engleski

RoPax Structural Design- Multi-level Decision Support Methodology

The novel decision support methodology for the concept and preliminary design of the multi-deck ship structures is described together with its application to the structural design of the next generation of the RoPax ships. The multi-criteria, multi-stakeholder design problem was solved with the support of the renown Mediterranean ship-owner, the Class Society and the Yard, within the EU FP6 project IMPROVE. Approach combines three design steps for the fast generation of different design variants regarding topological (no. of decks), geometrical (bulkhead and deck positions) and scantlings variables. Step 1: The generic ship 3D-FEM MAESTRO models (based on macro-elements), were analyzed according to BV rules and optimized for the cost, weight and VCG position w.r.t. the topological, geometrical and scantling variables. In the context of general design, designer’s selection was performed using appropriate design quality measures from the grid of six optimized variants. Step 2: Control structures (bays) of different ship segments were modeled, using the computationally very fast 2.5D FEM OCTOPUS models, in generation of design alternatives on the Pareto frontier. They were validated using the IMPROVE developed adequacy and quality measures (vibration, fatigue, robustness, safety and production cost). IMPROVE LC-Cost module was used in determination of the optimal combination of different generated substructures, as starting points for the next, preliminary design phase. Step 3: The full ship 3D FEM models were developed to validate and synthesize optimal design variants using safety, weight, cost, fatigue and vibrations criteria. Direct wave load calculations were applied to generate the design loads for the North Atlantic and the Mediterranean. Parameters having significant effect on design solution have been identified. Decision making implied MODM and MADM (optimization) procedures based on dual SLP and MOGA solvers combined with the stakeholders’ subjective decision making (selection) on the generated Pareto frontiers. Procedure resulted in the optimal structural design of the RoPax with two superstructure decks, the optimal parking area on lower decks, VCG position, etc., combined with the considerable savings in the ship lightweight and related savings in the fuel and other operational costs. Ship-owner profit has been significantly increased while at the same time the shipyard achieved the reduction in the production cost.

RoPax; structural design; decision support methodology; topology and scantling optimization

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