Bridge collapse in Minnesota!!!

I was thinking the very same thing. Like when your tape measure is stretched out and you twist it to the side and it snaps...

 

While not a structural engineer, I am a civil. I don't see this as a partisan issue, any politician who defers transportation funding (which happens on both sides) is equally at fault. This bridge actually fared well on the inspection reports compared to thousands of others which are still in use.

I highly doubt the construction impacted the collapse. The deck is a completely separate subsystem from the rest of the structure. My guess is that it will mimic other bridge collapses, in that there was a manufacturing defect in a component from the original construction which evaded detection, until it was loaded one too many times.

 

The info gets more bizarre...

 

they are now claiming that the number of missing people has dropped significantly, i think i heard 9 now instead of 30, which is good news but still disheartening.

 

As do I...

 

I think 9 is the number dead, not missing.

BTW, interesting link.
http://news.yahoo.com/s/ap/20070802/ap_on_re_us/bridge_collapse
I'm suspecting this is a factor.

 

I agree with you. However, after giving it some thought and consulting my son (civil engineer), I wonder about the following concept. If you have a four lane bridge designed to accept the fairly even distribution of weight on the whole structure, and if the structure is weakened with age, and, if you close one side of the bridge and throw all the weight to only one side; and you load that side up with solid gridlock traffic day after day; What happens?

 

Rather than load up my previous post, I want to give you folks an observaton. See if you agree.
Bridge work usually entails closing one lane and working on the other. I have never seen one whole side of a four lane bridge closed before while traffic was directed to the other side. Weight distribution should be evenly straight down. Not, to one side or the other. Considering that there is usually several feet of overhang outside of the bridge support, throwing the weight to one side could:
1. Cause undue up-pull on onside.
2. Undue down pressure on the other.

Just an idea.

 

Could very well be...but the forensics are not in yet of course.

I did notice that some engineering doctoral student did a stress analysis (to the point of failure!) in a computer simulation on this very bridge a few years back, and the NTSB says they are going to review this simulation against what little security cam film and other evidence they have to attempt finding a root cause. They hint that there may be some similarity between the simulation and the accident.

 

Naturally, I wasn't trying to second guess reality. I only had rudimentary physics in play. We will see what happens. The results should be instructive. Thanks.

 

The only thing, though, is that you only have half the load on the structure. Theoretically, the design load would at least cover having the entire deck parked bumper-to-bumper. The other thing, is that if it failed due to a weight distribution imbalance, I think the increased moment would have caused the deck to rotate as it fell into the river, instead of dropping straight down.

 

This is a logical point. What film there is shows it going straight down, domino fashion. But it shows only the final collapse - I could not see the origin.

I was wondering if an imbalance could have broken connections in that arch beam backbone at one end and triggered a chain reaction.

The artist's illustrations I saw show TWO of these beams, one supporting each half of the bridge. Each half extended quite a ways out into space outside the beam - undoubtedly an unusual design. This is what leads me to be suspicious of the design, but we shall see when they do the investigation.

I was pretty sure that 747 that went down outside NYC in 96 was brought down by a SAM rocket, too - until they proved it was a fuel explosion brought on by faulty wiring.

 

the death toll is at 6, 8 are still missing, and 110 injured,

 

they said the death toll is much less than they feared. I think im speaking for everyone here by saying: We all fear for there to be a death but there was more than that.

 

I think Im speaking for Everyone here(mn). Thank god I wasnt driving there when it happened.

 

You have a link to the video?

 

http://www.youtube.com/watch?v=EjCic0YlJwQ

 

Best photos... http://drugoi.livejournal.com/2280005.html

 

OK. We'll see. I am compelled to go with you but, let us think that rotation is not necessarily 180 degrees but, only 90 degrees considering the drop. Considering that, when the bed hits the river, it comes back to flat and that is where it lies. Not straight down but to one side. It wouldn't have to be a lot to the side. That might be in consonance with my idea and not a whole lot off from yours. We both could be close. What do you think?