| Budget Amount *help |
¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2006: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2005: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
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
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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
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