Patent EA-002289-B1 (EA)
Title: Earthquake compliant offshore platform jacket structure
Inventor: GLASSCOCK M SIDNEY
IPC: E02B17/00
Filed: 1998-06-08
Abstract: 1. An earthquake-compliant offshore platform jacket structure for use in an earthquake-prone body of water, comprising: a substantially vertical space-frame structure having a substantially uniform horizontal cross section extending upwardly from the floor of the body of water to a point located above the surface of the body of water; foundation means for attaching said space-frame structure to the floor of said body of water; and a deck structure attached to the upper end of said space-frame structure; wherein said space-frame structure, said foundation means, and said deck structure are designed such that the natural vibrational period of said space-frame structure is greater than the primary excitation period of earthquake energy and less than the primary wave period of storm energy in said body of water. 2. The earthquake-compliant offshore platform jacket structure of claim 1, wherein said substantially uniform horizontal cross section is a square cross section. 3. The earthquake-compliant offshore platform jacket structure of claim 1, wherein said foundation means comprises a plurality of skirt piles attached to the lower end of said substantially vertical space-frame structure and extending downwardly into the floor of said body of water. 4. The earthquake-compliant offshore platform jacket structure of claim 1, wherein said foundation means comprises a plurality of piles attached at any point along the length of said substantially vertical space from structure and extending downwardly into the floor of said body of water. 5. The earthquake-compliant offshore platform jacket structure of claim 1, wherein said natural vibrational period of said space-frame structure is between about 4 seconds and about 8 seconds. 6. An earthquake-compliant offshore platform jacket structure for use in an earthquake-prone body of water, comprising: a substantially vertical space-frame structure having a substantially uniform horizontal cross section extending upwardly from the floor of the body of water to a point located above the surface of the body of water; foundation means for attaching said space-frame structure to the floor of said body of water; and a deck structure attached to the upper end of said space-frame structure; wherein said natural vibrational period of said space-frame structure is between about 4 seconds and about 8 seconds in said body of water, taking into account the effects of said foundation means and said deck structure. 7. The earthquake-compliant offshore platform jacket structure of claim 6, wherein said substantially uniform horizontal cross section is a square cross section. 8. The earthquake-compliant offshore platform jacket structure of claim 6, wherein said foundation means comprises a plurality of skirt piles attached to the lower end of said substantially vertical space-frame structure and extending downwardly into the floor of said body of water. 9. The earthquake-compliant offshore platform jacket structure of claim 6, wherein said foundation means comprises a plurality of piles attached at any point along the length of said substantially vertical space from structure and extending downwardly into the floor of said body of water. 10. An earthquake-compliant offshore platform jacket structure for use in an earthquake-prone body of water, comprising: a substantially vertical space-frame structure having a substantially uniform horizontal cross section extending upwardly from the floor of the body of water to a point located above the surface of the body of water; foundation means for attaching said space-frame structure to the floor of said body of water; and a deck structure attached to the upper end of said space-frame structure; wherein said natural vibrational period of said earthquake-compliant jacket structure is greater than the primary excitation period of earthquake energy and less than the primary wave period of storm energy in said body of water. 11. The earthquake-compliant offshore platform jacket structure of claim 10, wherein said substantially uniform horizontal cross section is a square cross section. 12. The earthquake-compliant offshore platform jacket structure of claim 10, wherein said foundation means comprises a plurality of skirt piles attached to the lower end of said substantially vertical space-frame structure and extending downwardly into the floor of said body of water. 13. The earthquake-compliant offshore platform jacket structure of claim 10, wherein said foundation means comprises a plurality of piles attached at any point along the length of said substantially vertical space from structure and extending downwardly into the floor of said body of water. 14. The earthquake-compliant jacket structure of claim 10, wherein said natural vibrational period of said jacket structure is between about 4 seconds and about 8 seconds. 15. An earthquake-compliant offshore platform jacket structure for use in an earthquake-prone body of water, comprising: a substantially vertical space-frame structure having a substantially uniform horizontal cross section extending upwardly from the floor of the body of water to a point located above the surface of the body of water; foundation means for attaching said space-frame structure to the floor of said body of water; and a deck structure attached to the upper end of said space-frame structure; wherein said natural vibrational period of said earthquake-compliant jacket structure is between about 4 seconds and about 8 seconds. 16. The earthquake-compliant offshore platform jacket structure of claim 15, wherein said substantially uniform horizontal cross section is a square cross section. 17. The earthquake-compliant offshore platform jacket structure of claim 15, wherein said foundation means comprises a plurality of skirt piles attached to the lower end of said substantially vertical space-frame structure and extending downwardly into the floor of said body of water. 13. The earthquake-compliant offshore platform jacket structure of claim 15, wherein said foundation means comprises a plurality of piles attached at any point along the length of said substantially vertical space from structure and extending downwardly into the floor of said body of water.