Ocean structures and vehicles are exposed to severe ocean environment conditions such as waves, winds and currents. When such ocean structures and vehicles are designed, an accurate structure analysis is required to keep the system safely. Hydro-elastic analysis is one of key issues to design such structures and vehicles. In many previous investigations, numerical analyses for hydro-elastic problem have been used. In this study, an experimental analysis is carried out and the circular cylindrical shell is considered. Dynamical characteristics for a circular cylindrical shell are identified by experimental vibration analysis in air and water. The natural frequencies and mode shapes are compared in air and water to obtain hydro-elastic effects. Some interesting results are found in the variation of natural frequencies and damping ratios of the circular cylindrical shell for different water contact depths.
Ocean structures and vehicles are exposed to diverse sources of vibration, such as the vibration of the system itself or that from external load such as waves and wind. If the natural frequencies of an ocean structure and vehicles are close to the time varying external force applied to the structure or vehicle, it receives much damage due to much defection and fatigue on its structure. Research on the vibration characteristic of ocean structures and application of the knowledge to prevention of such harms are necessary. The characteristic vibration of structures is expressed by system parameter such as natural frequency, damping ratio, mode shape, etc. These properties are decided by the quality of the material, shape, or environment conditions. Circular cylindrical shell structure is the most commonly used form in designing ocean structures and submarines. Therefore it is of great importance to investigate the vibration character of cylindrical shell structure which is in contact with water.