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re: Francis Scott Key Bridge in Baltimore has collapsed - container ship wrecked into it
Posted on 3/26/24 at 3:44 pm to Obtuse1
Posted on 3/26/24 at 3:44 pm to Obtuse1
I just rewatched the GIF a little more closely and while I think it would have failed because of the loss of tension on the bottom chord I now think the failure occurred before that could happen. If you watch right before the upper and lower chords fail to the left of the right piling the upper chord actually goes into tension and the lower chord goes into compression (opposite of their designed states) and this shift lifts the portion of the span right of the piling up. Depending on the type of bearing used where the right portion of the truss span meets the concrete road bridge it either lifted off or stayed attached but either way excessive lateral torsional buckling in the lower chord and tensile failure in the upper chord would occur.
Posted on 3/26/24 at 3:49 pm to Obtuse1
quote:
I just rewatched the GIF a little more closely and while I think it would have failed because of the loss of tension on the bottom chord I now think the failure occurred before that could happen. If you watch right before the upper and lower chords fail to the left of the right piling the upper chord actually goes into tension and the lower chord goes into compression (opposite of their designed states) and this shift lifts the portion of the span right of the piling up. Depending on the type of bearing used where the right portion of the truss span meets the concrete road bridge it either lifted off or stayed attached but either way excessive lateral torsional buckling in the lower chord and tensile failure in the upper chord would occur.
I just gotta say... I don't know what any of that means... but it sounds darn impressive.
Posted on 3/26/24 at 4:22 pm to Obtuse1
Yeah, I see what you mean. It's like a seesaw with an uneven load where it lifts off the bearing on the right hand side(next to concrete roadway) only to crash back down.
I would make a bet that right hand side bearing wasn't holding a large % of the overall load with most of it going to the two supports under the two edges of the main span.
I will be very interested in the report(s) once it comes out.
I would make a bet that right hand side bearing wasn't holding a large % of the overall load with most of it going to the two supports under the two edges of the main span.
I will be very interested in the report(s) once it comes out.
Posted on 3/26/24 at 5:40 pm to Obtuse1
Failure was a given once the interior support of the 3-span continuous truss was obliterated. The span arrangement was 700-1200-700 feet. No way it could self-support 1900 ft. Everything else is just details. As you said before, it's all connected, so once the 1900 feet is going down, it's taking the rest with it.
The Dali had a dead weight tonnage of 116,000 and some change. No bridge on earth is designed for impact of that weight, so the design failure lies in not providing a dolphin system to protect piers straddling the navigable waterways.
The Dali had a dead weight tonnage of 116,000 and some change. No bridge on earth is designed for impact of that weight, so the design failure lies in not providing a dolphin system to protect piers straddling the navigable waterways.
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