STRUCTURAL DESIGN OF OIL TANKERS TRANSVERSE WEBS USING DESIGN OF EXPERIMENTS METHOD

The paper discusses the application of design of numerical experiments (DoE) method in structural design of ship structures. The object of the study is the design of transverse webs of double hull oil tankers in cargo tank area in accordance with the prescriptive requirements of Common Structural Rules (CSR). Even on preliminary stage of structural design process there is a need for some decision-making support. This is explained with the significant complexity of functional relations between design parameters. For oil tankers primary supporting members' main features are dependence of effective spans, design loads and effective breadth of attached plates on depth of the webs, as well as the dependence of bending moments on stiffness ratios. DoE methodology can help to find adequate correlations between design parameters determining scantlings and global characteristics of the structure (e.g. mass) as multifactorial regression equations (response surfaces) using a minimal number of analyses. Consequently, nonlinear mathematical programming method to determine the efficient solution can be used. In this paper application of these methods is presented as an algorithm for design process of transverse web in the center tank of VLCC tanker. Moments of inertia are used as variables. Goal function is presented as characteristic of mass of the structure. Constrains are formed with requirements of CSR Prescriptive primarily. The example with results of calculations is also given. It is shown that the goal function and constraints in this model can be accurately approximated with quadratic polynomials. The study shows that obtained results are rather close to the values for existing designs.