ESR8 - Fatigue of wind turbine concrete structures at COWI (10981)
INFRASTAR Marie Curie - Scientific project on fatigue and reliability of wind turbine concrete structures project?
INFRASTAR Marie Curie - Scientific project on fatigue and reliability of wind turbine concrete structures project?
Investigating the actual provisions for determination of fatigue loading and subsequently to develop optimised fatigue load determination models, e.g. by considering the statistical distribution of wind directions and by investigating the correlation between wind and wave loading for offshore structures. While this research mainly focuses on fatigue loading effects on structural elements in reinforced concrete of wind turbines; fatigue resistance of reinforced concrete (as investigated in task 2.1) will be adequately considered in the development of novel methods of examination of existing structures and fatigue design provisions for new structures.
YOU CAN MAKE A DIFFERENCE
The main aim is to investigate and develop new methods for assessment of the fatigue load and resistance for reinforced concrete in gravity based offshore wind turbine foundations. The influence of various design driving effects for fatigue will be investigated in order to optimize the current design philosophy and minimize the total cost of energy.
The main aim is to investigate and develop new methods for assessment of the fatigue load and resistance for reinforced concrete in gravity based offshore wind turbine foundations. The influence of various design driving effects for fatigue will be investigated in order to optimize the current design philosophy and minimize the total cost of energy.
The objective of this work package is to study and improve modelling of design and cost-driving aspects for gravity based foundation types of offshore wind turbines in order to achieve more cost-efficient solutions for future foundation designs.
Based on a review of the current methodology for assessment of fatigue loads for gravity based offshore wind turbine foundations, specific aspects with large optimization potential will be identified and analysed in more detail. It is very important to capture the various and complex interactions of the environment and individual subsystems within offshore wind turbines, e.g. leading to a pronounced aero-elastic behaviour. Adequate consideration of these interactions requires an integrated modelling approach for offshore wind turbines, their foundations and the environmental conditions. For the purpose of this project, an integrated offshore wind turbine and foundation model will initially be established by coupling of COWI's in-house tool IBDAS with an adequate aero-elastic simulation tool such as Flex5.
The design and load calculation tool will be used together with COWI's experience to establish a range of reference designs of gravity based foundations that are subsequently subjected to an identification of design and cost driving aspects.
The reference foundation designs, design methods and identified design and cost driving aspects are subsequently assessed with respect to their optimization potentials for more cost efficient design solutions. A selection of these will be subjected to more detailed investigations in order to achieve more cost-efficient gravity based foundations. Examples of such detailed investigations could include:
- Improved modelling of fatigue wave loading
- Improved modelling of combined wind turbine and wave loading, e.g. investigate length of time series, number of seeds for phase shift in wave load generation, wavelet discretization, resonant response
- Impact of fully integrated analysis compared to non-coupled design
In combination with experience from previous gravity, based foundations designed by COWI the most critical design load cases will be determined and investigated further. The further investigations will focus on the fatigue resistance and specifically the use of advanced non-linear damage material model for the verification of the concrete.
In most of today's projects the wind turbine suppliers provides the foundation designer with a summary of the loads in form of Markov matrixes, based on a load analysis assuming linear elastic material for the structure. The foundation is designed using linear damage accumulation according to Palmgren and Miner. This approach does consider neither the loading sequence nor the non-linear fatigue behaviour of the concrete. This simplification can lead to either conservative or unsafe design. Advanced material models can capture the stiffness and damage evolution in concrete under repeated loading. When these models are considered for the integrated load analysis, a more consistent design approach can be achieved.
The influence of using the advanced material models for assessment of the fatigue resistance for reinforced concrete compared to the traditional approach will be investigated for the developed reference foundation designs in order to assess the accuracy and optimization potential.
TASKS AND METHODOLOGY
- State-of-the-art modelling and fatigue load analysis of offshore wind turbines and gravity based foundations
- State-of-the-art models for fatigue verification of reinforced concrete
RESULTS
- Methodology for accurately assessment of fatigue loads in gravity based foundations for selected environmental loads and/or modelling assumptions
- Methodology for accurately assessment of the fatigue damage in reinforced concrete
- Illustrative implementations for reference foundation designs
- Successfully defended PhD thesis
DISSEMINATION
- Three peer reviewed papers
- Two presentations at national/international conferences
- Presentations at workshops and for potential end-users
PLANNED SECONDMENTS
- AAU, Aalborg, Denmark, month 14-16, Fatigue reliability of concrete wind turbine and bridge elements
- IFSTTAR, Paris, France, month 22, Analysis of load distributions resulting of combined actions (wind and waves) and derivation of the stress cycle variations inducing fatigue
- EPFL, Lausanne, Switzerland, month 29-30, Modelling of concrete strength subjected to fatigue load
QUALIFICATIONS REQUIRED
A M.Sc. or equivalent in Structural or civil engineering; knowledge of concrete design and basic knowledge of Wind energy.
A M.Sc. or equivalent in Structural or civil engineering; knowledge of concrete design and basic knowledge of Wind energy.
CONDITIONS
Please note the Marie Sklodowska-Curie Mobility Rule: Candidates must not have resided or carried out their main activity (work, studies, etc.) in the country of their host organisation for more than 12 months in the 3 years immediately prior to the reference date.
Please note the Marie Sklodowska-Curie Mobility Rule: Candidates must not have resided or carried out their main activity (work, studies, etc.) in the country of their host organisation for more than 12 months in the 3 years immediately prior to the reference date.
INTERESTED?
For further information, please feel free to contact:
For further information, please feel free to contact:
Henrik Niedermayer, Head of Section,
Marine and Foundation Engineering
E-mail: +45 5640 2135
We look forward to receiving your CV and application as soon as possible. Please apply on the INFRASTAR homepage here.
