Seismic Evaluation of the Tennessee River Bridges on I-24 in Western Kentucky

This report presents the seismic evaluation of the approaches and parallel bridges on I-24 crossing the Tennessee River between Marshall and Livingston counties in Western Kentucky. The main bridges are steel tied-arch bridges. The bridges are situated within the influence of the New Madrid Seismic Zone. The seismic evaluation program consisted of field testing, 3-dimensional finite element modeling and seismic response analysis. The dynamic properties of the main bridges are determined through field testing, and are used to calibrate the finite element models. The finite element model is then subjected to time histories of the 250-year and 500-year earthquake events. Stresses and displacements for these events are found to be within the acceptable limits. Analytical results indicate that the main bridge will withstand the 250-year and 500-year earthquakes without any significant damage and no loss-of-span. The supports with fixed bearings on the pier of the main bridge need to be retrofitted for the 500-year earthquake event. The approach spans are analyzed using the response spectrum method with simplified single-degree-of-freedom models. Some supports on the approach spans are found to be vulnerable to shear failure of anchor bolts under the 250-year earthquake. All supports on the piers of the approach spans need to be retrofitted for the 500-year earthquake event. Additional anchor bolts or other retrofit measures at the bearings are recommended.