ANALYSIS OF JACK-UP UNITS DURING TRANSIT WITH LEGS LOWERED

Conventionally jack-up units are transported from one location to another with the majority of their legs extended above the hull. On certain occasions, due to possible storm conditions, they must lower their legs below the hull significantly to maintain expected vessel motions within an acceptable level. During a storm, the unit will respond with six degrees of motion while afloat. The extended portion of the legs below the hull will be subjected to drag loads. Unlike the condition with legs extended in air, analysis of a jack-up with its legs lowered below the hull has not been widely reported in published literature. This paper reports the motion analysis of a jack- up for different leg drafts and indicates the safe limits up to which the leg can be extended below the hull without overstressing it.