Here is the breaking news from Minneapolis.
Obviously first thoughts are inadequate concrete but the bridge has been up for a long time and this is Minnesota where government is squeaky clean and concrete core density samples can’t be fudged or bribed away.
Fatigue cracks leading to catastrophic failure usually give some warning that is detectable during inspections.
Sometimes its a problem with inadequate ability to test that results in an administrative designation that is similar to viewing every tropical storm as if it were a hurricane.
As to the actual event, it seems the response was quite good. Some specialized dive teams probably should have been summoned sooner. Establishment of the on-scene ambulance assembly point/Triage Area seems to have been ‘okay’.
Trouble points seem to have been: lack of dispatching a cell-phone trailer to give added capacity in the area, lack of media alerts to relatives (please meet schoolchildren from the bus at point X, not at the disaster site), slow start to license plate readings on sunken vehicles.
Does anyone know if ‘Dive Shops’ of any sort where available and utilized? Scuba equipment, Scuba personnel?
Getting 100 percent of the fire department there is fine and dandy, but how many of them were equipped with diving gear of any sort?
Were lights and air bottles on usual apparatus of any use in this incident? I’m sure whatever dive teams and swift water rescue teams they have would have been overwhelmed given the number of victims and the short time period available for rescue.
Possible contributing factors in the collapse are the road construction activities taking place on the bridge, water erosion of the north piers which were partially toppled in the collapse, steel substructure defects especially near the south piers which toppled sideways in a scissors motion, problems with the bridge de-icing system, thermal heating and cooling of the structure and recent heavy rains and flooding on the I-35W highway. Also, a train that was under the bridge at the time may have been moving, which could have added more vibration.
I haven’t heard anything yet that would seem to even remotely account for a massive collapse. Based on what little I know about this it seems to me there was probably a huge structural defect in the bridge and the other contributing factors were minor ones. But I hope they don’t use this to suggest our bridges are unsafe, which is not a logical conclusion. Bridges like this almost *never* fail while we lose 100+ people in traffic accidents every single day.
I think water erosion of the north pier supports is unlikely as the surveillance camera clearly shows solely vertical displacement without any lateral movement at all.
Well, they seem to be looking at several design flaws involving gussett plates providing an inadequate margin of error. Larger, thicker and bolted rather than riveted plates might be better. And ofcourse rounded plates might be better too, but the bridge did stand for forty years, so that 100 tons of construction material probably played a critical role.
Crack concealing and corrosive. Pigeon dung!!
Just a question. I’m intending to make some calculations and I need rather reliable data on the average daily amount of dung produced per urban pigeon. Google has not helped yet. Anyone can help me? Thanks a lot.
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