Application Research On The Vibration Isolation Cone Of The Offshore Platform

Offshore platform structures are the basic establishment for exploitation oil and natural gas. They are always in atrocious sea environment. As many oil platforms are to be erected at the oceans covering with ice, more and more problems appear. In order to reduce the response of the platform vibration, some methods and devices must be found. From the view of design, there are mainly three solutions to depress this vibration: the first way is to enhance the collectivity stiffness of platform, it will make the structures heaver, that is to say, it can't meet the economic demand; the second way is to implement active control, however, it is difficult to be carry into execution and unable to decrease the expensive cost. The third way is to put negative isolation control in practice. For the whole, the last one is feasible and economic. This thesis research is based on the isolation technology.According to the field monitoring in Bohai Bay, it is proved that the ice breaking cone can avoid the serious steady-state vibration, however meantime the ice induced random vibrations yet imperil, hazard to personnel and facility. This article introduces the ice-induced vibration of fixation cone and ice force function. We can know that ice-induced vibration is a narrowband random course. From ice-induced function graph, so we can regard the ice force as impact load. Combining the ice breaking cone and the vibration isolation technique, we design a vibration isolation cone by impact isolated vibration theory which could isolate the vibration in the ice force source. And we illuminate the principle of the vibration isolation cone too. From the result of simulating, the effect of reducing vibration is very evident, when the inherence frequency of cone is far away from the inherence frequency of offshore platform .Isolated vibration cone design includes stiffness design and damping design. Rubber bearing is adapted to isolated vibration of cone for its large bearing the weight of vertical and moderate horizontal stiffness. Moreover, rubber has a long time of use and high resistance of eroding.Then combining the conical ice force and the dynamic character of the field platform, the mechanic model of the vibration isolation is constructed and analyzed. The numerical examples show that selecting appropriate parameter of the vibration isolation cone can obviously reduce the response of the platform. So according to the ice force and design value of the structure of Bohai Bay, the design parameters for the vibration isolation technique are given so as to let the vibration isolation cone to use in practical project.