MOTION RESPONSE SIMULATION OF A TWIN-HULLED SEMISUBMERSIBLE

The purpose of the study was to develop a prediction technique to simu late the motion response of a damaged platform under wave, wind and cu rrent forces. The equations of motion were obtained using Newton's sec ond law and the numerical solution technique of non-linear equations o f motion is explained for intact and damaged cases. The analysis techn ique employs large displacement non-linear equations of motion. Soluti ons were obtained in the time-domain to predict the motion characteris tics. In this study, analysis procedures were developed to calculate: (a) wave loading on-asymmetrical structural configurations; (b) hydrod ynamic reaction forces (inertia or moment of inertia, damping and rest oring forces) on asymmetrical shapes. During the damage simulation, ch ange in the mass of the structure as well as wave and hydrodynamic rea ction forces, were taken into account. The computer program developed for the time-domain simulation is introduced. In order to avoid slowly decaying transient motions of the structure due to wave excitation fo rces, an exponential ramp function is used. The application of a ramp function enables a quick convergence in the time-domain solution of eq uations of motion. Results of a numerical motion simulation program an d the experimental studies are also presented in order to make compari sons. Comparison of the test results with the numerical simulations sh ows good agreement far heave, roll and pitch motions. The formulations and the computational procedures given in this paper provide useful t ools for the investigation of the non-linear dynamic stability charact eristics of Roaring structures in waves for intact, damaged and post-f looding conditions in six-degrees of freedom. (C) 1997 Elsevier Scienc e Ltd.