Effect of Uncertainty on Slow Drift Motion of TLP

Offshore structures are subjected to nonlinear and irregular wave forces. These structures try to attain their stability in the neighbourhood of their designed equilibrium point through their responses. The excitation forces consist of harmonic inertial wave components and drag dominated forces which changes according to water plane area. Being a multi-degree of freedom system, coupling among these degrees of freedom poses difficulties in obtaining the response. Therefore, these nonlinear structures require investigation in a stochastic framework for understanding their behaviour (sub-harmonic motions, chaotic responses). This paper models the slow drift motion of tension leg platform using a nonlinear stochastic differential equation. These stochastic differential equations are attempted using stochastic methods such as higher order Milstein scheme in an Ito framework. The impact of varying uncertainty on the nonlinear dynamics of system is studied