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Analysis of coupled body mooring and fender systemGirija Sasidharan Pillai, Harish 01 November 2005 (has links)
The hydrodynamic excitation and response behavior of multi-body systems with
varying degrees of coupling presents many challenges for designers of offshore
structures. In this study, attention is focused upon the analysis and interpretation of
experimental data obtained for an unmanned deepwater mini-Tension Leg Platform
(mini-TLP) coupled to a tender barge. Each body has its own mooring system and the
bodies are connected by two breast lines extending from central points on the mini-TLP
to central points on the bow and stern of the tender barge. A fender system is located
between the two platforms. Thus the two floating bodies are constrained to move
together in surge and yaw while they are free to move independently in heave, roll and
pitch with some limitations on sway.
The data of the individual records are characterized using statistical moments,
including skewness and kurtosis, to examine the degree of non-Gaussian behavior.
Correlation analysis and cross spectral analysis are used to investigate the relationships
between selected measurements such as the motion of each vessel, tensions in the
mooring lines and tendons and the forces on the fenders. The analysis shows that the
coupling effects reduce the mooring line and tendon tensions significantly and that the
motions of the two vessels influence the line tensions and fender forces. The data
distribution patterns followed by the parameters and the corresponding extreme values
are also investigated.
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Characterization of coupled body response in random seaXie, Chen 25 April 2007 (has links)
The frequent use of two or more closely positioned vessels during offshore
operations makes the study of multi-body hydrodynamics an important topic, especially
for the design of deepwater offshore systems. This research investigation studies the
response behavior of a coupled mini-TLP / barge system in both head and beam sea
conditions. The design sea conditions were selected to represent the combined wind,
wave and current conditions for a target location off the coast of West Africa. Both the
mini-TLP and the barge were designed to have independent mooring systems. Coupling
between the two vessels is introduced through a connection consisting of two breast lines
and a fender system. This connection is designed to restrain the horizontal movements
of the two vessels while keeping a constant distance between them and avoiding
collisions.
The main focus of this study is to analyze the experimental data obtained during
the model testing, especially the motions of the two bodies and the values related to the
fender system, in order to characterize the behavior of the uncoupled and coupled system
configurations. A statistical approach is used for the data analysis and interpretation.
Statistical parameters are used to provide an overall characterization of system behavior,
and Gaussian and Weibull distribution functions are utilized to detect the importance of
non-linearity in the data with particular attention to extreme values. Correlations
between the two vessels in time domain and frequency domain are investigated. In
addition, auto and cross spectrum analyses of the data are used to contrast the motion
behavior of the uncoupled and coupled configurations. It is shown that the connection system reduces the horizontal vessel motions; however the forces exerted on the fender
system show significant variation depending on sea heading conditions.
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