FIU Bridge - What's missing from this picture

[jberryhill]

They put up the central span, and opened the street to traffic:



The completed bridge is supposed to look like this:



Genius.

[hlthe2b]

1. Oh my!

how could they have let this happen?!

[TheBlackAdder]

46. Perhaps someone's palms got greased somewhere along the way.

[Amishman]

2. Suspension features like that are sometimes cosmetic on small bridges

I wouldn't assume that the lack of the suspension component is a factor.

Far more likely is post tensioning of the concrete failing due to bad steel or incorrect technique. Improperly cured concrete is also a high possibility.

The unusual method of assembly is also a possibility. It was assembled on the ground and raised into place as one huge unit. This was done to minimize traffic disruption. Perhaps it was damaged in the lift.

[jberryhill]

4. That's a lot of money for cosmetics

Maybe someone signed off on the plan with the understanding that the bridge would support its own static load, but that's one heck of a cosmetic installation.

[Clarity2]

6. Yes

I believe there is functional support in that final design. Especially if its anchored into a support column below bridge.

[Amishman]

9. Not really, this was a very high profile project

The bridge project is connected to a downtown revitalization initiative as well as the construction of several massive new apartment complexes. This was a lot bigger of a deal than a normal foot bridge.

This bridge echos the Tampa Skyway bridge which was built by the same firm. The Tampa bridge is an cable stayed bridge

[jberryhill]

11. No, it was designed as a "cable stayed bridge"

The cables are structural:

http://www.miamiherald.com/news/local/community/miami-dade/west-miami-dade/article204506084.html

The architecturally distinctive, cable-supported bridge is the product of a collaboration between MCM Construction and FIGG Bridge Design, the firm responsible for the iconic Sunshine Skyway Bridge over Tampa Bay.

https://www.chronicle.com/article/Engineer-Connects-His-Research/142787

So we're going to build a pedestrian bridge with a unique design of the cable type that, especially with lighting at night, is going to become a postcard for this area. And we plan to do it following principles of sustainability and urban place-making.

[Amishman]

13. Huh, I stand corrected.

Thanks for the info

[jberryhill]

15. I'm trying to imagine the sequence of events

Either there was an assumption that vertical supports would be maintained below the bridge until the cables were attached, or someone was reading the instructions on the IKEA box wrong.

It reminds me of the hotel walkway in Kansas City where some genius decided it would be easier to use separate, offset support rods bolted to the walkway structure, instead of the design that specified single support rods through the walkway.

Or some person with a degree and a license believed it would stay up for a while that way.

[Dennis Donovan]

41. The Hyatt Regency walkway collapse

https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse



The Hyatt Regency walkway collapse took place at the Hyatt Regency Kansas City hotel in Kansas City, Missouri, on July 17, 1981. Two walkways, one directly above the other, collapsed onto a tea dance being held in the hotel's lobby. The falling walkways killed 114 and injured 216. It was the deadliest structural collapse in U.S. history until the collapse of the World Trade Center towers 20 years later.

</snip>

[samnsara]

51. i remember that..some kind of harmonic resonance..?

[Locrian]

52. nope

https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse

[Dennis Donovan]

53. That was the Tacoma Narrows Bridge - Galloping Gertie

It was a combination of mechanical resonance and aeroelastic flutter; basically, the wind caused it to twist at a frequency that the bridge couldn't withstand.

The Hyatt Regency disaster was caused by a design flaw in the rods that "hung" the walkways from the ceiling. The original design called for single rods to be used to hang the both the 2nd and 4th floor walkways, reducing the load on the ceiling beams the rods were attached to. But during implementation, a change was made to use two separate rods, one for the 4th and another, slightly offset from the first and hanging only from the 4th floor walkway, for the 2nd floor walkway . This doubled the load on the ceiling rod attach points. Add to that a large gathering, with large groups of people on both walkways at once, and down came the walkways...

