THE EFFECT OF LIQUID STORAGE TANKS ON THE DYNAMIC RESPONSE OF OFFSHORE PLATFORMS

An investigation of the dynamic interaction between the offshore platform and the sloshing of liquid in storage tanks is conducted using random vibration (RV) theory and statistical energy analysis (SEA). In Part I, the characteristics of the platform, of the loading, and of the sloshing in a tank are carefully reviewed, and the equivalent mechanical model of the system is formed. The sloshing is represented by an infinite series of masses, springs, and linear dashpots. Using this model, as analysis is performed applying RV theory and SEA. In Part II, numerical examples are given. The Buzzards Bay Tower (BBT), a U.S. Coast Guard Light Station, is used as the model for both the RV and SEA approach. The calculated natural frequencies and response spectra are compared to the actual data for RV, and the mean square velocity of the platform is examined by both RV and SEA. Finally, the possibility of using the first sloshing mode of the liquid in the storage tank as a dynamic damper is investigated for the BBT and a hypothetical 300 m class platform. The General procedure for designing an optimum tank as a dynamic damper is presented. It is concluded that liquid dynamic absorbers are economically feasible devices for reducing the dynamic response of offshore structures.

• Corporate Authors:

  Massachusetts Institute of Technology

  Department of Ocean Engineering, 77 Massachusetts Avenue
  Cambridge, MA  United States  02139
• Authors:
  • Mitome, S
• Publication Date: 1977-8

Subject/Index Terms

• TRT Terms: Damping (Engineering); Dynamic loads; Free surface; Motion; Offshore platforms; Sloshing; Stability (Mechanics)
• Uncontrolled Terms: Dynamic response
• Old TRIS Terms: Free surface effects; Motion response of platforms; Offshore platform stability; Platform motions
• Subject Areas: Bridges and other structures; Design; Marine Transportation;

Filing Info

• Accession Number: 00165284
• Record Type: Publication
• Source Agency: Massachusetts Institute of Technology
• Report/Paper Numbers: MS Thesis
• Files: TRIS
• Created Date: Nov 23 1977 12:00AM