| Abstract |
Among compliant platforms, the tension leg platform (TLP) is a hybrid structure which is generally used for deep water oil exploration. With respect to the horizontal degrees of freedom, it is compliant and behaves like a floating structure moored by vertical tubular members or “tethers”. These tethers are pretensioned due to the excess buoyancy of the platform, whereas with respect to the vertical degrees of freedom, it is stiff and resembles a fixed structure and is not allowed to float freely.
Dynamic analysis of squared and triangular TLP models under regular waves is presented, considering
the coupling between surge, sway, heave, roll, pitch and yaw degrees of freedom. The analysis
considers various nonlinearities produced due to change in the tether tension and nonlinear
hydrodynamic drag force. The wave forces on the elements of the structure are calculated using
Airy’s wave theory with Chakrabarti (1971) approaches and Morison’s equation, ignoring the
diffraction effects. The nonlinear equation of motion is solved in the time domain using Newmark’s
beta integration scheme.
Numerical studies are carried out in the time domain to examine the effect of change of wave
parameters (wave height and wave period) and coupling effect in dynamic response of a square and a
triangular TLP under a unidirectional surge wave force. Also, Numerical studies are conducted to
compare the coupled response of a triangular TLP with that of a squared TLP and the effects of
different parameters that influence these responses are then investigated. Computer MATLAB program
is developed in this work for nonlinear dynamic analysis for both triangle and squared TLP. The
program is capable of solving large displacement problem dynamically in the time
domain.
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