Wind, waves, sea storms, tsunamis, earthquakes, and floating ice impose dynamic loads on an offshore structure. These dynamic loads are in turn transmitted to the underlying soils and must be adequately accounted for in design. This paper reviews some considerations dealing with the applications of soil dynamics in the design of foundations for offshore structures. The motion characteristics associated with earthquake and storm wave loading are discussed. The necessity to consider earthquake load in addition to the environmental loads depending upon the location of the offshore structure is discussed. Since piles are often used in construction of offshore structures, a discussion on comparison of observed and predi~ted response of piles on is also included.
Offshore structures consist of production platforms, offshore storage facilities, combination storage and production structures and coastal research, and support facilities. These structures are subjected to combinations of static and dynamic loads. Dynamic loads arise due to the action of waves, sea storms, hurricanes, impact of floating ice, earthquakes and tsunamis. The discussion in this paper is confined to dynamic loading situations only. Design of marine structures was earlier based on the maximum wave and wind force likely to occur during the lifetime of the structure (Fisher, et al., 1975; Foss, et al., 1978). Consideration of earthquake loads was usually neglected because most structures were being constructed in seismically inactive areas. Although the wind, wave and earthquake loads are all cyclic in nature, they differ in regard to point of application on the structure, duration, frequency and amplitude. Figure 1 shows typical offshore structures with various loads acting. Taking an overall view of the problem, the design and analysis of the offshore structures under dynamic loads is essentially a problem involving dynamic soil structure interaction.
