Dynamic analysis of lift-off operation of offshore wind turbine jacket foundation from the transportation barge

Abstract

The lift-off operation of the offshore wind turbine jacket foundation from a barge is investigated in this study. Firstly, the hydrodynamic analysis of the two ships is carried out via AQWA, considering the series configuration and L-shaped configuration. The damping lid method is introduced to address viscous correction and validated by a frequency-time-domain validation. The damping lid factor for the two configurations are set to be 0.02 and 0.04. The time-domain simulation of multi-body lifting system, including lifting wires, slings, and deck fenders, are then carried out. In the nonstationary time-domain simulation, the sensitivity of wave direction, vessel configuration and deck fender stiffness are investigated, indicating that the most critical stage during the lift-off operation corresponds to when about 70% weight of the jacket is lifted by the heavy-lift vessel. The series configuration under head sea in 70% load transfer stage is chosen for subsequent steady-state simulations. Extreme value analysis is carried out based on the Gumbel distribution. The allowable sea states are then evaluated. The operability is obtained by using the 20-year hindcast wave data of three certain sites off Guangdong, Fujian and Zhejiang coast, which are 60%, 55% and 65%, respectively.