HMHS Britannic

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[Stuart2007]

I suppose an inch over a 600ft ship isnt going to be noticed. I really thought theyd be more rigid than that.

This has surprised me no end.

Stu

[LucAtC]

Hello Michael,
I thought most structural problems had disappeared, and that wreckages from that were a thing of the past, due to HR steel and finite elements calculations.
Looking for info, I found a thrilling IMO document (in French, alas)
edit: http://www.imo.org/includes/blastDataOnly.asp/data_id%3D2312/BulkCarriersfrench.pdf
It looks like I was wrong, wondering if it has improved since 2000, at least for bulk carriers.

And Stu ought to try Jupiler next time he is on board of a decent ferry, instead of Stella.
It is raining again __ on my fresh painted roof!
Regards,
Luc

[AriesDW]

To be perfectly honest, I've never really felt the need to sail.  I do love ships, Titanic being my favourite, but prefer dry land

Kinda strange really, because I love Ship Sim

Regards.

DJM.

Hrm . . . Interesting . . . .

[AriesDW]

So tell me, these links explain explain this spring system you mention? I am wondering, however, when I was on the Carnival Pride how I saw shifting in the superstructure if for lack of expansion joints. I just find it hard to imagine some of these long, tall, and quite hollow vessels would be without them . . .

[mporter]

Hello Michael,
I thought most structural problems had disappeared, and that wreckages from that were a thing of the past, due to HR steel and finite elements calculations.
Looking for info, I found a thrilling IMO document (in French, alas) http://www.shipsim.com/ShipSimForum/index.php?action=post;topic=206.50;num_replies=74
It looks like I was wrong, wondering if it has improved since 2000, at least for bulk carriers.

And Stu ought to try Jupiler next time he is on board of a decent ferry, instead of Stella.
It is raining again __ on my fresh painted roof!
Regards,
Luc

Hi Luc,

As to structural problems; first, HY steel ("high yield", maybe your HR?) is stronger but also more brittle than normal ASTM A36 "mild steel". And I think most big ships, unless something special is envisaged, manage without finite-element analysis. And then there are classification societies, and then there organizations masquerading as such.  And registries that do not insist on keeping ships up to class. But don't let me get started!   For fun, look at  http://www.parismou.org/
 (http://www.parismou.org/) They used to have a feature called "rustbucket of the month".

And even the best societies are reviewing their requirements in the wake of some widely-publicized disasters -- ships that (at least on paper) fulfilled all requirements. There is always someone who wants to do it cheaper, alas.

I'd be interested in the link, but it doesn'twork (French is not a problem).
EDIT -- it does now 

Best,
Michael

[mporter]

So tell me, these links explain explain this spring system you mention? I am wondering, however, when I was on the Carnival Pride how I saw shifting in the superstructure if for lack of expansion joints. I just find it hard to imagine some of these long, tall, and quite hollow vessels would be without them . . .

The steel simply flexes, and the interior work (cabins, etc) cannot be too rigid to flex with it. -- I think I mentioned somewhere on the same subject but a different thread (incipient Alzheimer's -- and short-term memory is the first thing that goes) the flexing of flat-bed trailers as they go down the highway with heavy loads, but you can see this any day on any interstate.

The design of newer cruise ferries with their open central atria is quite a problem.  Maintaining the required degree of stiffness without most of the central structure is indeed challenging!

Cheers,
Michael

[AriesDW]

Michael;

   Yes, thank you very much for your explanation. I do remember you mentioning the load on the trailer thing, which is something I have seen a lot in my life. However, a trailer with a heavy load seems like it would be on similar principles to the ship flexing, however, I would think that the ship would be a whole different ball game in how to maintain structural integrety, especially over a long service life. A trailer I do not mind seeing flex, because relatively speaking it is cheap and will often make so much money in it's service life for the owner that in the end it is a small deal. Hopwever, a 280 million $ cruise ship I would think there would be a lot more technology in place to take the slack of the flexing, thereby keeping the structure more "secure" and letting these, springs, expansion joints, or whatever do all the bending and groaning . . .

   Again, thanks for the information. I would love to find out more . . .  Being you are a maritime designer, I am sure you have a lot more facts to share.