On using vibration data to detect damage in model-scale reinforced concrete bridges

Pearson, Steven R. (2003) On using vibration data to detect damage in model-scale reinforced concrete bridges. PhD thesis, University of Nottingham.

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Abstract

This thesis reports the findings of an investigation into the feasibility of using vibration characteristics to monitor the structural health of bridges. The study is the second part of a larger project commissioned by the UK Highways Agency into the investigation of possible monitoring methods that can be used in a pass/fail/monitor inspection programme. To this end, ten one-quarter-scale 5m span reinforced concrete bridge decks were fabricated and loaded incrementally to failure in the laboratory. The dynamic properties of the decks were investigated at each of the loading increments to evaluate their sensitivity to structural cracking using both free and forced vibration.

The results indicated that, for the specimens tested, natural frequencies were, in general, more sensitive to the damage introduced than mode shapes. It was found that the support conditions affected the dynamic behaviour of the decks, and indeterminate boundary conditions caused significant variation in the vibration characteristics. This presented several problems in the analysis of the modal properties and, when combined with the damage introduced through static loading, caused some modes to disappear and new modes to be measured, whilst a number of modes also displayed an increase in natural frequency.

The application of finite element model updating to determine reduction in flexural stiffness in the damaged areas of the deck provided a systematic method to investigate the condition of the deck. Updating was performed based on the natural frequencies of one symmetrically and one asymmetrically loaded deck, and the cracking observed under the loading, and offered results consistent with expectations.

In summary, the evidence presented in this thesis suggests that the natural frequencies of the decks are, in general, more sensitive to the damage introduced than the mode shapes and consistent trends can be observed in the natural frequency change as the damage to the deck increases. However, the application of this method to indicate the structural condition of real bridges may be limited without further investigation as the vibration characteristics were affected by a number of factors arising from the realistic nature of the specimen, such as the three-dimensional distribution of the damage and the indeterminate nature of the support conditions.

Item Type:Thesis (PhD)
Supervisors:Choo, B.S.
Owen, J.S.
Uncontrolled Keywords:Structural health monitoring, Civil engineering, Structural engineering
Faculties/Schools:UK Campuses > Faculty of Engineering > Department of Civil Engineering
ID Code:1239
Deposited By:June Walsh
Deposited On:22 Apr 2010 11:14
Last Modified:22 Apr 2010 11:14

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