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1. WO2010085383 - PRELOADING TO REDUCE LOADS AND SAVE STEEL ON TOPSIDES AND GRILLAGE OF CATAMARAN SYSTEMS

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WHAT IS CLAIMED IS:

1. A method of preloading a catamaran system to reduce loading and material on a topsides for a fixed or floating offshore structure, comprising:

5 transferring a topsides having a weight onto at least two float-over barges; coupling the topsides with the barges to create the catamaran system; and at least partially counteracting a sagging bending moment caused by the weight of the topsides disposed between the barges.

2. The method of claim 1 , wherein at least partially counteracting the sagging I0 bending moment comprises adjusting a ballast condition of the barges.

3. The method of claim 2, wherein adjusting the ballast condition of the barges comprises adding a ballast disposed outwardly from a lateral center of gravity of the barges, at least partially removing a ballast disposed inwardly from the lateral center of gravity, at least partially redistributing a ballast i5 disposed inwardly from the lateral center of gravity to a location disposed outwardly from the lateral center of gravity, or a combination thereof.

4. The method of claim 1 , wherein coupling the topsides with the barges comprises coupling one or more bracing members between the topsides and the barges, a grillage system disposed on the barges, of a combination 0 thereof, the bracing members being disposed inwardly from a lateral center of gravity of the barges.

5. The method of claim 4, wherein at least partially counteracting the sagging bending moment comprises adjusting a ballast condition of the barges after coupling the one or more bracing members to create an upward force on the 5 bracing members to at least partially counteract the sagging bending moment.

6. The method of claim 4, further comprising: loading a ballast to the barges at any time prior to coupling the one or more bracing members; and coupling the one or more bracing members prior to completely transferring the topsides having the weight onto the at least two float-over barges.

7. The method of claim 4, further comprising loading a ballast to the barges at any time prior to coupling the one or more bracing members to create a 5 downward bias on portions of the barges disposed inwardly from the lateral center of gravity of the barges before coupling the one or more bracing members, and wherein adjusting the ballast condition of the barges comprises reducing the downward bias to create the upward force on the bracing members.

o 8. The method of claim 1 , further comprising transporting the catamaran system to a location for installing the topsides on the offshore structure, while at least partially counteracting the sagging bending moment.

9. A catamaran system created for a fixed or floating offshore structure, comprising: s a topsides adapted to be installed onto the offshore structure; at least two float-over barges adapted to support the topsides, the topsides being coupled to each of the barges with the barges being spaced apart from each other, the barges having a ballast condition adapted to create at least a partial counteracting moment to a sagging bending o moment created by the weight of the topsides on the barges.

10. The system of claim 9, wherein the topsides is coupled to each of the barges so that a center of the topsides is disposed between the barges and further comprising a bracing member coupled between the topsides and each barge at a portion of the barges disposed inwardly toward the center of the 5 topsides, the ballast condition being adjustable to create an upward force on the topsides through the bracing member to at least partially counteract the sagging bending moment.

11. The system of claim 9, wherein at least a portion of a ballast is disposed outwardly from a lateral center of gravity of the barges in a direction distal from the topsides coupled between the barges, the ballast adapted to at least partially counteract the sagging bending moment.

12. The system of claim 9, wherein at least a portion of a ballast disposed inwardly from a lateral center of gravity of the barges in a direction proximal to the topsides coupled between the barges is removed or redistributed to a location outwardly from the lateral center of gravity of the barges, the at least portion of the ballast adapted to at least partially counteract the sagging bending moment.

13. The method of claim 12, wherein the ballast condition comprises a ballast coupled to the barges to create a downward bias on a portion of the barges disposed inwardly toward the center of the topsides prior to the bracing member being coupled between the topsides and each barge, and wherein the ballast condition being adjustable to create the upward force on the topsides comprises a reduced ballast at the downwardly biased portion of the barges, an added ballast disposed outwardly from a lateral center of gravity of the barges, a redistributed ballast disposed at least partially outward from the lateral center of gravity, or a combination thereof to at least partially counteract the sagging bending moment.

14. The method of claim 9, wherein the catamaran system is transported to the offshore structure while the sagging bending moment is at least partially counteracted.