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Author Topic: I-35W Bridge in Mineapolis Collapses
Colonel Panic
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Icon 1 posted August 01, 2007 18:20      Profile for Colonel Panic         Edit/Delete Post   Reply With Quote 
It's pretty awful, right where the bridge crosses the river near University of Minnesota.

http://www.freep.com/apps/pbcs.dll/article?AID=/20070801/NEWS07/70801094

No signs of terrorism.

CP

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Rhonwyyn

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Icon 1 posted August 02, 2007 04:12      Profile for Rhonwyyn   Author's Homepage     Send New Private Message       Edit/Delete Post   Reply With Quote 
The NBC Today Show is playing footage of the crash this morning.

This is why I hate driving over bridges!!

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Stereo

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Icon 1 posted August 02, 2007 04:44      Profile for Stereo     Send New Private Message       Edit/Delete Post   Reply With Quote 
Strange... A concrete overpass collapsed a few months ago. Built about the same time ('60s). Following this, Quebec's transportation ministery has closed many more overpasses from the same era until detailed inspection, and found a fair number showing undue aging.

Maybe all north-american concrete structures should be examined the same way - the way concrete was done then may not age as well as it was thought.

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Galileo Galilei

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The Famous Druid

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Icon 1 posted August 02, 2007 05:44      Profile for The Famous Druid     Send New Private Message       Edit/Delete Post   Reply With Quote 
quote:
Originally posted by Stereo:
Maybe all north-american concrete structures should be examined the same way - the way concrete was done then may not age as well as it was thought.

Dunno about bridges, but a lot of tall buildings of the era were only designed to last 40 or 50 years. Half a century later, the owners are strangely reluctant to spend millions on replacing them.

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Stereo

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Icon 1 posted August 02, 2007 06:58      Profile for Stereo     Send New Private Message       Edit/Delete Post   Reply With Quote 
So I have seen the photos, and read a bit more about it. It was said that repairs were done on the sliding joints (or whatever you call that in English - the joints that allow for temperature-related length changes in concrete bridges). Another overpass collapsed (not the same I was talking about in my earlier post, as this one happened 5-10 years ago) from faulty sliding joints failure, and if memory serves, it's not just the same kind of failure. But again, a full 8-way bridge may not collapse the same than a 4-way overpass; the lenght of the work just isn't the same.

Anyway, if you haven't already, take a look at some photos (from Cyberpresse).

What strikes me is that the bank-side parts collapsed toward the land, and not the river, so I am let to think that failure happended in the part over the river, and the steel beams, weakened from corrosion (also stated in the article I read) suddenly having an unbalanced load, collapsed outward. Which leads to this question: what happened at the middle of the bridge? I could see no sign of it being a suspended bridge (no tall columns not plenty of cables), but not support pillar at the middle too, even though there are signs of some breaking right in the middle. If there was such support pillars, they have fallen into pieces, explaining why they would be mostly undistinguishable from the roadway. But if it was an overhanging bridge, I can see no other explanation than concrete failure.

But I'm not a civil engineer, so I could very well be wrong. I'll follow the investigation reports, for sure.

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Galileo Galilei

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Mac D
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Icon 1 posted August 02, 2007 07:10      Profile for Mac D     Send New Private Message       Edit/Delete Post   Reply With Quote 
I was about 2 miles away in Downtown Minneapolis when it happened. I was picking up a friend from work. HCMC was about 4 blocks from there. A lot of emergency vehicals around. The Guard was called in but not my unit since I am based up north about 2 hours away. Red cross was there and fire departments from the suburbs where called in.

But I saw a lot of Ambulances going back and forth. And not just the HCMC vehicals. They had them from different hospitals.

Edit: I would have been less then 2 miles. If you go on CNN.com and look at the photos in photo 8/13 you see part of downtown and you can see City Hall. It's the Castle lookig building with the green roof and you can see half the clock that has been stuck at 10:30 for almost a year now. I was accross the street from there at the Government center.

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drunkennewfiemidget
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Icon 1 posted August 02, 2007 10:21      Profile for drunkennewfiemidget     Send New Private Message       Edit/Delete Post   Reply With Quote 
damn it
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drunkennewfiemidget
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Icon 1 posted August 02, 2007 10:22      Profile for drunkennewfiemidget     Send New Private Message       Edit/Delete Post   Reply With Quote 
quote:
Originally posted by Stereo:
So I have seen the photos, and read a bit more about it. It was said that repairs were done on the sliding joints (or whatever you call that in English - the joints that allow for temperature-related length changes in concrete bridges).

Expansion joints.
quote:
Originally posted by Rhonwyyn:
The NBC Today Show is playing footage of the crash this morning.

This is why I hate driving over bridges!!

It's called mitigating risk. 2 bridges in North America (as far as I'm aware) have collapsed in the past while.

