Basic research on dynamic safety of large offshore structure

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A fundamental examination concerning dynamic safety of large offshore structure with buoyancy members was done in this research. Advancing an effective, positive use development of an oceanic space in our country becomes a very important problem. The circulating water tank experiment and the simulation analysis by the computer are done in this research.The main result of obtaining for this research is summarized as follows.1) Vortex induced vibration in each column is influenced by the interval of column member. As for the response by vortex induced vibration, the increasing tendency was seen at the case of single column when the interval of column narrowed. Moreover, it has been understood to cause torsion vibration as the entire structure by the difference of frequency where the vortex induced vibration of column in the back and forth is generated.2) If the responses of the structure subjected to separately wave force and seismic force were compared, a big difference was shown in ben … More ding moment stress because the position where these external force acted was different. However, it has been understood to show-a similar response in the structural model which is united with connected material when the structure is enlarged.3) The comparison on the design level response is done by using the reliability index for the wave force and the seismic force. In wave force, mean wave height, mean wave period, and duration are the main parameters. Moreover, the main parameter of seismic force is dominant frequency of the acceleration and surface layer. It has been understood that it is useful to be able to do the response evaluation to external force with a quite different dynamic characteristic by using the reliability index, and to evaluate the influence of each external force.4) The maximum response of offshore structure subjected to wave force depends greatly when the restoring force characteristic of the structure becomes linear and nonlinear. Especially, the maximum response to wave force with long duration understands the influence of a nonlinear characteristic is large. Therefore, it is important to clarify the influence in the evaluation of the design level response. Less