A contribution to the problem of the seasonal variation in the earth's rotation
The seasonal variation of the Earth's rotation is studied by the method of demodulation of a non-stationary sequence. The variations of the amplitudes and phases of the annual and semi-annual fluctuation of time UT1 — TAI in the years 1963 – 1976 have been calculated.
This study investigates the effects of Pierson-Moskowitz, Jonswap spectrum that are typical irregular wave spectrums for wind turbine system with jacket support structure. Also various offshore environmental parameters based on korean local condition were used in our study. The loads acting on the system was considered by referring to the Design Load Case from IEC guide line. And improved von Karman model was used as a turbulence model. As a result, various significant wave height and peak spectral period cause noticeable difference of extreme and fatigue loads prediction.