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A lot.
(lemm.ee)
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this post was submitted on 26 Mar 2024
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The bridge you linked likely wouldn't have been able to withstand the collision of this ship at one of its pillars. Assuming that the numbers are for a fully loaded ship at 120,000 DWT at 7 knots, it could only take about 90% of the momentum maximum that the Dali had (116,000 DWT at 8 knots) at once.
For my American friends that's about 27.56 fully loaded F-35Cs going max speed (Mach 1.6) at the same spot at the same time. Or 312 M1A2 Abrams.
I'd have to look at shipping logs and whatnot to say whether that specific protection system is sufficiently rated for the traffic going under that bridge.
And I mean, come on, the fact that a completely random protection system I pulled up can "only" withstand 90% of the impact we're interested in is not a fucking gotcha. It's evidence that this kind of system is completely reasonable for this kind of impact. Engineering, physics, and numbers don't work this way, but shit, scale it by 20%. Tada.
Ok but that relies on them knowing that they'd be hit by this exact size ship in the future. Hindsight is 20/20. The Delaware Memorial Bridge is within 10 ft of clearance and is about 2,000 ft longer than the Baltimore bridge, and both would take vessels of this size, why would they just randomly decide to scale the same kind of system by the number required to stop the bridge from collapsing from being hit in this specific scenario (or more) for the Baltimore bridge?
Also what's with the "only"? If it doesn't work, it doesn't work. It'd hypothetically still collapse the bridge even if the system were effective for ships 90% of this ship's weight.
Failure in an engineered system is rarely a binary condition, though the FSC bridge is a type that fails catastrophically once you fully remove that pillar. But, recognize that you can damage the pillar without removing it.
Anyway, the protection system necessary for the bridge isn't just a factor of the design of the bridge. Like I referenced in the previous comment, it's dependent on the traffic going under. The world's biggest bridge would never need a collision protection system if the boats going under were small enough.
This isn't a hindsight problem. Bridges have known traffic under them and should be rated to withstand impacts. It's extremely easy to predict what the largest possible impact is for a particular bridge and plan accordingly. Do you think this boat was lost? This particular boat probably passed under that bridge a hundred or more times before it malfunctioned and hit it.