Identification of Dynamic Characteristics of Wind Turbine Tower with Caisson Foundation
- Abstract
- The objective of this study is to identify dynamic characteristics of the wind turbine tower with caisson foundation via wave-induced vibration responses. Firstly, the operational vibration analysis methods are outlined. The frequency-domain and the time-domain modal analysis methods are selected to identify reliable modal parameters. Secondly, a finite element (FE) model of a structure example including a wind turbine tower, a caisson foundation and a foundation bed is simulated as a case study by using a FEM software, Midas FEA. The wave pressure acting on the structure is computed via using a computational fluid software, Flow-3D program. The wave pressure is then transferred into the Midas FEA to simulate the wave-induced vibration of the structure and extract the acceleration responses. Thirdly, dynamic characteristics of the target structure are analyzed under the eigenvalue and the wave-induced vibration analyses. The modal parameters are investigated under several wave conditions. Finally, damage assessment of the structure is performed under several damage scenarios via the extracted modal parameters.
- Issued Date
- 2018
- Awarded Date
- 2018. 8
- Type
- Dissertation
- Publisher
- Pukyong National University
- Affiliation
- 부경대학교 대학원
- Department
- 대학원 해양공학과
- Advisor
- Kim Jeong Tae
- Table Of Contents
- TABLE OF CONTENTS i
LIST OF FIGURES iii
LIST OF TABLES v
ABSTRACT vi
CHAPTER 1 INTRODUCTION 1
1.1 Background 1
1.2 Objective and Scope 3
1.3 Organization of the Thesis 3
CHAPTER 2 OPERATIONAL VIBRATION ANALYSIS METHODS 5
2.1 Introduction 5
2.2 Vibration Monitoring Condition of Offshore Wind Turbine Tower 5
2.3 Frequency-Domain Modal Analysis Method 6
2.4 Time-Domain Modal Analysis Method 7
CHAPTER 3 NUMERICAL MODELLING OF WIND TURBINE TOWER WITH CAISSON FOUNDATION 9
3.1 Introduction 9
3.2 Description of Target Structure 9
3.3 Numerical Modelling of Target Structure 13
3.4 Numerical Modelling of Wave Field 15
3.5 Wave-induced Vibration Responses 19
CHAPTER 4 DYNAMIC CHARACTERISTICS OF WIND TURBINE TOWER WITH CAISSON FOUNDATION 25
4.1 Introduction 25
4.2 Eigenvalue Analysis 25
4.2.1 Bending Modes along Wave Direction 25
4.2.2 Bending Modes across Wave Direction 27
4.2.3 Axial and Torsional Modes 28
4.2.4 Foundation Modes 30
4.3 Wave-induced Vibration Analysis 31
4.3.1 Bending Modes along Wave Direction 31
4.3.2 Bending Modes across Wave Direction 34
4.3.3 Axial and Torsional Modes 37
4.4 Modal Parameters under Different Wave Conditions 42
CHAPTER 5 DAMAGE ASSESSMENT OF WIND TURBINE TOWER WITH CAISSON FOUNDATION 45
5.1 Introduction 45
5.2 Damage Types of Target Structure 45
5.2.1 Damage Type 1: Loosening Bolts in Tower Flanges 45
5.2.2 Damage Type 2: Lost Infill Sand in Caisson Foundation 46
5.2.3 Damage Type 3: Scouring in Foundation Bed 47
5.3 Modal Parameter-based Damage Assessment 48
5.3.1 Identification Procedure of Modal Parameters 48
5.3.2 Variation of Modal Parameters due to Damage Type 1 (Loosening Bolts) 49
5.3.3 Variation of Modal Parameters due to Damage Type 2 (Lost Infill Sand) 54
5.3.4 Variation of Modal Parameters due to Damage Type 3 (Scouring) 59
5.3.5 Classification of Damage Types 63
CHAPTER 6 CONCLUSIONS 65
REFERENCES 67
ACKNOWLEDGEMENTS 71
- Degree
- Master
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