When all is said and done, it will be this....
Bumper to bumper traffic due to construction maximized the amount of traffic vehicles (weight) on the bridge.
Construction crews and their personal vehicles added more weight.
They were poring concrete and had numerous large concrete trucks (overly heavy loads concentrated in small areas).
They had many smaller liquid concrete vehicles moving and pouring concrete (bobcat size).
During this period, a train was passing by underneath, which caused a flexing (depression) of the ground support for the bridge, causing the girders to drop and flex.
This bridge has no center piers buried in the river bed like many others. It was supported only by the ends, and they couldn’t take all those forces at once.
All the high paid engineers in the world can come together and mindstorm this, and I’ll bet my last dollar ($4.00 actually) that this is the conclusion, if they tell the truth.
Someone missed out on pre-analysis of all the possible factors when they decided to allow heavier than normal concrete pouring vehicles to be on that bridge during bumper to bumper rush hour. They should have poured at night.
So, it depends on whose behind could get burnt, as to the ‘truth’ being told.
Look for a scapegoat to be picked, soon.
Right after MN. DOT has contacted their lawyers.
Bumper to bumper traffic due to construction maximized the amount of traffic vehicles (weight) on the bridge.
Never ever had bumper to bumper traffic before? Weren't lanes closed, reducing the weight?
Construction crews and their personal vehicles added more weight.
Yeah, those fat contractors...
They were poring concrete and had numerous large concrete trucks (overly heavy loads concentrated in small areas).
Didn't see one concrete truck in any of the photos or videos.
They had many smaller liquid concrete vehicles moving and pouring concrete (bobcat size).
Those fat contractors driving Bobcats.
During this period, a train was passing by underneath, which caused a flexing (depression) of the ground support for the bridge, causing the girders to drop and flex.
Don't know if the train was passing below at the time, but the tracks are not below the steel span. The tracks are below the concrete structure portion. See here
This bridge has no center piers buried in the river bed like many others. It was supported only by the ends, and they couldn’t take all those forces at once.
Yeah, right. They designed the bridge with center spans but forgot to install them.
Another good hypothesis.
I dont think it had anything to do with pouring new concrete or having rush hour traffic.
The bridge is most certainly designed to handle a full liveload capacity way more than if the entire bridge was a parking lot.
I bet there were some unidentified cracks in the steel and that the vibration work from removing the concrete top , and scoring new concrete led to a failure of one steel member in a critical location over the river span. The There is very little redundancy in that truss span design. As the main span dropped, it pulled down the spans over land.
I agree your analysis sounds reasonable.
I just moved to Minneapolis, and was first out househunting, then couldn't get internet access at the hotel.
I used to drive over that bridge all the time when I attended the U.
Prayers UP!
