Poor design led to I-35W bridge collapse?

No, I am not. I have tried installing equipment on a floor that had its rebar erode away (and the ground subside as well), and had a 6 foot drop over 200 feet.

It passivates the surface. The rebar does still corrode to the point of failure. I have experience with this.

So maintenance is required.

So maintenace is required, since the coatings erode over time.

David A. Smith

If their worldview is constrained to government employment then they deserve to be restricted. I didn't propose they can't go out and work in non-government employment.

Here's a novel idea. Unproductive graft doesn't wax and wane regardless of economic conditions or war. Look at the current economic status of your parents' home state right now compared to just about everyone else. Not a single dip in the unproductive graft to be found.

There are applications in which the rebar has a very good surface coating of epoxy in order to reduce/delay/eliminate (as much as possible) loss of strength to corrosion.

Microfracturing of the concrete allows penetration by salt water on highways in US states where salt is used for ice and snow control.

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Won't work on pre-stressed (like bridges) steel installations. Also won't work on more complex rebar structures that require welding, or torch cutting (like bridges).

Like Minnesota on this particular which had persistent problems with "black ice". And they used lots of salt before they switched to runway deicer.

And now the news comes out that heavy deposits of pidgeon poop were noted on the steel structure from the late 80's. Maybe they inspected that away too? By the way, pidgeon poop is especially hard on concrete.

There are no maintenance-free structures. I understand that many do not agree that concrete makes inspection impossible, but I don't believe for a minute it makes maintenance unnecessary.

David A. Smith

Usually done with cables, not rebar.

You probably ought to tell that to the people actually building the stuff. They clean the intersection, weld it, then paint it with epoxy paint.

Lots of north country continues to use salt.

Not real good for iron either.

Radar is now in common use. It tells us something about the reinforcement as well as locating a core drill for sample retrieval without destroying reinforcement or pre stressing elements. Core drilling destructive test specimens out of roadways (bridges and otherwise) tells us about the quality of the concrete.

I agree that piss poor engineering and perhaps less than qualified assembly are at fault, as well as for lack of the proper care on behalf of that spendy under structure, of which obviously never got done (at least not properly).

Except that now they're trying to blaim it all on bird poop.

What if anything was keeping that structure end-to-end under compression?

- Brad Guth

---------------- David are you a bridge engineer ?? if yes welcome now if yes you know that any new bridge has a loading test right after end of building it gives you about 5 to ten yers 'quite head'

afterthat if it is welld esighned than indeed some folowing inspection is needed but it is something very minimal

because experts know the 'weak points ' of the bridge and they go imediatelt to those points to check

4 it is only mathematocians in physics that never make mistakes and mis leadings ..(:-) (because the paper under their pencile is silent and they backup each other and are very happy with that (:-)

ATB Y.Porat

But that would cost pots of money. I don't think that's part of what we've been calling "inspection". One of last week's reports of what is wrong with the Big Dig is that the concrete used to "waterproof" tunnels was watered down. I haven't looked up the chemistry of concrete yet, but too much water doesn't allow the concrete to harden...does it?

/BAH

sigh! Maintenance includes cleaning.

/BAH

Suggestion: Read David McCollough's book about the Johnstown Flood. Notice how knowledge about how to care for the dam was lost over

/BAH

Naw. Ordinary concrete cutting contractors can afford the equipment which requires minimal training to use. Core samples are routinely taken from roads soon after construction to measure that the quality of the materials is up to spec, and as the road ages, to determine the extent of deterioration so that rebuild date can be better homes in on.

Cores are, radar is beginning to be.

I'm fairly certain they're addressing the Massachusetts Irish faction who thinks anything "watered down" is a bad thing. Taking the sorts of artistic liberties reports of that sort often do, the watering down of concrete was probably done by using some other filler material which robbed the concrete of its strength.

OTOH while excess water in concrete tends to make it cure more quickly and allows easier pouring and troweling, it does tend to rob the concrete of some of its potential strength (potential as in how strong could that blend of sand, gravel, and Portland cement become if properly used.)

For me there's a clarity issue with the report you're citing. But then, just how would you explain this to the Massachusetts Irish in as few words as possible? "They sanded down the concrete?" While probably true, that description is even worse. Maybe by reducing the amount of Portland cement, "they stretched the concrete"?

But the "watering down" is precisely why the government always takes core samples to testing whenever a new road is built. Even so it did take them a while to catch Palumbo in Chicago, who ground car interiors such as seats, door panels, and headliners into paving materials. Given Chicago's graft machine the contractor probably told the sample taker where to take the core samples and got by till some pavement deteriorated unexpectedly, revealing its contents prematurely.

I think the extent of their punishment was to be banned from bidding any public projects for

Mr Porat, Pleese usea spell checker when you composte your messages. You arfe giving us a headache. Thankks

On Aug 21, 4:14 am, snipped-for-privacy@aol.com wrote: ...

Certainly a lack of maintenance led to the deterioration of the bridge sooner than it's design lifetime. But that isn't why it collapsed.

Instead, it appears that there are a combination of factors that lead to the bridge actually failing. #1 - The bridge had been identified as structurally in question as evidenced by the University of MN testing, and outside Firm testing and increased inspection intervals. #2 - For some reason, MNDOT did not re-assess the load capacity of the bridge based on the previous findings and appeared to assume the bridge would be able to hold it's design load capacity. Either that, or MNDOT had re-assessed the load capacity but did not communicate that effectively within the organization. #3 - Unique and heavy loads were experienced during the decking of the bridge that should have been within the bridge design spec.

Thus far it appears that lack of communication is what led to the failure of the bridge.

Dear Y.Porat:

On Aug 23, 7:56 pm, "Y.Porat" wrote: ...

Currently doing waste treatment plants. Have desiged hydraulically operated structures for lifting 8000# tanks of liquid over-and-over.

Which has nothing to do with maintenance, or whether a concrete- encased steel structure is "set and forget".

Inspection did not save I35-W. And to listen to what you have said before, no conrete-encased steel structure need ever be inspected much less maintained.

Well, "death and taxes" is 100% insured. Beyond this entropy has sway.

God does make mistakes, when the "fruit of the tree of knowledge of good and evil" gives one the impression that one knows better than God how things are supposed to be. It is really clear to me that peace, war, life, death, renewal, corruption ... in other words "drama", is part of the Plan.

"Successive approximation" is divine. We learn by our mistakes, or at least we have the capacity to do so. We knew not maintaining this bridge was a mistake. We have a system that cannot learn from its mistakes.

I'd like to suggest that the various houses of government be placed under these structures, and that elected officials be required to be under them during rush hour. We support them, it is about time they support us back.

David A. Smith

Who are you agreeing with? Where has it been established that "piss poor engineering and perhaps less than qualified assembly are at fault"?

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See this document that contains the following sentence Every year the nation spends about $8.3 billion, directly from the cost corrosion in our national highway bridges. titled: Steel Rebar Reinforcement Corrosion in Concrete Bridge Design

The lack of communication led to the circumstances allowing the bridge to collapse. The structure had already effectively failed (considering failure the moment it no longer met design spec.)

He's just being aBradsive as usual.

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What Pasul O. sdaid. And yep, I no u looz brownee poynts pointin owt spelin errors but it shur doo feele gud when sumbodi comes on sewnding alle sooperior,

Brian W