Offshore Platforms Ice Induced Vibration Control

When an ice sheet moves against a flexible vertical structure, it may fail either by buckling or by crushing. Then the structure may be destroyed by the ice force. As many oil platforms are to be erected at the oceans coved with ice, more and more problems appear. Since 1960s ice researcher had begun to study the problems of ice-structures interaction. In order to reduce the response of the platform vibration, some methods and devices must be found. To mitigation the ice-induced vibration of platform has been the first problem in Bohai bay.Firstly this paper discussed the dynamic ice force when the ice interacted with vertical structure. After that a full-scale test system was introduced at JZ9-3 platform and JZ20-2 MSW platform in Liaodong Bay.Then, the methods and devices used in civil engineering have been development for many years, some of them are introducing in this paper in order to find out which is suitable for the platform. Vibration isolation is considering in mitigating ice-induced vibration of platform, the isolator which uses between the upset and jacket is LRB, the numerical simulation is used ANSYS. The result shows that the vibration of upset is reduced and the vibration of the jacket is little increase with isolators.Another method is to add tuned mass damper on the top of the platform. The platform is simply as a single-degree-of-freedom structure, the numerical simulation is done in MATLAB, the result shows that the response of vibration is reduced with TMD. As a kind of active control methods, an active tuned mass damper is used to reduce the vibration of the platform. More, an active and passive tuned mass damper (APTMD) is designed for the platform, the result shows that the APTMD is more better than TMD.In order to study the devices, a model for vibration control test is design in laboratory. The model is based on the scale theory. The date collection system is also introduced in this paper.