Abstract
This Ph.D. thesis deals with bucket foundations and their applicability for offshore wind turbines. The main concern is the establishment of an analytical model for frictional materials, combined with simulations of buckets with varying geometry.
An analytical model is proposed, consisting of different parts describing the
penetration resistance during installation, the phenomenon critical suction and
calculation methods for determination of the pullout force, respectively the response under combined loading, equivalent to ship impact, wave actions etc.
A series of experimental tests conducted at Aalborg University is simulated
numerically, and compared to the different parts of the analytical model. In the
numerical analysis two advanced constitutive soil models are compared with the
classical elastic perfectly plastic Mohr Coulomb model. The models, the Single
Hardening Model and the Mobilized Friction Model, are implemented as user defined material models in the commercial finite element program ABAQUS. The simulated tests are partly pullout tests, subsequent cyclic loading, partly drained tests on buckets subject to vertical, horizontal and moment loading. The numerical analyses are capable of simulating the change in size and shape of the failure locus in the H-M/D space, as revealed in the laboratory.
An economic comparison between different foundation concepts is made. The
advantages and disadvantages using bucket foundation are outlined.
Concluding a design chart is proposed, based on the performed numerical
simulations, the analytical models and concepts like penetration resistance and critical suction. The employment of finite element calculations in the design of bucket foundation is evaluated and found necessary in the detailed design. However, introductory the determination of the bucket dimensions is enabled through the analytical model, even though it has a number of limitations and restrictions. The new foundation concept is considered both economically and environmentally attractive for certain locations.
An analytical model is proposed, consisting of different parts describing the
penetration resistance during installation, the phenomenon critical suction and
calculation methods for determination of the pullout force, respectively the response under combined loading, equivalent to ship impact, wave actions etc.
A series of experimental tests conducted at Aalborg University is simulated
numerically, and compared to the different parts of the analytical model. In the
numerical analysis two advanced constitutive soil models are compared with the
classical elastic perfectly plastic Mohr Coulomb model. The models, the Single
Hardening Model and the Mobilized Friction Model, are implemented as user defined material models in the commercial finite element program ABAQUS. The simulated tests are partly pullout tests, subsequent cyclic loading, partly drained tests on buckets subject to vertical, horizontal and moment loading. The numerical analyses are capable of simulating the change in size and shape of the failure locus in the H-M/D space, as revealed in the laboratory.
An economic comparison between different foundation concepts is made. The
advantages and disadvantages using bucket foundation are outlined.
Concluding a design chart is proposed, based on the performed numerical
simulations, the analytical models and concepts like penetration resistance and critical suction. The employment of finite element calculations in the design of bucket foundation is evaluated and found necessary in the detailed design. However, introductory the determination of the bucket dimensions is enabled through the analytical model, even though it has a number of limitations and restrictions. The new foundation concept is considered both economically and environmentally attractive for certain locations.
| Original language | English |
|---|---|
| Place of Publication | Aalborg |
| Publisher | |
| Publication status | Published - 2001 |
Keywords
- Bucket Foundations
- Constitutive Soil Models
- Numerical Simulations
- Offshore Wind Turbines