Article

2007-08-02 -Short Attention Span Theater-

Lileks on the Minneapolis bridge collapse

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Posted by Mike 2007-08-02 05:57|| || Front Page|| [11144 views ] Top

#1 I was in a meeting yesterday discussing "fatigue prone details" on steel bridges. Seems that some 30-40 year old designs had steel details which were shown to lead to fatigue cracking after 20-30 years. They are being retrofitted when major rehab is done to a structure, (not quite 'whenever we get around to it'), but there is no formal program to upgrade them. Yet.

Posted by Bobby 2007-08-02 07:14|| 2007-08-02 07:14|| Front Page Top

#2 Local authorities say bridge passed recent inspections with no significant problems, but radio reports federal inspectors reported major deficiencies and recommended replacement.

Most major bridge collapses I know of over the last 40 years have been due to ships or barges hitting them, with a couple from earthquakes and a couple from truck collisions/fires; I can't think of ANY that just fell down of their own accord.

Like Lileks, I 'feel' the construction must have had something to do with it: Surfacing work should not have affected structural integrity, but it did have traffic re-routed to fewer lanes, which might have made the bridge 'off-balance' - though with lighter overall load.???

It is a bit refreshing to see authorities say 'We have no reason to suspect terrorism,' rather than the typical 'Terrorism was not a factor.' I certainly would not rule it out until finishing a careful inspection - for instance, could a construction worker have set some charges on key support members? Such would explain the 'bang' witnesses heard, and could cause a collapse, but if so, there WILL be evidence of it once the wreckage is examined. Minneapolis is known to have an obnoxious (at the very least) Muslim community.

Posted by Glenmore">Glenmore 2007-08-02 07:23|| 2007-08-02 07:23|| Front Page Top

#3 while it would seem intuitively that "unbalancing" could cause a problem, in real-life-engineering, it's a non-issue. All structures are designed for worst case, and unbalancing isn't it, except for individual member design. Fully loaded with an undamped harmonic vibration (think quake) would usually be worst case, otherwise you could never close a lane or two for fear of "unbalancing". Sounds like structurally deficient or material failure

Posted by Frank G">Frank G 2007-08-02 07:33|| 2007-08-02 07:33|| Front Page Top

#4 If deficient material or design, why would it fail then, with under half a normal peak traffic load? I guess microfractures could have accumulated over a period of peak loads, but not quite to 'failure', and then propagated and coalesced in an accellerated fashion under the sustained load of the bridge weight itself until reaching failure. Sort of like working out in the gym, pressing your ten reps, then holding the last one until you can't hold anymore.

I repeat though - can anyone recall any pure, untriggered bridge collapses? (I'm not saying they didn't happen, just that I can't remember them.)

Posted by Glenmore">Glenmore 2007-08-02 07:45|| 2007-08-02 07:45|| Front Page Top

#5 FrankG: "undamped harmonic vibration (think quake)"
Or Tacoma Narrows crosswinds? I sometimes wonder when I am stuck in traffic at the top of the Huey Long Bridge, and a big freight train comes rumbling over, and the bridge bounces, whether the 1926 engineers accounted for all the harmonics.

Posted by Glenmore">Glenmore 2007-08-02 07:47|| 2007-08-02 07:47|| Front Page Top

#6 Tacoma was an awesome demonstration of that, wasn't it? I think most every engineering student's seen that video. Bobby's comment about old steel details is spot on as well....

Posted by Frank G">Frank G 2007-08-02 07:52|| 2007-08-02 07:52|| Front Page Top

#7 Man, and i was pissed at my lawnmower's handle (the steel connection of the entire handle structure to the deck of the mower) shearing off yesterday. Coincidence that it happened just before this bridge collapse? Who knows, but I know I won't buy another cheap (probably chinese made) mower, that's for sure.

Posted by BA 2007-08-02 08:49|| 2007-08-02 08:49|| Front Page Top

#8 P.S. I'm not making light of the situation as my mower incident happened a few hours before the bridge collapse. My thoughts and prayers are with all Minneapolis-St. Paul folks.

Posted by BA 2007-08-02 08:50|| 2007-08-02 08:50|| Front Page Top

#9 Apparently they were resurfacing the deck, if they removed too much of the deck on a loaded, or even partially loaded bridge the chords might have deflected enough to cause a failure.

Posted by bigjim-ky 2007-08-02 09:07|| 2007-08-02 09:07|| Front Page Top

#10 One wonders about: cement saws, torches, repair equipment creating unbalanced loads, salt, a train moving underneath at the same time..

