Miami pedestrian bridge collapse

[Peter 315]

8 lane highway + college students + cell phones = problems.[/QUOTE

 

[CincyFlyer]

So this guy is under the bridge when it makes a snapping noise 5 hours before it fell. Then, there was a meeting of the minds 2-3 hours before it fell. Was there ANYONE worried about the cracks?
Miami FIU bridge collapse: Man hears crack before collapse | Miami Herald

All. Concrete. Cracks. All.

 

[ruffdog]

Now they are saying the DOT ordered the north support to be placed 11 feet further north (oct 2016). That not only delayed the project, but the span had to be redesigned on the end that failed.

Florida bridge collapse: Design change put project behind schedule, millions over budget - CBS News

 

[ruffdog]

All. Concrete. Cracks. All.

The cracks must have been bad enough to be the subject of a voicemail and a special meeting.

 

[CincyFlyer]

The cracks must have been bad enough to be the subject of a voicemail and a special meeting.

Perhaps, but it's likely that they were not critical, if one judges by the tone of the email. It's possible that handling the bridge section in a manner other than designed (not at the far ends) caused an issue. We'll see; this is sort of like guessing the cause of a plane crash; a zillion theories, and the answer usually involves more than one of them—a chain of events.

 

[California]

Eng-Tips has a whole lot of discussion, speculation, hypotheses by engineering professionals, that is more insightful than what we have in this thread.

Also much better photos.


Eng-Tips . com - Forums by Industry > Forensic Engineering > Engineering Failures & Disasters Forum

Miami Pedestrian Bridge, Part II - Engineering Failures & Disasters - Eng-Tips


One example: speculation that a 9 inch drain in the deck was the initial point of failure.

 

[Shield Arc]

I've worked on several bridges. In Washington, and California. I never was involved in the pre / post tensioning. Iron workers do that. I've drove thousands of concrete piles. They are pre-tensioned with strands. Good rule of thumb is never hit the concrete pile over 100-blows per foot with the pile driving hammer.
This is a picture of my oldest granddaughter at the Port of Oakland. She is 24-years old now.

 

[Streetcar]

The bridge was probably a signature gateway for the college and state was planning to widen the road, which would make the road harder to cross and delay vehicles for longer walk light

 

[California]

The bridge was probably a signature gateway for the college and state was planning to widen the road

I read the crossing went to a low-density neighborhood that was being bought up by developers to build a planned high rise, high density 'university village' community with more expensive (more profitable) apartments and student housing. I suspect lobbying by the developers got the bridge into the state transportation budget.

While this design is proving to be ridiculous, some sort of bridge is needed there for the increased pedestrian traffic that the new development will cause. It's a principal boulevard and a state highway.

You can expect half the students will cross the street, or bridge, with their noses in their phones oblivious to their surroundings. So there is a real traffic safety need for an overhead crossing. Hopefully a simple and proven design.

 

[Redlands Okie]

I read the crossing went to a low-density neighborhood that was being bought up by developers to build a planned high rise, high density 'university village' community with more expensive (more profitable) apartments and student housing. I suspect lobbying by the developers got the bridge into the state transportation budget.

While this design is proving to be ridiculous, some sort of bridge is needed there for the increased pedestrian traffic that the new development will cause. It's a principal boulevard and a state highway.

You can expect half the students will cross the street, or bridge, with their noses in their phones oblivious to their surroundings. So there is a real traffic safety need for an overhead crossing. Hopefully a simple and proven design.

A tunnel would have worked just fine, seen them in several places. Usually cheaper and not a traffic issue to install.

I suspect a police officers salary could be covered by citations to those who cannot follow directions. I am in a college town quite a bit and its beyond ridiculous on the lack of enforcement of pedestrians and bicycle operators following the rules.

 

[MossRoad]

A tunnel would have worked just fine, seen them in several places. Usually cheaper and not a traffic issue to install.

I suspect a police officers salary could be covered by citations to those who cannot follow directions. I am in a college town quite a bit and its beyond ridiculous on the lack of enforcement.

A tunnel in Miami? It's only a couple feet above sea level.

 

[Redlands Okie]

A tunnel in Miami? It's only a couple feet above sea level.

Hmm. Probably correct on that location. Good point.

Miami-Dade Water Table Map * Submerging the Sunshine: Explore Sea Level Rise in South Florida

 

[prichard]

A tunnel in Miami is probably not a great idea. Most of the city is close to sea level, they get hurricane flooding and they have a very high water table. Most of Florida you can quickly dig down to ground water with a shovel.

 

[dragoneggs]

Pedestrian tunnels, shopping malls are prevalent in Singapore. Due to the limited space and population density, they make excellent use of commercial space vertically, above and below sea level. Because of the high chance of flooding during seasonal storms, many of the pedestrian entrances to underground walkways, subways, shopping, etc. are actually elevated by three feet or so. Meaning you have to go up steps before descending down escalators, etc.

 

[California]

I think a tunnel wasn't considered for Miami because of risk of students getting mugged in it.

 

[Shield Arc]

I worked in the Pioneer Square Station of the Metro Tunnel under 3rd avenue in Seattle. We put over a million tons of falsework iron in that station.

 

[crazyal]

I actually think the concept was a great idea. We build houses off site to save time and costs. Around here the state just put in several "prefabbed" bridges. The cement beams were cast off site and a crane placed them. The roadway decking sections were somewhere around 8 to 10 feet wide and just bolted down to the beams. The end result was the removal of the old bridge and installation of the new one in under a year plus, other than pouring the abutments, all of the work could be done during the winter months. Around here usually in mid December things come to a halt and don't start back up until April.

If you go back to my earlier post what I said was that what usually happens is a change. That change doesn't get the full testing. In this case the DOT change in Oct 2016. That would of meant about 14 months to review the change, test the new design, and build it. That seams like a pretty short period of time. I wonder if the contractor started building the bridge before the DOT changed the design. If so it would of left two options, modify the existing bridge or start over adding extra costs which most likely they didn't have the funds for.

 

[medic0648]

As far as college kids paying attention, I have been working on a college campus for the last year, and have watched the kids walk into the side of trucks pulling into the job site, and even fences surrounding the site. Not all of them were on their phones.