Quadratic nonlinear terms are retained in the heave, roll, and pitch governing equations of motion for a semi-submersible platform in a regular sea and the method of multiple scales is used to predict the response. Due to nonlinear effects, unstable motions are found to occur when the wave frequency is approximately twice one of the natural frequencies (heave, pitch, or roll) of the platform and when the wave frequency is near either the sum of the heave and roll natural frequencies or the sum of the heave and pitch natural frequencies. The occurrence of the instabilities depends on the magnitude of wave excitation, and since the instabilities occur at wave frequencies where ample energy from the sea exists for excitation, the possibility of large platform motions is enhanced.

Media Info

  • Features: References;
  • Pagination: p. 9-15

Subject/Index Terms

Filing Info

  • Accession Number: 00135376
  • Record Type: Publication
  • Source Agency: Engineering Index
  • Files: TRIS
  • Created Date: Jul 13 1976 12:00AM