Many offshore structures have to be installed sub-surface by means of lift operations. Such operations are traditionally conducted by semisubmersible crane vessels but nowadays more and more of smaller monohull vessels with relatively large crane capacities are deployed. Solid workability criteria are crucial for both the safety and the feasibility and economy of the operation, especially in harsh weather climates where the work has to be completed in a narrow time window. Operational limits today are often set in terms of statistical wave height based on vessel response and sometimes on a lift dynamics analysis with multi bodies.

For the above water phase and the deeply submerged situation, multibody lift dynamics can be simulated and these computational methods have proved to work well [1]. The phase where the structure is passing the splash zone requires special attention. In the upper wave zone, however, the structure is subject to non-linear wave action including non-linear viscous effects. Although some work is reported on the computational approaches [2], [3] and scale model verification, a thorough full scale validation is required to understand the possibilities and limitations of computational models and to provide input for further developments.