Study On Dynamics Behavior Of Jack-up In The Process Of Lifting And Landing Legs

A key part of jack-up dynamics research is the process of lifting and landing the legs.Landing legs is the process of legs from platform to seabed,and lifting legs is the process of legs from seabed to platform.Jack-up is in the free floating state in the process.With the legs up and down,the relative position between the legs and the body is constantly changing.Some structural parameters of the platform such as the center of gravity,buoyancy,will change as well,causing the platform dynamics properties including natural frequency,stiffness evolve over time,as well as the external environment load carried by the platform.Meanwhile there is complex interaction between jack-up system motion and platform structural response.When legs ground the seabed,jack-up system will bear huge impact load,which will seriously affect the platform operation safety.So based on the kinetic analysis software and finite element analysis software,this paper carried out dynamics response research of platform and lifting system in the process of lifting and landing the legs,and the main work is described as follows:(1)Considering the jack-up floating state in the process of lifting and landing the legs,the floating kinematic response of platform should be analyzed firstly.Based on AQWA software and ADAMS software,this paper carried out kinematic analysis of platform in six degrees of freedom.On this basis this paper researched the RAO of jack-up under different leg position,and analyzed sensibility factors of jack-up kinematic response,such as sea scale,leg motion,leg flexibility and wave direction.This research provided a theoretical basis for jack-up operation safety.(2)A key part of jack-up is lifting device,which bears heavy loads and dynamic loads during lifting legs,so it is very necessary to research the dynamic characteristics of lifting system.Based on ADAMS software,this paper carried out dynamic analysis of jack-up coupled model,then researched the kinematic and dynamic characteristics of lifting system.This paper mainly analyzed the kinematic characteristics and contact load of gears during legs lifting and grounding,and contrastive analyzed influence factors of lifting system dynamic characteristics.(3)With the legs lifting and landing,the platform dynamics properties evolved over time,as well as the external environment load carried by the platform.Based on ANSYS software,this paper carried out modal and strength analysis of jack-up,obtained natural frequency and vibration mode of jack-up in different legs position and analyzed the structure strength of legs and jacking frame.This research provided a theoretical basis for jack-up operation safety.