Floating offshore structures with round pontoons

1. A floating offshore structure, comprising:

a buoyant hull including a first column, a second column, and a pontoon coupled to the first column and the second column, wherein each column is vertically oriented and the pontoon extends horizontally from the first column to the second column;

wherein each column has a central axis, an upper end, and a lower end;

wherein the pontoon includes a first tubular member and a second tubular member positioned laterally adjacent to the first tubular member, wherein each tubular member has a central axis, a first end coupled to the lower end of the first column, and a second end coupled to the lower end of the second column;

where the central axis of the first tubular member and the central axis of the second tubular member are disposed in a common horizontal plane;

wherein each column comprises a plurality of vertically oriented tubular members, wherein each tubular member of each column has an upper end, a lower end, and an outer cylindrical surface;

wherein a first connection assembly couples the first end of the first tubular member of the pontoon to the lower end of one of the tubular members of the first column;

wherein a second connection assembly couples the first end of the second tubular member of the pontoon to the lower end of one of the tubular members of the first column;

wherein each connection assembly comprises a plurality of vertical brackets disposed along the outer surface of the corresponding tubular member of the column, wherein the vertical brackets of the first connection assembly define a circular recess that receives the first end of the first tubular member of the pontoon and the vertical brackets of the second connection assembly define a circular recess that receives the first end of the second tubular member of the pontoon.

2. A floating offshore structure, comprising:

a buoyant hull including a first column, a second column, and a pontoon coupled to the first column and the second column, wherein each column is vertically oriented and the pontoon extends horizontally from the first column to the second column;

wherein each column has a central axis, an upper end, and a lower end;

wherein the pontoon includes a first tubular member and a second tubular member positioned laterally adjacent to the first tubular member, wherein each tubular member has a central axis, a first end coupled to the lower end of the first column, and a second end coupled to the lower end of the second column;

wherein the central axis of the first tubular member and the central axis of the second tubular member are disposed in a common horizontal plane;

wherein the pontoon includes a heave plate fixably coupled to the first tubular member and the second tubular member, wherein the heave plate extends horizontally between the first tubular member and the second tubular member, wherein the heave plate extends axially relative to the central axes of the tubular members from the first ends of the tubular members to the second ends of the tubular members, wherein the heave plate is configured to be disposed subsea to dampen vertical motion of the floating offshore structure.

3. The offshore structure of claim 1 , wherein a first edge plate extends from the first tubular member and a second edge plate extends from the second tubular member, wherein the first tubular member, the heave plate, and the second tubular member are disposed between the first edge plate and the second edge plate.

4. The offshore structure of claim 3 , wherein the first edge plate extends axially relative to the central axis of the first tubular member from the first end of the first tubular member to the second end of the first tubular member;

wherein the second edge plate extends axially relative to the central axis of the second tubular member from the first end of the second tubular member to the second end of the second tubular member.

5. The offshore structure of claim 4 , wherein the first edge plate extends horizontally from the first tubular member and the second edge plate extends horizontally from the second tubular member.

6. The offshore structure of claim 5 , wherein the first edge plate, the second edge plate, and the heave plate are vertically centered relative to the first tubular member and the second tubular member.

7. The offshore structure of claim 1 , further comprising a first external deck coupled to the lower end of the first column and a second external deck coupled to the lower end of the second column;

wherein the first deck extends horizontally beyond an outer perimeter of the lower end of the first column and the second deck extends horizontally beyond an outer perimeter of the lower end of the second column.

8. The offshore structure of claim 7 , wherein each column comprises a plurality of vertically oriented tubular members, wherein each tubular member of each column has an upper end, a lower end, and an outer cylindrical surface;

wherein the first external deck closes off and seals the lower end of each tubular member of the first column and the second deck closes off and seals the lower end of each tubular member of the second column.

9. The offshore structure of claim 1 , wherein each tubular member of the pontoon has a circular cross-sectional shape.

10. The offshore structure of claim 9 , wherein each tubular member of the pontoon includes a plurality of axially spaced internal annular stiffeners.

11. A floating offshore structure, comprising:

a buoyant hull including a first column, a second column, and a pontoon extending from the first column to the second column;

wherein each column is vertically oriented and has a central axis, an upper end, and a lower end;

wherein the pontoon includes a first cylindrical tubular member and a second cylindrical tubular member oriented parallel to the first tubular member, wherein the second cylindrical tubular member is positioned laterally adjacent to the first cylindrical tubular member, wherein each tubular member is horizontally oriented and has a central axis, a first end coupled to the lower end of the first column, and a second end coupled to the lower end of the second column;

wherein the pontoon includes a heave plate fixably coupled to the first tubular member and the second tubular member, wherein the heave plate extends horizontally between the first tubular member and the second tubular member, wherein the heave plate extends axially relative to the central axes of the tubular members from the first ends of the tubular members to the second ends of the tubular members, wherein the heave plate is configured to be disposed subsea to dampen vertical motion of the floating offshore structure.

12. The offshore structure of claim 11 , wherein a first edge plate extends horizontally from the first cylindrical tubular member and a second edge plate extends horizontally from the second cylindrical tubular member.

13. The offshore structure of claim 12 , wherein the first edge plate extends axially relative to the central axis of the first cylindrical tubular member from the first end of the first cylindrical tubular member to the second end of the first cylindrical tubular member;

wherein the second edge plate extends axially relative to the central axis of the second cylindrical tubular member from the first end of the second cylindrical tubular member to the second end of the second cylindrical tubular member.

14. The offshore structure of claim 12 , wherein the heave plate, the first edge plate, and the second edge plate are disposed in a common horizontal plane.

15. The offshore structure of claim 11 , further comprising a first external deck coupled to the lower end of the first column and a second external deck coupled to the lower end of the second column;

wherein the first deck extends horizontally beyond an outer perimeter of the lower end of the first column and the second deck extends horizontally beyond an outer perimeter of the lower end of the second column.