Simulating Costa Concordia

I have to correct myself.
In fact the last sheets (i.e. the 12th PDF) of Duffy's links does contain a steel plan of midship section and other frames.
It also includes field of vessel's particulars among which also the volumetric displacement (i.e. 55000 m**3) and the block coefficient (i.e. 0.7536) for the scantling draught at 8.30 m is stated.
Interestingly it also states the bending moments in hogging condition.
Maybe you can help me professor?
I don't know what is meant by that because I would have assumed still water bending moments to be mentioned here (light ship?),
whereas hogging condition to me is when the ship is amidship on a wave crest.
Of course, because there is much more buoyancy around mid ship than at the hull ends the effect in still water at even keel will always be a hogging bending moment.
Is it this what was meant?

I took a screenshot from the field with the particulars.
I hope the attachment's upload worked.

 

http://gcaptain.com/60-minutes-special-on-salvaging-the-costa-concordia-video/

 

Thank you for posting Peter.
Interesting footage of the salvage operation.
The only thing that puzzles me, where are the remaining 4/5 of the 60 minutes, especially when it is touted as "FULL EPISODE" in capitals?
Does anyone know how the operation turned out to perform?
The shooting as it seems was taken in summer.

 

'60 minutes' is the name of the documentary series, and they do three or four 'items' per 60 minutes - so the salvage would not be the entire program.

 

It seems that this vessel hoggs with both wave crest amidships (max) and at the ends (min). This suggests a substantial excess weight associated with machinery 3/4 aft and a very full form amidships with little buoyancy forward. Both conditions should be associated with the full load condition at 8.2m for which the ships structural strength is calculated. Sorry for the long delay in responding - hope this helps!

 

Thank you for the explanation Prof. Winkle.

That's what I thought too, i.e. the tendency to hogging, which doesn't surprise me with a ship of that fullness and of that type.
I can imagine that this may cause high bending stresses in the sheer strake or in elements of the superstructure's upper parts.
Such may also have been the cause of a wide crack which appeared a couple of months ago in the P&O cruise ship VENTURA's superstructure.

In this regard I have a question how to interpret or translate the term "Scantling Draught"?
I would translate it as Festigkeitstiefgang into German and my notion is that it is the maximum permissible draught a vessel may be laden to in order to guarantee the hull's strength.
Because for modern cruise ships like the CONCORDIA or for container ships sufficient freeboard out of floatability and intact stability considerations isn't an issue
the threshold for maximum submergence is rather given by the scantling draught.
Is my layman's interpretation of the term correct?

 

Scantling Draught

This is the maximum operational draught applying to the structural design calculations (i.e. the structural scantlings) and is often a little greater than the summer load line which corresponds to the maximum operational draught at which the ship is registered to operate under the freeboard or load line rules. The summer load line will also define the survival conditions associated with the distribution of watertight transverse bulkheads under SOLAS Regulations. Given the number of passengers and length, Costa Concordia should have been designed to sustain 3 adjacent compartment damage at all points along her length. C. C's maximum operational draught of 8.2m appears to correspond to the summer load line rather than the scantling draught of 8.3m and is definitely linked to minimum freeboard which is surprisingly small for such massive vessels - being only just over the depth of one deck! The apparently large freeboard is mostly non-buoyant superstructure with no transverse submission to restrict flooding. Conversely, the apparent freeboard of large container ships is true freeboard as they are volume carriers which cannot fill themselves with enough weight of cargo to bring them down to their design freeboard or summer load line which is calculated from their highest visible deck, also their bulkhead deck.

Hope this helps.

 

Half a billion dollars!!

THAT'S expensive salvage.

And all they're going to do is cut it up for scrap.

Nice contract.

 

Maybe they can make a few bucks from the scrap by auctioning some as memorabilia if deference for the drowned permits this.

 

Many thanks for the explanation.

I wasn't aware that CONCORDIA had so little freeboard according to proof of load line.
Btw. do they still use the 1966 Load Line Convention?
But especially since the HERALD OF FREE ENTERPRICE and ESTONIA disasters with that many losses of lives there must have been introduced a few SOLAS amendments meanwhile.
On the other hand those were mainly caused by free surface effects on the partially flooded RoRo decks, if I remember correctly.
So the bulkhead deck on CONCORDIA had a pretty low depth?

 

How relevant are current Regulations?

As far as I am aware the freeboard rules for C.C. would have been the latest amendments to the rules which came into effect Jan 2005 - i.e. the 2003 amendments to the 1988 Protocol, which would not be greatly different in general terms from the 1966 Convention.

