Damaged Ship III
London, 25-26 March 2015
Polski Rejestr Statków S.A., Gdańsk
Conventional offshore damage stability evaluations for a generic jack up platform
The paper presents conventional stability calculations for a generic jack up platform, investigated in a number of papers at recent STAB conferences and workshops. These calculations are routinely carried out for a freely floating unit, longitudinally balanced at each heel angle. In such cases the GZ-curve is ambiguous, as it depends on the way the ship is balanced. Three cases are discussed: when the ship is balanced by rotating her around the trace of water in the midships, around a normal to the ship plane of symmetry (PS), and around a normal to the initial waterplane, fixed to the ship. In all these cases the direction of the righting moment in space is preserved, and the area under the GZ-curves, which is the lowest possible. Angular displacements (heel and trim) are the Euler's angles related to the relevant reference axis. Exemplary calculations illustrate how the way of balancing affects the GZ-curves.