Dynamic Response and Reliability Evaluations of an Offshore Platform with Pile-soil Foundation System due to Wave and Seismic Forces

摘要

For the reliable design of an offshore platform, it is very important to accurately evaluate the effects of both wave and seismic forces on the platform. The eigenfunction method was applied to calculate the wave force on the offshore platform having permeable cylindrical structures. Especially, it has been well recognized the importance of dynamic soilstructure interaction for several structures founded on soft soils. In order to examine the effects of soil-structure interaction, the substructure method is applied to the dynamic response evaluations of the platform. For the idealized three-dimensional platform with the pile-soil foundation system, the dynamic response evaluations were carried out through the modal analysis. On the other hand, the uncertainty effects of dynamic forces and structural properties play very important roles on the reliability evaluations of the platform. The Monte Carlo Simulation (MCS) method is very effective to access these influences. If the limit state function is given by the most critical situations of dynamic responses, the reliability evaluations of the platform can be effectively calculated by the reliability index with the results obtained from MCS. The reliability evaluations of offshore platform influenced by severe waves and seismic forces were examined from the reliability index. Since the uncertainty of the wave and seismic forces is important for dynamic response evaluations, it is necessary for the reliable design of the offshore structure to clarify the effects of uncertainties.