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Design synthesis of complex ship structures

The paper presents the principal steps in the definition of a practical design model for multi-criteria synthesis of complex thin-walled ship structures in concept and preliminary design. It elaborates the general requirements on the design procedure, balanced and applicable combinations of design models and a practical example of the basic analysis models/IT modules within the MAESTRO/OCTOPUS design support system. System identification from the multi-stakeholder perspectives of owner and society, and the formulation and solution to the dimensionally large-scale structural designs are presented as a step towards the practical implementation of multi-criteria decision-making in ship design practice since only a joint effort could lead to the satisfaction of all stakeholders in todays challenging ship-building industry. The practical structural design procedure/methodology, capable of embedding multiple design quality criteria, is demonstrated using a benchmark case study on the innovative RoPax ship.

Safety as Objective in Multicriterial Structural Optimization

Multicriterial design methodology with safety as one of the design objectives is presented. The aim of the paper is to analyze the influence of safety based design objectives on generated nondominated designs on the Pareto frontier. Possible improvements in nondominated designs are investigated by comparison to ones obtained with the standard design procedure when safety criteria are used as design constraints only. It is assumed that safety based objectives and targets act as attractors, driving nondominated designs along the constant cost/weight contours in design space towards its safer regions. Global safety objectives (for hogging/sagging modes), are based on the maximization of ultimate longitudinal strength in vertical bending calculated via the extended IACS incremental-iterative method. Applied compound safety measures for gross-panel (stiffened panel with associated girders) are based upon 34 failure modes, belonging to serviceability/collapse subsets. Objectives based on the maximization of safety measures are applied together with standard design objectives such as minimization of initial cost and weight. The following problems were solved with different sets of objectives: (a) minimize cost and weight objectives subject to safety constraints (used for reference), (b) only the maximization of local safety measures is added to (a) as additional objectives, (c) only the maximization of global safety measures is added to (a) as additional objectives, (d) maximization of safety measures ad (b) and (c) are added to (a) as additional objectives. For each of the problems (a–d) the developed design procedure is executed. It contains two basic tasks for structural design of realistic (non-academic) problems: (1) multicriterial optimization with topology / geometry design variables; (2) multicriterial optimization of gross-panels with scantling / material design variables. Design procedure steps are executed using a fast and balanced collection of analysis and synthesis modules/methods of the OCTOPUS design system: • Determination of design load sets; • MOGA / MOPSO based generation of nondominated designs for the selected ship structure; • For each design the following analysis blocks are executed: – calculation of ship’s primary and racking response fields, – calculation of ship’s ultimate longitudinal strength, – calculation of serviceability and collapse safety criteria on the gross-panel level. Comparisons of results, based on generated Pareto hyper-surfaces and on subset of preferred designs, are given for problems (a–d). Insights into the results of optimization process, using 5-D graphics for design and attribute spaces, are also presented. Design problems of modern RoPax and SWATH structures are used in case studies.Copyright

Optimization of tetanus toxoid ammonium sulfate precipitation process using response surface methodology

ABSTRACT Tetanus toxoid (TTd) is a highly immunogenic, detoxified form of tetanus toxin, a causative agent of tetanus disease, produced by Clostridium tetani. Since tetanus disease cannot be eradicated but is easily prevented by vaccination, the need for the tetanus vaccine is permanent. The aim of this work was to investigate the possibility of optimizing TTd purification, i.e., ammonium sulfate precipitation process. The influence of the percentage of ammonium sulfate, starting amount of TTd, buffer type, pH, temperature, and starting purity of TTd on the purification process were investigated using optimal design for response surface models. Responses measured for evaluation of the ammonium sulfate precipitation process were TTd amount (Lf/mL) and total protein content. These two parameters were used to calculate purity (Lf/mgPN) and the yield of the process. Results indicate that citrate buffer, lower temperature, and lower starting amount of TTd result in higher purities of precipitates. Gel electrophoresis combined with matrix-assisted laser desorption ionization–mass spectrometric analysis of precipitates revealed that there are no inter-protein cross-links and that all contaminating proteins have pIs similar to TTd, so this is most probably the reason for the limited success of purification by precipitation.

The Design Methodology with the Sequencer for Efficient Design Synthesis of Complex Engineering Systems

,The paper presents the design synthesis methodology and environment for the formulation of the Decision Support Problem (DSP) for complex engineering systems. The environment will be tested on a concept design of monotonous thin-walled metallic structures. DSP is based upon coordinated multi-criteria structural optimization and generation of the Pareto frontier. Underlying mathematical models, analysis/synthesis modules and the OCTOPUS software implementation are elaborated. Environment also includes flexible Sequencer for easy definition of optimization sequence necessary for efficient solving of complex engineering problems. Application of the developed design environment will be shown on example of concept design of tank car carrier

Structural design and analysis of a large ‘open type’ livestock carrier

ABSTRACT ‘Open type’ livestock carriers are multi-deck ships characterised by the large openings in the superstructure side shell and with the absence of transverse and longitudinal bulkheads in the superstructure. The height of the superstructure is approximately equal to the height of the lower hull and the influence of hull-superstructure interaction on longitudinal strength is very important and should be taken into consideration during determination of the structural scantlings in very early design phase. This kind of ship topology generates two main structural challenges in: (1) longitudinal strength due to partially effective participation of the superstructure in global hull girder bending and (2) transverse/racking strength due to absence of transverse bulkheads in the superstructure. Since relatively small number of vessels of this kind currently exists, their specific structural aspects are poorly documented in the literature. This paper discusses and highlights basic challenges in the structural design and analysis of the ‘open type’ livestock carriers, using ULJANIK shipyard Newbuilding 526 as an example.

Ship structural design support methodology for the reliability based design optimization (RBDO)

The objective of the paper is to present the structural design support system (DeSS) rationale for the reliability based design optimization (RBDO) in the concept design phase. Basic steps are as follows:• Interactive identification of the design problem (design variables, constraints, objectives) as well as design problem variates and their distribution parameters. Safety related design criteria are used as objectives and as constraints in the presented procedure;• Calculation of the cross section ultimate longitudinal strength criteria based on the extended Smith’s method; based on the Report SSC-398;• Selection of non-dominated designs (Pareto-optimal, NDD points) for the given deterministic design criteria;• Calculation of reliability/deterministic safety measures. Novel FASTREL code, based on the Dimension Reduction Method (DRM) is used for the reliability calculations;• Generation of insight into the Multi Attribute Decision Making (MADM) process with 5D graphic presentation of designs in design and attribute spaces in the interactive OCTOPUS Designer (Demak/DeView) IT modules.Practical application of the developed concept design methodology and of the design environment to the structural design of the verifiable test example corresponding to SSC-398 report. DeSS was used in fast generation of optimal designs using MODM (MOSLP) and MADM (MOPSO) techniques. To speed up the RBDO design process deterministic and probabilistic formulations of design problem were run concurrently and supporting each other are presented using the safety related design attributes (deterministic and reliability based) for the NDD supported decision-making technique.Copyright