Big Boo-Boo on 950 tons of bridge

Bolts made in China, or south FL Mafia company ?:-} ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Jim Thompson
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Sounds plausible, but it seems to be in a weird place if that's the explanation. Normally it would be at the end of the structure.

Seems stupid to have a single point of failure like that, in a structure as simple as a footbridge. Didn't they learn anything from the Mianus River bridge?

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Phil Hobbs

They get real weather in Florida. The dynamic loading from a Cat 5 (*) is pretty intense, so something dead like concrete is quite comforting.

Cheers

Phil Hobbs

(The only Cat 5 in Arizona carries Ethernet.) ;)

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Dr Philip C D Hobbs 
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Phil Hobbs

some construction is pre-tension, some is post-tension

someone must have screwed up, they should have made the beam so the top is flat under normal load

Reply to
Lasse Langwadt Christensen

I read some speculation they had put extra tension in places to compensate for having to put the movers closer to the center of the bridge because of obstructions at the side of the road

Reply to
Lasse Langwadt Christensen

Indeed ;-) (But now mostly CAT 6)

Amend my span comment: I pulled up the AZDOT camera in the vicinity... there's a support pylon in the median between the east- and west-bound lanes. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Jim Thompson

Further amendment... our newer bridges and freeway structures are _earthquake_ survivable. AND we do have some pretty nasty winds here in AZ... look up "haboob"...

...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Jim Thompson

It is pretty close to the end of the structure, and it's tied directly at the point of failure where the bridge snapped.

The blue cylindrical thing at the end of the tensioning bolt is the tensioning device, with what appears to be its (hydraulic?) hose still hanging.

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The engineering documents indicate the span was *supposed* to be self-supporting, independent of the suspension cables.

Not clear if it's the root problem, but it looks like the span was intended to be supported from the ends, but last-minute adjustments were made to transport the span from alternate support points. That could really screw things up.

In place, it started cracking, with at least one call being made two days before the failure.

In this video of the collapse they're re-setting the tensions. The tension bolt fails, then the terminal segment of each deck immediately snaps off and the bridge falls.

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James Arthur

Reply to
dagmargoodboat

Yikes. That bolt looks pretty skinny for the job--only an inch or so diameter.

Cheers

Phil Hobbs

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Phil Hobbs

te:

concrete with giant bolts.

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That's not a bolt, it's a cable. And it doesn't run in a straight line. Tut orial here:

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nsioned-slabs_o Apparently tolerances are very tight and the tensioning is instrumented. I' m guessing they erred in properly curing the concrete which would explain h ow the tensioning process cracked the concrete. There are many hundreds of concrete mixes used for the many hundreds of applications. These people wer e obviously using a fast cure rate mix, and they were on the margins of its performance where there probably wasn't a whole lot of industry experience if any.

e
Reply to
bloggs.fredbloggs.fred

Concrete can come in at 150 lbs/cu ft, that's about on the same order as solid granite, especially with all the embedded steel. It doesn't take much geometry to add up to a huge weight. You do the math.

Reply to
bloggs.fredbloggs.fred

For some reason, those who don't have to pay with their own money seem to delight in unnecessarily complex designs.

This monstrosity of a footbridge was recently built near where I live. It replaced a much less visually intrusive concrete arch bridge which was removed to allow an underpass to be built.

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Note the needless cantilevered curve design which increases the distance that the pedestrians have to walk. Also, plenty of metal that will have to be painted in future years.

View of the entrance

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Few people use this bridge, since apart from a few pedestrians living in houses on the far side using it to reach a shopping mall, there's no reason for anyone to cross the road there. There are no bus stops at that point on the far side - all the buses going along there loop around to stop outside the shopping mall. Cyclists can use the bridge, but I haven't seen any doing so.

Note the sides of the bridge, which are apparently there to deter giant pigeons, and it seems to work.

Sylvia.

Reply to
Sylvia Else

I thought the sides were to keep miscreants from tossing crap down on the cars below? Or were referring to another feature?

