scholarly journals Design Optimization of Conical Concrete Support Structure for Offshore Wind Turbine

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4876
Author(s):  
Hyun-Gi Kim ◽  
Bum-Joon Kim
Keyword(s):  
Structural Analysis ◽  
Wind Turbine ◽  
Design Optimization ◽  
Time History ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Support Structures ◽  
Support Structure ◽  
Analysis And Design ◽  
Natural Frequency Analysis

Various types of support structures for offshore wind turbine have been developed, and concrete structures have attracted attention due to many advantages. Although many studies have been conducted on the design of the existing steel structures, information and research on the design of concrete support structures are insufficient. Therefore, in this paper, a structural analysis model of conical concrete support structure (CCSS) is established and design optimization is presented. A detailed performance evaluation and the design of prestressed concrete were performed under the marine conditions of Phase 1 test site of southwest offshore wind project in Korea. The fluid–soil–structure interaction (FSI) was applied using the added mass method and soil spring model to represent the effects of water and soil. With the result of quasi-static analysis, a post-tensioning design was implemented by applying prestressing steel, and CCSS showed sufficient rigidity. From the natural frequency analysis, CCSS has a dynamic structural stability, and, in response spectrum and time-history analyses, the CCSS was safe enough under the earthquake loads. The methods and conclusions of this study can provide a theoretical reference for the structural analysis and design of concrete support structures for offshore wind turbines.

Strength Assessment of Jacket Offshore Wind Turbine Support Structure Accounting for Rupture1

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Baran Yeter ◽  
Yordan Garbatov ◽  
C. Guedes Soares
Keyword(s):  
Wind Turbine ◽  
Low Cycle Fatigue ◽  
High Stress ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Small Scale ◽  
Support Structures ◽  
Support Structure ◽  
Strength Assessment ◽  
High Stress Concentration

The objective of the present work is to carry out the strength assessment of jacket offshore wind turbine support structures subjected to progressive rupture. A defect existing in a structure made during the fabrication may turn into a small-scale rupture and because of the high-stress concentration and low-cycle fatigue load. Therefore, the ultimate load-carrying capacity of the support structure is analyzed accounting for the progress of the rupture until the leg component experiences a full rupture along its circumference. The effect of imperfection severity is also investigated. The moment–curvature relationship of the structure concerning the studied cases is presented. Furthermore, the jacket support structures, at different water depths, are also analyzed and discussed. Finally, some of the leg components are removed one by one to study the redundancy of the jacket support structure at 80-m water depth.

scholarly journals Design Optimization and Reliability Analysis of Jacket Support Structure for 5-MW Offshore Wind Turbine

2014 ◽  
Vol 28 (3) ◽  
pp. 218-226 ◽  
Author(s):  
Ji-Hyun Lee ◽  
Soo-Young Kim ◽  
Myung-Hyun Kim ◽  
Sung-Chul Shin ◽  
Yeon-Seung Lee
Keyword(s):  
Wind Turbine ◽  
Design Optimization ◽  
Reliability Analysis ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Support Structure

scholarly journals A fracture mechanics framework for optimising design and inspection of offshore Wind Turbine support structures against fatigue failure

2020 ◽  
Author(s):  
Peyman Amirafshari ◽  
Feargal Brenan ◽  
Athanasios Kolios
Keyword(s):  
Fracture Mechanics ◽  
Wind Turbine ◽  
Fatigue Failure ◽  
Cost Benefit Analysis ◽  
Cost Benefit ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Support Structures ◽  
Benefit Analysis ◽  
Support Structure

Abstract. Offshore Wind Turbine (OWT) support structures need to be designed against fatigue failure under cyclic aerodynamic and wave loading. The fatigue failure can be accelerated in a corrosive sea environment. Traditionally, a stress-life approach called the S-N curve method has been used for design of structures against fatigue failure. There are a number of limitations in S-N approach related to welded structures which can be addressed by the fracture mechanics approach. In this paper the limitations of the S-N approach related to OWT support structure are addressed, a fatigue design framework based on fracture mechanics is developed. The application of the framework to a monopile OWT support structure is demonstrated and optimisation of in-service inspection of the structure is studied. It was found that both the design of the weld joint and Non-destructive testing techniques can be optimised to reduce In-service frequency. Furthermore, probabilistic fracture mechanics as a form of risk-based design is outlined and its application to the monopile support structure is studied. The probabilistic model showed to possess a better capability to account for NDT reliability over a range of possible crack sizes as well as providing a risk associated with the chosen inspection time which can be used in inspection cost benefit analysis. There are a number of areas for future research. including better estimate of fatigue stress with a time-history analysis, the application of framework to other types of support structures such as Jackets and Tripods, and integration of risk-based optimisation with a cost benefit analysis.

