Miami Pedestrian Bridge, Part XIV 78

[JAE]

A continuation of our discussion of this failure. Best to read the other threads first to avoid rehashing things already discussed.

Part I
thread815-436595

Part II
thread815-436699

Part III
thread815-436802

Part IV
thread815-436924

Part V
thread815-437029

Part VI
thread815-438451

Part VII
thread815-438966

Part VIII
thread815-440072

Part IX
thread815-451175

Part X
thread815-454618

Part XI
thread815-454998

Part XII
thread815-455746

Part XIII
thread815-457935

 

[jrs_87]

Time to pivot discussion to replacement?

http://panthernow.com/2019/10/31/de...fiu-bridge-are-insensitive-and-irrisponsible/

 

[SFCharlie]

FIU Hosts 2019 International Accelerated Bridge Construction Conference
They will not be discussing last year's deadly bridge collapse the NTSB ...

SF Charlie
Eng-Tips.com Forum Policies

 

[Alistair_Heaton]

I suspect they have to rebuild something otherwise they have to do something else with the money that they received back.

Plus also I suspect that the student accommodation that was going in on the other side of the road in anticipation of the bridge is now all complete and full.

So they have a huge issue with them crossing the road anyway possibly killing more kids than the bridge collapse did inside 5 years if there isn't a bridge.

 

[waross]

There is another construction issue that I don't understand.
The use of the back span to "capture the node".
I think that this was just some after the fact bafflegab to cover their assets.
If it had been a design intent that the back span would provide needed support to the main span, then why was the back span not completed and in place before the main span was placed.
If the back span was seriously intended to provide needed support to the main span, then in addition to the other shortcomings we can add an inappropriate construction schedule and another failure of oversight.
The point is probably moot as the span was badly damaged even before it was placed.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[3DDave]

If that was to be considered they would have cast it as part of the pier and butted the span against it and grouted it. So I'll put that in the burn bin along with the (paraphrased) 'we used multiple longitudinal post-tension cables to make the bridge a redundant structure.'

The pylon was going to use the two spans as part of its formwork so it could not be in place until the two spans were in place. Perhaps the audience for that comment was meant not to notice.

 

[human909]

Yep the same thing occurred to me. Everything I've seen suggests this was designed as two simply supported trusses with an architectural pylon and faux pipe stays. The presented calculations show that their previous calculations were all based on independent trusses.

 

[FortyYearsExperience]

'we used multiple longitudinal post-tension cables to make the bridge a redundant structure.'

This is close to an admission of liability for the failure. They provided multiple longitudinal post-tension cables, but they did not connect those cables to the 1.5 million pound load heading north in diagonal strut #11. The 1.5 million pound load moved northward because it was not restrained by any other force. (Newton, First Law of Motion, discovered 332 years ago; see, "Principia Mathematica Philosophiae Naturalis" pub. Cambridge University, 1686)

 

[Vance Wiley]

Aaaaghhhh! There's that old Newton stuff again. That guy has been dead 300 years and who remembers what he said?
Heck, it probably doesn't even work anymore, it has been so long. We have computers today and they take care of all that stuff so we don't have to worry about it.
Wiley's First Law of Computers: Garbage Out is directly proportional to Garbage In.

 

[LittleInch]

40YE,

"because it was not restrained by any other force"

It was restrained, but just not enough.

I do agree though with sentiment - all they really needed to do was connect those cables via strong enough end beam to resist the end force.

I just hope that the results of this investigation prove to be a key learning point in bridge / concrete truss design for decades to come.

However I don't think there will be too many designs similar for a long time due to this collapse. There was no redundancy and the design and execution was flawed.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[SFCharlie]

Garbage Out is directly proportional to Garbage In.

Definitely, but remember, computers can multiply (garbage)

SF Charlie
Eng-Tips.com Forum Policies

 

[FortyYearsExperience]

There was no redundancy . . .

I would respectfully submit that the oft repeated assertion of "no redundancy" misses the mark.

