Page 77 - Practical Design Ships and Floating Structures

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directly with an automatic search for optimum sizing (scantling). Design variables (plate thickness,
stiffener dimensions and their spacing) are freely selected by the user.

LBR-5 (Figure 1) is composed of 3
basic modules (OPTI, CONSTRAINT
and COST). The user selects the
relevant constraints (geometrical and
structural constraints) in external
databases. Standard constraint sets are
also proposed to users.

This paper describes briefly the
rational optimization procedure, the
innovative concept and methodology,
and the way they are implemented. It
focuses on the “Module-Oriented
Optimization” concept and on the
CONSTRAINT module. The LBR- Figure 1 : LBR-5 flow chart including some
5’s major uniqueness is how the
different modules interact. available sub-modules (constraints and cost data).

A detailed application on the Selection and initialisation of design variables (XI) e
optimization of a floating storage and lower-uppa bounds (Xmm 5 XI 5 Xmax).
offloading unit (FSO) and the CONSTRAINT MODULE
relevant information on the Geomebical mnrtraints (C(xi)) and sensitivities (X/&i).
mathematical algorithm of the OPTI Structural Constraints related to the global srmchlre
module are available in Rig0 (2001 .b). and sensitivity analysis (stress, displ .cement$... )
Detailed information on the COST
module is available in Rig0 (2001.c). Computation of deformations,

As its advantages appear mainly at
this level, application fields of LBR-5
include hydraulic structures and naval Other Structural Constraints and Sensitivities.
structures and concern the - Plate 1
preliminary design stage. It is indeed - Stiffeners I Buckling ...
during the first stages of the project -Stiffened Plates J 1 Ultimate Strength ...
that flexibility, modelling speed and - Box/Hull Girder
ease of use provide precious help to
designers. At this momentfew , , ,, - --. ,
parmetersldimensions have been
definitively fixed and a coarse OPTI-MODULE
Research of the Optimum qGb
modelling by standard finite elements Link with data from the CONSTRAINT and COST modules.
is often unusable. For ships, the New XI
application domain is clearly the Updating the Design (dimensions) with new values for the
ship’s central part (cylindrical and design variables provided by CONLRJ
prismatic zone of cargo ships,
passenger vessels, etc.). This zone is
the most important in length for the OPTIMUM SOLUTION
big floating units.
Figure 2: Chart of the LBR-5 model with
CONSTRAINT. COST and OPT1 modules.