Date of Degree
PhD (Doctor of Philosophy)
Civil and Environmental Engineering
Salam F. Rahmatalla
First Committee Member
Second Committee Member
Third Committee Member
Fourth Committee Member
Vibration-based damage detection methods are used in structural applications to identify the global dynamic response of the system. The purpose of the work presented is to exhibit a vibration-based damage detection algorithm that calculates a damage indicator, based on limited frequency bands of the transmissibility function that have high coherence, as a metric for changes in the dynamic integrity of the structure. The methodology was tested using numerical simulation, laboratory experimentation, and field testing with success in detecting, comparatively locating, and relatively quantifying different damages while also parametrically investigating variables which have been identified as issues within similar existing methods. Throughout both the numerical and laboratory analyses, the results were used to successfully detect damage as a result of crack growth or formation of new cracks. Field results using stochastic operational traffic loading have indicated the capability of the proposed methodology in evaluating the changes in the health condition of a section of the bridge and in consistently detecting cracks of various sizes (30 to 60 mm) on a sacrificial specimen integrated with the bridge abutment and a floor beam. Fluctuations in environmental and loading conditions have been known to create some uncertainties in most damage detection processes; however, this work demonstrated that by limiting the features of transmissibility to frequency ranges of high coherence, the effect of these parameters, as compared to the effect of damage, become less significant and can be neglected for some instances. The results of additional field testing using controlled impact forces on the sacrificial specimen have reinforced the findings from the operational loading in detecting damage.
The purpose of the work presented is to exhibit a damage detection algorithm that measures changes within a structure through a process of monitoring how the structure vibrates. The methodology was tested using computer modeling, laboratory experimentation, and field testing with success in detecting, comparatively locating, and relatively quantifying different damages while also investigating variables that have been identified as issues within similar existing methods. Among these variables include temperature effects, loading conditions, and sensor placement. The presented methodology shows that the damage indicator metric is more sensitive to effects of damage than from these geometric and environmental variables because of how the damage indicator is calculated.
publicabstract, Algorithm, Coherence, Crack, Damage Detection, Vibration
xiv, 131 pages
Includes bibliographical references (pages 124-131).
Copyright 2015 Charles Schallhorn
Schallhorn, Charles Joseph. "Coherence-based transmissibility as a damage indicator for highway bridges." PhD (Doctor of Philosophy) thesis, University of Iowa, 2015.