Abstract
This study addresses numerical analysis of the installation of a tripod foundation using a heavy lift vessel (HLV). Limiting sea states are firstly predicted in the frequency domain based on crane tip vertical motions using linear transfer functions. Then, numerical modelling and simulations are carried out in the time domain to analyse the coupled dynamic system taking into consideration of the nonlinearities of the system. In time-domain analysis, two lifting phases are brought into focus, i.e., the lift-off and the lowering phases. For the lift-off phase, two scenarios are considered, i.e., lift-off from the own deck of the HLV and lift-off from a transport barge. Moreover, comparative studies using two types of installation vessels, a floating vessel and a Jack-up, are investigated for the lowering process. Critical responses including the motions of the tripod and the lift wire tensions are presented and compared under various environmental and loading conditions.
Highlights
1.1 Background and motivationWind is a clean, free and readily available renewable energy source
Regarding the response aptitude operators (RAOs) of vessel pitch (Figure 4.5), it is obvious that the values are much smaller in the beam sea and the peak occur in idir9 (120-degree)
It is kind of interesting to investigate which wave direction would prevail in the RAO of the crane tip which results from the motion combination among the heave, the roll and the pitch
Summary
Free and readily available renewable energy source. Everyday around the world, wind turbines are capturing the wind’s power and converting it to electricity. A spectacular drop in price, by any measure, which has certainly defined a range for ‘the new normal’ in mature northern European offshore wind markets at well below €100/MWh (GWEC, 2016) This is another driving factor for efficient and reliable offshore installation. Marine lifting operations play a key role in the installation of turbines and bottom-fixed foundations They are typically carried out by a floating or jack-up crane vessel. Floating vessels with onboard heavy crane are more effective especially for the mass installation of wind farms, because of their fast transit among specific turbine sites. The foundations are to be lifted off, positioned and lowered to the sea bed by use of a floating or a jack-up vessel with onboard cranes. Phase Lift off Object hanging in air Splash zone crossing Deeply submerged Landing
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