Least Cost Optimization of Large Passenger Vessels

The LBR-5 software allows optimizing ship structures according to objectives of higher
inertia, less weight and/or lower cost. This last criterion offers the choice between two approaches of
calculation. The first approach is based on a simplified assessment of the cost in which the total cost
is described by rather simple analytical functions which bring into play on the one hand the design
variables and on the other hand 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 ship building 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 out 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.