Numerical modeling of load transfer unit of the float-over installation

Abstract

Recently, the float-over installation is used to install the topside deck module of offshore structure. The main advantage is the modular installation of the large topside without lift vessel. It gives short installation time and avoids the rental difficulty of the lift vessel. And the cost reduction is also expected because all of fabrication and inspection on the topside is done in onshore. The most important stage of the float-over installation is mating operation. In this stage, the topside, substructure and barge are connected by special load transfer units like Leg Mating Unit (LMU) and Deck Support Unit (DSU). Ballasting operation of the installation barge is also carried out to perform load transfer in this stage. During ballasting process, the hydrodynamic characteristics of the vessel can be changed with respect to draft conditions. In this study, the float-over installation is numerically investigated by applying time-domain simulation method. Focus is made on the numerical modeling of LMU and ballasting operation in mating stge. LMU is modeled based on the characteristics of its geometry. The impact forces acting LMU are observed under the different loading conditions and ballasting operation. Copyright ？ 2014 by the International Society of Offshore and Polar Engineers (ISOPE).