BTW a bike path was reported under it. Did the bridge impact the path and was anybody on it?

Posted by 3dc 2007-08-02 09:12|| 2007-08-02 09:12|| Front Page Top

#11 We were waiting for dinner at the table when every TV in the restaurant changed with volume pumped up to channel 9 just minutes after the bridge went. Shock shut down the table conversations as a great number of us were waiting on friends who normally take that bridge.

For 15-20 minutes we waited to see emergency services move in. It took time and even longer for the water rescue to get on station. Watching them negotiate the wreckage was painful to watch. Brave souls.

In true Minnesotan fashion average Joes and Janes volunteers started grabbing the injured and taking them to hospitals almost immediately. Many of whom had rushed to the accident on foot.

At the very moment the bridge went down a fully loaded train was crossing under the structure and it was just barely past rush hour. In 2005 a report listed the bridge as deficient. The U of M had been involved studying the bridge and report. That stress test involved stacking sand filled dump trucks on key placements. I have yet to hear if any of the beams were x-rayed and to make matters worst the steal is painted which greatly screws with the engineers visual inspections.

It was built in the same year (1967) as the Ohio Silver bridge. Which went down in an eerily similar fashion.

For video of the bridge actually falling go here. You can exactly see where the bridge broke off. Compare to the Silver Bridge. Both were similar in design.

With as many workers and engineers as there were working daily on the struture, Muslim terrorism is unlikely but can not be ruled out.

It also pales in comparrison with the Hinckley Fire. Following an extended drought, up to 1,000 burned alive, 400+ square miles burned to the ground. Fire speeds were at one point so great that it almost overtook one train. I only mention this because I'm fricking tired of hearing Twin Citie dweebs calling the bridge's collapse as one of the largest Minnesota disasters.

Having gone over the bridge hundreds of times gives no validity to my opinon but it appears it was just the bridge's time. The pure miracle is the low number of deaths.

Posted by Icerigger">Icerigger 2007-08-02 09:22|| 2007-08-02 09:22|| Front Page Top

#12 Apparently they were resurfacing the deck, if they removed too much of the deck on a loaded, or even partially loaded bridge the chords might have deflected enough to cause a failure.

No the layers removed were purely cosmetic.

No word on the bike path but typically that trail is lightly used.

Posted by Icerigger">Icerigger 2007-08-02 09:25|| 2007-08-02 09:25|| Front Page Top

#13 A great photo of the bridge's steel structure.

Posted by Icerigger">Icerigger 2007-08-02 09:50|| 2007-08-02 09:50|| Front Page Top

#14 A University of Minnesota Civil Engineer in a report to MN-DOT recently noted that this bridge is considered to be a non-redundant structure. That is, if any one member fails, the entire bridge can collapse. A key factor is that there are only four pylons holding up the arch. Any damage to any one pylon would be catastropic. The textbook example of a non-redundant bridge is the Silver Bridge over the Ohio River. It failed shortly before Christmas in 1967 resulting in 46 deaths. A single piece of hardware failed due to a tiny manufacturing defect. But that piece was non-redundant, and the entire bridge collapsed into the icy river. Today, bridge engineers design bridges so that any single piece of the bridge can fail without causing the entire bridge to collapse. It is tragic that the I-35W bridge was built a few years too early to benefit from that lesson.

Posted by tu3031 2007-08-02 09:54|| 2007-08-02 09:54|| Front Page Top

#15 You can get metal fatigue, coupled with some corrosion (they do use deicing salt up there, IIRC), and you can get some nasty member failures. Public infrastructure maintenance, improvement, and replacement are long term commitments that have been neglected on a large scale in this country, as funds normally allocated for this important but mundane area have been diverted to feel-good programs that are fluff but no substance.

Posted by Alaska Paul">Alaska Paul 2007-08-02 10:14|| 2007-08-02 10:14|| Front Page Top

#16 From the human side, I was so impressed with Minnesota public safety authorities and the public in their response to this disaster. They had emergency response plans in place, they implemented them in a timely fashion. Emergency vehicles and vessels moved in quickly to save lives, put out fires, and evacuate victims. The public responded immediately and did what they could do on their own initiative. Contrast this with the New Orleans response to Katrina. It would be good to have someone on the MSM comment on this, but I will not hold my breath on it.

Posted by Alaska Paul">Alaska Paul 2007-08-02 10:18|| 2007-08-02 10:18|| Front Page Top

#17 In that attached video a report is given that said that a 2006 inspection reported warped and cracked steel. Sounds like the bureaucracy may have dropped the ball big time.

