Yield envelope and bearing capacity of the modified suction caisson subjected to inclined loading in sand

Floating offshore technology becomes a key issue when exploring wind energy in deep or ultra-deep waters. The modified suction caisson (MSC) is an innovative type acting as floating offshore wind turbine foundation. Numerical simulations are carried out in this study to estimate the pull-out capacity of the MSC and to establish the H-V yield envelopes under inclined loading. Results show that when the padeye is located at the outer wall of the external structure, the normalized yield envelopes are basically the same at different padeye positions. For the pull-out load acts on the outer wall of the internal compartment, the yield envelope area gradually decreases inward as the padeye shifts downward. The yield envelopes in the H-V load space can be described by a normalized formula considering different padeye positions. In addition, the formulas of estimating the inclined pull-out bearing capacity by taking the dimensions of the MSC, the loading angle and the padeye embedded depth into account are put forward based on the limit equilibrium method.