Abstract
Many aging large offshore platforms are facing the problem of decommissioning and dismantling. In this paper, a method of removing the upper module of the platform by using a twin marine lifter system (TML) is proposed. In order to study the reliability of this method, added mass, damping, wave force and RAO of the three-ship system are analyzed, and the influence of three-ship interaction and water depth on the hydrodynamic parameters of the three-ship system are investigated. The hydrodynamic analysis is carried out under different environmental conditions, and the variation characteristics of the hydrodynamic parameters of the ship in the three-ship system are obtained. The results show that when three ships are alongside, the interaction of the three ships will have a significant effect on the hydrodynamic parameters, and the interaction of the three-ship system on the hydrodynamic parameters is mainly in the wave frequency range; The system is sensitive to changes in sea state conditions, and the motion response is maximum when the wave angle is 90° and minimum at 0°, but there is still some lateral motion. In practical operation, it is necessary to avoid the wave frequency and the direction of environmental load when the motion response is large, and consider the relevant effects in mooring and dynamic positioning.
