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Bridge over the Mississippi River has collapsed, sending cars into the water

Wow what a tragedy the showing it on cnn now. :Oh crap

Wow yeah thats unreal. Big wide bridge too, looks like 4 lanes total..

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Originally Posted by PR_Tom (Post 12856755)

Wow yeah thats unreal. Big wide bridge too, looks like 4 lanes total..

yeah its a decent sized bridge. Gives me chills reminds me of the Sunshine skyway bridge collapse here in 1980. We just got over it and was about a mile away and you could hear and feel it breaking apart.

Quote:

Originally Posted by Brother Bilo (Post 12856765)

No Links? WTF?!?!

cnn just had a bulletin on there site no links yet.......

Witness said it was bumper to bumper traffic, some workers were working on the bridge this person says, and he says he felt a jackhammer vibration right before it collapsed. Said about 100 vehicles were on it when it collapsed.

http://www.kare11.com/

Thats the local television station that is feeding the national news. Links there.

ive driven over that bridge 1000 times. Still waiting to hear back from some people that I know take it during their commute. ***fingers crossed***

damn, hopefully everyone survives

crazy another bridge fell down somewhere yesterday too

Quote:

Originally Posted by Sosa (Post 12857067)

damn, hopefully everyone survives

3 dead:Oh crap

This is insane, pffft news media is already asking about terrorists..

I hope they recover everyone, and everyone is ok.. :( Especially those kids in the bus.

Guy being interviewed on fox just said "Shit" then the reporter says well we wont use that. Opps. Terrible tragedy. :(:(

Quote:

Originally Posted by Casa Nova (Post 12857087)

This is insane, pffft news media is already asking about terrorists..

I hope they recover everyone, and everyone is ok.. :( Especially those kids in the bus.

Everything I've heard was that the kids got off the bus and are ok.

Quote:

Originally Posted by ghostshadow (Post 12857107)

Everything I've heard was that the kids got off the bus and are ok.

That's a good result - it could have been far worse. Amazing there were not more fatalities - last I heard was six, but chances are there will be more as the recovery process continues.

Quote:

Originally Posted by Casa Nova (Post 12857087)

This is insane, pffft news media is already asking about terrorists..

Serious?? Sheesh... would they like to believe - anything for more drama :)

What a tradgedy..terrible news :(

Very sad. I hope something like this can be avoided for the many other bridges pushing 40+ years in age.

Damn that is horrible :(

watching it on CNN right now as well. :(

any ideas what made the bridge colapse that way????

I live here and I'm still waiting to hear from friends.

In the meantime heres some interesting reading

http://www.kstp.com/kstpImages/Technical%20Report.pdf

And here are some pics from a u of m student

http://flickr.com/photos/adamwolf/se...55421362/show/

something form another site

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From my brief skim of the article it seems as though the bridge was built in the late 60's. Serving for 40 years isn't an engineering flaw in the design. The article said that the bridge deck was being repaired, my guess is that the problem lies in that. Almost always a concrete bridge deck is counted on to act compositely with the steel underneath, that is maintain strain compatibility and allow the steel to act primarily in tension with the concrete taking most of the compressive force. This is beneficial since steel nearly always fails do to compression related stability (i.e. buckling). If the contractors removed critical concrete from the bridge deck, that could cause a shift in the plastic neutral axis and the steel beams would likely fail due to lateral torsional buckling. Of course, there is no way to know this for sure...

more comments

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This is crazy... the pics posted are just nuts... Obviously nobody can know the cause of all of this until studies/tests are done, but I'm really looking forward to an update on all of this... BTW, a bumper to bumper traffic jam on the bridge would have a design load of 62 pounds per square foot. A pedestrian bridge gets designed at 75 pounds per square foot. Nowadays, most bridges are designed for vehicular load and then checked for full pedestrian load, since that is often times the governing case. Also to consider is partial live loading of trucks. From the looks of the pics above, the bridge was made of relatively slender members. Generally, structures are designed to be very ductile so that a structural failure does not equal total collapse. To do this, tension member yielding is set as the weakest link, since tension yielding is a very ductile process. However, fatigue loading tends to bypass the yielding phase and cause tension rupture, a brittle failure. Also, compression member buckling is a very sudden failure.

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Another observation... The pic of the bridge before collapse shows that the structure was continuous over supports (you can count 3 separate spans). This means that the bending moments range from positive at the center of the main span, to negative over the supports. What this means is that in the center, the bottom chord of the truss is in tension and the top is in compression, this lends itself very well to composite beam theory, as mentioned earlier. However, with negative moment, the concrete deck is now in tension and the bottom chord changes to compression. If the deck was designed to have sufficient rebar to carry tension forces, and that rebar was disturbed, that could be very bad. The rebar is the deformed "spaghetti" like steel in the pics above. Under uniform loading, the negative bending moment will be slightly larger than the positive moment. Since the truss cannot utilize composite action at these sections, the truss is typically made deeper over continuous supports (as was the case here). This means that at a certain point on the bridge, the top and bottom chords each change from tension to compression (or vice versa) and essentially go through zero stress at one point. This is referred to as an inflection point and it only experiences shear stresses. Often times in old bridges (older than this one), engineers placed hinges at these points (since hinges can carry shear, but not moment and no moment transfer is required) to make an indeterminate structure determinate. The more you know...

I have pics, and a bunch of them however my server might not handle it. If anyone can put them up hit me up 19630281

Quote:

Originally Posted by TampaToker (Post 12856769)

I was a little girl when that happened, and my dad used to take me to work with him..I remember driving over that bridge with him the day it was reopened going southbound, and being absolutely petrified. I was only 3, and I am pretty certain it's the first memory I have. It just made that much of an impact, you know?

just seen - horrible pics on european tv