Ph.D. 1: Numerical modelling of soil-wind turbine interaction An important design criterion for offshore wind turbines is to ensure that the eigenfrequencies are sufficiently far from the main excitation frequencies. The stiffness of the foundation gives an important contribution to the global stiffness and the eigenfrequency. The aim for this study will be to improve the calculation methods for stiffness and damping of the foundation-soil interaction. The study will include finite element modelling, development of constitutive models for practical application to wind energy foundations and modelling of stiffness and damping applicable for fatigue life evaluations. Low strain stiffness of the soil will be addressed in particular. The study may also include accumulation of plastic strains during cyclic loading.
Ph.D. 2: Revision of the p-y curves to improve their applicability to monopile foundations The p-y curves defined in current design standards (API, DNV) are based on field tests on more flexible and smaller diameter piles than the typical monopiles for wind turbine foundations. Applying the conventional p-y curves may result in over conservative foundation design. The main focus of this study will be to evaluate and improve the current p-y curves based on back calculation of instrumented full scale wind turbine foundations. The study may also include model tests on piles with length- diameter-stiffness ratios representative for typical monopile foundations. In addition the study may include the effect of scour on stiffness and capacity of wind turbine foundation.
Ph.D. 3: Soil variability and application of statistical methods The aim with this topic is to develop statistical methods to determine characteristic soil properties with a reliability level comparable to the other parts of the design and improve on the current costly over-design practice. The study may include soil data evaluation to identify soil properties and aspects of soil variability that affect the performance of offshore wind turbine foundations. The study may also involve developing probabilistic models that encompass important soil variability. The probabilistic models may further be integrated in to design methods using for instance the First Order Reliability Method or Monte-Carlo simulation.
Ph.D. fellowships are awarded for a total of 3 years.Applicants should hold a master’s degree within geotechnical engineering or equivalent and must be qualified for admittance to Ph.D. study at NTNU. Ph.D. fellows are remunerated in the salary level 48-56 on the Norwegian State salary scale, gross NOK 391 100 to NOK 448 100 per year (before tax). Ph.D. students with limited or no work experience after graduation are normally remunerated at level 48. A pension contribution to The Norwegian Public Service Pension Fund (Statens pensjonskasse) of 2 % of gross salary will be deducted.
Scholarship Deadline: 9 March 2012
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