In recent years, the research group proposed a moving-window least-square fitting method and numerically
demonstrated its effectiveness in the identification of discrete cracks and the evaluation of flexural rigidity. In this
study, the proposed fitting method was experimentally validated with testing of a full-size concrete box girder bridge
under a concentrated impact load. The fitting method used the dynamic measurements from a locally dense array of
accelerometers or linear variable differential transformers and the relation between discrete cracks/flexural rigidities
and static deflections/curvatures after the measured deflection and curvature time histories have been integrated over
time. The so-developed detection algorithm for cracks and/or rigidity changes was highly sensitive to small damage
and can thus locate the damage accurately. Due to the integration of dynamic responses, the performance of the
damage detection algorithm is affected little by the noise that is usually included in field measurements. To validate
the proposed method, the full-size box girder was statically loaded to cracks and then subjected to impact loading by
a 200-lb drop weight. Using the moving-window least-square fitting method, the damage indicator at any segment
within the moving window is evaluated from the measured dynamic responses. It was dramatically amplified at the
location of cracks. The local amplification corresponded well to the width of cracks. These results clearly validated
the proposed method with the real-world bridge structure.
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