Quantifying the Bump at the End of the Bridge with Inertial Profilers Pilot Study: Comparing Deep versus Shallow Foundation Systems

The bump at the end of the bridge has been extensively studied, yet the problem continues to be one of the most chronic issues affecting long term bridge performance. Besides serving as a nuisance to drivers, the bump also amplifies impact loads which can affect deck durability and deterioration at the bridge approach transition; this often leads to repeated maintenance activities throughout the life of the bridge. To alleviate the bump, many transportation agencies have started to use geosynthetic reinforced soil (GRS) both for bridge foundations and approaches. Based on anecdotal experience of driving across these bridge systems, users describe a smooth transition, but the magnitude of differential settlement across the bridge approach transition had not been quantified. This paper describes a pilot study by the Federal Highway Administration to measure the bump at eight bridge sites using inertial pavement profilers and to compare the performance of those bridges supported by GRS to those built with more conventional methods on deep foundations. The results indicate an improvement when using GRS. In addition, the investigation also provides insights on how to use inertial profilers as a transportation performance management tool to monitor bridge approaches.