ABSTRACT:

An efficient and automatic modeling preprocessor is developed for the finite element structural analysis of three dimensional cargo holds of typical commercial ships, i.e. oil tankers, bulk carriers, and container ships_ A hull module structure is divided into three groups for easy data handling: longitudinal members, transverse members, and transverse bulkheads: Based on classification rules and design practices at shipyards, the processor can create finite element nodes, elements, boundary conditions, and loading automatically. Automatic mesh discretization interface with MSCINASTRAN, direct wave load calculation interface, and graphic user interface technology in the process of input data preparation are included. By connecting the preprocessor with ANSYS and MSCINASTRAN programs, we can obtain the results of ship structural analysis more efficiently.

INTRODUCTION

At the initial stage of ship structural design process, the simple beam theory is a good approximation for safety assessment of a hull girder. More accurate analyses than the simple beam theory have been developed to increase the accuracy at the design stage, Among them, the modern beam theory is useful even for longitudinal-torsional strength calculations of hull girders (Fujitani, 1991). During last decade, the development of computer technologies in hardwares and softwares enables ship designers to analyze ship structures with high precision, mostly using finite element method. Three-dimensional finite element modeling of a whole structure requires costly computing time and man-hour, but gives little understanding of physical meanings of ship structural responses. For rational analyses of ship structures as a part of optimization, Hughes(1983) suggested a hull module analysis which has flexibility between the simple beam analysis and the full finite element analysis of a ship structure. In practices, the hull module analysis is called the three-dimensional cargo hold analysis since the hull module is actually a part of cargo holds at the parallel middle body of a ship.

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