Interstate 35W Bridge in Minnesota Collapses

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Interstate 35W Bridge in Minnesota Collapses

Postby Shapley » Thu Aug 02, 2007 8:49 am

Bridge Collapse

My prayers are with the victims and the rescue/recovery workers. A sad day.
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Postby Trumpetmaster » Thu Aug 02, 2007 9:01 am

Terrible terrible
Very sad...
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Postby piqaboo » Thu Aug 02, 2007 11:39 am

So sorry for all those involved in the collapse. :(

The hindsight will be 20-20 after this.
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Postby barfle » Thu Aug 02, 2007 12:47 pm

It's going to be interesting who gets blamed for it, especially since it was being "repaired" when it fell.
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Postby jamiebk » Thu Aug 02, 2007 2:41 pm

Though not in the construction indusrty, I have a lot to do with it. My understanding is that the repairs were very superficial....surfact patching etc. Nothing structural was being touched. This sounds like structural failure. Time will tell.
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Postby Selma in Sandy Eggo » Thu Aug 02, 2007 2:51 pm

From the pictures, it was indeed a major structural failure. If the text of the news articles is to be trusted, the bridge was designed with a long central span to avoid pylons in the river - and the pictures show multiple shorter slabs of road that appear to have separated along straight lines. It looks a little like the pieces of the Oakland freeway that collapsed in the quake.

As a first suspicion, I'd want to check whether the long span was composed of attached smaller slabs, and if so whether the attachment hardware had suffered fatigue over time? Of course, this is all speculation until we get some forensic engineers in there.

Right now, it looks like body recovery and clearing the river are the first priority. It's a disaster, all right, and I hope it can be figured out in time to prevent future problems with similar structures.

I still drive the San Diego bay bridge with perfect unconcern, twice each day. I love the view. I hope the hardware's OK...
>^..^<
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Postby Trumpetmaster » Thu Aug 02, 2007 2:53 pm

Don't the engineers check for stress, wear and tear over time?
It just doesn't make sense.....
Someone has a lot of explaining to do..........
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Postby BigJon@Work » Thu Aug 02, 2007 2:57 pm

Sure they do. But it is the insidious corrosion that often gets you in the end. Have you ever seen a rusty pipe sticking out of the ground? Unless you go up and wiggle it, you’ll never know if it is fully supported by the ground or it will come off in your hand.
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Postby Selma in Sandy Eggo » Thu Aug 02, 2007 3:08 pm

Metal fatigue is one of the huge concerns with our aircraft, and it's sneaky in that nothing obvious shows until the part fails. Temperature variations, vibration, age, load, the nature of the alloy that the part was originally made from - all these things contribute to the crystallization of the metal. Intergranular corrosion can also be invisible until the part breaks and you can put the broken edge under a magnifier or microscope.

Given the pictures on the news websites, I'm amazed that so many people managed to ride the thing down and still got out alive and walking. At rush hour, no less!
>^..^<
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Postby Shapley » Thu Aug 02, 2007 3:17 pm

An engineer interviewed on CNN last night said that the majority of bridge failures occur due to undermining of the support piers. A very minor shift in position can result in a loss of structural stability. This morning there was some mention of structural analysis that reported that the structure lacked redundancy features that are commonly required in bridges designed in the past few decades. According to MSNBC, the bridge is about 40 years old. That would put it one of the earliest in the interstate highway system, unless it predates the interstate highway that runs over it. I can't imagine that an eight-lane bridge was built in 1967, so I would expect that it had to be modified to handle the increased volume in traffic at some point, but I've not found mention of that on the web. There was a photo on CNN earlier that showed it under construction, but I can't find the photo now.

In any case, it is a tragedy.
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Postby barfle » Thu Aug 02, 2007 4:29 pm

Trumpetmaster wrote:Don't the engineers check for stress, wear and tear over time?
It just doesn't make sense.....
Someone has a lot of explaining to do..........

While I'm not making excuses for anyone, this bridge is pretty old (built about the time I graduated from high school), and was built on the Mississippi River, which is notorious for eroding its banks and anything that might be between them.

I don't know what the parameters for inspection of bridges might be, and I'm not about to second guess the guys with a career of experience. Clearly this is one of those situations where the status quo will no longer apply.

Maybe it's just that I'm paying more attention, but I can recall a handful of bridges collapsing with deadly results in recent years. There was the Amtrak bridge in Alabama, I-10 during the Northridge earthquake, the Embarcadero Freeway and Cyporess viaduct collapse in San Francisco, and that tanker fire in San Francisco that caused a ramp to collapse.
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Postby jamiebk » Thu Aug 02, 2007 4:54 pm

Also the Sunshine Skyway bridge in Tampa Bay area, athough that was because it was hit by a ship/barge etc.
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Postby dai bread » Thu Aug 02, 2007 5:16 pm

This made our TV news last night and our newspapers this morning. It seems a lot of people were very lucky, and it's just as well traffic was reduced to 2 lanes because of resurfacing. All 8 lanes of commuter traffic going into the river doesn't bear thinking about.

