Addressing the issue of insufficient information in data-based bridge health monitoring : final report.
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2015-11-01
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Abstract:One of the most efficient ways to solve the damage detection problem using the statistical pattern recognition ; approach is that of exploiting the methods of outlier analysis. Cast within the pattern recognition framework, ; damage detection assesses whether the patterns of the damage sensitive features extracted from the response of ; the system under unknown conditions depart from those drawn by the features extracted from the response of ; the system in a healthy state. The metric dominantly used to measure the testing feature’s departure from the ; trained model is the Mahalanobis Squared Distance (MSD). Evaluation of MSD requires the use of the inverse of ; the training population’s covariance matrix. It is known that when the feature dimensions are comparable to the ; number of observations, the covariance matrix is ill-conditioned and numerically problematic to invert. When ; the number of observations is smaller than the feature dimensions, the covariance matrix is not even invertible. ; In this work, four alternatives to the canonical damage detection procedure were investigated to address the ; issue: data compression through Discrete Cosine Transform, use of pseudo-inverse of the covariance matrix, use of ; shrinkage estimate of the covariance matrix, and a combination of the three techniques. The performance of the ; four methods was first studied for solving the damage identification problem on simulated data from a four DOFs ; shear-type system, and on experimental data recorded on a four story steel frame excited at the base by means ; of the shaking table facility available at the Carleton Laboratory at Columbia University. Finally, the proposed ; techniques were also investigated in the context of damage location applications on simulated data from a bridge ; deck model.
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Main Document Checksum:urn:sha256:d9a68de3ea8ffeea39e321072aad80dc6d5953d610ef85ebb927cf70d13153a2