Vol 75 No 2 75206

Abstract

Offshore assembly and disassembly operations represent a multi-billion-dollar market potential. Collaborative lifting by multiple vessels has emerged as a new operating paradigm for integrated offshore facilities assembly and disassembly. Hence, this paper investigates the hydro-dynamic interaction of dual lifting vessels in collaborative lifting operations. The coupled motions during multi-body operations are simulated using the commercial software SESAM. The feasibility of the numerical model for coupled motions in collaborative lifting is verified by comparing the numerical results of topside motions, vessel motions, and vertical lifting arm loads against experimental measurements. The effects of wave heading and period on the hydrodynamic responses of the topside module, dual lifting vessels, and lifting arms during collaborative operations are studied. Their influence patterns and mechanisms are analysed in detail. The results show that transverse waves and head wave induce significant heave and pitch motions of the topside module and vessels, but the maximum vertical loads on the lifting arms occur in oblique waves. The motion responses of the topside module and vessels increase with longer wave periods under the oblique sea condition, and roll motions are more sensitive to large periods compared to the gradual rise in heave and pitch.