Posted by AlanC">AlanC 2007-08-02 10:26|| 2007-08-02 10:26|| Front Page Top

#18 Yeah, this bridge was waiting to fall. The money was prolly earmarked already for the bridge, but went to local corruption instead.

Posted by wxjames 2007-08-02 10:34|| 2007-08-02 10:34|| Front Page Top

#19 Fully loaded with an undamped harmonic vibration

Could there have been a combination of vibrations from the resurfacing and the train passing underneath that might have aided the collapse?

Posted by Mike N. 2007-08-02 10:58|| 2007-08-02 10:58|| Front Page Top

#20 Icerigger, thanks for the local info and story.

Posted by Steve White">Steve White 2007-08-02 11:07|| 2007-08-02 11:07|| Front Page Top

#21 Link where you can order the results for the 2001 U of Minn study

Abstract
This research project resulted in a new, accurate way to assess fatigue cracking on Bridge 9340 on I-35, which crosses the Mississippi River near downtown Minneapolis. The research involved installation on both the main trusses and the floor truss to measure the live-load stress ranges. Researchers monitored the strain gages while trucks with known axle weights crossed the bridge under normal traffic. Researchers then developed two-and three-dimensional finite-element models of the bridge, and used the models to calculate the stress ranges throughout the deck truss. The bridge's deck truss has not experienced fatigue cracking, but it has many poor fatigue details on the main truss and floor truss system. The research helped determine that the fatigue cracking of the deck truss is not likely, which means that the bridge should not have any problems with fatigue cracking in the foreseeable future. As a result, Mn/DOT does not need to prematurely replace this bridge because of fatigue cracking, avoiding the high costs associated with such a large project. The research also has implications for other bridges. The project verified that the use of strain gages at key locations combined with detailed analysis help predict the bridge's behavior. In addition, the instrumentation plan can be used in other similar bridges.

What sort of liability does that statement expose them to?

Posted by 3dc 2007-08-02 11:21|| 2007-08-02 11:21|| Front Page Top

#22 Well we know for sure that in the next few days we will find out that this was caused by one of two things. Bush and Global Warming. Maybe both.

Posted by tu3031 2007-08-02 11:23|| 2007-08-02 11:23|| Front Page Top

#23 specs and pre-drop photos of bridge structure

Structure ID: NBI: 9340.
Location: River Mile 853.20.
River Elevation: 725 Feet.
Highway: I-35W.
Daily Traffic Count: 140,000 (2002).
Bridge Type: Steel Arch Deck Truss Bridge.
Length: 1,907 Feet, 458 Foot Longest Span.
Width: 8 Traffic Lanes, 108 Feet.
Navigation Channel Width: 390 Feet.
Height Above Water: 64 Feet.
Date Built: Opened November 1967, Failed August 1, 2007.
Claim to fame: was built with a single 458 foot long steel arch to avoid putting any piers in the water to impede river navigation.

This bridge features an anti-ice system. A series of PVC pipes carries a deicer fluid to outlets that are drilled into the deck of the bridge. When the temperature for ice is right, the deicer fluid is pumped onto the bridge deck. This system has proven to be successful enough that it is being installed on other bridges in Minnesota.

The National Bridge Inventory contains a report on this bridge from 2003. It reports the following items:

* Deck Condition: Fair.
* Superstructure Condition: Poor.
* Substructure Condition: Satisfactory.
* Scour: Foundations determined to be stable.
* Bridge Railings: Meets currently acceptable standards.
* Structural Evaluation: Meets minimum tolerable limits to be left in place as-is.
* Water Adequacy Evaluation: Superior to present desirable criteria.
* Bridge Sufficiency Rating: 50%

A University of Minnesota Civil Engineer in a report to MN-DOT recently noted that this bridge is considered to be a non-redundant structure. That is, if any one member fails, the entire bridge can collapse. A key factor is that there are only four pylons holding up the arch. Any damage to any one pylon would be catastrophic.

Posted by 3dc 2007-08-02 11:25|| 2007-08-02 11:25|| Front Page Top

#24 If nobody's seen it, here's the video of the actual collapse

http://www.cnn.com/video/#/video/us/2007/08/02/vosli.mn.i35w.bridge.collapse.side.view.cnn

Posted by tu3031 2007-08-02 11:52|| 2007-08-02 11:52|| Front Page Top

#25 Well we know for sure that in the next few days we will find out that this was caused by one of two things. Bush and Global Warming. Maybe both.

The KKKos KKKiddies (well, some of 'em, anyway) are already there.

