Evaluation of flexibility-based damage indices using different modal response data

Abstract eng:
Modal flexibility is a robust and promising damage index for large civil engineering structures where only a few fundamental modes are measurable. Flexibility matrix of a structural system can be reliably obtained from a truncated set of lower modal parameters with sufficient accuracy. Unfortunately, the conventional flexibility methods based on displacement mode shapes are still unable to provide the required accuracy and reliability for damage localization due to their low sensitivity to small and multiple damages, and high sensitivity to measurement noise. In most cases, the modal para­meters of the structures in the healthy state are required as baseline. Hence, alternative dynamic parameters such as rotational and strain mode shape measurements have been recently explored for better damage identification. This paper presents modified flexibility-based damage indices using rotation and modal macro-strain data from fiber-optic sensors. The uniqueness of modal macro-strain flexibility, rotational flexibility, and the conventional (displacement based) is first established. Finally, the performance and sensitivity of the flexibility indices based on the three measurement data are comparatively investigated for localization of realistic small-to-moderate damage cases when baseline of the structure in the intact state is not available.

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