The reliability evaluation on the offshore platform of an idealized three dimensional model subjected to wave and seismic force is carried out using the MCS approach in the present study. It is important to verify the response properties of the offshore structure with uncertainties to dynamic forces and structural properties. In order to enhance the performance based design of the offshore structure, it would be important to examine the uncertainty on the nonlinear response situation due to severe dynamic forces. It is suggested that the available estimation of performance based responses on the offshore structure can be carried out the reliability index evaluated with the MCS simulation to dynamic forces with considerably different characteristics.
Damage evaluations of the structure subjected to severe wave forces and seismic forces give important roles on the reliable design of the structure. The strength demand spectrum is one of the most useful methods to be treated with the nonlinear response effects on the structure subjected to severe seismic motions. In order to implement the reliable design of the offshore structure, it is important to verify the effects on the uncertainties to the maximum response estimation as well as the nonlinear responses. For the offshore structure subjected to dynamic forces, the dynamic response is usually carried out with the time domain analysis and spectrum analysis. While the wave force should be most important dynamic force, it should be considered to clarify the combined contribution with the seismic force for the offshore structure located in seismic active area. For the structure subjected to severe seismic motions, it is very important to carry out the reliable evaluation with respect to damage situations. There are several available methods on the damage evaluations of the structure subjected to seismic motions.