[NCTraveler]

19. When going to Boca Grande or some other location just south of me.

I add and hour plus to my trip because I can't go over the Skyway. My snowflake side comes out and I get too scared because of it's height. I live very close to it and have only gone over it ten or so times. I did something that was very unsafe to other drivers last time I went over it so I simply don't do it anymore. I have a big time irrational fear of heights.

[marble falls]

18. I agree. That suspension feature was highly engineered for just a cosmetic structure....

The first picture just plain looks unfinished.

[Wounded Bear]

8. Looks like they skimped on the arch, too...

That's a long span for such a flat surface.

And you're right, those "suspensors" look cosmetic to me. I would think normal construction would have the verticle installed and the suspendors prepped before the transit surface is set in. This was one of those quick-up prefab jobs from the commentary I'm hearing. Looks like someone threw away the instructions and winged it.

[jberryhill]

12. Innovative "rapid construction"....

https://www.chronicle.com/article/Engineer-Connects-His-Research/142787

[haele]

16. Weather down there has been miserable. Concrete curing could definately be an issue.

It's also wetlands area, moist sandy soil. No matter how deep the foundations, the supports still could have shifted during the extreme weather conditions (hot/cold/wet cycles) and weather delays over the past month before the span was raised.

People are used to seeing photos of the Golden Gate and the Brooklyn Bridges while they were under construction. The spans went across last - but then, those bridges were huge and there were quite a few different stresses involved.

I've watched a couple of similar style pedestrian overpasses go up in San Diego over the past ten years; while they didn't have the suspension components in place, they typically had all the uprights/towers completed before putting the span in place. Even so, the suspension components were attached within a week or so after the span was raised and set on the supports The only difference here that I can see at this point of the installation was that it seems the engineers didn't have the central tower completed before they put the span on.

Haele

[Brother Buzz]

20. They used a weird new 'self cleaning' concrete, a first for a bridge

Could be, not everyone was up to speed on all its properties.

[Awsi Dooger]

30. Weather has not been miserable

I have no idea where you get that. This is the dry season. We had a very warm February, but March has been nicely cooler. But no threat of heavy rains or storms or anything but typical South Florida conditions for this time of year.

[Clarity2]

3. Wow

I was looking at pics of the intact bridge, and thought it didnt look right. No metal support along the expanse of concrete (except supposed rebar). Well, there are the missing supports.

[malaise]

5. Because they didn't want to inconvenience folks

in an election year.

Just wait for the law suits. That fugging bridge was not secure.

[Initech]

23. No they didn't want to inconvenience themselves.

The engineering department at FIU had proposed a way to build bridges quickly and cheaply, and they sold it as a way to fix this country's ailing bridge problem. It sounded like a good idea in theory but when they actually tried one - problem is - they did it too quick and too cheap. It's essentially big business republican policies put into practice.

https://news.fiu.edu/2017/07/building-better-bridges-an-fiu-professor-is-leading-the-nations-efforts-to-make-infrastructure-safer/112618

[OneBlueDotBama]

7. Similar incident in Quebec

We were driving from the mountains into Montreal for the F1 race on a very quiet Sunday when we hit a traffic jam, very unusual for a Sunday... same deal. new bridge collapsed.

Boulevard du Souvenir overpass collapse

On June 18, 2000, the southern portion of the Boulevard du Souvenir overpass in Laval, which crosses Quebec Autoroute 15, collapsed into the roadway, killing one and injuring two when cars were crushed underneath the structure. Sixteen beams weighing about 70 tons each fell. The highway was closed for several days while workers removed the debris. The remains of the structure were later demolished as well for safety reasons according to then–Quebec Transport Minister Guy Chevrette. A new overpass was built less than three years later. Another collapsed overpass incident occurred on September 30, 2006, also in Laval, on Autoroute 19 where the collapse of the De la Concorde overpass killed five, although this was for totally different reasons.