Out of how many?

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TheMoMan
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Icon 1 posted August 02, 2007 10:51      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
Hi All __________________________ Just a thouht, Yesterday was the third day in sucession of plus Ninety F. temps could the expansion joints have gone to full travel and no more room. Causing the support columns to tilt outward from the river.

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Stereo

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Icon 1 posted August 02, 2007 13:10      Profile for Stereo     Send New Private Message       Edit/Delete Post   Reply With Quote 
quote:
Originally posted by TheMoMan:
Hi All __________________________ Just a thouht, Yesterday was the third day in sucession of plus Ninety F. temps could the expansion joints have gone to full travel and no more room. Causing the support columns to tilt outward from the river.

It is possible, but I doubt so. My reasonning is pretty simple: expansion joins are usually not very big (concrete heat-expansion is much more limited thant steel, for example), and they are usually evenly distributed. This means that if the whole expansion space was taken up, the concrete would probably have gone *envenly* into compression. And concrete supports compression forces very well. So the movement of the steel pillar shouldn't have been more than a few cm; lower than a great wind would cause.

If it had happened in the first few days of much cooler temperature, one could have assumed that the concrete was damaged while on compression, and releasing the pressure allowed it to crumble and loose integrity close to the joints. On the other hand, were such temperatures not normal (like in "never seen in recent history of the area when building the bridge") and thus not taken into account, it would be conceivable that the bridge went into compression at day, and relaxed at night, causing cycle damage - exactly what expansion joints are meant to avoid.

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Galileo Galilei

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Rhonwyyn

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Icon 1 posted August 02, 2007 14:54      Profile for Rhonwyyn   Author's Homepage     Send New Private Message       Edit/Delete Post   Reply With Quote 
IIRC from this morning's news broadcast, it was a single arch bridge, so the only supports were on either side of the river.

The sheriff was interviewed on NPR this afternoon. He said they'll treat it as a crime scene. One of the tell-tale signs is if iron visible at any cracks they find is rusty (meaning it's an old crack) or shiny (meaning it's new). What they'll do at that point, I'm not sure 'cause I stopped at a roadside stand to buy a homegrown cantaloupe.

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Doco

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Icon 1 posted August 03, 2007 07:36      Profile for Doco   Author's Homepage     Send New Private Message       Edit/Delete Post   Reply With Quote 
I had to answer a few phone calls from relatives letting them know I was ok. While I live in the cities area - I am rarely close to downtown and therefore never thought about the spread out relatives worrying about us.

From what I know (the local news is of course saturated - as is the water cooler talk):

It wasn't a suspension bridge. The main span (and some of the lead-up spans I think) is a steel arched truss. It was designed to span the river in one span so there is little chance that it failed due to one of the supports having eroded away or being damaged from a barge.

The local paper has a good graphic about the bridge

I wonder about finding old vs new cracks. It will be days/weeks to get a lot of the wreckage out of the river. It doesn't take long for fresh steel to get a good layer of rust. Hmmmm - maybe they can measure the thickness of the oxide an age the crack from there. But that has to be dependent on a lot of variables, like how much moisture, salinity, oxygen, etc is available.

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Stereo

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Icon 1 posted August 03, 2007 08:09      Profile for Stereo     Send New Private Message       Edit/Delete Post   Reply With Quote 
Thanks, Doco. It was nice to see what it looks like before.

So what we know: it was a single-arch double-triangle steel-structured bridge. Concrete failure is no longer an option for the cause of the wreck. But recent inspection has shown structural damage from rust, and there were works on the pillar support (in Doco's linked image, it's where you can barely read "roller bearings"). There was also reports on the use of a pneumatic drill, although I doubt the vibrations would compare to the ones caused by the traffic.

The weird thing is that it failed when only half the lanes were open; so its load was below usual. So one has to wonder if the failure is due to a mishap while doing the repairs. Another hypothesis I read this morning is water eroding the ground the pillars were on - then no matter the charge, if one pillar moves just a bit too much, the whole thing goes down. And for what I know, the Missisipi river is known to carry a lot of mud, which could hasten the erosion of its banks.

A good case for the engineering-inclined geeks, and possibly the geological ones, if anything.

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Galileo Galilei

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Mac D
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Icon 1 posted August 03, 2007 09:40      Profile for Mac D     Send New Private Message       Edit/Delete Post   Reply With Quote 
quote:
Originally posted by Stereo:
And for what I know, the Missisipi river is known to carry a lot of mud, which could hasten the erosion of its banks.

But we are in a moderate drought and the river is low. This would mean less water by the pillers.

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Aditu
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Icon 1 posted August 03, 2007 11:04      Profile for Aditu     Send New Private Message       Edit/Delete Post   Reply With Quote 
I can't weigh in on the engineering of it all, but I am certainly glad that you guys are safe.
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