Least cost optimization of a large passenger vessel

The LBR-5 software allows optimizing ship structures according to objectives of highest inertia, least weight and/or least cost. This last criterion offers the choice between two approaches of calculation. The first approach is based on a simplified assessment of the cost described by rather simple analytical functions which include on one hand the design variables and on the other some empirical parameters. In the second approach, the calculation of the cost is based on data specific to the shipyard. The material cost is analyzed according to the first approach while the cost of the labor considers each relevant operation of the shipbuilding with respect to the LBR-5 model. A survey of all the tasks was carried out at Aker Yards, France and a thorough study made it possible to develop assessment tools of the labor cost for each operation as functions of the design variables. Plate straightening operations are also considered in this analysis. This paper presents a cost based optimization study carried on a large passenger ship structure with more than 600 design variables, by the use of the detailed approach for the cost calculation. The structural model has been formulated on the basis of technical documentation prepared by Aker Yards, France. The loads and strength criteria applied on the model are considered according to classification society rules (Bureau Veritas). Results and conclusions of the study are presented