A mixed-integer heuristic for the structural optimization of a cruise ship

peer reviewedA heuristic approach is proposed to solve the structural optimization problem of a cruise ship. The challenge of optimization is to define the scantling of the structure of a ship in order to minimize the weight or the production cost. The variables are the dimensions and positions of the constitutive elements of the structure: they are discrete by nature. The objective functions are nonlinear functions. The structure is submitted to geometric constraints and to structural constraints. The geometric constraints are linear functions and the structural constraints are implicit functions requiring a high computation cost. The problem belongs to the class of mixed-integer nonlinear problems (MINLP). A local heuristic of the type “dive and fix” is combined with a solver based on approximation methods. The solver is used as a black-box tool to perform the structural analysis and solve the nonlinear optimization problems (NLP) defined by the heuristic. The heuristic is designed to always provide a discrete feasible solution. Experiments on a real-size structure demonstrate that the optimal value of the mixed-integer problem is of the same magnitude as the optimal value of the optimization problem for which all the variables can take continuous values

Multicriterion Scantling Optimization of the Midship Section of a Passenger Vessel considering IACS Requirements

peer reviewedIn the scantling design of a passenger ship, minimum production cost, minimum weight and maximum moment of inertia (stiffness) are conflicting objectives. For that purpose, recent improvements were made to the LBR-5 software (French acronym of “Stiffened Panels Software”, version 5.0) to optimize the scantling of ship sections by considering production cost, weight and moment of inertia in the optimization objective function. Moreover, IACS requirements regarding bending, shearing and buckling strength are currently available in LBR-5. Until now, only raw scantling optimizations were performed with LBR-5. Thanks to new developments using heuristics, it is now possible to realize discrete optimization so that a standardized and “ready to use” set of optimum scantlings can be obtained

Assessment of Ultimate Bending Moment of Ships from a Reliability Point of View, Using Independent Perturbations Method

peer reviewedThis paper presents a method to asses hull girder ultimate bending moment distribution, taking into account parameters uncertainty. This method is a part of a research activity carried out at University of Liege. The method is able to compute four statistical moments of ultimate strength distribution: average, standard deviation, skewness and kurtosis. Geometry parameters, material parameters and initial imperfections (initial deflections and residual stresses) are considered as random variables and a distribution is associated to each of them. Ultimate bending moment algorithm is a progressive collapse analysis based on Smith method and associated with the load-end shortening model proposed by Bureau Veritas and Joint Bulker Project Rules (JBP). In order to perform a reliability analysis, this algorithm is coupled with independent perturbations method. The advantage is a lower number of simulations compared to the standard Monte-Carlo procedure and a good use of the initial information that is available. The paper contains also a comparative analysis between the presented method and a linear sensitivity analysis performed by the ISSC 2000 “Ultimate Strength” committee for a VLCC structure

Differential Equations of Stiffened Panels and Fourier Series Expansion

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Discussion on Paper D04 “Ultimate limit state design technology for aluminium multi-hull ship structures, SNAME Transactions, Vol.113, (2005)”

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Scantling Optimization of Double-Hull Structures to Minimize their Production Cost

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Comparaison de plusieurs modes de prise en compte de la sécurité dans la vérification de la capacité portante des fondations superficielles

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Simulation et Optimisation d'un Atelier de Construction Navale

peer reviewedThis study concerns the simulation of a shipbuilding workshop, and its optimization to improve its productivity. Usually, simulation is used to improve efficiency but this optimization is often done manually, particularly for shipbuilding workshop. This is due to the particularity of pieces to be manufactured: almost each of them is different and required thus particular operations. The automation is not so much present as, for example, in automotive industry. In spite of high CPU time for that kind of simulation, we will try to use optimization methods to improve productivity. Algorithm used is a genetic algorithm

Optimization of a Rolling and Floating Lock Gate for the Port of Antwerp

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