Wednesday, August 23, 2017

I-35W over Mississippi River in Minneapolis, MN


(Update: RoadTraffic-Technology article)

John Weeks posted
Ten years ago today, my obscure little hobby of hunting down, photographing, and writing about bridges intersected with a major American news story when the unnamed I-35W bridge over the Mississippi River collapsed during the height of rush hour on August 1, 2007.
I vividly recall the first time I saw the underside of this structure. My impression was that there wasn't really that much holding that puppy up for being such a major highway crossing. And like the World Trade Center and the Space Shuttle, it proved to be a fleetingly temporary monument to the era when human engineering technology was invincible.
Another lesson from the affair is that people, especially when acting in groups, tend to not take action on problems until they become an unavoidable crisis. Those concerned about global climate change should take note of this and realize that nothing significant is likely to be done until there is some unavoidable crisis like Washington DC or New York City flooding from rising sea levels or a billion people dying of heatstroke. Folks need to plan according to group mentality rather than to what makes sense.
Here is a link to the 3rd and final edition to my E-book on the bridge disaster:

Birds-Eye View

The bridge has ten traffic lanes.

Daniel Rudelt posted two photos with the comment: "My first bridge project. I-35 W Minnesota 2008."
Bob Miller Derik Wolfe that was Amix’s 4600 series 3 ringer series 2 s/n 1039 with #35 boom.

Kevin Copple commented on Daniel's post
There were two 4600 ringers on that job. One was Lampsons set up on bohemian flats. And that is the one I ran. The red one on the barge I think came in from somewhere in Washington state. It had a fixed cab and two separate motors. Andy Garcia was the operator.

Kevin Copple posted
Lampson 4600 ringer at lay down yard for segments on I35 bridge rebuild 2006-07. Green iron in back ground is from the collapsed bridge and where NTSB did some of their investigation.

Stacks Edwards posted
Pretty sure that's from the I35 bridge collapse in Minneapolis a few years back.
[The comments contain links to four videos about the collapse.]
I knew a couple State of Minnesota bridge inspectors. This was a real wake-up call. Their standard procedure was to judge the bridge’s current condition against its when-built condition. No one questioned the original design. In the case of the 35W bridge in Minneapolis, cantilevered lanes had been added, and a re-decking project was in progress - with all construction materials stored on the bridge itself for lack of space elsewhere. According to the original engineering, it was still well within its design strength. However, the original engineering was flawed. The gusset plates connecting the various members were 1/2” thick, when they should have been double that. Bridge inspections had noted some of those 1/2” gussets as having 1” deflection. But the loss of cross-section from corrosion was within limits, so no problem. It’s ultimate failure was a chain reaction that started when one very overloaded gusset plate gave up.
Eric Hopp
 What did this bridge in was several factors. It was originally built with 6 lanes in 1967. It was widened to 8 lanes over time. As you mentioned, they were cantilevered in. It originally had a road base that was 6.5 inches thick of reinforced concrete. When the roadway was widened to 8 lanes, the road base was increased to 8 inches thick. The construction equipment and materials that were stored on the bridge added an additional 300 or so tons of weight on the bridge. Too thin of gusset plates, and frozen roller expansion bearings on the mounting feet all contributed to the failure of the bridge. 

Every one of my postings for a bridge in the Illinois (wwIll label) or Mississippi (wwMiss label) should have a link to John's work at the top of the post. He started taking bridge pictures early enough that the old truss bridges along the Illinois River were still standing. By the time I started taking pictures (2014), they had been replaced by steel girder bridges.

Please access John's link to more information on the old and new bridges, and the disaster.

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