Nonlinear Response Analysis Of A
SeaStar Offshore Tension Leg Platform
In Six Degrees Of Freedom
Author(s)
M. J. Ketabdari & H. Alemi Ardakani
Abstract
Tension Leg Platforms (TLPs) are used for deep-water oil/gas exploration.
Among the compliant platforms, TLPs are vertically moored structures with
excess buoyancy. Therefore the tethers can be tensioned to such an extent that
heave, roll and pitch motions of the platform induced by ocean waves are
virtually eliminated. SeaStar is a new generation of mini-TLPs, which is similar
to a spar and has the favorable response features of a TLP. In this paper, a
computer program was developed to evaluate the dynamic response of a typical
SeaStar TLP to regular wave forces. In this analysis, coupling between the
degrees of freedom surge, sway, heave, roll, pitch and yaw have been
considered. Wave forces on the elements of the platform are calculated
numerically employing linear wave theory and Morison's equation. However the
effect of diffraction has been ignored due to the small ratio of cylindrical
elements diameter to wavelength. The nonlinear equations of motion are solved
numerically by Newmark’s beta integration scheme in the time domain.
This yields to motions of the platform in six degrees of freedom. The results
have also been presented in the frequency domain and the response amplitude
operator for each motion of the platform has been calculated. The results show
that for this typical platform the movement of the TLP is considerable in some
degrees of freedom. However, changing the dimensions of the platform can
affect the values of these movements. This can give us a guideline for optimum
design of this kind of platform.
Keywords: SeaStar TLP, response amplitude operator, Morison equation.
Keywords
SeaStar TLP, response amplitude operator, Morison equation.
Related Book
Other papers in this volume
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