Response of a Typical Oklahoma Bridge to the September 3, 2016, 5.8-Magnitude Earthquake near Pawnee, Oklahoma

Abstract

Since 2006, the number of M3.0 and larger earthquakes occurring in Oklahoma has increased dramatically. Four M5.0 and larger events have caused damage to residential structures, which raises a concern about the potential for damage to Oklahoma’s highway bridges and their components. This study evaluates the potential for damage by assessing the seismic response of the most common bridge class in Oklahoma. The Oklahoma DOT bridge inventory is used to determine the most typical bridge class, and a representative bridge is modeled using nonlinear finite elements. A series of transient analyses were conducted to assess its performance under a suite of recorded bidirectional ground motions (GMs) from the September 3, 2016, M5.8 Pawnee earthquake (the largest event to date). Transient time history analyses were performed and responses (bearing deformation and column curvature) were recorded and presented. Slightly nonlinear responses were observed for the measured GMs. An incremental dynamic analysis was performed to assess the response of the typical highway bridge under higher intensity shaking closer to the epicenter in which seismic stations were not present. The measured GMs from seismic station GS.OK005 were incrementally scaled to AASHTO design levels (S1 = 0.10g) and to intensities derived by a USGS GM mapping product near the epicenter (S1 = 0.20g). Bearing responses indicative of slight damage, such as failure of anchor bolts and sliding of bearings, were predicted, and maximum column curvatures reached 80% of their yield curvature. This study has shown that future earthquakes with comparable or higher levels of shaking may well damage bridges, especially close to the epicenter in which shaking intensities are higher.