Baltimore's Key Bridge struck by cargo ship, collapses • Hacker News Board

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#391

Post by G0dchi1d » Tue, Mar 26, 2024, 2:18 PM UTC

xoa wrote: post #296

dathinab wrote: post #202

Earlier quoted context omitted.

At least in the links with the video now you can see that the container ship directly hits one of the two main (and in the central area only) pillars completely collapsing it. No matter(1) the engineering there is no pretty much way to not lose the whole large middle area and left area leading to the destroyed pillar in that situation. Such a collapse crates so much force (tension vibrations etc.) so that the collaps…

Just to put some numbers on this: The MV Dali (IMO#9697428) is a little over 95000 GT, or ballpark-ish probably around 114000 tons loaded (and it seems to have been loaded, which would make sense on departure). If it was going even 5kn (2.6 m/s) that'd be about 300 million newton-seconds, or about 3.3 times the momentum of a large jumbo jet like a 747 shortly at cruising speed (around 560 mph). It'd still have the sa…

Thank you, I've been trying to get a ballpark on the weight, appreciated.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#392

Post by hermannj314 » Tue, Mar 26, 2024, 2:18 PM UTC

ericyd wrote: post #339

IG_Semmelweiss wrote: post #206

This port has a very large volume of car shipping. The ro-ro shipping costs are expected to go much higher as a result of this accident. If you were in the market for a car in the US east coast , act now before prices go up!

A bunch of people die and this is your response?

There is no reason to expect someone to have a rational approach to transportation-related fatality in any direction.

Drunk drivers will kill approximately 40 people today in America. Most people won't care about that or demand a congressional response or blame politicians, etc., so it is no more heartless to not care about a few dead people on a bridge either.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#393

Post by tomatotomato37 » Tue, Mar 26, 2024, 2:19 PM UTC

WarOnPrivacy wrote: post #344

Reason077 wrote: post #279

Earlier quoted context omitted.

When Florida's Sunshine Skyway bridge was partly collapsed by a similar incident in 1980, the replacement bridge was built with a series of "structural dolphins" and concrete barriers to protect against ship strikes. You can see them in the image linked below: https://en.wikipedia.org/wiki/Sunshine_Skyway_Bridge#/media/...

> the replacement bridge was built with a series of "structural dolphins" and concrete barriers to protect against ship strikes. Given how the Skyway collapse is burned into the local consciousness, I suspect some of the benefit comes from their visibility. I truly don't know how the dolphins would fair against a massive ship strike but I can imagine them doing their job. (ship passing): https://pbs.twimg.com/media/F…

I would also add those barriers seem to depend on the ship staying intact during collision. Given the immense inertia involved on the bigger ships I could just as easily see a scenario where the barrier ends up ripping through the lower hull while the rest of the ship continues forward.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#394

Post by patrickwalton » Tue, Mar 26, 2024, 2:20 PM UTC

TaylorAlexander wrote: post #66

Somehow I find it surprising how completely the bridge collapsed after the damage. I understand that a container ship collision is serious, but you could imagine a scenarios where the bridge slumps or buckles but doesn’t just disintegrate like that. It’s surprising that ships capable of doing this damage were probably regularly driving past it, and its safety as a thoroughfare depended entirely on those collisions no…

In many structures, catastrophic failures are far more likely than graceful failures.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#395

Post by btbuildem » Tue, Mar 26, 2024, 2:20 PM UTC

tokai wrote: post #377

btbuildem wrote: post #338

Earlier quoted context omitted.

If you think about this for a minute, you'll realize that what you're asking for is pretty much impossible. What would these artificial islands be made of? Sand, gravel, concrete rubble? This is a river, the constant current of the water erodes anything that resists it by staying in place. Piling up enough material to resist erosion and create a meaningful obstacle to 70000 tonnes in motion, that would significantly…

I have thought about it for hours by now, and read literature on the matter. It is definitely possible to build berms that protects a bridge from catastrophic failure in case of a ship collision, and it is widely done during modern bridge construction. Please be less sure of yourself when you clearly don't have any actual knowledge on the subject.

I'd love to see a few examples, since you're so versed on the subject. I'm not a civil engineer by any means, but I imagine the people who designed and built that bridge knew what they were doing. There are likely limitations imposed by the site bathymetry and other things we don't know about.