Posted by Mike 2007-08-02 11:58|| 2007-08-02 11:58|| Front Page Top

#26 I expected the Bush stuff, but I've found the Dems' politicians already at work. Started last night with the Gov's conference. Mentioned how he had heard from Speaker Nancy offering all help that the House of Reps could provide. Something just felt "strange" about that. He spoke no words of any other federal help.

As an aside, I heard before 7:10 CST, that Bush was speaking at 11:00 EST. Just before 8:00, I heard, Gov had scheduled a news conference, at 10:00 CST. Bumping the Pres I guess, is good.

Press conference this morning, both Fed Senators there. Coleman spoke, talked sensibly about money allocations, were coming, etc.

Lady Senator, after expressing condolences and thanks to responders, launched into how she had already spoken with Schumer, Reid, Patty Murray, and other senator that seeming have nothing to do with a bridge collapsing-- see a pattern here?

Coleman stood calmy, with somewhat a blank look at her, but almost like, "I can't believe what you are saying!"

You know it, it's the comparison to how Dems are reacting so fast compared to Bush's Repubs with that horrible response to Katrina. I turned the sound down till a more reasonable person appeared.

Just my thoughts on this.

Posted by Sherry">Sherry 2007-08-02 12:45|| 2007-08-02 12:45|| Front Page Top

#27 Yeah, it's all about the war. Think of all the good things we could have if we didn't spend any money on defense. There's no waste, graft, or corruption in Social Security or public housing, Immigration, public schools, public hospitals or the VA, or Health and Human Services. Bush & Bechtel. Cheney & Halliburton. Dianne Feinstein' husband and URS oops....

All fifty State DOT's do not have enough money to maintain the existing system the way they should, and there's not enough to build the additional capacity needed to relieve traffic congestion. It's been that way since the beginning of the Interstate System 50 years ago.

So, yeah, it must be Bush's fault.

Posted by Bobby 2007-08-02 12:54|| 2007-08-02 12:54|| Front Page Top

#28 not a time to be snarky at all, and it is not intended, but what are the odds of the Alaska Bridge to Nowhere funds getting diverted to Minneapolis?
the news that so far only 4 confirmed deaths at a time when the bridge was packed is good news; although the final count will not be known until all the submerged vehicles are pulled out / examined. odds are good that there will be some folks never found. God rest their souls.

Posted by USN, Ret. 2007-08-02 14:23|| 2007-08-02 14:23|| Front Page Top

#29 Tacoma was an awesome demonstration of that, wasn't it?

Rarely do you get a chance to see a major structure clearly undergo first, second and then third order harmonic vibration in such a vivid fashion.

a train moving underneath at the same time..

That's the one thing still sticking in my mind. Moving at a constant velocity with regularly spaced load packets (freight cars), long freight trains can set up some significant ground wave oscillations. I live near one of Silicon Valley's largest switchyards and occasionally my house undergoes some mild shaking. Perhaps it's just the dramatic image but the bridge pinning that train seems like more than coincidence.

The KKKos KKKiddies (well, some of 'em, anyway) are already there.

Unless these maggots are speculating about terrorism they'd better not show their faces in Minneapolis. This "troother" bullshit is getting out of control [looks Rosie's way].

Of far more importance is the high quality Emergency Response and citizen participation. The image of that school bus really gave me the heebie jeebies. Minnesotans should be proud of their fellow citizens. They certainly have my sympathies in this time of trial.

Finally, my hat's off to Rantburg. After seeing the snark in that Fark thread it was a deep pleasure to know that this board's members can rise above such infantile behavior.

Posted by Zenster">Zenster 2007-08-02 14:34|| 2007-08-02 14:34|| Front Page Top

#30 Zen -- one reporter stated over and over, folks thought the train was moving. But it wasn't. It was stationary.

One eyewitness said as she sat in her car, people raced to that bus and were literally throwing kids off the bus, someone else caught then and ran to high ground. Wonderful folks, our Midwestern friends.

Posted by Sherry">Sherry 2007-08-02 14:57|| 2007-08-02 14:57|| Front Page Top

#31 Zen -- one reporter stated over and over, folks thought the train was moving. But it wasn't. It was stationary.

Thank you for that clarification, Sherry. Still, routine exposure to sympathetic vibrations caused by trains moving in such close proximity to the bridge may have made some negative contribution.

Lastly, the scene at the schoolbus rekindles some of my lost faith in humanity.

Posted by Zenster">Zenster 2007-08-02 15:12|| 2007-08-02 15:12|| Front Page Top

#32 This is a good graphic that really makes some sense of the photos were are seeing. I couldn't get the continuity together. This does it for me, being the visual person I am.

