Modal parameter identification of Civil Engineering structures by using an output-only system identification technique için kapak resmi
Modal parameter identification of Civil Engineering structures by using an output-only system identification technique
Başlık:
Modal parameter identification of Civil Engineering structures by using an output-only system identification technique
Yazar:
Ceylan, Hasan, author.
Yazar Ek Girişi:
Fiziksel Tanımlama:
xi, 109 leaves: color illustraltions.+ 1 computer laser optical disc.
Özet:
Civil engineering structures are designed for a limited lifetime. Due to environmental effects and degradation of these structures, engineers need to decide on their structural safety and sustainability from time to time. To this end, structural health monitoring techniques could be employed to determine the current structural state. Current conditions of structures could be investigated by system identification techniques that is based on the modal parameters (modal frequencies, modal damping ratios and mode shapes) of structures. In this thesis, output-only system identification of civil structures is studied to estimate modal parameters of two different types of structures. For this purpose, a combination of the Natural Excitation Technique (NExT) and the Eigensystem Realization Algorithm (ERA) is coded within Matlab environment. The first study consists of a numerical and an experimental phase. In the numerical phase, the technique is implemented on the mathematical model of a three-story model building. In the experimental phase, it is implemented on the physical model of this three-story model building. 10 different scenarios of structural conditions are simulated by means of changes in story masses of the structure. By using NExT-ERA, the calculated modal frequencies and mode shapes are in good agreement with the results of the eigenvalue analysis. Further, the simulated mass change in each scenario is detected by a least squares approach. Changes in story masses are detected within reasonable errors. In the second study, a methodology is proposed to acquire measurements of large structures by using a few sensors, only. These sensors are used in a segmental way to measure the whole structure. The sensors are grouped and the groups of sensors are shifted on the model to obtain the response measurements from the whole structure. Then the grouped response measurements that are obtained at different time frames are transformed into the equivalent response data as if being acquired at a single time interval. To implement the methodology, a finite element model of a continuous beam bridge is constructed. Modal parameters of the model are estimated by using NExT-ERA and the results show that the first 10 modal frequencies are consistent with those of the eigenvalue analysis of the model, but only the first 6 mode shapes are successfully identified.
Yazar Ek Girişi:
Tek Biçim Eser Adı:
Thesis (Master)--İzmir Institute of Technology: Civil Engineering.

İzmir Institute of Technology: Civil Engineering--Thesis (Master).
Elektronik Erişim:
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