Oklahoma Earthquakes and Their Effects on Highway Bridges

Abstract

Oklahoma is presently experiencing a higher rate of earthquake activity than historically observed. Historical data on earthquake-induced damage to Oklahoma bridges is limited, so the Oklahoma Department of Transportation (ODOT) is concerned about their bridges. The first part of this research develops smart inspection radii for ODOT. These radii incorporate both the demand on and capacity of Oklahoma bridges. Demand is quantified by the ground-motion intensity, in this case spectral acceleration at a period of 1.0 s (S 1). Capacity is characterized by HAZUS fragility curves for bridges. Then, Oklahoma ground motions are compared to current attenuation models. Current models tend to over predict Oklahoma shaking levels, so a bias factor was calibrated to better represent Oklahoma earthquake attenuation. This is followed by performing a seismic response analysis for the Interstate 35 bridge over the Cimarron River located approximately 40 miles north of Oklahoma City in Logan County, Oklahoma. The results from this study can also be used to verify and adjust the fragility curve parameters needed for the development of ShakeCast–OK. Seismic response analysis has shown that the potential for structural damage is low under the considered loading conditions. Finally, ShakeCast–OK is developed. This real-time program sends notifications to ODOT indicating which bridges to inspect after an earthquake. This saves ODOT time and money by reducing the number of unnecessary inspections.