The influence of wave force linearisation methods on fatigue damage predictions for jack-up rigs is investigated, using Sesam software as the basis for comparison. The possible risk of significantly underpredicting fatigue damage is highlighted. Dynamic spectral fatigue analysis methodology is applied to a representative jack-up rig in 30 and 70 m water depth in the North Sea. Transfer functions are computed using two approaches: regular waves of constant steepness with capping of wave height at low frequencies; stochastic linearisation based on a single sea state per wave scatter diagram. It is concluded that stochastic linearisation based on a single sea state per scatter diagram is insufficient to provide an adequate characterisation of nonlinear drag forces for the dynamic spectral fatigue analysis of jack-up rigs. Superharmonic resonance effects, due to nonlinearities associated with variable submergence and drag forces, are found to be significant when computing transfer functions of structural dynamic response.
An investigation into the influence of analysis methods upon fatigue damage predictions for jack-up rigs
Ships and Offshore Structures ; 17 , 6 ; 1321-1331
2022-06-03
11 pages
Article (Journal)
Electronic Resource
Unknown
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