Posted on 08/01/2007 4:28:27 PM PDT by ButThreeLeftsDo
Just turned on the news. 35W bridge collapsed in the Mississippi River. Cars, trucks, semis.....
Fires burning, tanker trucks, at least one school bus, more than ten cars......
Just now breaking.......
Abigail
Adams wrote:
The NTSB is saying they didn’t find anything significant on the south side of the bridge, and are now
focusing on the north side to find the cause of the collapse. How does that figure into your figurings? I’m
not an engineer, so I only understand about half of your notes, LOL!
***********
I’m guessing there’s one guy saying this, to reporters dogging him, and who may or may not be closely working with the NTSB.
It might also be a case where there’s nothing obvious on top of a fair sized rubble pile, so they want a quick look atop the northern rubble piles before they start digging. You know, for something real obvious, like a splintered wooden crate with the letters “ACME” on the side and curly wires leading to a plunger.
NTSB is pretty careful and tedious in putting together a polished, finished, report.
They haven’t really started digging yet, eyeball estimate says at least three quarters of the superstructure is under heavy rubble, and at least a third of that is still underwater.
From the north shore of the river, all the way to the north end of the bridge, stood there several seconds after the rest fell in the water and the splash subsided.
It’s very unnlikely that something failed on the north side, but caused the south side to drop first.
If you go back to the first set of force resolution diagrams, to the panel for assymetric loads, you can see that weights placed near one end load that end’s support structures more so than the far end. That’s a pretty basic principle of bridge design. Failures on the north end would shift loads to north end supports first, and they’d have to resist those loads, and at the same time, shed them to the south end to make the south end fall first.
Heads or tails, something on the south end failed first.
If the flipped coin stands on edge, the trigger event happened on the north end.
Here is a poignant article about those who lost their lives in the bridge collapse.
http://www.thenewstribune.com/news/nationworld/story/126104.html
This is ironic. So many good people died that day, and this creep survived:
http://minnesota.publicradio.org/display/web/2007/08/07/survivorarrested/
Interesting article about inspection findings:
http://www.startribune.com/10204/story/1350090.html
Comments?
Well, the reporter seems intent on hyping the crack reports as much as possible, but then, the bridge did fail, and maybe that’s not such a bad thing. Maybe it’s time to tighten up our bridge maintenence standards.
It bothers me that nobody seems to be looking at how the cracks seem to group, and why that might be so. Most of the cracks by far are tack welds on stiffeners, inside box beams and reinforcing webs. I always prefer bolts over welds, but even so, you have to look at whether these members are getting twisted, pulled or squeezed beyond design limits.
If so, why?
The frozen expansion joints and roller bearings might be a good place to start. They’re there for a reason.
Which brings up the second most numerous grouping of cracked members, direct damage resulting from frozen expansion joints and roller bearings.
Right there, you have all the reason you need to spend whatever it takes to keep those joints and bearings moving freely.
Thank you for the link. Florida’s not getting much MN news or impressions since the mine collapsed in Utah and there’s been a lot of crime here lately.
That’s something I can’t stand about the media....it’s “OK, now on to the next story ...Miners trapped...move on everyone.”
Meanwhile, the bereaved in Minneapolis are burying their dead. Some are still waiting to find the remains of their beloved ones.
Three black kids executed in Newark, 6 white miners buried under a mountain...what’ll the big story be today, Wolf, Shep, Greta?
Oh, yah, Paris and Lindsay and Nicole are acting up again.
Mediots, I call ‘em!
Wrongo! Will Britney lose custody to K-Fed?
Shheesh! I forgot all about that adorable (NOT) couple.
Tonight in the news they said the NTSB is looking at gusset plates, their design and the material they are made of.
Thanks! The discussion here is much more intelligent.
If you’re interested, I’ll post up some links to the local media here that are reporting on the latest re: structural defects in question.
It’s been the lead story this evening...
I was pointing you to the story...not so much the comments.
;-)
Sure, thanks. I am local too.
http://www.startribune.com/10204/story/1350971.html
http://kstp.com/article/stories/S162683.shtml?cat=1
Sorry, I should have known that.....
(Red with embarrassment)
‘salriiiigggghhht...
Thanks, I hadn’t seen that one from KSTP yet!
In the first link that shows the examination of ( a gusset plate assembly ) why is the outer plate so badly curved out ward?
They’ve recovered two bodies this afternoon (so far). Thank goodness they are making progress!
I just thought of something on the harmonics/jackhammer theory on bringing down bridges. No, I don’t think a jackhammer can bring down a bridge.
Question: Was the crew overlaying the deck with asphalt? If so, could that asphalt compaction equipment be enough to shake loose a few things?
If this was a big asphalt job the crew may well have had 6 or 8 vibratory rollers working the asphalt. Rollers these days can get over 2000 rpms and throwing a lot of weight and vibration to the deck. Anyone, offer you thoughts on the vibratory rollers.
The harmonice possibilities are endless - but check out the russian pix in the other thread - it seems to show the collapse directly under a bunch of cement trucks that delivered material to the construction site.
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