HYDRODYNAMIC ANALYSIS OF A SPREAD MOORED PLATFORM IN THE OPEN SEA

Results of a theoretical study and laboratory and field study of a moored construction type platform excited by irregular surface gravity waves are presented in this report. The field study consisted of observations and measurements of water level variations, chip rotations and accelerations, mooring forces, and wind velocities in several sea states for a platform which was spread moored by four 2-1/2-inch die-lock chains in about 165 feet of water in the open Pacific for an additional sea state. The analysis method of the recordings for both the prototype and model tests was based on time series techniques to provide apparent amplitude response operators for all ship motions and mooring forces. The linear theory of ship motion was used to predict the motions of the barge when excited by regular uniform surface gravity waves. The fundamental analytical tool used in the computations was the slender-body theory. Comparison between theory, model and prototype results indicate excellent agreement for surge, sway, roll, heave, and pitch motions, but poor agreement for yaw motion. Based on this study, the author concludes that the most probable value of the annual maximum force induced on any of the moorings is 120 kips and that the present mooring configuration possesses sufficient reserve strength to preclude failure of the moorings due to wave induced motions. The discussion is supplemented with illustrations, a tabular summary of results and computations, and a listing of computer programs utilized in this study.

• Corporate Authors:

  Naval Civil Engineering Laboratory

  Port Hueneme, CA  United States 
• Authors:
  • Muga, B J
• Publication Date: 1964-8

Media Info

• Features: References;
• Pagination: 215 p.

Subject/Index Terms

• TRT Terms: Dynamic loads; Floating structures; Hydrodynamic pressure; Moored structures; Mooring; Offshore platforms
• Uncontrolled Terms: Floating bodies
• Old TRIS Terms: Hydrodynamic forces
• Subject Areas: Bridges and other structures; Marine Transportation; Terminals and Facilities; Vehicles and Equipment;

Filing Info

• Accession Number: 00048052
• Record Type: Publication
• Source Agency: National Maritime Research Center, Galveston
• Report/Paper Numbers: R-440 Tech Note
• Files: TRIS
• Created Date: Oct 31 1974 12:00AM