You can get a good look at the aftermath here: https://www.youtube.com/watch?v=WssFXRzRVLU

I'll be interesting to see how they choose to rebuild it.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#396

Post by bmelton » Tue, Mar 26, 2024, 2:21 PM UTC

mannykannot wrote: post #283

kamaal wrote: post #263

Earlier quoted context omitted.

>>But I guess I thought that maybe there was... typically some kind of earthen buffer around the pillar to prevent such an impact? It does look reasonable to have such a buffer. But any preventive measure will have limits as what and how serious an impact it can deal with. In this case the ship this massive is something that is carrying ridiculous inertia, and its highly unlikely even a buffer could stop such an impa…

> But any preventive measure will have limits as what and how serious an impact it can deal with. The recent grounding of a large container ship in Baltimore's harbor channel demonstrates that a sufficiently massive berm will stop any ship. What's needed is the will to do something about low-probability but catastrophic events (though large-ship collisions, groundings and fortuitously harmless steering failures are f…

Starting from xoa's calculations above, assuming you can pack a berm with well-compacted soil enough that it can absorb 1,000 joules per cubic meter, you'd need a buffer of something like 10 meters surrounding each piling with 3 meters of depth to keep it safe from this kind of impact. That's 10 meters in every direction from the center of the support -- let's assume the support has a thickness of 0 meters for the sake of the math, and acknowledging that the gaps between structural supports on the bridge is approximately 30 meters -- the only way to protect it with earth is to make the bridge impassable by water. Of course, this would protect it from ship strikes.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#397

Post by boringg » Tue, Mar 26, 2024, 2:21 PM UTC

This is a tragedy for those involved.

My rough calculus points that the amount of force of this collision is on par with a large scale natural disaster. Everyone being surprised at the bridge collapsing needs to reconcile with the amount of force that struck the bridge - it is a truly significant amount of Newtons that hit the bridge. More than a train going from full speed to a full stop. Unbelievable amount of force.

I am also a bit surprised at how many people don't grasp this or grasp engineering, magnitude of forces and design principles.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#398

Post by toss1 » Tue, Mar 26, 2024, 2:22 PM UTC

rpeden wrote: post #153

armchairdweller wrote: post #133

Earlier quoted context omitted.

Thanks! So why are huge—ass container ships allowed to navigate underneath fragile public bridges with single points of failure? The not unlikely worst case is that the ship is out of control for some reason…

Because the Port of Baltimore is a very major port, and not allowing ships under it really isn't an option. Vertical clearance for ship traffic might have been the reason this kind of bridge was built in the first place. Otherwise, something lower and more causeway-like might have been sufficient.

>>Because the Port of Baltimore is a very major port, and not allowing ships under it really isn't an option.

It is now a very large port that is completely closed off from the sea.

And two sides of the city no longer linked

The damage from this accident is only beginning.

Even if loss of control of a large container ship was considered in the design of the city, port, and that particular bridge, ships were not even close to the order of magnitude of mass of today's ships.

And, it lost power at almost exactly the worst moment. What are the odds?

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#399

Post by swader999 » Tue, Mar 26, 2024, 2:24 PM UTC

boringg wrote: post #397

This is a tragedy for those involved. My rough calculus points that the amount of force of this collision is on par with a large scale natural disaster. Everyone being surprised at the bridge collapsing needs to reconcile with the amount of force that struck the bridge - it is a truly significant amount of Newtons that hit the bridge. More than a train going from full speed to a full stop. Unbelievable amount of forc…

And many here have engineer in their job title.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#400

Post by [deleted] » Tue, Mar 26, 2024, 2:25 PM UTC

cool_dude85 wrote: post #166

TaylorAlexander wrote: post #66

Somehow I find it surprising how completely the bridge collapsed after the damage. I understand that a container ship collision is serious, but you could imagine a scenarios where the bridge slumps or buckles but doesn’t just disintegrate like that. It’s surprising that ships capable of doing this damage were probably regularly driving past it, and its safety as a thoroughfare depended entirely on those collisions no…

The Mathews Bridge in Jacksonville was clipped by a container ship a few years back and did not collapse. Despite being almost 75 years old, they fixed it up and it opened back up after a year or two. The difference is that the boat did not hit a pylon.

[deleted]