| dc.description.abstract | From this study, lift-off process of monopile in single crane vessel scenario and two vessels scenario are all considered. Challenges from environmental conditions and upending process are all cleared. In the single crane vessel scenario, the vessel was assumed as jack-up and floating structures respectively. Different lifting methods were concerned under former assumption, such as constant angular velocity, vertical lifting velocity, vertical lifting forces, fixed crane tip and horizontal moving crane tip. Some suggestions about lift wire force and lifting velocity were listed from these analysis. Regular translation and rotation motions of crane vessel were concerned under latter assumptions. Results of time series of three concerned forces(lift wire, horizontal and vertical support force) were studied with heave and roll motions of crane vessel. Based on this analysis, vessel motion had little effects to concerned forces compared with upending process.
In order to minimize maximum value of three concerned forces, different sea states and upending process were considered. High sea state(means large Hs and Tp) just leaded large standard deviation, which means environmental load was not very important. Then smaller lifting velocity was used to minimize challenge to safety.
When the two vessels scenario concerned, distance between transport barge and crane vessel was the main factor. Effects to hydrodynamic factors and ballast due to such distance were cleared. Moreover, time series of lift wire force in this scenario was also got to show critical step | |
