This report presents the findings of a seismic evaluation of the Brent-Spence bridge. The bridge is a double-deck cantilever through truss which was constructed in 1961; it is a critical highway link conveying 1-75 over the Ohio river. While not yet subjected to a moderate or major earthquake, the bridge is within the influence of the New Madrid, Wabash Valley, and Anna seismic zones.

The seismic evaluation program consisted of field testing and seismic analysis. The vibrational properties of the main bridge were determined through field testing and used to calibrate a 3-D finite element model. The model was then subjected to time histories of projected earthquakes in the aforementioned seismic zones, including a maximum credible earthquake of magnitude 8.5 on the Richter scale at New Madrid. The Covington approach spans were analyzed using simple models and response spectrum analyses.

Analytic results indicate that the main bridge will survive the projected maximum credible earthquake in the elastic range without significant damage and no loss of span; however, the Covington approach spans are vulnerable to loss of span failure in this event. Hence retrofit and a thorough seismic analysis of the approach spans is required.

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The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky, the Kentucky Transportation Cabinet, nor the Federal Highway Administration. This report does not constitute a standard, specification or regulation. The inclusion of manufacturer names or trade names are for identification purposes and are not to be considered as endorsement.