On the Program System for Design and Analysis of Offshore Structures

Various types of offshore structures including drilling rigs, platforms, etc. have been built. These days, they are requested to have better working performance in severer state of sea and weather, and as a recent trend, they are becoming larger in size and more complex.However, they appeared just several decades ago, and the data to design them is not accumulated so much as general ships. These structures are to be designed under the rational and synthetic estimation of behaviors in sea, and the safety is also to be confirmed experimentally or analytically.For that purpose, the authors have developed the total system of computer program for design and analysis for floating offshore structures. The system made it possible to realize the rational and consistent evaluation on the behaviors and the safety of them.This system consists of an integrated group of individual programs which includes hydrostatic calculation, tank capacity calculation, trim and stability calculation for intact and damaged condition, analysis on the oscilating motion of the structures among regular waves and wave force calculation, the statistical analysis on each response of the structures among irregular waves, etc.Furthermore, this system can be used individually or successively according to the needs in every stage of design or analysis.In this paper, outline of this system is presented with examples of calculation using this system for the existing semi-submersible catamaran drilling rig, from which the reasonable results were gained.