The NTSB is saying they didn’t find anything significant on the south side of the bridge, and are now focusing on the north side to find the cause of the collapse. How does that figure into your figurings? I’m not an engineer, so I only understand about half of your notes, LOL!
Yes there are photos of a train on tracks that run under the bridge, partially crushed by the bridge.
>>I haven’t been able to determib\ne if that was a moving train or spotted cars. The railroad people I know are debating if the line under the southern approaches was active at all.<<
In 1967, Northern Pacific ran under a south approach span, the Great Northern ran under the north side approach span (where the RR cars are today). Neither was a heavy freight line, used mainly for passenger trains to access the Great Northern Station (at Hennepin and the river).
The RR line clearance was the reason the bridge was so high. It had to have a fair bit of clearance over the river channel (30’, 40’?), and if it went under the RR tracks it wouldn’t have enough river clearance. So it ramped up over the RR tracks at both ends, making it extremely high over the river gorge.
Today, the bridges used by both RR lines are ped bridges, the tracks on the south have been abandoned, and the tracks on the north are just a spur line to the grain elevators. Used for storage. If there was a train in motion there at the time of collapse, it was probably switching cars at about 5 mph, with a 10 mph speed limit.
Since the collapse started on the south cantilever platform or in the middle of the span, it’s unlikely a train under a north approach span had anything to do with it.
Abigail
Adams wrote:
The NTSB is saying they didn’t find anything significant on the south side of the bridge, and are now
focusing on the north side to find the cause of the collapse. How does that figure into your figurings? I’m
not an engineer, so I only understand about half of your notes, LOL!
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I’m guessing there’s one guy saying this, to reporters dogging him, and who may or may not be closely working with the NTSB.
It might also be a case where there’s nothing obvious on top of a fair sized rubble pile, so they want a quick look atop the northern rubble piles before they start digging. You know, for something real obvious, like a splintered wooden crate with the letters “ACME” on the side and curly wires leading to a plunger.
NTSB is pretty careful and tedious in putting together a polished, finished, report.
They haven’t really started digging yet, eyeball estimate says at least three quarters of the superstructure is under heavy rubble, and at least a third of that is still underwater.
From the north shore of the river, all the way to the north end of the bridge, stood there several seconds after the rest fell in the water and the splash subsided.
It’s very unnlikely that something failed on the north side, but caused the south side to drop first.
If you go back to the first set of force resolution diagrams, to the panel for assymetric loads, you can see that weights placed near one end load that end’s support structures more so than the far end. That’s a pretty basic principle of bridge design. Failures on the north end would shift loads to north end supports first, and they’d have to resist those loads, and at the same time, shed them to the south end to make the south end fall first.
Heads or tails, something on the south end failed first.
If the flipped coin stands on edge, the trigger event happened on the north end.