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Damage Detection in Offshore Jacket Structures Using Invers Vibration Problem (IVP)Technique with a Look on Probabilistic Bayesian Network Modeling

Ahmadi, Ali | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56026 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Abbaspour, Madjid; Tabeshpour, Mohammad Reza
  7. Abstract:
  8. Damage detection in all kinds of human-made structures has been given serious attention as one of the main branches of engineering sciences, and significant progress has been made in this field, especially in the field of civil engineering, aerospace and heavy industries. However, although this topic is discussed academically in the field of offshore structures for two decades, not much development has happened in practice and it is still in the stage of knowledge development. One of the most important characteristics of practical online damage detection methods is the ability to be used knowing little information about the modal characteristics of the structure. In this research, an attempt has been made to use the Inverse Vibration Problem (IVP) technique and apply an iterative technique to the process of damage detection in offshore jacket platforms using incomplete modal data that are obtained at a few points of the platform. It has also been tried to investigate and identify the best methods to reduce the dimensions of the stiffness and mass matrices, as well as to calculate the equivalent stiffness of different levels of platform that are used in the implementation of the IVP technique. In this regard, the method chosen to calculate the equivalent stiffness of different levels of the platform has an error of less than 2% and the method chosen to reduce the dimensions of the mass and stiffness matrices of the structure has an error of less than 0.5% in the reconstruction of the modal characteristics of the structure. Also, the damage detection method developed based on the iterative IVP technique, predicts the damage severity with 1% accuracy and detects the damage position accurately
  9. Keywords:
  10. Offshore Jacket Platform ; Online Damage Identification ; Inverse Vibration Problem ; Modal Characteristics ; Natural Frequency ; Mode Shapes ; Matrix Model ; Equivalent Stiffness Matrix ; Dimensionality Reduction ; Slave Degree of Freedom ; Master Degree of Freedom

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