heartfelt thoughts to our friends in MN

[fascination]

our thoughts and best wishes to the dance community in st paul and minneapolis minn. and the larger community in general

[Peaches]

Yes, ditto that.

[samina]

dear me... i drove that bridge more times than i could ever count...
what a thing... it's amazing that more people weren't lost in such a crazy tragedy... giving thanks for that & sending prayers...

[samina]

pretty view of the bridge as i remember it:
http://en.wikipedia.org/wiki/Image:I35W_Bridge.jpg

[samina]

and another angle. the available post-collapse pix are so mangled...
http://en.wikipedia.org/wiki/Image:I-35W_Bridge_2.jpg

[cornutt]

Thoughts and prayers to everyone in the Twin Cities area. It's a part of the country I've always wanted to visit.

And thanks for posting those pix, samina. I've been looking for something that showed the structure of the bridge. It's a matter of professional interest to me.

[samina]

at first i wondered if it was the one i climbed on a date once when i was 20... but that one's the next one up the river, connected to the NE side of the city. this is SE. and that bridge has a broad cement structure, with pillars all the way across -- can't imagine such a thing ever collapsing.

this one was famous for not having pillars in the water, apparently, and the understructure looks far more delicate.

[cornutt]

I'm thinking that the bridge was actually a cantilever type, and that all that steel was just secondary support to keep the center span from bouncing up and down. A cantilever is basically a big beam that's balanced on a center support. I noticed in looking at the video last night that there appear to have been secondary collapses of the approach spans on either side of the river. On each side there is a large slab that is now leaning up against a substantial concrete support. I'm thinking that those were actually the primary supports -- the balance point for the cantilevers. For some reason the center section failed and broke loose. That left the cantilevers unbalanced, which would explain why the approach spans collapsed when the concrete supports appear to still be intact.

Mind you, I'm just thinking out loud here. And I don't intend to show disrespect by appearing to be so cool about it. As an engineer, the thing you want to do in a situation like this is to find out what they physical cause is, so you can take steps to make sure it doesn't happen again.

[samina]

yes, i observed the same thing from the collapse video. i wonder what the nature is of the construction that was occurring on the bridge at the time of the collapse...

[fascination]

Thoughts and prayers to everyone in the Twin Cities area. It's a part of the country I've always wanted to visit.

And thanks for posting those pix, samina. I've been looking for something that showed the structure of the bridge. It's a matter of professional interest to me.
it is a beautiful area cornutt...my dh was a civil engineer in a former life and I am sure he has a view on it....in fact I am curious as to tthe designers of the bridge...and even a bit freaked out that traffic continues on the one just like it...I hope they are able to ascertain the reason for the failure rapidly...and that the missing are found quickly

[SPratt74]

I've been on that bridge! I couldn't believe it when I saw it. I have cousins that live in Minnesota, and we've been on that bridge many times. I feel for the people that were on that bridge at the time, and my prayers go out to all of them and their families.

[LucyDiamond]

Thanks fasc for starting this thread. My thoughts and prayers are with everyone in the Twin Cities area.

[Sagitta]

our thoughts and best wishes to the dance community in st paul and minneapolis minn. and the larger community in generalditto

[cornutt]

yes, i observed the same thing from the collapse video. i wonder what the nature is of the construction that was occurring on the bridge at the time of the collapse...

The reports I've heard are, they were re-paving. That in itself shouldn't have had anything to do with the collapse. However, what I note about that is that they had traffic down to one lane in each direction. If these were lanes at either edge of the bridge, away from the centerline, I wonder if that might have placed a torque or side load on the bridge that wasn't anticipated in its design. 40 years ago, they didn't have spiffy CAITA systems to model loads on structures. Sometimes when engineers model old structures like this one on modern systems, they find surprising things about the design that the original designers couldn't have worked out with slide rules.

[quixotedlm]

Security Camera video of collapse -

OKK7rWfEpe4

[meow]

It has been on the news here. It is horrifyingly scary and deeply sad and disturbing. My best wishes go to all who are touched by this tragedy.

[Joe]

I'm thinking that the bridge was actually a cantilever type, and that all that steel was just secondary support to keep the center span from bouncing up and down. A cantilever is basically a big beam that's balanced on a center support.
Actually a cantilever doesn't have to be balanced on a central support. If you stick a beam in a wall, it's a cantilever, yet it's only supported on one end.

From the photos I've seen the bridge does not appear to be a cantilever. It had one pier on each side of the river, plus at least one pier in the floodplain on each side.