Patent ID: 7011472

Claim:
A semi-submersible offshore vessel ( 1 ) exhibiting a first end ( 2 ) and a second end ( 4 ), said vessel ( 1 ) comprising: a substantially rectangular ring-pontoon ( 6 ) including a first transverse pontoon section ( 10 ) located at the first end ( 2 ) of the vessel ( 1 ); a second transverse pontoon section ( 12 ) located at the second end ( 4 ) of the vessel ( 1 ), said second transverse pontoon section ( 12 ) being parallel to the first transverse pontoon section ( 10 ), the ring-pontoon ( 6 ) further including two mutually parallel longitudinal pontoon sections ( 14 ) extending between said first ( 2 ) and second ends ( 4 ) of the vessel ( 1 ); at least four support columns ( 16 , 18 , 20 , 22 ) extending upwardly from respective edge-portions ( 23 ) of said ring-pontoon ( 2 ), said support columns ( 16 , 18 , 20 , 22 ) being arranged in a first column pair ( 24 ) located at the first end ( 2 ) of the vessel ( 1 ) and a second column pair ( 26 ) located at the second end ( 4 ) of the vessel ( 1 ); and an upper deck structure ( 28 ) positioned upon said support columns ( 16 , 18 , 20 , 22 ), wherein the first transverse pontoon section ( 10 ) has a vertical mean cross-section area (A) which exceeds the corresponding vertical mean cross-section area (B) of the second transverse pontoon section ( 12 ), and the support columns ( 20 , 22 ) in the second column pair ( 26 ) each has a water-plane area (E) which exceeds the water-plane area (D) of each of the support columns ( 16 , 18 ) in the first column pair ( 24 ).