Bearing behaviour of tripod bucket foundations for offshore wind turbines in sandy seabeds under combined V-H-M loadings

Description

Tripod bucket foundations for offshore wind turbines (OWTs) installed in weak saturated sandy seabeds are subjected to combined vertical, horizontal and moment loading. To investigate their bearing behavior under combined loading, a three-dimensional finite element model was developed in PLAXIS 3D using the Mohr-Coulomb constitutive model. Failure envelopes in the V-H, V-M, H-M and V-H-M loading spaces were established using fixed load-ratio and combined load–displacement loading approaches, and the effects of load combination and bucket spacing were systematically examined. The results show that the failure envelopes in the V-H and V-M planes first expand and then contract, with the failure mechanism evolving from overall rotational failure to punching shear failure. In the H-M plane, the failure envelope is slender and approximately elliptical. Under co-directional H and M loading, the failure mode remains essentially unchanged, whereas under opposite loading directions it depends on the dominant load component. In the V-H plane, the envelope shrinks inward with increasing moment load, although the dominant failure mechanism is unaffected by moment loading. Increasing the bucket spacing ratio S/D from 2.0 to 4.0 increases the ultimate H, V and M capacities by about 94%, 1% and 100%, respectively, and enlarges the envelope areas in the V-H, V-M and H-M planes and the envelope volume in the V-H-M space by about 195%, 128%, 146% and 414%, respectively, while only marginally affecting the envelope shape. These findings provide valuable insights into the load-interaction behavior and spacing optimization of tripod bucket foundations for OWTs applications.

Institutions

• Dalian Maritime University

  Liaoning, Dalian

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