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Structural Health Monitoring Considering Mass and Stiffness Modification

Seyedrezaei, Mirmahdi | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51199 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Mohtasham Dolatshahi, Kiarash
  7. Abstract:
  8. Damage detection of civil structures and infrastructures using partial modal information has been an interesting field of research. So far, three main algorithms are introduced for health monitoring of structures. The first method relies on identifying stiffness and mass properties, as physical parameters, of structures using inverse eigenvalue problem considering mass modifications in 2D and 3D shear-frame models of structures. Comparing the identified matrices with the primary values, one can detect the damage occurrence, its level and severity in the structure. Applicability of this method in health monitoring of offshore jacket platforms as one of noteworthy civil infrastructures has been evaluated as an example. Despite neglecting soil flexibility effects in parametric identification of structures in many researches, the second introduced method is a powerful tool for considering soil-structure interaction in health monitoring procedure assuming two springs as transitional and rotational stiffness of underlying soil. This method uses inverse vibration problem and auxiliary structures by adding stiffness to each structural level. By implementing defined method and using natural frequencies of structure as input data, physical parameters of interacted soil layer can be identified and then, stiffness of structural levels can be monitored in continuous base. The third method presents an algorithm by which, lower half levels of a structure can be identified using parameters of the upper half levels and the natural frequencies of the overall structure by introducing a new approach of double dimension problem. This is a robust method for system identification of structures like offshore jacket platforms which evaluating the health statue of some of their structural levels is a complex task. Computing partial information of mode shapes using natural frequencies of main and modified structures is a common process of these methods. Based on assumptions of introduced models in these methods and considering available input data, each of these methods can be applied for monitoring desired structures and infrastructures. Finally, usages, scopes and benefits of these three methods are presented and based on limitations of them, few proposals have been presented for future relevant researches in this area
  9. Keywords:
  10. System Identification ; Structural Health Monitoring ; Damage Detection ; Offshore Jacket Platform ; Inverse Vibration Problem ; Soil-Structure Interaction ; Mass Modification

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