control harmonic oscillations.

I'm guessing this will end up being a tension failure of the lower deck due to either faulty materials, improper installation or gross miscalculation in the initial engineering, or some combination thereof.

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

 

[DiscoJer]

It's been 25 years since I took any engineering courses, but I'm pretty sure a smallish pedestrian bridge really shouldn't even need a suspension tower and cables

My guess is they got cute with the design and it backfired on them


I mean, hell, if you live in a big city, you've probably see skyways between two large buildings

 

[iamblades]

It's been 25 years since I took any engineering courses, but I'm pretty sure a smallish pedestrian bridge really shouldn't even need a suspension tower and cables

My guess is they got cute with the design and it backfired on them


I mean, hell, if you live in a big city, you've probably see skyways between two large buildings

This is certainly true, no matter what the final cause of the collapse ends up being. No one needed a giant 15 million cable stayed foot bridge.

The level of overkill is probably not directly related to the engineering failure, but it does make it more embarrassing.

 

[yet_another_alt]

If we're talking about overkill, there's also a perfectly good crosswalk right there.

 

[Droxcy]

 

[Dubloon7]

exactly. i studied structural engineering in college, and this is very basic engineering. From my previous comment I immediately thought the failure was based on the lack of support, above and below. Obviously the PM, the PE, the Engineer who stamped the drawings, and the KTR are going to lose their licenses and hopefully they are all put in prison for lack of professional judgement.

 

[OH-MyCar]

If we're talking about overkill, there's also a perfectly good crosswalk right there.

Of all the things they’ve catastrophically screwed up on, they indeed needed the bridge at that spot. There have been 5 or 6 pedestrian casualties in even the past couple of years because Miami drivers tend to look at pedestrians like they’re playing Carmageddon. Add college kids into the mix and...

 

[yet_another_alt]

That bridge did equal that number in one go. I guess I'm lucky I live in an area where pedestrian accidents aren't common.

 

[camelCase]

That's awful, I wonder how this even happened. The thing looks pretty heavy to begin with but like you said I'm no engineer.

 

[iamblades]

That's awful, I wonder how this even happened. The thing looks pretty heavy to begin with but like you said I'm no engineer.

Of course it's heavy, but that construction method has been used for decades in much larger and heavier spans:

https://en.wikipedia.org/wiki/Shibanpo_Yangtze_River_Bridge
https://en.wikipedia.org/wiki/Stolma_Bridge

Granted those were box girder designs, not I-beams, but the overall construction method is the same. Main advantage of the box girder over the single I beam is that it is stronger in torsion, but this bridge shouldn't have been subjected to any real torsional force. Now that we have heard they were retensioning the tendons during the collapse makes me thing that something went horribly wrong during that process and they caused either an asymmetrical tension that put the bridge in a torsion scenario that it wasn't designed for or something broke during the tension and the rebound forces from that caused a chain reaction of further failures.

Which brings up a bunch of questions about why the tendons were loosening up in the first place, I don't believe this is exceedingly rare, but I am not a structural engineer.

 

[Narroo]

Someone clearly fucked up, but seeing how beefy that truss span is, it looks like it should have been fine on it's own(if it was properly engineered and/or built), which brings up the question of why the fuck are you building a ridiculously over-engineered cable stay pedestrian bridge anyway when a truss bridge should suffice just fine, but government waste is the least surprising thing about this.

ETA:

Just found the design proposal for the bridge, and the truss was supposed to exceed the load requirements on it's own, the cable stayed part of it was intended to control harmonic oscillations.

I'm guessing this will end up being a tension failure of the lower deck due to either faulty materials, improper installation or gross miscalculation in the initial engineering, or some combination thereof.

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

It's a University, and Universities public or private tend to over build things a lot for vanity. On the bright side, I doubt that tax payers funded this much, if at all.

 

[-Minsc-]

The same fellow has posted another video compiling discussion from the comments of the previous video. Some puzzle pieces discussed are changes in configuration of the temporary supports for moving the bridge in to place and how it could lead to tension failure.

 

[OH-MyCar]

It's a University, and Universities public or private tend to over build things a lot for vanity. On the bright side, I doubt that tax payers funded this much, if at all.

From the internal student email we got at FIU:

Did FIU design and build the bridge?
As part of a 2013 US Department of Transportation TIGER grant, FIU awarded a Design-Build contract for the bridge through a competitive, public process, but FIU did not design or build the bridge. The bridge was designed by FIGG Bridge Engineers and built by MCM Construction. Barnhart Crane and Rigging operated the equipment that placed the bridge on its supports.

 

[Cybrwzrd]

The same fellow has posted another video compiling discussion from the comments of the previous video. Some puzzle pieces discussed are changes in configuration of the temporary supports for moving the bridge in to place and how it could lead to tension failure.

I love AvE. (It sounds like the tensioning rod just wasn't skookum, and then they over chooched it.)

 

[Narroo]

From the internal student email we got at FIU:

Did FIU design and build the bridge?
As part of a 2013 US Department of Transportation TIGER grant, FIU awarded a Design-Build contract for the bridge through a competitive, public process, but FIU did not design or build the bridge. The bridge was designed by FIGG Bridge Engineers and built by MCM Construction. Barnhart Crane and Rigging operated the equipment that placed the bridge on its supports.

Welp, that settles that.