As the offshore industry moves to deeper waters, riser collision becomes a more crucial concern. Riser interference assessments need to rely on time domain simulations due to nonlinearities such as hydrodynamic interferences, but one difficulty is that riser collision is an extreme event. In a recent work, the authors proposed an efficient procedure for predicting the probability of riser collision, based on extrapolating the dynamic response characteristics, thus obviating the need to capture actual collisions during simulation. However, the prior work considers randomness only from the irregular waves. This paper extends the prior work by developing a method to account for multiple uncertainties. The random variables considered herein are current, drag coefficient, vessel motions and riser mass. The proposed method is computationally efficient; the additional simulations necessary to incorporate four random variables are only slightly more than the original simulation case. Taking a top-tensioned riser system as a case study, the likelihood of collision predicted by the proposed method is found to compare well with Monte Carlo simulation. Moreover, it is shown that the random variables can increase the probability by an order of magnitude, and all the considered variables contribute meaningfully to this increase.
Predicting the Probability of Riser Collision Under Stochastic Excitation and Multiple Uncertainties
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He, JW, & Low, YM. "Predicting the Probability of Riser Collision Under Stochastic Excitation and Multiple Uncertainties." Proceedings of the ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. Volume 2A: Structures, Safety and Reliability. Nantes, France. June 9–14, 2013. V02AT02A032. ASME. https://doi.org/10.1115/OMAE2013-10381
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