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Various structures are used in the exploitation of offshore energy from oil, gas and wind. These structures are designed to accommodate severe environments typically with large cyclic loads from waves and wind. Structures are typically either subsea on the seabed (e.g. pipelines,risers, templates etc.), platforms founded on the seabed (e.g. Jackets, Gravity Base, Jack-ups etc.) or floating structures moored to anchors installed in the seabed soil.

The permanent and cyclic loading, the foundation and anchor geometry, and the nonlinear soil behaviour may be very complex, and many interrelated aspects must be considered in the geotechnical design of the foundations. Finite-element analyses (FEAs) are used increasingly to deal with these complexities and offer the potential to reduce the risk and cost in the design process.

This webinar presents the most important geotechnical aspects that need to be consider in the design of foundations for offshore structures. Examples from various projects and finite element analyses carried out at NGI to deal with these aspects are given. A brief review of the procedure used at NGI to obtain soil stress-strain-strength relationships from cyclic laboratory tests is included. It is demonstrated that FEA offers several benefits over classical methods, such as limiting equilibrium calculations.