Trans RINA, Vol 152, Part A2, Intl J Maritime Eng, Apr-June 2010
That stated, we feel the need to point out that the main rationale for us has not been to promote any intermodal shift as
such, but rather to identify and address
inconsistencies and sub-optimal practice and –solutions in the ship design basis and the process: Where the “design brief” goes too far in presuming certain facts, the designer and indeed the design process should address this and potentially also identify the consequences of such constraints.
The second issue that Prof. Bertram is addressing is a part of the twin complex that is also the main challenge to our approach in terms of making it a general approach to ship design:
Much of the world fleet is not employed in what may be broadly services”, but
vessels, offshore construction vessels, icebreakers, etc. Where the “transport chain” concept is as vague as this, how then are the optimization criteria restated?
How may a vessel that is intended for the spot market, i.e. an unknown operating pattern, be optimised with respect to a transport chain?
One potential solution to the first part problem could be to define alternative
definitions of “benefit” than
transport work in the cost/benefit equation. In fact, such approaches are already widely used in the shipping business through benchmarks such as “fuel consumption per day in DynPos mode”, “square km seismic data”, etc. The main challenge is to define meaningful metrics that will apply to a wider segment and thus also have the potential to be a known and accepted parameter across the business. The objectives would in such cases be more focused on optimising a “mission” than a “transport chain”.
The second part problem is more of a conundrum and most likely there is not a single solution. The authors have applied two different approaches in practice when this problem has come up: Either prepare a representative operating profile (or route, service, mission, loop) for the transport problem in question based on the available information and the knowledge of the design team, or use the more general approach of using representative trades for the vessel type. Quite often we find that even such small modifications to the design basis will have significant effects.
But having said this, what Prof. Bertram points at is indeed a major issue. The conclusion might very well be that the chain and vessel connection will be insignificant in the design problem, i.e. that the vessel and chain are decoupled.
The third and last issue that Prof. Bertram is raising relates, in the perception of the authors, to the robustness of the solution, i.e. the ability to cope with changes in the
categorised as “transport other purposes: Cruise
market or other operating conditions. One response
would be to go “brute force” with simulations and scenario analyses, in contrast to more qualitative analysis techniques.
This is a very difficult issue. The design of a ship in a longer term perspective for a risk-prone client
expectedly differ from that for a risk-averse client, and it is thus difficult to find the correct measure to use in directing the design. There is, in our view, not one single approach to take.
Our aim is to be able to represent potential future scenarios
(including different fuel
environmental legislations), and present the effect of different design decisions on each of those. A designer will thus be
prices, different able to view the potentially adverse
consequence of optimising for one particular scenario (possibly based on the current situation) with respect to another scenario for the future.
The long-term task would then in theory be to give probabilities to these future scenarios,
in order to
optimise for a long-term perspective. However, the danger is that the design task becomes very complex and difficult to penetrate, in effect becoming a black box where the complexity itself becomes a risk to the client, who then may resort to the old “I know what I have, but not what I get”.
In order to meet these concerns, we feel that we need to be able to adapt the toolkit and the process to the problem at hand. If the client is concerned about
performance in the future, we should be able to address those concerns in the design process through evaluating design scenarios. If not, we should at least be able to highlight hotspots by pointing at particularly sensitive aspects of the design with respect to risk.
REFERENCES 23. 24.
25. 26. 27.
LEVANDER, K: “System Based Passenger Ship Design”, IMDC 91, Kobe, May 1991. ANDREWS, D J and
PAWLING, KOENIG, P, CZAPIEWSKI,
ANDREWS D J: “Marine Requirement
P Design Elucidation rather Proceedings R.
“SURFCON – A 21st Century Ship Design Tool.” Proceedings of IMDC 03, Athens May 2003.
HOOTMAN, J C:” Synthesis and analysis of future naval fleets”, SAOS 2008 Vol. 3 No. 2 pp. 81–89.
Requirement Engineering”, IMDC 03, Athens, May 2003.
ANDREWS, D J (Ed): “State of Art Report on Design Methodology”, in
IMDC09 (Edited Erikstad, S O), Trondheim, May 2009.
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