| Being clean and renewable energy, there are several advantages for wind energy exploitation, such as fuel security and power cost stability and environment friendly. So it is significant for us to improve national energy structure and environment, and wind energy exploitation is becoming important part of sustainable development strategy in the world. Constrained by land resource, noise and grid capacity, the large-scale development of offshore wind energy is prior to land, especially for shallow sea with the depth within15m in the coming dedaces.In China eastern coastal region, most of the mud bottom surface depth is more than10m and the wind turbine are sometimes influenced by typhoon. So the cost of the construction and installation of the offshore turbine is higher than abroad. The pile foundation and tower support structure of offshore wind turbine is a typical slender and tall structure which undertakes the wind, wave, earthquake and other environmental loads. The structure dynamic analysis and foundation dynamic optimum design is an important research subject in aspect of safety and reasonable economy.The foundation structures suited for China eastern coastal region, the base-tower dynamic analysis method and foundation dynamic structural optimization of offshore wind turbine were discussed and studied in this paper.(1) Contrary to offshore geological characteristics of China, this paper put forward and designed several new jackets structure, including the improvement of three piles (or four piles) jacket structure and the new composite piles jacket structure. Above of the new jacket structures can reduce the difficulty of the maritime connections, pile penetration, jacket leveling, etc, which suited for offshore area with the depth of water less than10m and the current construction level of China.(2) According to the theory of harmonic superposition method, this paper choose the suitable spectrum model and programed using Matlab to simulate fluctuating wind velocity and wind loads, wave height, wave loads, etc, and the program was corrected with real-measured wind and wave data. The simulation results can effective response the dynamic characteristics of measured wind and wave, provide inputting basis for dynamic response analysis of offshore wind turbine structure system. Otherwise, this paper analyzed the effect on structure of Soil wave, effective peak acceleration (EPA), Tianjin wave, EL-centro wave. The calculation results show that, the effect by Soil wave is the biggest, because the soft soil has amplification effect for high structure. Using Soil wave analysis results for earthquake fortification is more safely.(3) The high precision vibration monitoring instrument was the firstly installed in offshore wind turbine structure system, which obtained the important monitoring data of base-tower system vibration characteristics. combining with the real-measured wave and wind data, the arranged and analyzed results were showed as below:â‘ As the standard deviation of wind speed increases, the vibration acceleration of base-tower system also increases.â‘¡Offshore wind turbine structure system have serious vibration in wind, waves and other environmental loads, and the vibration of tower top is the largest, and the vibration gradually decrease along the structure system from top to bottom. (4) Based on pulse duration of field wind and wave data, dynamic FEM analysis model was build. The variances and correlations were analyzed between calculation results and site monitoring results, and the correlation is quite good. The model of this paper is suitable for the dynamic analysis of Xiangshui offshore area in Jiangsu province, and can provide reference for the similar engineering.(5) Through dynamic optimization for the new jacket structure and the foundation structure of Xiangshui offshore wind turbine, the amount of steel pipe pile material was reduced about15%, which has obviously optimization effect. The stress and bending displacement of optimized foundation structure meet the requirements of relevant standards. The order1and order2natural frequency of the Xiangshui offshore wind turbine foundation structure were decreased slightly, and just avoided the wind turbine1P and3P frequency. The order1and order2natural frequency of new jacket structure (composite pile structure) can avoid the wind turbine1P and3P frequency, and the structure is reasonable.(6) The possibility of building optimization model combining with the genetic algorithm and FEM analysis software (Midas) was realized, which resolved effetely the dynamic optimization design problem of Midas by programming. Based on the design variables of pile obliquity, diameter and thickness, the function of several reconstruction FEM analysis models was achieved, which can further promote the application of Midas on the dynamic optimization design. |
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