Occurrence of Nonlinear Oval-Type Vibration Under Large Sinusoidal Excitation: Experiment

This study describes the vibration experiment which examines the vibration characteristics of a cylindrical water storage tank caused by the coupling between the beam-type and the oval-type vibrations in detail. A small or large acceleration excitation test is performed by a shaking table using a 1/10 reduced scale model of a large-scale tank. The sinusoidal waves with the resonance frequency of the beam-type vibration are used as the input. By using accelerometers, displacement sensors and strain gauges, the vibration characteristics and the vibration modes of the tank model are investigated. The beam-type and the oval-type vibrations are excited simultaneously and the oval-type vibration of fundamental harmonics is excited in the small or large acceleration excitation test. In the large acceleration excitation test, however, the oval-type vibration of subharmonics of order one-half appears suddenly and grows rapidly when the amplitude of the oval-type vibration of fundamental harmonics increases to some magnitude. At the same time, the response of the beam-type vibration of the tank is reduced rapidly. This result shows that the occurrence of the oval-type vibration of subharmonics of order one-half and the response reduction of the beam-type vibration are in close relationship.