Abstract

Studies for specific arctic offshore structures-drilling and production platforms, offshore terminals, piers, and underwater (under-ice) storage - confirm the advantages of concrete caissons: mass, low-temperature performance, economy, and speed of installation performance, economy, and speed of installation at the site. Stability is attained by sand and gravel fill, piles, or prestressed anchors.

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The proper development and exploitation of the resources of the Arctic Ocean requires that structures be developed which are suitable to the environment, offer a high degree of security, are economical, and are practicable for construction during the extremely short working periods available.

The Arctic Ocean presents, of course, a wide spread of environmental zones, varying from the shallow water lagoons to the offshore ice pack area. Ice dominates all design criteria pack area. Ice dominates all design criteria although seismic forces on occasion may approach the same order of magnitude. The dynamic nature of ice failure by crushing necessitates that any structure have ductile behavior throughout the entire temperature range to which it may be exposed. The resonant period of the structure should be substantially longer than the period of ice crushing, that is, longer than about 1 second; thus, mass is required. Of over-riding consideration in structures planned for such widely varying and extreme planned for such widely varying and extreme conditions, is the nature of failure under overload. It cannot be brittle nor subject to self-propagating cracking. Environmental considerations require that every possible step be taken to prevent pollution in an accident.

Thus, a structure for Arctic Ocean service bears a great deal of resemblance to a nuclear reactor pressure vessel. In design, one must take the structure through a whole series of limit states, each with its own probability and degree of security or safety factor.

Economics play a major role also, for successful development of the resources of the arctic requires that structures and systems be economically feasible. The utilization of the resources, such as oil, is in the temperate zone Production in the arctic therefore, must be Production in the arctic therefore, must be matched with transport systems in order to be economically competitive with other sources of oil and ultimately other sources of energy.

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