Influence of Lateral Movements of Approach Embankments on Bridges: A Case Study

Abstract

Several modes of bridge distress related to interactions with approach roadways have been observed in Oklahoma through routine maintenance inspections. Upon closer review it was found out that there are two main mechanisms for a category of distress that includes bearings tilting, anchor bolts bending or shearing, concrete slope walls cracking, and girders pushing against the backwall. One of these mechanisms is the lateral movement of approach embankments. This movement tends to happen early in the life of a bridge and pushes the abutment toward the bridge and closes the bridge expansion joints. The other mechanism is the pressure from rigid approach pavements due to closed or nonexisting joints on pavements. The pavement pressure exerted on the bridge deck also closes the expansion joints. This paper focuses on the lateral movements of approach embankments. As a part of this research an extensive instrumentation and monitoring program was undertaken on a five-span bridge in Ada, Oklahoma, showing the characteristic signs of this distress. Through review of routine inspection reports and analysis of recorded data from installed instruments; a rehabilitation plan was developed and implemented. Following the rehabilitation, the instruments were monitored for an additional 3.5 years to verify the repairs were successful. Through this research it was found that if lateral embankment movement is the mechanism of distress, a successful rehabilitation plan can be implemented once lateral movement has stopped. The rehabilitation involved installing new bridge expansion joints and changing some of the girder end conditions for the monitored bridge. As a result of this research the Oklahoma Department of Transportation expanded their bridge inspection protocol to identify these two mechanisms for this category of bridge distress.