The overpass was under construction at the time the incident occurred. The company in charge of the project was Beaver Ridge, a company that was under bankruptcy protection and was without a construction license for about four months. Dessau-Soprin was an engineering firm that was supervising the project operations

https://en.wikipedia.org/wiki/Boulevard_du_Souvenir_overpass_collapse

[SoCalMusicLover]

10. Taxpayers Will Be The Ones To Pay

Don't worry, those responsible have already been paid. Taxpayers will be on the hook for the many lawsuits which will be filed any moment now.

[superpatriotman]

14. Article about the 'Instant Bridge' from last week

http://www.miamiherald.com/news/local/community/miami-dade/west-miami-dade/article204506084.html

'The innovative installation method significantly reduced risks to workers, pedestrians and motorists and minimized traffic disruptions, FIU said. The architecturally distinctive, cable-supported bridge is the product of a collaboration between MCM Construction and FIGG Bridge Design, the firm responsible for the iconic Sunshine Skyway Bridge over Tampa Bay.

[LisaL]

43. Sure doesn't look like this innovative installation method reduced the risk for people

who were smashed by this bridge when it collapsed.

[MineralMan]

17. Someone screwed up big-time on that project.

Clearly, the cable supports were needed just to hold the deck up. Someone misread something. Someone didn't follow the plans. Someone's going to pay a helluva lotta money for this mistake. Sadly, it looks like people died.

[Eliot Rosewater]

26. City of Miami? Republican run? County? Who is responsible? Lawsuits galore

[mia]

47. Live in Miami.

The bridge borders Sweetwater and Unicorporated Miami-Dade County.

http://www.miamidade.gov/planning/library/maps/municipalities.pdf

Sweetwater is #25 on the map and The City of Miami is to the East toward the coast. The Mayor of Miami-Dade is Republican and supports Trump on many issues. The mayor of Miami is a Democrat.

[malaise]

34. The stress test in rush hour

without closing that section of the street led to this disaster.
Scott can kiss that victory goodbye right now.
This was clearly an all ReTHUG project with some nice Fed money from Elaine Chao.

[malaise]

21. I'm watching Local 10 Florida

Calvin just said there are reports that they were doing a stress test when the bridge collapsed.

If that is true, you'd think they'd close that section of the road.

[Awsi Dooger]

31. Yes, I heard that on the radio here in Miami

A stress test with 8 to 10 employees standing on top of the bridge when it collapsed.

An FIU employee now being interviewed on Channel 10 heard the collapse, was at the scene quickly, took pictures, and claims there were at least 18 cars trapped below the collapsed bridge. That is much higher than the estimates that have been provided publicly.

[Initech]

22. The fact that it was built quickly, cheaply, and with no inspections?

[malaise]

25. More confirmation of a stress test

being conducted when it collapsed. Why didn't they close that section of the street?
Local 10 is talking about this quite a bit.

[Lucinda]

24. And this jerk spews his hate trolling a teen on twitter:

Link to tweet

[OneBlueDotBama]

27. Trump will soon claim

He would have rushed in and held up the bridge till help arrived....

[rzemanfl]

33. Held. n/t

[OneBlueDotBama]

35. ty, n/t

[rzemanfl]

36. De nada. n/t

[Iggo]

42. The answer to Mr Cramer is: "Bridges aren't designed to kill people." (n/t)

[Lucinda]

48. +1 - And I still am angry that he trolled a HS student who has lost friends due to violence

I know WHY they are doing it. Hogg, and the other students, are smart, motivated, and well prepared. It must scare them all silly.

[kentuck]

28. Holy Shit!

Someone will be held accountable.

[msongs]

29. shoulda gone to peru and hired some rope bridge builders. those things can be awesome strong nt

[Awsi Dooger]

32. Cables were apparently being tested when it collapsed

Essentially a stress test and the bridge failed the test.

Hard to believe they didn't close 8th St. and do that type of test in the middle of the night. It is not feasible to close 8th St. during the daytime.

[Awsi Dooger]

37. Witnesses saying cars were stopped for a red light during collapse

Cars directly under the bridge.

