Full Content is available to subscribers

Subscribe/Learn More  >

Airgap on Semi Submersibles: A Practical Guide on the Implementation of a Stochastic Approach

[+] Author Affiliations
Otto DaSilva, Harris Knecht

Exmar Offshore Company, Houston, TX

Paper No. OMAE2011-49278, pp. 197-203; 7 pages
  • ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering
  • Volume 2: Structures, Safety and Reliability
  • Rotterdam, The Netherlands, June 19–24, 2011
  • ISBN: 978-0-7918-4434-2
  • Copyright © 2011 by ASME


Several articles in the literature cover methods for the prediction of semi submersible airgap. In general, using these methods, the reader will have to take care of the implementation, because in most cases not all factors that influence the final airgap are covered. This paper will describe the practical implementation of a calculation methodology covering all environmental aspects that affect the airgap for semi-submersibles. The proposed method utilizes a frequency domain stochastic approach (spectral method) to combine all known factors that can be calculated and that affect the airgap. These effects include the first order vessel motions under an undisturbed wave field, diffracted wave elevation along the free surface under the platform, slow drift quadratic transfer function (QTF), vessel set down and heel effects due to mooring stiffness into a single airgap prediction. Wave run up is not accounted in this procedure due to its high non-linearity, its difficult prediction and measurement. This is a local effect that is considered in the design phase by assuming that wave run up will hit the structures near columns and these components should be designed accordingly. The method proposes the combination of these statistical processes to be utilized for both the initial and final stages of the design. Model test results are also presented which show good correlation to the proposed method. A discussion of the limitations of this stochastic method, time simulations and model tests is also presented.

Copyright © 2011 by ASME
Topics: Submersibles



Interactive Graphics


Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature

Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In