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Baltimore's Key Bridge struck by cargo ship, collapses

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

#741

Post by wiml »

trilbyglens wrote: post #582
jordanb wrote: post #495

Earlier quoted context omitted.

The problem is with steering. The rudder on a ship this big is going to be wall of steel several stories tall with gears as big as car. Warships have several independent backup steering options reducing finally to a worm gear at the top of the shaft with a winch handle big enough to put a gang of men on it. But ships like this will have none of that. They will have a small wheel or joystick on the bridge and if power…

Wouldn't a ship like this have bow thrusters? Seems like otherwise it would be impossible to get into port without a tug.

My understanding is that they simply use a tug when they're maneuvering by the dock. That's what a lot of tugs do all day.

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

#742

Post by bobthepanda »

PeterCorless wrote: post #717
bobthepanda wrote: post #646

Earlier quoted context omitted.

the modern practice is layers of defense; in addition to building a bridge that doesn't fail at a single point of failure, you also generally design what's around a bridge pier to stop or at least slow down the ship (by, say, running aground onto a bed of rocks around a pier)

For a bridge such defenses are called dolphins. "A notable example of dolphins used to protect a bridge is the Sunshine Skyway Bridge across the mouth of Tampa Bay. In 1980, the MV Summit Venture hit a pier on one of the bridge's two, two-lane spans causing a 1,200-foot (370 m) section of the bridge to fall into the water, resulting in 35 deaths. When a replacement span was designed, a top priority was to prevent shi…

That's also a thing.

But note how the main bridge piers are on giant islands much larger than the pier itself: https://en.wikipedia.org/wiki/Dolphin_(structure)#/media/Fil...

If you really want to make it unblockable you build a bridge+tunnel. https://en.wikipedia.org/wiki/Bridge%E2%80%93tunnel

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

#743

Post by jordanb »

bmitc wrote: post #679
jordanb wrote: post #464

Earlier quoted context omitted.

According to this book: https://www.amazon.com/Tankship-Tromedy-Impending-Disasters-... It is quite common and vessels often have outages that leave them Not Under Command. Usually they are safely at sea when this happens and they can drift for hours without causing problems. But of course there's always a possibility of it happening at exactly the wrong moment. The reasons for this are the usual: lack of redundancy,…

Thanks for the link to that book. I don't know if it's the because of this catastrophe, but it looks to be unobtanium at the moment. Will have to find it in the library. > lack of redundancy This is what I am surprised at from many angles. It seems to me that the ship, the port (in the form of lack of tugboats), and the bridge (in the form of lack of secondary protection of the pillars) all had a lack of redundancy a…

The author GPLed it and put it on the internet at one point: http://martrans.org/documents/2006/safety/The%20_tankership_...

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

#744

Post by efitz »

thekid314 wrote: post #597
paddy_m wrote: post #568

Earlier quoted context omitted.

On ships like this the propulsion is separate from the steering. There is a separate rudder that is close to, but not attached to the prop and propshaft. The propshaft is fixed. The rudder doesn't just "restart in a random position" it would remain in the previous position unless there was a physical piece that broke in the rudder gear. The fact that ship was able to reverse hard ( as evidenced by the slowdown), indi…

Was there a harbor pilot on board, or the normal ship pilot? Were there tug boats helping with the exit? I have often felt that the harbor protocols were overkill, but this is one of the times they could have helped.

The video referenced in the parent post stated that the two tugs assisting with undocking had already disengaged (0:54).

AP News [1] is reporting that harbor pilots were on-board and were nominally in control of the ship at the time of the accident.

[1] https://apnews.com/article/baltimore-bridge-collapse-53169b3...

Update: added timestamp, link

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

#745

Post by DennisP »

scoot wrote: post #661
DennisP wrote: post #629

According to this Baltimore news report, after 9/11 state officials had looked at putting bumpers around the piers that could have protected the bridge from an impact like this, but it was too expensive. https://www.youtube.com/watch?v=l_-CpdVaHGg

Even compared to the economic impact of a bridge collapse and resulting port closure?

Yeah I'm guessing just replacing the bridge will cost a lot more than the bumpers would have, even without counting the broader impacts.

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

#746

Post by vundercind »

tekla wrote: post #345
b33j0r wrote: post #208

Earlier quoted context omitted.

Interested in this claim, because it sounds about right, except that I can’t name a bridge constructed in the past 50 years. The bridges we can all name are pushing 100+ right?

I can't imagine how it is to be so insulated from the world to not be able to name a single major bridge construction in the past 50 years.

If you don’t live somewhere with famous/major bridges it’s really easy. I doubt I could name ten bridges period that aren’t in my mid-sized city (and I can only give the correct name for two of the ones here, neither of which is famous). I can only identify maybe four by sight from outside my city—I can name a few that I couldn’t pick out of a lineup of photos.

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

#748

Post by jameshart »

rightbyte wrote: post #575
jcgrillo wrote: post #555

Earlier quoted context omitted.

I'm not sure what configuration of props a ship like this has, but in my experience with a 40ft sailboat with a single propeller you have absolutely no rudder authority while reversing. I've read that some large ships also are direct drive--there's no transmission between the engine and the propeller, so "reversing" (if it's even possible) entails shutting down the engine and restarting it in reverse. This can be don…

> my experience with a 40ft sailboat with a single propeller you have absolutely no rudder authority while reversing. I have to protest here. Reversing and using the rudder on a 40ft boat works perfectly fine. I've done it on multiple sailing boats. You need to hold tight so that the rudder wont slap you if using a stick.

Isn’t there a pretty big difference in how much rudder authority you get between just making way astern, and having the engine in full reverse while still traveling forwards at seven knots?

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

#749

Post by reactordev »

paddy_m wrote: post #568
araes wrote: post #541

Earlier quoted context omitted.

Current personal suspicion after watching your linked video (excellent discussion by the wgowshipping author) is: Catastrophic engine failure (1:24) causing wide scale power loss. No rudder control, rudder drift, and ship alignment drift (1:24-1:25:30) Power restored and ship reengages prop with bad ship/ruddder alignment (1:25). However, ship is now pushing itself into a further bad turn. Pilot likely stomps the bra…

On ships like this the propulsion is separate from the steering. There is a separate rudder that is close to, but not attached to the prop and propshaft. The propshaft is fixed. The rudder doesn't just "restart in a random position" it would remain in the previous position unless there was a physical piece that broke in the rudder gear. The fact that ship was able to reverse hard ( as evidenced by the slowdown), indi…

At this point in the journey, they were cleared of the docks but not the channel. There wouldn't be a docking pilot on board nor would there be any tugs. It was cleared and under it's own propulsion until it wasn't.

My sailors guess from the footage and the reports is diesel generator failure(s) resulting in loss of power, restoration of power, then loss of power again. Bypassing the diesel generator (which provides power to hydraulics too) and manually throwing the engines in reverse. The billow of black smoke. This could have possibly burned out an engine, blowing the camshaft or propshaft or transmission.

The reverse was too late as the ship was already heading for the bridge pylon. Even at full reverse, you couldn't slow it down fast enough. Tragic.

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

#750

Post by doer1984 »

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…

Anyone know about backup steering power on these vessels? I know they typically keep emergency generators, but does this provide adequate steering power?
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