That's bad timing. Otherwise at that time of day there could have been a lull. Of course, some cars would have undoubtedly been full speed toward the bridge as it happened. Likely a pile up.

Now the local news is saying Rick Scott is headed to FIU. No kidding. He is going to try to win points toward the senate election. Unfortunately as sitting governor he gets tons more coverage than Bill Nelson whenever one of these tragedies occurs.

[muriel_volestrangler]

40. Without the span on the other side of the central support, those cables couldn't take much weight

You'd be putting a massive bending moment on the tower, pulling it from just one side, if they had any tension in them. So the span will have been designed to support its own weight over that span. Since the beams from floor to roof look fairly large, that's quite believable. The cables give it extra strength for loads on it, especially concentrated ones in the middle of the span. I'd suspect it was a failure at a joint.

If they really did send workers out onto it to 'test' it, it does seem stupid to have done it when the road was open.

[Awsi Dooger]

44. Cameras will be blocked when the bridge is lifted

They don't want the grim images shown and plastered all over social media.

Nearby parking garages are being cleared to prevent cameras used from those areas. But obviously there is nothing to prevent videos from the nearby apartment complexes or other tall buildings.

Heavy machinery has been brought in and the bridge remains will be lifted soon.

[malaise]

45. But it will be dark thankfully

so I don't expect too many of those grim images

[FarCenter]

49. Engineer Connects His Research With Campus Bridge Project

Atorod Azizinamini, 57, is director of the Accelerated Bridge Construction University Transportation Center, at Florida International University, and a professor and chair of civil and environmental engineering there. A university-led partnership recently won an $11.4-million grant from the U.S. Department of Transportation to make it easier to get from the university to neighboring Sweetwater and other parts of Greater Miami. Mr. Azizinamini is lending his expertise on principles of accelerated bridge building for part of that project, an innovative pedestrian cable bridge that will connect the campus and Sweetwater. Here he explains the project and his role.

https://www.chronicle.com/article/Engineer-Connects-His-Research/142787

[whopis01]

50. Whats odd is they say the cables were being tightened when it collapsed

This article claims that the cables had loosened and were being tightened when it collapsed. But I certainly don’t see anything that looks like cables or even the central tower they would have been attached to in any of the pictures.


https://www.cnn.com/2018/03/16/us/bridge-collapse-florida/index.html

[KY_EnviroGuy]

56. Here are my guesses.

(engineer but not structural, here) Any or all guesses may be wrong....but for the sake of discussion:

Picture this assembly as the same design as a typical steel truss such as those used for commercial (Butler-style) building roofs, except this truss is made of concrete. It helps to sketch it out on paper.

Next, string a cable up through one of the outer angled truss members, with that cable going up to the "roof". Now, continue that cable horizontally along the roof, then take it down through the outer angled truss member near the center. I would guess the cables were routed through steel pipes embedded in the concrete members.

You therefore have formed a geometric isosceles trapezoid, which is quite a strong structural member for bridges.
See: https://en.wikipedia.org/wiki/Isosceles_trapezoid

They may also have cables inside some or all of the other truss members, to fine-tune the strength of the truss. When I sketch this assembly from the photos, I can see several ways that cables could be arranged to strengthen the truss.

Next, picture the truss sitting flat on the ground and we pre-tension the cable(s). Now, you can see that if we lifted the assembly at both ends, the flat lower deck will bow with its own weight, and you can see that some of your cables would go slack, while others may get tighter.

Therefore, after the assembly was placed on its support columns, the cables had to be re-tensioned to remove any slack and provide additional strength to the entire truss. Cable tension instruments are available for this purpose (used for TV tower guy wires).

My second guess in this situation is that the stress test was a routine application of a test weight on the span (at or near center) in order to observe the amount of additional bowing of the span. If the bowing was excessive, they would apply additional tension to the cables. Normally, such a stress test would not involve weights that would endanger the span.

[lapfog_1]

54. I have a question for engineers

I saw a virtual 3D animated fly-through of this bridge yesterday.

