Bridge Collapse in MN 29

[bimr]

It is somewhat obvious from the video that the bridge failure occurred where the construction crew was working.

If you look at the pictures, it appears that new concrete on the bridge deck is covered with visqueen. There was supposed to be a thunderstorm later that night.

What happened to the construction workers?

 

[minorchord2000]

The cantilevered spans were only about 37' at each end. The main span is 456' with 265'approach spans at each end.

I tried downloading the report that WillisV posted but it is very slow and never finishes. But from what I read, fatigue is a very real issue with this structure.

 

[RichBridge]

From the way it dropped straight down, it doesn't seem like it would be a fatigue or fracture failure. What are the chances of both trusses going at the exact same time? If one failed, it would start falling first and twist the bridge and bring down the other truss.

I suspect foundation failure most likely due to scour. Even though the piers were at the edge of the water, it still looked like they were in the water. I guess it's that or something in an adjacent span that pulled or pushed the main span off its bearings.

It still seem weird the way it dropped straight down.

 

[resqcapt19]

I have the same problem reading the right end of the posts. Can the poster of the picture resize it?

 

[unclesyd]

In my previous post the professor that was giving commentary concerning the UM report and the design features of the bridge mentioned something about the connections at he the ends. I didn't catch all his comments but he was worried about the ends being pinned or not being pinned. He tried to clarify this and was rudely interrupted.

He also stated in it's day this was a every inexpensive way to construct a bridge, less steel and lots of labor. Today it would be very expensive construction due to labor cost.

Some of you bridge guys help me out a little on this one. He also made the statement that this type of truss would fail completely if any one component failed.

 

[bimr]

If you look at the picture above, it looks like they were pouring concrete.

Maybe, the concrete formwork collapsed onto a lower structure member.

 

[proud2banerd]

RichBridge - I had the same thoughts (although I am definitely NOT a bridge expert). What was the name of that bridge in NY that short-sheeted itself a while back? (when the pier shifted slighly from scour, moving the beam support just enough to cause a chain reaction with the spans). Could some minor shift of occured and somehow gone undetected? If so, could a hot day's expansion, evening rush hour and the construction have aggrevated the problem? Sorry if these ideas are way off base--I'm a water person (and an occasional structural wannabe)

 

[jike]

It still seem weird the way it dropped straight down.

Gravity

sorry....I couldn't resist!

 

[agrater]

I'm aware that structural analysis software have birth/death options for structural elements, but do they also automate the death of such elements in order to check for redundancy due to the failure of random elements?

 

[JAE]

OK - I resized it and deleted the other one. I'll red flag that post and get it deleted.

Here is the 1/2 sized photo...hopefully this will work better.

 

[bimr]

The piers are on land and from the pictures do not look like they shifted. You can clearly see the north end piers sticking out of the debris in this picture.

The entire bridge did not fail straight down. If you look at the picture below, the bridge did not come straight down at the north end. The debris at the north end of the bridge shows that the top of the north end of the bridge fell or twisted to the west.

The south end of the bridge came straight down, following the failure of the north end.

 

[PackerFan]

Bird poop and de-icing spray. I can remember back in college at the U of M they had massive problems with bird droppings in this bridge due to the open tubes used for the trusses. They would have to constantly clean out the corrosion from the droppings. A couple of years ago they even installed plastic caps on all the openings to prevent nesting. Then a couple of years ago, they installed a new de-icing system that sprays down the bridge everytime it snows. This was an experimental formulation at the time. My guess is corrosion is going to be the culprit.

 

[IRstuff]

In the photos on the Yahoo website, on the other end of the bridge, the entire portion of the pier above ground is tilted toward the river.

TTFN

FAQ731-376

 

[SteelMover]

Some of the commentary about the event on news programs has been incorrect. The photo shown above by BIMR is of the south end of the bridge. Locks are on the south side of the river here, train tracks are on the north side. The video footage looks like it was taken from a camera that looks at the locks, and is facing north.

 

[concretemasonry]

After going to school within a miles or so, being around the hydraulics laboratory that is near there on the north/east bank, boating and fishing for smallmouth bass, I would think that the piers are probably onon the limestone ledge that is common all through the area.

Thst stretch of the Mississippi river is not typical of the area below St. Paul (10-15 miles downstream by water). It ihas lower flows and is carved out of the limsestone that very close to the surface.

Sorry, but I could not see all of my post for corrections

 

[unclesyd]

IRstuff,

I was just watching the news and they showed the same thing, the support on one end is leaning toward the river.
It showed the support in the water.

I was having trouble with whether this was a camera angle problem or the real thing. They came back to this area in another shot and sure enough the support is leaning.

 

[archeng59]

Thanks for resizing the photo, JAE. But the original photo is still causing something to be messed up. Doesn't really matter. I can get the gist of what's being said.

 

[casseopeia]

Didn’t the bridge have a center pier in the water? It looks like it from the one photo. I tried to confirm this from Google Earth, but all I got was a Salvador Dali version of the bridge, melted-looking.

I watched the news conference with the engineers. I believe they mentioned corrosion at the roller bearings. I haven’t worked in bridge engineering for awhile, but this seems worth investigating.

"If you are going to walk on thin ice, you might as well dance!"

 

[COEngineeer]

No, it looks like there is nothing in the water. Check this link.

http://www.msnbc.msn.com/id/20089341/

Never, but never question engineer's judgement

 

[COEngineeer]

I think for sure the collapse is originated from the middle span.

Never, but never question engineer's judgement