Page 297 - Practical Design Ships and Floating Structures

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degree to which they satisfy the goal. There can exist several such levels in the structure, detailing the
selection criteria through the consideration of various decision attributes, such as fuel consumption and
steel weight. The final lower level contains the actual alternatives from which the one that best
satisfies the goal is selected.

An example of the various levels of an objective function of the problem at hand is as follows:

LEVEL1 Derive effective subdivision arrangements and layouts that
maximise safety, whilst minimising the incurred costs
LEVEL 2 Selection Criteria 0 Income
Building cost
Operational cost
Machinery selection
Performance indicators
Safety indicators

LEVEL 3 Detailed Attributes Lower level attributes, pertinent to the criteria above, that can be
enumerated
LEVEL 4 Merit Function Compose and iterate based on necessary improvements

This approach to construct the objective function is illustrated in Figure 1 in broad terms. Even though
this kind of approach is widely used for problems related to selection and ranking of derived
alternatives, the iteration proposed aims at the introduction of the approach at the design synthesis
process. The objective of the iteration is not to alter any of the broad specifications (Le. the goal or the
selection criteria), but rather to allow focusing in specific areas of the process where attention should
w
be paid.
LEVEL 1:

v

LEVEL 2:
SELECTION CRITERIA

LEVEL 3:
DETAILED ATTRIBUTES

LEVEL 4:
MERIT FUNCTION
Figure 1: Objective Function
3.2 Design Parameters and Mathematical Model