The roof structure over the bridge appears to be made of concrete... and rather thick concrete supported by thick angled beams of concrete ( probably over steel beams ).

Why add so much weight to the structure for something that blocks the sun and maybe rain ( but not if the wind is blowing )?

A simple steel "cage" bridge with perhaps a thin walkway of glass or tile or even wood ( treated against weather ) with a canvas covering (replaceable) for a roof would have weighed a fraction of what was built, probably not requiring any suspension support. Would have cost less as well.

Or forget the roof covering altogether ( most pedestrian walkways over freeways here are like that ).

Just wondering why so much concrete was required.

[zipplewrath]

55. Cheap

concrete is VERY cheap. Pre-cast concrete is even cheaper. It also is extremely durable against weather and sunlight. And finally, Florida is a hurricane zone. A roof like this is designed for something like 240 mph winds. We have covered walkways around here at work. They are all pre-cast concrete structures on steel poles. They're 50+ years old and they've survived innumerable hurricanes and have been in the Florida sun for as long as well. A coat of paint once and a while and you're good to go.

[muriel_volestrangler]

58. An engineer said that was notable; he suggested it was for aesthetic reasons

The bridge’s superstructure was something Verrastro said he’s not seen in 42 years of designing bridges. Rather than using steel trusses, it employed heavier concrete trusses. The bridge also had a concrete roof, adding even more weight.

“This was a very long span and then they used very heavy material,” he said. “The majority of pedestrian bridges are steel.” Steel bridges are about one-tenth the weight of concrete, he said.

Verrastro, an expert in accelerated construction who has spoken at FIU’s bridge engineering program, suspects that using concrete was part of the bridge’s aesthetic, rather than structural, design. The FIGG Bridge Group that designed the bridge is known for its signature bridges, he said.

“They typically get involved in ones that look fancy, but they’re competent,” he said.

http://www.miamiherald.com/news/local/community/miami-dade/article205422719.html

[lapfog_1]

59. the whole thing reminds me of the KC Hyatt disaster

The company I worked for back then did the post analysis engineering simulation of the "Sky Bridges" and found that, as built, they should have failed under their own weight.

Also, one of the people I worked with at that company died in the "accident" (along with his wife).

If they had been built "as designed" they would have held up even overloaded with people dancing on them.

This bridge in Florida just seemed to be wrong for a lot of reasons.

Concrete roof? Who even needs a roof for a pedestrian walkway over a busy 8 lane highway? Mesh steel span with some sort of glass or wooden floor and some sort of solid railings (to keep people from throwing stuff onto the cars passing underneath) should have been much cheaper and more sturdy. And if you needed a cover, canvas with "flaps" (so it doesn't turn into a big sail) that can be removed when a hurricane threatens would have been my choice. Or even a series of large umbrellas across the span with tables and seating - if they really wanted that - would have been preferable.

I simply did not get why they would put a concrete "sunshade" over the walkway. That alone had to weigh tons.

[Nac Mac Feegle]

60. Are we Monday Morning Quarterbacking?

There are only a few people that have the combination of Engineering knowledge and full knowledge of the intricacies of this particular structure.

Remember that we can only make guesses of various levels of education.

A Failure of this magnitude will be dissected to the molecular level by people that Really Know What They Are Doing.

We are probably self appointed "experts" making erroneous diagnoses from incomplete information.

Being too quick to blame someone or something does no one any justice, least of all yourself.

Get the facts first, then assign blame.

Otherwise, we're acting like conservatives and showing our ignorance. /sarcasm/

[Blue_Adept]

61. HEY! I'm on the internet and my opinion is as valid as any expert opinion!

[jberryhill]

62. Is this an internet discussion forum?

If you answered yes to that question then, yes, you have managed to hit the nail directly on the head.

If you are the Internet Forum Police and are going to cite me for speculation, then I'm going to have ask to see a warrant first.

[jberryhill]

63. You might enjoy this one