Structural Identification Study of a Steel Multi-Girder Bridge Based on Multiple Reference Impact Test

A round robin style investigation to demonstrate best practices for the integration and application of technology to mitigate performance deficiencies of bridges was conducted. The structure selected for study, typical of Northeastern US construction, was part of a relatively large population of steel bridges older than 25 years. Teams from around the world visited the bridge and performed various experiments to conceptualize its performance. The research team conducted a series of multiple reference impact tests (MRIT) on one span of the bridge. The modal parameters were identified from the test data and used to generate modal flexibility. To mitigate epistemic uncertainty in the estimation of modal flexibility, the effect of reference point selection was investigated. A statistic analysis of deflections generated by modal flexibility was compared with displacements measured during a static truck load test and several conclusions and observations were including the identification of the effect of a large pier cap crack within the modal data.