88planoAg said:
Wrighty said:
aggiehawg said:
The Mississippi River reopened to vessel traffic near Memphis on Friday, the U.S. Coast Guard said, ending a shutdown of a part of the waterway that disrupted shipments of oil and corn and caused a backlog of more than 1,000 barges.
I imagine they opened it because of huge business and political pressure, not because it was deemed safe. I'm sure there are technical people at the DOTs that are quite stressed out right now, and I would bet that river traffic is closed down again within days.
I expect they'll close it again soon, and patch on some "emergency repairs" (scab on some side plates and weld it up) that will preclude a catastrophic collapse, and then safely allow river traffic again, while they study it and develop permanent solution.
If there is no traffic on the bridge, how unsafe is it to travel under? I'm not being snarky, just have no idea.
With no traffic on it, you're right the bridge is not seeing its max design loads. However, from its own self weight I'd assume the bridge is still sitting at some reasonably high percentage of that design load. I dont know but lets call it 60%? I think this part of the equation is easy to define and understand for the appropriate engineers.
I think the hard part is that the bridge is reacting to the self weight loads differently than it was designed for. While the overall weight/load on the bridge is reduced, its possible that the new load path puts some locally higher loads somewhere that it wasn't planned for (probably the "sister beam" on the other side of the bridge that is taking most of the tension now?). So I imagine the engineers will need to study quite carefully the new load path, and whether any connections or beams are seeing too high a load given the new load path.
Generally, I'd be surprised if this level of detailed review by a responsible engineer has taken place this quickly, and is complete to the point that an engineer has signed off that this is safe. Instead of that, I'd guess that this decision was made by someone who's not responsible technically, but has made their own judgement, and that decision may be revisited as the engineers have more input and everyone starts clarifying whos responsible and liable etc. just me guessing here. I dont envy the responsible people here.
