Prioritizing Scour Vulnerable Bridges Using Risk

Abstract

The purpose of this study is to develop a method for assessing the risk associated with scour threat to bridge foundations. In response to numerous scour-related bridge failures, the Federal Highway Administration has mandated that states evaluate all bridges over water for scour. The Federal Highway Administration recently released HEC-18 to serve as a guidance manual in evaluating scour. In evaluating bridge scour, however, foundation information is needed to quantify vulnerability to scour damage, and this information is not available for many bridges. The methodology developed in this study will set priorities for bridge foundation information gathering. The risk of scour failure is calculated as the product of the cost associated with failure and the probability of scour failure. The method is based on data (much of which is subjective) contained in the National Bridge Inventory. The risk determines the ranking of bridges for foundation data gathering in support of scour evaluation; high-calculated risks could vanish if substantial foundations are discovered.