The subject bridge lacked any functional connection between strut #11 and the multiple longitudinal post-tension cables in the deck. If the absence of such connection were to be repeated in two trusses running parallel to each other, such a bridge would have "redundancy" but would certainly also collapse. The problem was not a lack of redundancy. It was a lack of a critical connecting element. No matter how many times you repeat that error, you are not going to fix the bridge. And yet, if that connection had been provided only once, the bridge would have stood for 100 years without possessing any "redundancy".

If the term "no redundancy" is defined to mean "lacks a critical element" -- well then we have an argument about the meaning of language, and not about civil engineering.

 

[MikeW7]

Aaaaghhhh! There's that old Newton stuff again. That guy has been dead 300 years and who remembers what he said?
Heck, it probably doesn't even work anymore, it has been so long.

Newton's Laws of Motion were actually replaced in 1915 by Einstein's relativity theories (1905 & 1915) but they're still "good enough" for everyday engineering.

Was doing some reading about Scientic Laws and came across these nuggets:

(Physical) Laws differ from scientific theories in that they do not posit a mechanism or explanation of phenomena: they are merely distillations of the results of repeated observation. As such, a law is limited in applicability to circumstances resembling those already observed, and may be found false when extrapolated.
:
Some laws are only approximations of other more general laws, and are good approximations with a restricted domain of applicability. For example, Newtonian dynamics ... is the low-speed limit of special relativity ... Similarly, the Newtonian gravitation law is a low-mass approximation of general relativity.

So the definition of a scientific law kinda sounds a lot like a traffic law: just because a 35MPH speed limit means "up to 40MPH is OK" in your city doesn't mean it will be the same in all cities.

 

[Wetlander]

Review of FIGG calculations on another bridge, and the consultant has "identified an issue" with design of the pylon legs. Link

 

[Tomfh]

Review of FIGG calculations on another bridge, and the consultant has "identified an issue" with design of the pylon legs

You'd pretty much have to wouldn't you?

 

[SFCharlie]

TxDOT fires FIGG from $800M Harbor Bridge design

SF Charlie
Eng-Tips.com Forum Policies

 

[hpaircraft]

From the Constructiondive article:

"...WJE’s detailed research, in-depth analysis, and physical testing shows that faulty construction of the Florida bridge — which FIGG had no hand in — was to blame for the collapse, not its design.”

That is such completely unmitigated horseshit, one wonders whether anybody would trust WJE if they said the sky was blue.

 

[Earth314159]

It is hard to see Figg surviving. Who would hire them? They have to keep 100 employees busy.

 

[Vance Wiley]

That piece was from FIGG - naturally that is their interpretation of the WJE test - but the test and how it was performed - what it addressed - missed the point that FDOT and AASHTO joint requirements are much different. In other words it is double talk or conflagration or - horse+++t - how much WJE is to blame is a question. Never cease being critically objective.
I recall the Sunday show that exposed all the bad things - and a lot of them really got me steamed up.
When they got to the point of criticizing JEEP because they could be turned over by an idiot driver I quit watching. They lost all credibility with me. Then I learned they rigged the Chevy PU gas tank explosion.
In court they say "one lie, all lies" or something to that effect.
Thanks, and Happy New Year to all.
What do we hear from the EOR these days? Looking for a job or hiring an agent to sell his book?

 

[JStephen]

From the Florida board a while back: "FBPE will monitor developments as the other agencies complete their investigations. If the cause is determined to be an engineering issue, FBPE will take any necessary steps, including disciplinary actions, to ensure public health and safety." So I expect that's an upcoming little obstacle to deal with at some point.

 

[LittleInch]

So can anyone with a knowledge of proceedings let us all know what happens next / is happening?

NTSB report was pretty damming of FIGG amongst others, but they hide behind their defence of "if the joint was made properly" which seems not able to stand p to serous scrutiny.

So any more hearings?

Court cases?

Anything new?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.