Response Analysis of a Truss-Pontoon Semisubmersible With Heave-Plates

[+] Author and Article Information
Nagan Srinivasan

 Deepwater Structures, Inc., Houston, TX 77459-3983

Subrata Chakrabarti

 Offshore Structure Analysis, Inc., Plainfield, IL 60544-7096

R. Radha

 Prairie View A&M University, Prairie View, TX 77446

J. Offshore Mech. Arct. Eng 128(2), 100-107 (Dec 27, 2005) (8 pages) doi:10.1115/1.2185679 History: Received June 30, 2005; Revised December 27, 2005

An offshore platform that is efficiently designed to reduce the wave excitation forces and increase the separated-flow damping could qualify as a platform operating even near its resonance. Such design could make this concept cost-effective, as well as operationally more productive with minimum downtime. The principal purpose of this paper is to describe an offshore platform design that could face the resonance efficiently. The paper applies the concept of both hydrodynamic added mass and separated-flow damping intelligently in the design of a large deepwater floating vessel on column-stabilized principle. The platform is designed to face resonance due to extreme waves and utilizes the damping to control its motion, thereby qualifying its field application. The design is justified and verified with the results of a scaled-model study in a large wave tank. The results of the correlation of theoretical study with the model test results are presented herein. A few variations of the deepwater platform concept are discussed.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 17

Truss-pontoon semisubmersible platform for PDQ application

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Figure 18

Truss-pontoon semisubmersible telescopic keel tank

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Figure 19

Heave and pitch RAO for the dry tree TPS

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Figure 20

Architect view of the extended TSP applied to an LNG terminal

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Figure 1

Conventional semisubmersible platform (GVA 27000-Atlantis) (PQ)

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Figure 2

Truss-pontoon semisubmersible platform (TSP) in present study

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Figure 3

Measured heave decay and linear fit of the semisubmersible model

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Figure 16

Computed heave response

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Figure 4

Measured pitch decay and linear fit of the semisubmersible model

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Figure 5

Regular wave and response time history for run No. Reg1

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Figure 6

Wave and heave power spectra for JOSWAP random wave run RN1

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Figure 7

Wave and heave power spectra for PM random wave run RN2

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Figure 8

Heave RAOs of the Truss pontoon model designed for heave resonance

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Figure 9

RAO of the conventional semisubmersible with 26s heave resonant

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Figure 10

Regular wave time history for Reg1

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Figure 11

Wave and pitch power spectra for JONSWAP random wave run RN1

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Figure 12

Wave and pitch power spectra for PM random wave run RN2

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Figure 13

Pitch RAO of TSP from regular and random wave tests

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Figure 14

Pitch RAO of a conventional semisubmersible

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Figure 15

Percent damping factors from tank tests




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