Dynamic characteristics evaluation and structural health monitoring for offshore structures

Previous long-term measurements of the Uldolmok tidal current power plant showed that the structure’s natural frequencies fluctuate with a constant cycle—i.e., twice a day with changes in tidal height and tidal current velocity. This study aims to improve structural health monitoring (SHM) techniques for offshore structures under a harsh tidal environment like the Uldolmok Strait. In this study, lab-scale experiments on a simplified offshore structure as a lab-scale test structure were conducted in a circulating water channel to thoroughly investigate the causes of fluctuation of the natural frequencies and to validate the displacement estimation method using multimetric data fusion. To this end, the numerical study was additionally carried out on the simplified offshore structure with damage scenarios, and the corresponding change in the natural frequency was analyzed to support the experimental results. In conclusion, (1) the damage that occurred at the foundation resulted in a more significant change in natural frequencies compared with the effect of added mass(3) displacement estimation using data fusion was valid compared with the reference displacement using the vision-based method.(2) the proposed damage index was able to indicate an approximate level of damage and the nonlinearity of the lab-scale test structuremoreover, the structural system became nonlinear when the damage was severeChapter 1. INTRODUCTION 1.1 Research Background 1 1.2 Literature Survey 3 1.3 Research Objectives and Scope 4 Chapter 2. THEORETICAL BACKGROUND 2.1 Added mass 6 2.2 Displacement Estimation Using Data Fusion 8 2.2.1 Example of Displacement Estimation Algorithm 10 2.3 Damage index(β) 15 Chapter 3. EXPERIMENTAL STUDY 3.1 General Information on the Lab-scale Experiments 18 3.2 Information on the Lab-scale Test Structure 20 3.3 Outline of the Lab-scale Experiment 25 3.4 Analysis of Experimental Results 27 3.4.1 Added Mass Effect 27 3.4.2 Boundary Damage Effect from Current Velocity Change 31 3.4.3 Damage Index (β) 33 3.4.4 Displacement Estimation 35 Chapter 4. VERIFICATION OF THE EXPERIMENT 4.1 Outline of the Numerical Modeling 41 4.2 Added Mass Effect 43 Chapter 5. CONCLUSION 5.1 Conclusion 45 5.2 Future Study 47 References 5

Deep Point Cloud Reconstruction

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