Offshore structure IS usually subjected to dynamic forces with random characteristics. The evaluations of these forces provide important roles on the reliable design of the structure. If the reduction of the dynamic response can be Implemented with some method, the design of the structure will be more efficient and reasonable. The passive control and active control methods have recently been applied to dynamic response reduction methods of civil engineering structures such as bulldogs and bridges. The tuned mass damper(TMD) is one of the most typical passive control method. Although the active control method requires some external forces on the structure, but it will provide more effective reductions of the dynamic responses. In this study, the TMD system subjected to the active control force is applied for the reduction of the dynamic response of the jacket type offshore structure. The reduction of the response due to wave force is examined using the active control forces which can be obtained with the instantaneous optimal control method in the time domain approach.
The dynamic force with random characteristics is one of the most important excitations to the design of offshore structures. Although the reliable and safety design of offshore structure is generally performed with exact evaluations of the dynamic responses, the passive and active control methods seems to provide more important roles on the design of the offshore structures. In order to implement the dynamic response reduction of the structure subjected to randomly exciting forces, it requires to increase the rigidity of structure and the structural damping. However, it is not always easy to install such situations of the structures Applying the control methods to offshore structures subjected to wave force, it seems to provide effective roles on the response reduction of structures. The wave force is clearly one of the most important forces which are subjected to the offshore structure.
