engleski

STRUCTURAL OPTIMISATION METHOD FOR THE CONCEPT DESIGN OF SHIP STRUCTURES

Methodology for the structural concept design decision making using coordinated multicriterial structural optimisation is presented. Procedure is based on FEM response analysis, set of prescribed structural safety criteria and the goal coordination approach using multilevel decomposition of the design problem for coupled subsystems. The developed design system includes analysis and synthesis calculation modules. Modules used in the concept design model generation and analysis include : (1) modules for the structural FEM model data generation, (2) modules for loading generation, (3) modules for determination of the minimal scantlings following selected class. society rules, (4) modules for direct calculation of the longitudinal strength. Shear flow and corrected stresses in bending and warping torsion are calculated using original extended beam theory (5) modules for the transverse strength calculation. . Newly developed 8-node stiffened panel macroelements are used for modeling of the transverse structural response. (6) modules for the structural safety calculation based on the library of structural serviceability and ultimate strength criteria, (7) modules for the graphic presentation of the model, loading, deformations, stresses, safety factors, corrosion data, etc. Model compatibility with selected safety criteria is achieved via set of descriptors. Modules used in synthesis include : (1) Module for calculation of the sensitivity of the structural response w.r.t. design variables based on the longitudinal strength module (4), (2) The same for transverse strength based on analytical module (5). Derivatives of the deformation fields in both cases are based on concept of force derivatives, (3) Global level optimisation module for optimal distribution of cross-section material and generation of coordination constraints based on the acceptable levels of response, (4) Local coordinated subsystems are solved using sequential application of the methods based on theory of experiments. Local constraints are based on the nonlinear formulae for structural subsystem safety.(5) Control module for multilevel optimisation process, (6) Module for updating of model data in analytical module (1) for final design analysis. Application of the developed methodology to the structure of 3500 lanemeter Ro-Pax ship will be presented as practical example.

multicriterial structural optimisation; FEM response analysis; synthesis calculation modules

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