7 research outputs found

    Design method for safe ship structures

    Get PDF
    At present ships are designed to satisfy the minimum requirements for safety. And history shows that this practice does not suffice, and nor is it sustainable. A new paradigm is needed. This thesis aims to contribute in that respect by proposing a design method that should move ship safety beyond the minimum requirements as much as possible and as long as it is economically sound. The thesis focuses mostly on environmental safety in the event of accidents such as collisions and grounding. A special feature is the consideration of maritime stakeholder preferences regarding safety and profitability. This is an underlying element in all the analysis performed and conclusions reached. This design method features new approaches in multi-objective optimization of ship structures and in advanced decision making for design selection. The multi-objective optimization is based on evolutionary algorithms, more precisely the genetic algorithm (GA) with advanced treatment of design constraints and objectives. Through the approach of vectorization, the GA becomes not only more efficient, but also more flexible in use, bearing in mind the complexity and demands of accident analysis for optimization. The decision making is established on the concepts of Game Theory, resulting in a new criterion for design selection, the Competitive Optimum, based on the maximal concurrent satisfaction of stakeholder preferences. The proposed design method is intended in particular for ship structural design projects, permitting the definition of hull structural scantlings, or even hull topology if desired. The approaches to multi-objective optimization and design selection that are introduced possess a wider basis of application, and are extensible to other fields in maritime safety and naval architecture. The results of the thesis provide several relevant conclusions with an impact on practical naval architecture. For example, i) by increasing ship crashworthiness, significant risk reduction can be attained, ii) raising safety is economically justified if the benefits to the public are considered alongside those of the industry, and iii) the crashworthiness of ships can be controlled effectively with conventional double-bottom and double-sided structures

    ‘Healing’ and ‘repairing’ techniques for faster optimization with genetic algorithm

    Get PDF
    This paper presents two techniques, the ‘healing’ and ‘repairing’ that can reduce optimization time when using genetic algorithm for structural optimization. The techniques can be applied to: (a) quickly find feasible designs from completely infeasible set of alternatives, and (b) to make the best infeasible designs feasible. These procedures are implemented into a genetic algorithm ‘VOP’. The performance of the original and the modified version of the algorithm are compared with the widespread genetic algorithm ‘NSGA-II’ for the weight optimization of a 40 000 DWT chemical tanker midship section. The results show that these procedures can decrease the optimization time by approximately half.Peer reviewe

    Vectorization in the Structural Optimization of a Fast Ferry

    Get PDF
    Vectorization assumes the conversion of constraints into objective functions. It turns a singleobjective, or scalar, optimization into a search for a Pareto optimal set, which will enhance the search for the optimum. Vectorization is studied here within a structural optimization of fast ferry’s midship section for the minimum of steel weight. Optimization applies a simple genetic algorithm (GA), whose performance is observed over both scalar and vectorized problem formulations. The obtained results show that the applied GA can improve the referenced design, and that the improvement can be signifi cantly better if vectorization is applied
    corecore