| The offshore platforms serviced in the offshore environments will subject to earthquakes, waves, wind, ice and the loads of machinery and equipment on the platform and will cause strong vibrations. Harmful vibration will affect human health, the equipment can not be normally used and cause the platform damage. Although the technical data needed can be obtained by the numerical computations, the reliability of the results is sometimes unsatisfactory since many assumptions or empirical data are used in the computations. Marine engineering is still agreed that the physical model experiment's result is most reliable, as the standards of the offshore platform's design, construction. Therefore, the design, construction and the experiment of similar model appear especially important. Some researches on the offshore platform's vibration analysis and the similar model experiment, which is associated with a research project sponsored by National Natural Science Foundation of China. The major aspects of the research of the dissertation are shown as follows.Firstly, with reference to W12-1 and other offshore platforms, designs an offshore platform for oil storage. This platform is composed of the upper deck and lower deck, four floors horizontal jackets, six vertical king posts and some supports. In order to design a higher stability of the marine platform, the design of the platform framework is six-line structure. At the same time, in order to enable the design of offshore platforms to meet the requirements of use, some researches on the materials selection, design of platform storage volume for oil, structural design, stiffness and strength of platform design, and through the establishment of three-dimensional model of the platform, the simulation analysis of static force and dynamic force are studied. The results show that the offshore platform designed to meet the requirements.Secondly, the similar model design is studied. Study influence of material damping to the similar model design and experimental data analysis. The results show that material damping does not affect the geometry of similar model. Material damping has little effect on the natural frequency, so it can be ignored. But the influence of model's dynamic response is so great that material damping must be taken into account in the analysis of experimental data. In order to facilitate research and application, the transformation relations of damping ratio and the damping factor which are known are given in this article. Based on this, obtains when determine simulated condition of model, may divide two stages to analyze, which are the model design stage and the model experiment stage, and obtained the response simulated condition.Thirdly, through the application of similar conditions, the similar offshore platform model is designed using PVC materials, the structural design, platform's stiffness and strength calculations are done, and the similar test for design data are studied. Through the similar test of data to draw that it meets similar conditions, which verify the design for the similar model is correct.Fourthly, based on the design of similar model, the physical model of offshore platform's similar model is constructed. The vibration mode experiment of similar model is done; the experimental system of vibration mode is developed. Taking into account the more model measuring points and to save the sensor, the experiment uses the method of multi-point vibration and single-point output measurement. The excitation by hammering, Encouraging signals and respond signals were picked up by forced sensors and accelerometers in experiment. In order to get the signal reliability higher, when excitation by hammering, rap each measuring point 4 times, get 4 data. When transfer function analysis we may carry on 4 averages. AZ016G collection boxes is used for data acquisition which is made in Nanjing Software Engineering Co., Ltd. CRAS V6.1 is used for data analysis, curve fitting and identify structure dynamic characteristic parameters include including natural frequency, mode and shape damping ratio.Fifthly, in order to study the dynamic characteristics of offshore platform, distinguishes its modal parameters, including natural frequencies, vibration mode and the space damping ratio and so on. Carries on the analysis and processing to the vibration mode experimental data of offshore platform's similar model.Compared the data of the experiment of similar model with those of the simulation of prototype, which can be better tally. These not only show the reliability of the experiment, but also prove the consistency of design and construction for offshore platform similar model. The experimental data error of similar model of offshore platform at the design, construction and experiment three aspects were analyzed.Sixthly, in order to study the influence of the platform equipment's own vibration to the platform, the power response is studied. Obtains when exerts the excitation to the model, necessary to take into account three parameters, namely excitation force F, excitation frequencyωF, incentive duration t. Compared the data of the experiment of similar model with those of the simulation of prototype ,which can be better tally. The experimental data errors of similar model of offshore platform were analyzed.In conclusion, the theoretical analysis, simulation analysis and experimental show that the design for similar model and prototype of offshore platform meet the similar conditions, establish the foundation of the next study. The damping control is applied to similar model, the vibration control of offshore platforms should do further study in the follow-up research.
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