Site Investigation of Bridges Along the I-24 in Western Kentucky

This report presents a seismic rating system and a detailed evaluation procedure for selected highway bridges on/over I-24 in Western Kentucky near the New Madrid Seismic Zone (NMSZ). The rating system, based upon structural vulnerability, seismic and geotechnical hazards, and socioeconomic factors, was used to rank 127 (82 on and 45 over I-24) bridges on/over I-24. A total of 14 bridges were selected and subsequently evaluated using a capacity/demand ratio method outlined in the Seismic Retrofitting Manual for Highway Bridges by the Federal Highway Administration. The focus was on four bridge components; namely the expansion joints, bearings, columns, and footings. The process involved creating a finite element model of all bridges, and proceeded by a dynamic analysis based on a given time-history spectra response of a 250-year event. The methods and results of the analyses are presented herein. The results indicate that the rating system is an effective means in terms of determining and prioritizing highway bridges for seismic evaluation and retrofit.