Big Boo-Boo on 950 tons of bridge

Sure, but the weight of the bridge has not much to do with its load capacity. In fact, with a 950 ton bridge the extra load by the people is way way less than by the weight of the bridge itself.

Well, probably the 950 tons was the total for the entire bridge, not only the part that failed now (it was far from completion).

However, for the next try they should definately try some more modern construction at 10% of the weight.

schreef in bericht news: snipped-for-privacy@googlegroups.com...

Original installation completed, they thought they were so clever:

Now this- ugly:

Structural failures are all runaway, much worse than electronics.

No lack of maintenance this time. But what?

Bad engineering?

Too many engineers replaced by managers, bookkeepers or other bureaucrats?

No doubt they'll find someone to blame but will we ever hear the thruth?

petrus bitbyter

Mafia concrete. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

      Understanding is a fountain of life to one who has it, 
      But the instruction of fools is folly.  Proverbs 16:22

They forgot to click "alternate solver".

Their simulation programming language of choice used a stock unsigned data type that just let you add pascals to newtons with no sanity checking whatsoever. The bridge's load-bearing capacity of 43,000 kilonpasctewtons was grossly exceeded.

FIGG issued a statement Thursday saying the company was ?stunned? by the collapse and promising to cooperate with every authority investigating the collapse.

?In our 40-year history, nothing like this has ever happened before,? the company?s statement said.

Well, that is actually not true, but what do you expect from a company statement that is intended more to limit the damage than to uncover the nasty truth...

: e

ity.

There are live loads and dead loads on the structure. Live loads can be con siderable and end up requiring lots of structural mass to prevent a catastr ophic deflection.

Much of that weight might be attributable to South Florida being located in one of (if not the) highest wind speed ratings in the country (to survive CAT-5 hurricane force winds)?

But why is concrete being used at all? Such a footbridge with only limited load should be made of a construction material with a much better strength/weight ratio, e.g. steel, in a "box" (hollow) construction.

Well, it was emplaced days earlier, but the bridge wasn't completely installed (wasn't taking traffic). The likely scenarios for failure include premature removal of temporary bra\cing, like in the famous Husky Stadium collapse (caught on camera). The issue there, was that temporary bracing was removed before a concrete pour was stiffened enough to take over the diagonal-brace stress.

The complete design may have been stable, but collapse can happen at a stage when the construction is NOT complete, in a part-built configuration with unplanned structural character.

Maybe, maybe not. There's a buildiing not far from here, where a foundation includes a 500-truckloads concrete pour. It was necessary to stabilize the nearby hillside with an interstate highway running over it. The building did NOT need that much structural strength, and in fact the steel in that part was very sparse.

ng a week-old bridge fall down is impressive.

alled (wasn't taking

temporary bra\cing,

there, was

nough to

age

Melbourne had one of them too, while I was still there. A couple of the guy s who had been working were I was had moved to jobs in the bridge construct ion, and they showed up at work looking very shaken a day or two later, ver y glad not to have been amongst the 35 killed by the collapse.

That was a box-girder bridge, designed by Freeman, Fox and Partners, who ha d already had similar bridge fail in a similar way during construction in the UK. Some engineers can get dangerously complacent.

The bridge did get completed, and is still working fine.

--
Bill Sloman, Sydney

That worked out well over the Tacoma Narrows. Concrete is often used

*because* it's heavy. Pre-stressed steel/concrete is pretty strong. This one was a money-maker for the university, gone way wrong. The money is going to be going the wrong way.

• Looks a lot like an overhead gantry.

Mainly they are guessing a lot of the time. If they knew,it would not be "practice".

Normally cable stays are installed first. This bridge was heavier than its load, so how could it ever be expected to stand before the stays were installed?

There are some truss-like members on top of the deck that were supposed to hold the deck during the installation of the pylon and cables, but the post-tensioning on one of them failed when it was being tightened as part of the reconfiguration after moving the deck in place. (during the move it was held some distance from the ends, and now it was resting on the ends, so the tension changed and the rod in one of the members was being stressed using a hydraulic cylinder. the rod failed and the bridge collapsed at that point)

Why were 950 tons of concrete needed to hold up a few students?

I think this massive bridge and its intended overhead stay structure were a "statement", not rational functional design. Like the new half of the SF Bay Bridge, unnecessary and insanely expensive structure for cosmetic reasons.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

It sounds like if it had been designed to stand without cables, like bridges that size usually are, then it wouldn't have failed.