DESIGN AGAINST COLLISION FOR OFFSHORE STRUCTURES

The main objective of this project was to develop a set of procedures and recommendations regarding the design of steel offshore structures so as to limit the extent of damage arising from accidental collisions. In order to achieve this main objective the following steps were taken: (1) development of an analytical theory for predicting the energy absorbing capability of typical steel tubular members of offshore structures (FY 81/82); (2) study and derivation of the structural layouts and the combination of structural parameters that can provide the best overall energy absorbing capability for the structure (FY 82); and (3) development of an appropriate fender systems for the protection of offshore installations (FY 83). In this paper, the force deflection curve for a rigid-plastic circular cylinder subjected to transverse loading applied by a sharp wedge is derived following an energy approach. A local deformation field is assumed and global deformation of the cylinder acting as a beam is neglected. The concept of the moving hinge with no slope discontinuity is used. The effects of the global deformation of the cylinder are then taken into consideration, and the overall force-deflection curve of the member acting as a beam is calculated. The above obtained force-deflection curve, in combination with the equivalent curve for a ship's bow, and also the foundation stiffness of a platform are used as spring data for a simplified two-mass dynamic model with linear and nonlinear springs. This model is then used to determine numerically the plastic deformation on one platform member (leg or brace) due to a collision with a ship. Finally, a method is outlined for a cost-benefit analysis of a minor collison vs. strength of a platform, using probabilistic data on the risk of such a collison, and the platform's damage calculation method presented above.

  • Supplemental Notes:
    • Report
  • Corporate Authors:

    Massachusetts Institute of Technology

    Sea Grant Program, 77 Massachusetts Avenue
    Cambridge, MA  United States  02139
  • Authors:
    • Mavrikios, Y
    • De Oliveira, J G
  • Publication Date: 1983-4

Media Info

  • Features: References;
  • Pagination: 176 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00661039
  • Record Type: Publication
  • Source Agency: Maritime Technical Information Facility
  • Report/Paper Numbers: MITSG-83-7
  • Contract Numbers: NA81-D-0069
  • Files: TRIS
  • Created Date: Jul 21 1994 12:00AM