Study on Dynamic Characteristics of Substructures for Development of Offshore Wind Turbine

由于日本适合建造海上风电机组的浅水区不多，加上海况变化量大等经济劣势，有必要开发安全、经济、抗疲劳能力强的子结构，即塔架和海底底座。为此，1)提出了与土壤条件、水深和风浪条件相适应的水下基础；2)明确了由叶片和吊舱、支撑塔和海底基础组成的水下平台在风浪作用下的动力特性；3)建立了评估水下平台耐久性的疲劳分析方法。实际上，在2001年，我们开展了以下工作：1)水平和垂直轴风力机在近海的可行性调查；2)OWT对固定式海底基础结构如单桩、沉箱、导管架和浮动基础的应用研究；3)水平风力机在b…中的应用4)回顾了2002年雨量统计方法的概况，编制了计算循环次数和应力范围的计算程序，并应用于模拟年风浪联合作用下的应力历史模拟，将应力范围与应力范围的关系拟合为双参数威布尔分布，利用Miner法则对疲劳损伤进行了评估计数程序基于三种计数方法，即雨流计数法、距离对计数法和通常的零点上交法。2)假设一台500kW的海上水轮机设置了15m的水压力，对20年来的脉动风浪载荷进行了模态分析，并对应力时程进行了分析，得到了累积的应力范围数。最后，我们比较了不同的计算方法，包括评价威布尔分布方法在疲劳寿命估计中的适用性。较少

As there is not so many shallow water areas appropriate for offshore wind turbine (OWT) in Japan, as well as economical disadvantage such as the magnitude of variability of sea conditions, it is necessary to develop substructures i.e. tower and sub-sea base, which should be safe, economic and having high fatigue resistance. To do this, we conducted to 1) propose appropriate sub-sea base corresponding to the soil condition, water depth, and wind and wave conditions, 2) to make clear the dynamic characteristics of OWT consisted of blades and a nacelle, a supporting tower and sub-sea base subjected to wave and winds, and 3) to establish fatigue analysis methodology to evaluate the endurance of OWT. Actually in 2001, we carried out as follows,1) Survey of horizontal and vertical axis wind turbine possible to use in offshore,2) Study for OWT on application of fixed sub-sea base structures such as a mono-pile, a caisson and a jacket along with floating base3) For horizontal wind turbine to b … More e feasible for OWT with large Mega Watt capacity, time domain dynamic structural analysis program based of modal analysis together with the fluctuating wind and wave loadings generator routines, indicating the effect of the sub-sea base property to the vibration characteristics of OWT.4) Survey of counting method such as the rain flowIn 2002, we also conducted as follows,1) Development of counting program that calculates numbers of cycle and stress ranges,2) Application for simulated stress histories with annual combined occurrence of waves and winds,3) Fitting the analyzed relation of stress ranges and numbers to a two- parameter-Weibull distribution and evaluation fatigue damage by Miner rule.In detail, the counting program is based on three kinds of counting methods i.e. rain flow, range pair and ordinarily zero up cross. About 2), assuming that a 500kW offshore turbine set a water of 15m, we conducted the modal analyses against fluctuating wind and wave loadings during twenty years, then stress time histories were analyzed to get cumulative numbers of stress ranges. Finally, we compared the difference of counting methods, including evaluation of applicability of Weibull distribution method for fatigue life estimations. Less