Nonlinear Oscillation Responses of Cylindrical Shell Tank with Water on a Shaking Table

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Observing a cylindrical shell tank with water on a shaking table, we can find a lot of responses of which occurring mechanism is no known by linear vibration theory. For example, there are vibration components corresponding to 1/2-subharmonic and 1/3-subharmonic oscillation that happened to take place in some external frequency region and became extreme large vibrations. We have been studying the nonlinear vibrations in both theoretical and experimental aspects. In order to grasp global behavior of the nonlinear oscillations, we have to experiment with many vibration models with various water levels. Because nonlinear oscillations happen to take place at a specimen but never occur another.Adopting response data of eight specimens, we clarified several requirements of instability regions of subharmonic oscillations. The instability regions might be in neighborhood of external frequency regions corresponding to two times large value of a frequency of a vibration mode that happens to occur there.