Live data from Hacker News

Baltimore's Key Bridge struck by cargo ship, collapses

wbaltv.com

991–1000 of 1001 posts

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

#991

Earlier quoted context omitted.

The video is surreal, it looks like it barely bumps the bridge and 2 seconds later the entire thing is gone. I don't know what I was expecting, the bridge just looked extremely fragile, makes me wonder what other bridges are at risk of an event like this.

When you play about with game engines long enough, you start to realise that momentum is the key metric to track rather than speed. Especially in water magnitude can be very deceiving but to give some quick math, this vessel had a momentum at impact of about 154,000,000kg⋅m/s. For a car to have equivalent momentum it'd have hit the bridge at 156,580 mph. Humans are just less adept at appreciating mass vs velocity.

Spot on.

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

#993

Earlier quoted context omitted.

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 the…

There are real world examples of what it would look like, they're called "dolphins": https://en.wikipedia.org/wiki/Dolphin_(structure)#/media/Fil ... "The new bridge is protected by 36 dolphins: four large dolphins protecting the two main pylons supporting the cable-stayed main span plus 32 smaller dolphins protecting bridge piers for 1⁄4 mi (1⁄2 km) to either side of the main span"

See my response to the other copy of your comment above

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

#994

Youtube tracking analysis from a knowledgeable mariner. He says that at about 1:24 AM the ship loses power (from video feed) while traveling 8.5 knots. at 1:25.30 power is restored. at 12:25.59 the ship shows smoke. The ship has already drifted in the channel. It is believed that at this time the ship applied full reverse power as evidenced by the black smoke. (My analysis: the ship drifted but hasn't turned in the c…

How common are power outages on ships? I get that the captain might not have responded to it correctly but that seems like a thing that shouldn't happen, at least in my completely uneducated opinion.

The American courts should hit Maersk really really hard financially and get them to foot the bill for all losses of the bridge collapse. Shipping companies should not be driving vessels of these huge tonnages with such poor levels of redundancy and poor levels of manning.

It is insane for a 100,000 tonne vessel, that takes so long to stop due to its incredible inertia, that can find itself many thousands of miles from land, to rely on one engine, one gearbox, one shaft and one rudder; without sufficient secondary and tertiary back-up systems. Why was there no battery back-up, or motor on the shaft? Surely the bow thrusters should have a battery back-up to stop such a lurch to starboard.

How can all of the generation and all electrical busbars fail at once? Even if the fuel was bad, surely the generators should draw on separate fuel tanks. For such a large and relatively modern ship to suffer a total power failure is complete corporate incompetence.

If, as some allege, the refrigeration containers were causing problems, and total power outages occurring before sailing, the vessel should not have sailed, certainly at night. If this is the case, The Master needs locking up. But, poor man has to take the blame, because he is cheaper than a Danish Master and his Singaporean employer (if he is employed and not a contractor) also operating in a cheaper flag state than Denmark. The Singaporean Company also needs hitting hard if the culture was the cause of the Captain sailing after such alleged pre-sailing power outages.

Maersk outsource to reduce personnel and running costs. They use the cheapest crews, cheapest ships and need hitting very very very hard. We might then stop this culture of wealthy shipping companies using every method possible to avoid complying with IMO and more rigorous Nation State standards, operating in the shadows and ducking accountability and responsibility.

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

#995

Earlier quoted context omitted.

> Whereas in reality maintenance standard in the west have fallen In the context of this incident, are you saying that we _previously_ used to go around retrofitting our 50-year-old bridges with more modern defenses, and then at some point since then we stopped doing this? Obviously if we're talking about new construction, it stands to reason that standards have only _increased_, but this was an old bridge built to o…

Literally, yes, someone is responsible > 46,154, or 7.5% of the nation’s bridges, are considered structurally deficient, meaning they are in “poor” condition. Unfortunately, 178 million trips are taken across these structurally deficient bridges every day

That doesn't answer the question I asked regarding the specific claim that maintenance standards have fallen.

For example, it's possible maintenance standards never changed and the old bridges simply got older and more exposed to risk as the years went on.

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

#996
post #897

Lack of redundancy. Also a major contributing factor in the 737 MAX crashes. Redundancy is a low price to pay for peace of mind.

Very, very few bridges have redundant support structures. Also the 737 MAX is a case of how redundancy DOESN'T always solve issues

The crashes were a result of a single sensor being a point of failure. The update uses two sensors and they must agree with one another.

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

#997
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…

What's needed is the will to do something about low-probability but catastrophic events

In general I share your sentiment society could do more to insure itself against lower-probability catastrophes. But overbuilding every bridge would probably cost more than rebuilding the occasional one that's taken out when an unusual event like this occurs. Maybe in a different environment that would make sense, like a warzone (although I think even then there's more tendency to rely on redundant infrastructure and mobile, power-at-a-point defense).

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

#998

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…

Most bridges nowadays (say last century) depend on a careful balance of forces that are transferred through a chain of members in tension and compression. When any piece in the chain of those forces breaks, the entire structure loses ability to transfer forces and breaks. This arrangement is what allows us to build these structures in the first place. There is careful calculations of forces and risks and allowance fo…

Many homes also incorporate lightweight trusses that can fail in a similar fashion. They pose a unique risk for firefighters, which is why New York went so far as to require warnings be posted outside such structures: https://www.finehomebuilding.com/2015/01/28/new-york-now-req...

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

#999

Earlier quoted context omitted.

> direct the force into destroying the ship Nice immovable object you've got there.

You put it ahead of the pylon so that even when the dolphin or bollard is destroyed, it redirects the ship to—at worst—a glancing blow with the pylon. You don’t need to dissipate every joule of kinetic energy in the vessel. You just need to redirect it away from the pylon. That horizontal component can be done with bollards and dolphins sufficiently that even a relatively direct original angle should only damage the…

> direct the force into destroying the ship

> You put it ahead of the pylon so that even when the dolphin or bollard is destroyed

Dude, seriously? That has nothing to do with what I was replying to.

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

#1000

Earlier quoted context omitted.

All pilots are "harbor pilots". Crew members who control the ship outside of port are just called crew members (captain, first mate, 2nd Officer, that kind of thing), never pilot.

All pilots are "harbor pilots". In California, at least, that's not strictly true. They get paid quite handsomely ($400–500k as of a decade ago) to avoid hitting stuff in specific waterways around the Bay Area. https://sfbarpilots.com One had a nasty pill habit and crashed an oil tanker under his purview into the Bay Bridge. https://www.justice.gov/opa/pr/guilty-plea-case-cosco-busan-...

I put in the quotes because the person asking the question picked the exact phrasing, which as we both pointed out isn't correct. They're just pilots. The normal crew driving the boat are crew, not pilots.
Post reply on HN