Modeling the dynamic reponse of structures to support offshore wind turbines

Abstract

In this thesis, it was the goal to design, analyze and subsequently perform an optimization of the structure of a monopile-type offshore wind turbine. First, it was necessary to study and subsequently analyze the theories that would allow us to carry out the thesis. This consists in finding a theory that allows modeling of the soil and another that allows the application of the forces corresponding to the wind and the sea. Soil modeling theory considers the soil as a distributed spring model, which according to the literature it is considered a more reliable representation of the soil. As for the theory of force application for the water and wind, the worst possible environmental conditions are considered to carry out the last load test. The last load test is to analyze the structure for the worst situation that could occur, and therefore this represents the worst conditions of wind and sea together, at the same time. It is important to note that modal analysis techniques are used to calculate the eigen frequencies and modes of the structure. This analysis is very important in the design, because it will mark the dynamic behavior of the structure. Second, once the literature discussing the different theories to be taken into account is well examined, first design of the structure is modeled and realized by taking into account a benchmarks case discussed in the literature. A remark should be made that for this first design some parameters defined in another thesis are considered, such as the characteristics of the turbine, because it seeks to compare the results obtained with this thesis. In this way we analyze and compare the results obtained, as shown in the thesis can be seen these results as good, because they achieve the same response values during the last load test and modal analysis from the discussed reference, but with a much simpler design. Following this analysis, we performed an optimization of the initial design, but we tried to achieve a better response in all analyzes resulting in a less expensive design. This process takes place successfully because considering that the first design could be regarded as good for the values obtained, these values are improved response in around 10% in all respects. Finally we can consider that the goal of this thesis achieved by optimizing the design of the turbine foundation.