You can even click on it, making it larger, to get the detail. It's shows the location of the landmarks, like the school bus.

Snapeshot of a Disaster - a Timeline

Posted by Sherry">Sherry 2007-08-02 15:21|| 2007-08-02 15:21|| Front Page Top

#33 Sherry thanks for the train comment. I was just looking at the photos of the train and it, at least at the time of the collapse, wasn't moving. Not to say it wasn't earlier but the photos clearly show it stationary.

Also that track has been their for decades and tremor damage can accommodate.

Also it's interesting that you pick up on Amy Klobuchar's tasteless political pandering. R Senator Coleman is pretty much useless, has been since being Saint Paul mayor and not dealing with Chief Finny and his rapist son (met the detectives on that one).

At least Coleman didn't take the political whore route like Senator Amy Klobuchar. What the hell was that mindless twit thinking?

Sorry but I've dealt with her office.

Anyways we will keep the rest of the Burgers up to steam as pertinent on the ground info comes up.

Posted by Icerigger">Icerigger 2007-08-02 16:01|| 2007-08-02 16:01|| Front Page Top

#34 Icerigger, thank you for all you have already shared. And thanks for backing me up on Senator Amy. I was sitting in my office, was streaming from Fox... and I just sat here, with month open, and you know the rest!

Our thoughts and prayers are with all of you there. Spent some time in your beautiful city throughout the years. Also, in my traveling days, I got a kick out of how many times I was crossing the Ole Miss.

Keep us posted.

Posted by Sherry">Sherry 2007-08-02 16:11|| 2007-08-02 16:11|| Front Page Top

#35 Sadly, it sounds like the number of fatalities will be climbing sharply over the next few days. Authorities have stated there are multiple vehicles submerged in the water or under heavy debris that rescuers just can not get to without placing themselves in danger. I would not be surprised to see the death toll reach 20 over the weekend.

Posted by Dar">Dar 2007-08-02 16:39|| 2007-08-02 16:39|| Front Page Top

#36 Will do Sherry. I was afraid I was the only one noticed Klobuchar's bad taste.

Dar looks like you are right. The divers right now are having trouble working on the cars. Diving visibility is 6 to 12 inches. Right now they are trying to lower the level of the river by another foot. To many currents set up by the fallen debris.

One civilian diver went down shortly after the accident. The poor boy came out pretty shaken. River rescue body recovery is not pretty.

Posted by Icerigger">Icerigger 2007-08-02 17:16|| http://coonlakebeach.com/support_mn_troops.htm]">[http://coonlakebeach.com/support_mn_troops.htm] 2007-08-02 17:16|| Front Page Top

#37 Ice, please carry the very best wishes to Minneapolans from here in Silicon Valley. I'm hoping your municipality can cobble up some sort of temporary mass transit solutions that will alleviate the traffic nightmare this is bound to cause. If you know of an online condolences guest book that we can sign, please let us know.

Posted by Zenster">Zenster 2007-08-02 20:23|| 2007-08-02 20:23|| Front Page Top

#38 I echo Zen's and Sherry's comments, Ice. My best to you and your City from Hot-lanta.

Posted by BA 2007-08-02 20:57|| 2007-08-02 20:57|| Front Page Top

#39 On CBS News they made sure that they mentioned the GOP and their upcoming convention in the twin cities.

Posted by Cyber Sarge 2007-08-02 21:25|| 2007-08-02 21:25|| Front Page Top

#40 Hi-rez photos by Minnesota Daily (U 0f M student paper) here

More "before" pictures (WCCO) here

Posted by Old Grouch 2007-08-02 22:34|| oldgrouch.mee.nu]">[oldgrouch.mee.nu] 2007-08-02 22:34|| Front Page Top

#41 Magnitude 6.0-7.0plus quakes all over the PACRIM, from Vanuatu to Siberia and Alaska?, plus collapsing bridges in Minnesota + California. *Okay, I'll bite, besides large purple-colored stellar explosions whose the marketing-promo company that forgot the fiery asteroid graphic on the CARS PLUS commercials, D *** ng it?

Posted by JosephMendiola 2007-08-02 23:13|| 2007-08-02 23:13|| Front Page Top

#42 Thanks folks. Nothing like living in America. We truly appreciate all your thoughts and prayers.

Posted by Icerigger">Icerigger 2007-08-02 23:22|| http://coonlakebeach.com/support_mn_troops.htm]">[http://coonlakebeach.com/support_mn_troops.htm] 2007-08-02 23:22|| Front Page Top

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