Battered column semi-submersible offshore platform

Abstract

A semisubmersible platform includes a deck supported on the upper ends of support columns extending upwardly from a horizontally disposed pontoon-ring. The columns are battered inwardly and upwardly from the pontoon-ring to the deck. Mooring lines passing through fair leads on the outer faces of the base nodes anchor the platform to the seabed. The footprint of the battered columns is greater than the footprint of the deck supported on the upper ends of the columns.

1 . A semisubmersible floating platform, comprising:
 a) horizontally disposed pontoons interconnected by base nodes to form a substantially rectangular pontoon-ring, said base nodes having a height profile substantially matching said pontoons;   b) at least four battered support columns extending upwardly from said base nodes; and   c) a deck supported above a water surface on upper ends of said battered columns.   
   
   
       2 . The platform of  claim 1  wherein said support columns, said base nodes and said pontoons define a continuous load path between said deck and said pontoon-ring. 
   
   
       3 . The platform of  claim 1  wherein said battered columns support said deck inboard of the outer face of said pontoons. 
   
   
       4 . The platform of  claim 1  wherein said battered columns incline inwardly at an angle less than about 20 degrees from vertical. 
   
   
       5 . The platform of  claim 1  wherein the restoring moment of said platform increases as the draft of said platform decreases. 
   
   
       6 . The platform of  claim 1  wherein said battered columns have an aspect ratio of about 1.4. 
   
   
       7 . The platform of  claim 1  wherein said battered columns are substantially rectangular in cross section with rounded corners. 
   
   
       8 . The platform of  claim 1  wherein said battered columns include a transition portion at the lower ends thereof. said transition portion having an end cross-section substantially matching the profile of the top surface of said base nodes. 
   
   
       9 . The platform of  claim 1  wherein the ends of said pontoons define a width dimension that is equal to, less than, or greater than the width dimension of said pontoons at an intermediate portion thereof. 
   
   
       10 . The platform of  claim 1  including risers secured to an inner or outer surface of said pontoons.