Safety evaluations of an large offshore structure subjected to dynamic forces

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Performing the dynamic response evaluations for the offshore structure subjected to wave forces, uncertainties on the characteristics of the structure and wave forces have to take into accounts for the response evaluations. It is very important to evaluate the uncertain parameter effects on the maximum response evaluation for the reliability evaluation. The Monte Carlo simulation (MCS) gives an effective method on the evaluations of the uncertainties. The MCS approach is applied to evaluate effects of the uncertainties on the offshore structure in the present study. It is shown that since the uncertain parameters play the important roles on the maximum response evaluations, it is important for the reliable design of the offshore structure to account for the effects on uncertainty with respect to the response. The main results are summarized as follows :(1)Since the uncertainties with respect to the wave force evaluations play important contributions on the response properties, it is essential for the reliable design of the structure to make it clear the response properties due to uncertainties. For enhancing the safety of the offshore structure subjected to severe wave forces, it is important to account for the uncertain parameter effects.(2)The uncertainties such as the drag coefficient and the inertia coefficient play relatively small effects on the reliability index in the present situation. The other hand, since the variations of the mean wave height ant and mean wave period give important effects on the maximum response evaluation, it is important for the reliable design of the structure to account for the uncertain parameter contributions with respect to reliability index.