Reply to
krw

You're probably right. If there's an uglier way of achieving that result, I don't know what it might be.

Sylvia.

Reply to
Sylvia Else

This one is nice, at the top of Hospital Curve. It starts with a sweet little park, spirals up, crosses over US101, and ends at a community garden and a park on the other side.

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After we move our shop, I plan to park on the Pot Hill side and hike over every day. Clicking a mouse isn't very aerobic.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin

he real complexity of what is going on, or at least not in projects that in volve real development, as opposed to generating more of the same with a di fferent paint-job.

there is no effective program management.

I didn't say that the program management was ineffective, but the Gantt cha rts weren't a big contribution to the effectiveness of the management.

I once got a black mark for refusing to generate one more set of Gantt char ts representing what we could do with extra engineers that we weren't going to get, preferring to spend my time sorting out the documents specifying t he hardware those engineers were going to have to design in detail.

One of the problems with computer generated numbers is that people take the m much too seriously, and don't think about where they came from, or what t hey actually mean.

nd many more sub contractors. Say on the order of the Saturn V program?

The Saturn V program was large - $6.417 billion in 1964?1973 dollar s worth of work. There aren't many projects around of that size.

The electron-beam microfabricators that I worked on sold for a bit more tha n a million mid-1980s US dollars, and the one for which I knew the numbers would have cost 3.8 million UK mid-1980 UK pounds to complete when it was c ancelled (and it cost the the company 3.8 million UK pounds to buy itself o ut of the obligation to complete it).

If what Thompson-CSF had sold us a pre-production prototype had been that c lose to production - as opposed to the proof-of-principle machine it really was - the story would have been different, and the PERT charts a lot more stable and useful.

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Bill Sloman, Sydney
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bill.sloman

e

the real complexity of what is going on, or at least not in projects that i nvolve real development, as opposed to generating more of the same with a d ifferent paint-job.

n there is no effective program management. Have you ever worked on a prog ram involving multiple prime contractors and many more sub contractors. Sa y on the order of the Saturn V program ?

Krw can't learn that it's communists who believe in central planning, and t he the socialist movement kicked out the proto-communists - and Karl Marx - in 1872 because they though that the approach was undemocratic and likely to lead to tyranny.

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ionary-vested-him-in

Actual socialist governments in Scandinavia and Germany and happy to leave the regulated free market to distribute resources where they will do the mo st good, with the same sort of anti-monopoly regulations that the US has ha d in place for the last hundred years or so.

And since krw is just as stupid as Dan, he hasn't realised that my objectio n was to taking tools like Gantt charts and PERT diagrams all that seriousl y, when what they are is representations of guess-work. It's perfectly poss ible to manage a complex project effectively, and Gantt charts and PERT dia grams can help, but only if they are continuously up-dated to represent cur rent knowledge.

The whole business of a development project is to develop a clearer idea of what one is going to build, until one can actually build it and see if it works.

The project plan has to be updated to reflect these progressively clearer ( and ideally, more accurate) ideas. Wasting energy on polishing the project plan, as opposed to getting on with the project, is one of the more frequen t management failings.

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Bill Sloman, Sydney
Reply to
bill.sloman

Since it cross a motorway, it's more likely designed to stop the local yobs from dropping things on cars going under the bridge.

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I can remember similar stories from the UK when we lived there (and we left in 1993). Some kinds of bad behaviour do seem to come up repeatedly.

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Bill Sloman, Sydney
Reply to
bill.sloman

Another public-private partnership success story.

Reply to
bitrex

Hand taxpayer money to nincompoops in government and Americans lose their minds.

Hand taxpayer money to nincompoops in industry and Americans aren't particularly concerned.

Hand taxpayer money to the nincompoops in government to then hand to the nincompoops in industry by proxy to build bridges that collapse and trains that crash on their maiden runs and you get the Trump Infrastructure Plan.

Reply to
bitrex

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