Control of extreme wave-induced vibration of offshore jacket platform using deck isolation

The paper investigates the performance of passive deck isolation for a fixed offshore jacket platform under both regular and irregular wave loading, corresponding to an extreme sea state. The control efficiency in reducing the deck responses is presented over a wide range of the isolation layer flexibility and damping. A detailed numerical study is conducted on an example 90 m high platform located at 80 m depth of sea. It is seen that deck isolation can substantially mitigate the deck acceleration response and that there is an optimum damping for a selected value of the isolation layer flexibility. The control of deck displacement is moderate and requires high isolation layer damping. This is due to the shift in the fundamental period of the isolated structure towards the dominant wave period. Bearing displacements under wave load are not found to be of equal concern as in the case of seismic loading.