Application of cyclic strain contour diagrams to assess cyclic effects on axially loaded driven piles

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4. Application of cyclic strain contour diagrams to assess cyclic effects on axially loaded driven piles

Driven piles are a popular foundation type for fixed-bottom Offshore Wind Turbine Generators (WTGs) supported by jacket structures. These jackets are subjected to numerous load cycles due to offshore environmental conditions during their operational lifespan. Cyclic loading induces push-pull mechanisms in the piles to resist repetitive loading cycles. This loading impacts the shaft resistance along the pile penetration, potentially degrading or increasing it compared to the monotonic response. This paper presents a practical application of a cyclic strain contour diagram database. It consists of cyclic testing results of various soil types and drainage conditions as a function of conventional soil properties, used to assess the effects of cyclic loading on the shaft resistance of axially loaded piled. The cyclic effects, whether degradation or improvement in strength, are quantified based on the cyclic load components arising from the mobilisation of repetitive push-pull mechanisms of axially loaded piles, where load specific cyclic and average stress paths are plotted on cyclic strain contour diagrams, extracted for given soil conditions and assessed against the corresponding stress-strain curves. A case study for a North Sea Offshore Wind Farm (OWF) is presented to demonstrate the benefits of adopting this method.

5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)

9 - Monopile design to cyclic loads: quasi-static, dynamic and seismic loads