It may surprise you to learn that the subdivision rules for C.C. varied little from the actual subdivision of Titanic which was used as the basis for the first SOLAS convention in 1914 and only slightly modified in SOLAS 1929 to raise ships of this size and passenger numbers to a 3 compartment standard. With the exception of post 1990 larger cargo ships and passenger or or ferries, these same rules applied up to the adoption of the 2008 amendments to SOLAS 74 in 2010. Even the replacement probabilistic approach is only set to give equivalent survivability to the average of ships in the 1960's from which the Required Subdivision Index, R is established.

The impact of recent ro ro losses has been to tighten up on the residual stability standards after damage with maximum angles of heel and residual stability defined in terms of GM, GZmax and range of residual stability. No ship is supposed to heel beyond 15 degrees after equalisation of any asymmetric flooding. This process did not start until SOLAS 60 following the capsize of Andrea Doria even though ships such as Lusitania were lost during WW1 in around 18 minutes with immediate heel of 20 degrees to starboard through asymmetric flooding of wing coal bunkers which prevented the launch of any port lifeboats!

The current situation where ships are carrying greater and greater top weight through enlargement of their passenger spaces, requires that the breadth increases on a relatively fixed low draught of no more than 8 to 8.5 m to increase the operational BM values to match the ever rising KG. This results in significant BM loss in serious damage scenarios due to effective loss of waterplane area (or free surface effect if you think of an added weight approach) which cannot be matched by the rise in KB. It is therefore easy to see how the C.C. lost stability despite any significant asymmetric flooding. Older designs such as Titanic were able to remain effectively upright despite a loss of waterplane area no less significant than C.C. It therefore seems that stability and the risk of capsize after significant damage has become one of the primary considerations for large passenger ships, but it is far from clear that the regulations reflect the much more serious impact to passenger evacuation associated with serious heel and capsize. It is my view that capsize should have a much higher claim on ship safety than conventional foundering scenarios and limitations should be placed on ship proportions accordingly.

 

CC Full investigation report (from italian MAIB)

Here is the full report from the italian technical investigation body regarding the "Costa Concordia".

Includes some interesting details in line with this thread...

Prof.Wrinkle many of your thoughs are confirmed in this report.

Neverthelelss Italian investigators insist on the effect of free surfaces during the flooding during the intermediate phase (up to "ceilings" ilevels in the different flooded compartments).

 

A rather superficial (and long-winded) Report

Many thanks for this. Just got back from my French/Italian 'vacance', so a little late in responding. It is not a very easy read and many of their assumptions are not clearly stated. However, it does confirm that with a Factor of Subdivision of 0.386 she was essentially a two compartment vessel, but the calculations discussed in the report (page 127) confirm that at least in the Machinery Spaces she was effectively a 3 compartment vessel, as she meets all SOLAS Regs with any combination of three compartments flooded. However, the Regs assume the flooding of all relevant double bottom spaces and it is not clear whether this was in fact the case. This will have a significant effect on any marginal stability as the KB (and therefore the KM) will be reduced if the DB tanks are not fully flooded. The photo on page 124 is the same as I used in my own analysis and it is clear from the waterline that my estimate of 13.2 degrees is just a little greater than suggested by the simulation and significantly less than the 18 degrees suggested by the bridge inclinometer. I would therefore conclude that the picture relates to a little before the final grounding, slightly earlier than KEYPOINT 10 associated with the bridge inclinometer reading. This is also borne out by the somewhat higher flood water content suggested at this stage than in my own analysis (based on the photo).

I do not see many constructive suggestions for improvements in design other than double skins in way of the M/C spaces. These would probably have had a sufficient mitigating effect to prevent the ultimate capsize - the exact same recommendation which came from the Titanic disaster 100 years earlier which were built into her sisters Olympic and Britannic!

 

May be it was really impossible not to be long-winded in such technical report !

My feeling is that the document is eventually quite disappointing on stability matter aspects .

Nevertheless I have been interested in their "free surface" approach during the intermediate stages of flooding.

I deeply regret Italian Administration has not tried to compare deterministic calculations with probabilistic ones ("Solas 2009") on such a terrible case. It would have been a unique opportunity to analyse both corpus of rules. Probabilistic rules of "Solas 2009" have been established as equivalent (roughly speaking) to "Solas 90" deterministic rules (on which "Costa Concordia" is based). They have also been introduced to treat the issue of such large passenger vessels and to overcome the drawbacks of deterministic rules. Are we afraid of such a comparison ?

Engineering subjects in the report are more interesting ; they have tried to explain the difficulties to run the emergency diesel on the emergency switch board but again a lot of words without any drawings or even sketches ("single line" drawing, electrical production principles, position of main switchboards, etc).

I will not comment quality of English for such high level report (being French I am not in position to do it...) and formal aspect as well (no author names, no signature, etc...).