I'm surprised at the number of bridges that apparently have collapsed in the U.S. in recent years. I thought American engineering was better than that. I'm also surprised you call a 40-y-o bridge "old". Most or ours are much older than that, and the one across Auckland's harbour was opened in 1959.
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Postby Shapley » Fri Aug 03, 2007 8:27 am

Dai,

I don't have the statistics, but I suspect that America has more bridges than most anywhere else in the world. I do agree, however, that a 40-year-old bridge is not that old. The Railroad bridge over the Mississippi River near my home was opened in 1905, and continues to carry trains much heavier than the steam-powered trains it was designed for.

The Interestate Highway system was designed by President Eisenhower in the mid 1950s. My comment was that a bridge built in the '60s would be one of the oldest in the system, and therefore would probably have been designed to different standards than the bridges currently in the system. In my opinion, the bridges built by the government for the Interstate Highway system are designed lighter and more cheaply than bridges built prior to them. I realize there are new technologies and all that jazz, but my own unqualified observations lead me to believe that they have a lesser safety factor than 'traditional' bridges.

V/R
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Postby Shapley » Fri Aug 03, 2007 9:29 am

Famed Brroklyn Bridge Fails Latest Inspection

2,027 bridges in New York City alone! Of course, that would include everything from the concrete-slab-over-a-ditch type all the way through to the majestic Brooklyn Bridge.
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Postby jamiebk » Fri Aug 03, 2007 9:37 am

Shapley wrote:Famed Brroklyn Bridge Fails Latest Inspection

2,027 bridges in New York City alone! Of course, that would include everything from the concrete-slab-over-a-ditch type all the way through to the majestic Brooklyn Bridge.


Our DOT (CalTrans) chief spoke last night and assured us that every bridge in CA was absolutely safe and that we have an excellent bridge program. I find that hard to believe considering that we are 46th in the country for highway quality, in spite of having the 3rd largest budget in the country (what's wrong with this picture??).

In any event, he mentioned that there were some 12,000 bridges in CA. VA has about 13500. The USA has about 160,000 and there was one report that said 70,000 of them were "deficient" (whatever that means)
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Postby Selma in Sandy Eggo » Fri Aug 03, 2007 10:30 am

There's been a list of "deficient" bridges on one of the news websites - I don't recall which one and I'm too lazy to go hunt it up again. The San Francisco - Oakland Bay Bridge was on it. Twice.
>^..^<
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Postby jamiebk » Fri Aug 03, 2007 11:50 am

Selma in Sandy Eggo wrote:There's been a list of "deficient" bridges on one of the news websites - I don't recall which one and I'm too lazy to go hunt it up again. The San Francisco - Oakland Bay Bridge was on it. Twice.


And that is exactly why we are spending 1.6 billion dollars to have a new one built!
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Postby BigJon@Work » Fri Aug 03, 2007 12:43 pm

Shapley wrote: I do agree, however, that a 40-year-old bridge is not that old. The Railroad bridge over the Mississippi River near my home was opened in 1905, and continues to carry trains much heavier than the steam-powered trains it was designed for.

The Interestate Highway system was designed by President Eisenhower in the mid 1950s. My comment was that a bridge built in the '60s would be one of the oldest in the system, and therefore would probably have been designed to different standards than the bridges currently in the system. In my opinion, the bridges built by the government for the Interstate Highway system are designed lighter and more cheaply than bridges built prior to them. I realize there are new technologies and all that jazz, but my own unqualified observations lead me to believe that they have a lesser safety factor than 'traditional' bridges.


There was a "dip" in bridge safety factors in the 50s and 60s. With the start of the 70s, new bridge codes required redundancies to prevent all-at-once failures like we witnessed in Minneapolis. Did you see the security camera footage of the bridge going down? It was a house of cards once one span collapsed. The early 1900s bridges you still see, have massively redundant members so that no individual element failure endangers the entire bridge.

We can discuss the details of the engineering design processes for this SF dip if you wish, but it will be a somewhat technical conversation. In summary, it was not malicious, but it was a result of what were known as the best engineering practices at the time and the limitations of the tools and information available to the designers.
Last edited by BigJon@Work on Fri Aug 03, 2007 1:10 pm, edited 1 time in total.
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Postby jamiebk » Fri Aug 03, 2007 12:47 pm

It's such a tragedy....I am thankful that not more were killed. Its a miracle really
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