Dynamic analysis of soil-structure systems

Offshore technology is a rather new field which requires the close cooperation, and expertise of specialists in many areas. One such area deals with dynamic aspects. There are several reasons why dynamic analyses play an important role in the overall design process, such as: New technologies and structural systems in a new environment necessitate careful analysis. The experience with existing structures is not sufficient and does not allow the application of simple design rules (offshore structures are not covered by normal engineering codes). The trial and error methods are not admissible from the economical and environmental point of view (oil catastrophe). The experimental studies with prototypes are not feasible due to the high cost and to the fact that each location needs its individual, tailored structure. Although many components of the overall system can be tested independently, however, these experiments remain essentially small scale with respect to the complete system, both in dimension and applied forces. The effects of loading with very low probabilities of occurrence, such as, earthquakes and maximum waves, have to be predicted. The owner, responsible government agencies, and insurance companies who have to cover possible losses will assess the risk of a particular structure. Insufficient safety criteria and high risk will either lead to a withdrawal of the production licence, non-issuance of the building permit or insurance premiums will be prohibitive. This could force the owner to reconsider the design and operation mode of a particular project.