The Dynamic Response Characteristics And Control Researchof Jack-up Platform

As humans continually development of Marine resources, Jack-up become the important technical equipment for offshore oil and gas resources exploration and exploitation. However, harsh marine environment will cause the excessive speed and displacement of Jack-up, which will make the yield and fracture failure, and long-term hull vibration will make the fatigue failure occur easily. Thus, the dynamic response of Jack-up platform will affect the whole platform’s work safety performance. In this paper, the mechanical properties of Super M2 Jack-up platform’s legs and jacking and locking system were studied. The dynamic response of Jack-up platform and TMD device control characteristics of Jack-up platform’s dynamics response were studied by using Abaqus/Aqua module. The main research contents and conclusion are as follows:1) The mechanical properties of legs under each feature angles was analyzed based on the elastic-plastic theory, i.e., the change curve of leg’s displacement and the lateral force, and a kind of leg’s equivalent modeling method was proposed based on the bending deformation of integral method. The natural frequency and vibration mode of detailed leg model, equivalent leg model and generalized leg model were compared and analyzed by using the model analysis. Among them, the first two order natural frequency’s error rate of generalized leg model is 84.65%, while the first two order natural frequency’s error rate of equivalent leg model is only 2.92%-15.86%.2) The detailed numerical model of Jack-up platform’s jacking and locking system was proposed, and the mechanical properties of jacking and locking system was analyzed under each feature angle. The connection stiffness curve of upper/under guides, and locking system’s horizontal, vertical, torsional and ways were obtained. Whereby, the connection stiffness of upper/under guides,and locking system’s vertical, torsional is a constant. While The connection stiffness curve of locking system’s vertical and ways present the anisotropic and nonlinear properties.3) The dynamic response analysis model of Jack-up platform was proposed based on the above research results and the relevant specification requirements. The natural frequency and vibration mode of Jack-up platform under working and storm condition were obtained by using the model analysis. The first three order natural frequency of Jack-up under working condition respectively is 0.0503494 Hz, 0.051409 Hz, 0.0597066 Hz, and the first three order natural frequency of Jack-up under storm condition respectively is 0.0533153 Hz,0.0544372 Hz,0.0632236 Hz. Which are respectively very close to the wave frequency under working and storm condition.4) The dynamic response of Jack-up platform under the each angle of marine environment were analyzed by using Stokes wave theory. TMD devices control characteristics of Jack-up platform’s dynamics response was analyzed based on Sadek’s calculation method of TMD devices’ optimal parameters.The effect of TMD device and Jack-up platform mass ratio, stiffness ratio and damping ratio on the platform motion parameter were discussed respectively. The results show that: Jack-up platform’s maximal displacement and velocity appeared in the characteristics of the angle is 90° under working and storm condition, and TMD devices have significant control effect on Jack-up platform motion parameters.X and Y direction of Jack-up’s displacement and velocity amplitude reduced 59.4%,68.16%,35.01%,48.72% respectively under 90° storm load.