Flex-Leg Offshore Structure

Abstract

A leg assembly for a compliant offshore tower provides a structure allowing foundation drive piles to be driven and attached entirely externally to the space frame of the tower, and simultaneously providing restraints on bending forces within the drive pile—flex leg connection structure, allowing for ease of construction and assembly and greater strength and life-expectancy for the structure.

1 . A leg assembly for use in supporting a compliant offshore tower, said assembly comprising
 a drive pile inserted essentially vertically into the sea floor,   a drive pile sleeve connected to said drive pile,   a flex leg comprising an upper section and a lower section, wherein said lower section of said flex leg is connected to said drive pile sleeve, and   a support leg, wherein said upper section of said flex leg is connected to said support leg,   wherein said drive pile, said drive pile sleeve, said flex leg, and said support leg are constrained from relative horizontal motion.   
   
   
       2 . The leg assembly of  claim 1 , comprising a plurality of drive piles. 
   
   
       3 . The leg assembly of  claim 1 , comprising a plurality of flex legs. 
   
   
       4 . The leg assembly of  claim 2 , comprising a plurality of flex legs. 
   
   
       5 . The leg assembly of  claim 4 , wherein the number of flex legs is less than the number of drive piles. 
   
   
       6 . The leg assembly of  claim 4 , wherein the number of flex legs is equal to the number of drive piles. 
   
   
       7 . The leg assembly of  claim 1  wherein said flex leg is a telescoping flex leg. 
   
   
       8 . The leg assembly of  claim 3 , wherein said flex legs are telescoping flex legs. 
   
   
       9 . The leg assembly of  claim 2 , wherein said drive piles are not symmetrically arrayed with respect to said support leg. 
   
   
       10 . The leg assembly of  claim 3 , wherein said flex legs are symmetrically arrayed with respect to said support leg. 
   
   
       11 . The leg assembly of  claim 1 , comprising a plurality of vertically separated constraints, wherein said drive pile, said drive pile sleeve, said flex leg, and said support leg are constrained from relative horizontal motion by said plurality of vertically separated constraints. 
   
   
       12 . The leg assembly of  claim 11 , wherein the compliant offshore tower comprises a space frame comprising horizontal bracing levels, and said plurality of vertically separated constraints are connected to said space frame at essentially the vertical position of one of said horizontal bracing levels. 
   
   
       13 . The leg assembly of  claim 12 , wherein said plurality of vertically separated constraints are connected to said space frame at essentially the vertical positions of a plurality of said horizontal bracing levels.