Study Of Several Key Parameters On The Dynamic Analysis Of TTR

Marine risers are deemed as key equipments of subsea fundamental structures. However, they are also regarded as one of the most vulnerable equipment in those structures. The global dynamic behavior is an important factor that influences the operation and performance of the riser. Therefore, study on the dynamic analysis of marine risers has become one of the hottest spot in engineering world.Based on national high technology program "Key Technologies of Deep water Top Tension Riser design and Installation", this paper presents some researches on a target top tensioned riser working on a TLP. The analysis method to analyze the nonlinear dynamic behavior of TTR is studied, and the dynamic behavior of the TTR has been successfully simulated by Abaqus/Aqua. According to stochastic wave theory, linear superposition method is used to scatter stochastic wave spectrum into time domain series. Combined with target TLP's amplitude response operator (RAO), the surge motion of TLP is calculated. The mechanism of the tensioner in the TTR system has also been illustrated, and spring element has been used to simulate the tensioner system. The effect of geometric nonlinearity is considered and time domain analysis method is used to predict the response in the splash zone and lower portion of the production riser.Detailed responses for displacement, bending moment and stress are given for the further investigation of dynamic effects by several crucial parameters, such as, Top Tension Factor (ttf), motion of the TLP and current profile. This paper also presents further studies on the sensitivity of each parameter to the response of the TTR.Results show that while the increase of the top tension reduces riser deflection, it still increases the Equivalent stress of the riser, and TLP motion greatly affects the behavior of the riser. The equivalent stress at the top end increases with the increase of the ttf, while the equivalent stress at the bottom end decreases. Riser design should be at a "Balance point". Different ttfs should be set to different load cases.TLP motion; wave and current all affect the dynamic behavior of the riser. TLP motion dominates the riser's dynamic response in large displacements, while wave only affects the wave splash zone, and current affects the whole riser.