Online

Brand, Matthew

Civil and Environmental Engineering

2016

MS

The leading cause of bridge failure has often been identified as bridge scour, which is generally defined as the erosion or removal of streambed and/or bank material around bridge foundations due to flowing water. These scour critical bridges are particularly vulnerable during extreme flood events, and pose a major risk to human life, transportation infrastructure, and economic sustainability. Climate change is increasing the intensity and persistence of large flow events throughout the world, further straining bridge infrastructure. Retrofitting the thousands of undersized and scour critical bridges to more rigorous standards is prohibitively expensive, and current countermeasures inadequately address the core problems related to bridge scour. This research tested the efficacy of using approach embankments as intentional sacrificial "fuses" to protect the integrity of bridges with minimal damage during large flow events by allowing the streams to access their natural floodplain and reduce channel velocities. The concept was evaluated using the Hydrologic Engineering Center's River Analysis System (HEC-RAS) models. Steady flow models were developed for three specific bridges on two river reaches. Bayesian streamflow return period estimators were developed for both river reaches using available United States Geological Survey (USGS) stream gauge data to evaluate sacrificial embankments under non-stationary climatic conditions. Fuse placement was determined to be a cost effective scour mitigation strategy for bridges with suboptimal hydraulic capacity and unknown or shallow foundations. Additional benefits of fuses include reductions in upstream flood stage and velocity.