Motion and Structural Analysis of Floaters Float-over during the Mating Operation

A new type of float-over method, called floaters float-over (FFO), is innovated and presented in this paper. FFO concept is to float the deck using two groups of floaters at the deck opposite sides. By ballasting and deballasting of the floaters, the system will be able to raise the deck from the transportation barge, move it and then lower it down above the jacket/spar (Geba 2013). FFO can work in wider range of sea states more than conventional float over methods. Also, it eliminates the need to design the platform for a "float through". In this paper, the concept and design philosophy of the FFO are presented. The comparison between the FFO motion characteristics and the results from model experiments shows good agreement. A time domain analysis during mating is performed, where the impact forces between deck and jacket legs are computed to investigate the sea states limitation. From the structural point of view, with the FFO the deck is exposed to a static sagging condition as the deck is hinged from its extreme sides rather than its original support locations. The additional stiffening required for the deck, globally and locally, is discussed and compared to other types of installation techniques.