Upper bound solution of the moment bearing capacity of the pile-bucket composite foundation of offshore wind turbines

Offshore wind turbine superstructures impart significant moment forces onto their foundations due to their elevated positioning. The pile-bucket composite foundation effectively combines the load-bearing advantages of monopiles and suction caissons, substantially enhancing the foundation system's moment resistance. Establishing an analytical upper bound formulation for its ultimate capacity is therefore crucial for advancing practical implementation. Initially, a validated finite element model was established within Abaqus, based on small-scale physical testing. Following successful validation, bearing performance and associated soil failure patterns were systematically examined across varying geometric proportions (H/D). Subsequently, employing limit analysis principles and kinematic velocity field derivation, an upper bound solution for moment capacity was established. Experimental data rigorously benchmarks the proposed model's rationality and precision. This work provides essential theoretical support for the engineering design of moment capacities in pile-bucket composite foundations.