Tension leg platform (TLP) is a suitable type for very deep-water oil production. The
TLP is a compliant structure behaving like a floating one. It can be modeled as a rigid
body with six degrees of freedom (6-DOF), which can beconveniently divided into two
categories, those controlled by the stiffness of tethers, and thosecontrolled by the
buoyancy. The former category includes motion in the vertical plane and consistsof
heave, roll and pitch (stiff DOF); whereas the latter comprises the horizontal motions of
surge, sway andyaw (flexible DOF). This paper investigates the nonlinear response of
the Square TLP configuration under different random wave approach angles, 0o and
30o. Random waves were generated according to Pierson-Moskowitz spectrum and
acts on the structure in the surge direction. The hydrodynamic forces evaluation is
based on the modified Morison equation. Coupling effect and added mass are
considered in the developing of the equation of motion. The nonlinear equation of
motion is solved in the time domain utilizing the modified Euler scheme. Time history
responses, phase planes, and Power spectrum densities (PSD) for the nonlinear
responses for both approach angles are shown. It was found that, Variation of wave
approach angle activates specific degrees of freedom like sway and roll which
otherwise are not activated under unidirectional wave force. |
