Study on optimal structure used for offshore wind turbine facilities

为了将西北欧新兴的海上风电场扩展到日本，我们必须应对我国特有的自然环境条件，如严重的台风、地震、松软的海床和陡峭的水深。风力机的下部结构应具有适当的刚度和强度，以抵御风荷载。由于脉动的风、浪和各种机械振动作用于它们，因此需要避免共振，减少这些激励和疲劳损伤。因此，我们提出了一种钢管桁架来替代传统的钢制圆柱形塔架，用于固定底部或浮动设施。为了验证其适用性，我们在一台5 MW风力发电机上进行了这两种子结构的设计，并进行了考虑桩土相互作用的风洞模型试验和数值研究。最后得出以下结论：1)由小直径…杆件组成的桁架塔架的子结构。更多的夹克比圆柱形的塔架和单柱好。虽然钢材的重量较大，约为1.7倍，但抗弯刚度以1.5倍为宜。2)特征值分析得到的2.5s的第一自振周期可长于旋转叶片与塔架相交的1.0-2.0s周期，而短于3.0-6.0s的旋转周期。这些与尾流导致的塔影效应有关的时间段带来了不同的成员力。3)桁架塔架的平面外加速度和振动荷载均小于圆柱形塔架。4)带导管架基础的桁架塔具有足够的延性，其倒塌变形是Pushover分析屈服时变形的4~5倍。较少

So as to expand offshore wind farms emerging around North-West Europe into Japan, we have to cope with natural environmental conditions such as severe typhoons, earthquakes, the soft seabed and steep bathymetry peculiar to our country. Substructures of a wind turbine should have due rigidity and strength with the configuration as to ward off wind loads. Since fluctuating winds, waves and various mechanical vibrations are acting on them, resonance evasion, reduction of those excitation and fatigue damage are required. So we have proposed a steel tube truss alternative to a conventional steel cylindrical tower for fixed bottom or floating facilities. To confirm the applicability, we carried out design of both substructures onto a 5MW wind generator, a wind tunnel model experiment and numerical study taken the pile and soil interaction into consideration. Finally, we concluded as follows ;1)The substructures made of a truss tower composed of small number of members having small diameter a … More nd jacket is better than a cylindrical tower and monopile. Although the weight of steel materials is larger about 1.7 times, the flexural rigidity is appropriately 1.5 times. This implies that proposed substructure takes advantage from the fatigue perspective.2)The first natural period of 2.5s obtained by the eigenvalue analyses can be longer than the period of 1.0-2.0s that a rotating blade intersects the tower, and shorter than rotating period of 3.0-6.0s. These periods pertaining to tower shadow effects due to wake bring varying member forces. Thereby, the optimal design avoiding the resonance from the natural period of the facility may be done.3)The measured out-of-plane accelerations and oscillation loads in the truss tower were smaller than those of the cylinder tower. The electricity generated by the truss tower is slightly larger.4)The truss tower with jacket foundation has enough ductility, such that it can deform four or five times during collapse compared with the deformation at yielding by a pushover analysis. Less