Numerical analysis of jacking operations for a self-elevated jack-up unit

Localized failure and collapse of a jack-up unit may take place during installation on site, especially under severe sea state conditions. To minimize the loss, structural behavior is predicted before construction. When the hull of a unit is elevated from sea water level, the structure system varies with time. This means that normal structural analysis is difficult to satisfy the relevant requirements. To capture the system status at different times, an innovative method is proposed and incorporated into Finite Element Analysis (FEA). With a full model of a jack-up unit having been built and with the techniques developed, behavior such as Rack phase difference (RPD), vertical reaction forces of the pinions and footing reactions, etc., under different loads and boundary conditions can be determined by FEA in the time domain. These valuable data would be helpful in re-designing the unit, and also provide guidance for site installation. To determine the general characteristics of a jack-up unit, case studies on a practical design have been done, with some important findings concluded.