Strength Assessment of Jacket Offshore Wind Turbine Support Structure Accounting for Rupture

2018 ◽  
Author(s):  
Baran Yeter ◽  
Yordan Garbatov ◽  
C. Guedes Soares
Keyword(s):  
Wind Turbine ◽  
Low Cycle Fatigue ◽  
High Stress ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Small Scale ◽  
Support Structures ◽  
Support Structure ◽  
Strength Assessment ◽  
High Stress Concentration

The objective of the present work is to carry out the strength assessment of jacket offshore wind turbine support structures subjected to progressive rupture. A defect existing in a structure made during the fabrication may turn into a small-scale rupture and because of the high-stress concentration and low-cycle fatigue load. Therefore, the ultimate load-carrying capacity of the support structure is analysed accounting for the progress of the rupture until the leg component experiences a full rupture along its circumference. The effect of the severity of the imperfection is also investigated through 3 case studies that are created by varying the amplitude of the waves. The moment-curvature relationship of the structure with respect to the studied cases is presented. Furthermore, the jacket support structures, at different water depths, are also analysed and discussed. Finally, some of the leg components are removed one by one to study the redundancy of the jacket support structure at 80-m water depth.

scholarly journals Reducing the number of load cases for fatigue damage assessment of offshore wind turbine support structures using a simple severity-based sampling method

2018 ◽  
Vol 3 (2) ◽  
pp. 805-818 ◽  
Author(s):  
Lars Einar S. Stieng ◽  
Michael Muskulus
Keyword(s):  
Wind Turbine ◽  
Design Optimization ◽  
Fatigue Damage ◽  
Simple Procedure ◽  
Computational Effort ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Support Structures ◽  
Fatigue Assessment ◽  
Operational Conditions

Abstract. The large amount of computational effort required for a full fatigue assessment of offshore wind turbine support structures under operational conditions can make these analyses prohibitive, especially for applications like design optimization, for which the analysis would have to be repeated for each iteration of the process. To combat this issue, we present a simple procedure for reducing the number of load cases required for an accurate fatigue assessment. After training on one full fatigue analysis of a base design, the method can be applied to establish a deterministic, reduced sampling set to be used for a family of related designs. The method is based on sorting the load cases by their severity, measured as the product of fatigue damage and probability of occurrence, and then calculating the relative error resulting from using only the most severe load cases to estimate the total fatigue damage. By assuming this error to be approximately constant, one can then estimate the fatigue damage of other designs using just these load cases. The method yields a maximum error of about 6 % when using around 30 load cases (out of 3647) and, for most cases, errors of less than 1 %–2 % can be expected for sample sizes in the range 15–60. One of the main points in favor of the method is its simplicity when compared to more advanced sampling-based approaches. Though there are possibilities for further improvements, the presented version of the method can be used without further modifications and is especially useful for design optimization and preliminary design. We end the paper by noting some possibilities for future work that extend or improve upon the method.

Reliability of Offshore Wind Turbine Support Structures Subjected to Extreme Wave-Induced Loads and Defects

2016 ◽  
Author(s):  
Baran Yeter ◽  
Yordan Garbatov ◽  
C. Guedes Soares
Keyword(s):  
Service Life ◽  
Wind Turbine ◽  
Crack Growth ◽  
Low Cycle Fatigue ◽  
Limit State ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Cycle Fatigue ◽  
Support Structures ◽  
Support Structure

The probability of existence of defects, fatigue damage and crack growth in the offshore wind turbine support structures subjected to extreme waves and wind-induced loads is very high and may occur at a faster rate in a low cycle fatigue regime and crack growth, leading to a dramatic reduction in the service life of structures. It is therefore vital to assess the safety and reliability of offshore wind turbine support structures at sea. The aim of the present study is to carry out a low cycle fatigue and crack growth reliability analysis of an offshore wind turbine support structure during the service life. The analysis includes different loading scenarios and accounts for the uncertainties related to the structural geometrical characteristics, the size of the manufacturing and during the service life defects, crack growth, material properties, and model assumed in the numerical analyses. The probability of failure is defined as a serial system of two probabilistic events described by two limit state functions. The first one is related to a crack initiation based on the local strain approach and the second one on the crack growth applying the fracture mechanic approach. The first and second order reliability methods are used to estimate the reliability index and the effect of low cycle fatigue and crack growth on the reliability estimate of the offshore wind turbine support structure. The sensitivity analysis is performed in order to determine the degree of the significance of the random variables and several conclusions are derived.

scholarly journals Reliability-based design optimization of offshore wind turbine support structures using analytical sensitivities and factorized uncertainty modeling

2019 ◽  
Author(s):  
Lars Einar S. Stieng ◽  
Michael Muskulus
Keyword(s):  
Wind Turbine ◽  
Design Optimization ◽  
Optimization Methods ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
High Fidelity ◽  
Reliability Based Design Optimization ◽  
Support Structure ◽  
Reliability Based Design ◽  
Gradient Based

Abstract. The need for cost effective support structure designs for offshore wind turbines has led to continued interest in the development of design optimization methods. So far, almost no studies have considered the effect of uncertainty, and hence probabilistic constraints, on the support structure design optimization problem. In this work, we present a general methodology that implements recent developments in gradient-based design optimization, in particular the use of analytical gradients, within the context of reliability-based design optimization methods. By an assumed factorization of the uncertain response into a design-independent, probabilistic part and a design-dependent, but completely deterministic part, it is possible to computationally decouple the reliability analysis from the design optimization. Furthermore, this decoupling makes no further assumption about the functional nature of the stochastic response, meaning that high fidelity surrogate modeling through Gaussian process regression of the probabilistic part can be performed while using analytical gradient-based methods for the design optimization. We apply this methodology to several different cases based around a uniform cantilever beam and the OC3 Monopile and different loading and constraints scenarios. The results demonstrate the viability of the approach in terms of obtaining reliable, optimal support structure designs and furthermore show that in practice only a limited amount of additional computational effort is required compared to deterministic design optimization. While there are some limitations in the applied cases, and some further refinement might be necessary for applications to high fidelity design scenarios, the demonstrated capabilities of the proposed methodology show that efficient reliability-based optimization for offshore wind turbine support structures is feasible.

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