INVESTIGATIONS ON THE DYNAMICS OF MOORED STRUCTURES IN WAVES

This study was instituted to investigate the dynamic characteristics and restraining forces of a moored, floating offshore drilling platform subjected to surface waves. A 1:144 model of the proposed structure was utilized during the experimental phase. To minimize structure motion, the design incorporated submerged buoyancy members and a mooring system to compensate for the net buoyant force on the structure. A combined experimental and analytical approach to the problem was used and included its treatment as a forced vibration problem. This further involved investigations of the natural frequency of the system and methods of improving platform performance by varying the natural frequency of the platform. Theoretical considerations included wave kinematics, wave forces on rigidly restrained bodies, and the theory of mechanical vibrations as applied to analysis of a submerged sphere and to the analysis of a floating platform, whereas experimental considerations included rigidly restrained and partially restrained tests of both spheres and the design model platform. Based on results of the study, the authors conclude that except in the region of second resonance, the maximum horizontal and vertical components of the total mooring system force decrease as the net buoyancy and natural frequency are decreased. Further study is recommended regarding behavior of such systems in the regions of second resonance and also the effects of the elevation of the platform center of gravity on slacking of the mooring system.

  • Corporate Authors:

    Massachusetts Institute of Technology

    Hydrodynamics Laboratory
    Cambridge, MA  USA  02139
  • Authors:
    • Harleman, DRF
    • Shapiro, W C
  • Publication Date: 1958-7

Media Info

  • Features: References;
  • Pagination: 108 p.
  • Serial:
    • Issue Number: 28

Subject/Index Terms

Filing Info

  • Accession Number: 00044466
  • Record Type: Publication
  • Source Agency: National Maritime Research Center, Galveston
  • Files: TRIS
  • Created Date: May 23 1973 12:00AM