| Abstract: | There are more than 580,000 bridges in the United States, 83% of which span streams and rivers. