| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2006: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2005: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2004: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
Cylindrical tanks on a horizontal shaking table driven by periodic sinusoidal force generally show responses with the same period of the force. However, they happen to branch out responses with sub-harmonic vibrations component of significance under certain frequency region of the external force. The mechanism of these sub-harmonic vibrations has not been clarified yet. Several cylindrical tank specimens were used to research the vibrations.
Changing amount of water in the tank, we obtained response data of the tank under external frequency region from 30Hz to 540Hz. Then, the data was analyzed to show response curves of each vibration component and each vibration mode, where components are corresponding to fundamental, sub-harmonic with the 1/3, the 1/2, and the 3/2 order, and higher harmonics with the 2nd, and the 3rd order, and vibration modes include Fourier series numbers n=0,1,2,3,4,5,6,7,8 in circumferential direction of the cylindrical shell.
Then, we find that response of the 1/2 sub-harmonic vibration may branch out under the condition when the external frequency is in neighborhood of added frequency of two vibration modes with n=0,4,5,6 etc. Many responses of the 1/3 sub-harmonic vibration may occur with the 1/2 sub-harmonic vibration. These results enable to foresee a frequency region where these sub-harmonic vibrations may branch out.
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