Structural uncertainty identification using mode shape information

Riefelyna, Siska (2012) Structural uncertainty identification using mode shape information. Doctoral thesis (PhD), University of Sussex.

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This thesis is concerned with efficient uncertainty identification (UI) – namely the nonlinear inverse problem of establishing specific statistical properties of an uncertain structure from a practically-limited supply of low-frequency dynamic response information. An established UI approach (published in 2005) which uses Maximum Likelihood Estimation (MLE) and the Perturbation Method of uncertainty propagation is adopted for the study using (for the first time) mode shape information rather than just natural or resonant frequencies. The thesis develops a method based on the use of selected coefficients in a generalized displacement model i.e. a weighted series of spatially-continuous multiply-differentiable base functions to approximate the structural free-vibration response of an uncertain structure. The focus is placed on the estimation (from relatively small data sets) of the statistical properties of the location of an attached point-mass with normally-distributed position.

Simulated data for uncertain point-mass-loaded linear beam and plate structures is initially used to test the method making use of as much exact or closed-form differentiable information as possible to obtain frequencies and mode shapes. In the case of plate structures, extensive use is made of the Rayleigh Ritz method to generate the required response coefficients. This is shown to have significant advantages over alternatives such as the Finite Element method. The approach developed for use with free vibration information is then tested on measured experimental data obtained from an acoustically-forced clamped plate. Structural displacement measurements are taken from the plate using Vibromap 1000, a commercially-available ESPI-based holomodal measurement system capable of wide-field vibration response observation in real-time, or quantitative displacement response measurement.

The thesis shows that the developed uncertainty identification method works well for beams and plates using simulated free-vibration data

Item Type: Thesis (Doctoral)
Schools and Departments: School of Engineering and Informatics > Engineering and Design
Subjects: T Technology > TA Engineering (General). Civil engineering (General) > TA0630 Structural engineering (General)
Depositing User: Library Cataloguing
Date Deposited: 22 Jan 2013 13:04
Last Modified: 08 Sep 2015 13:45

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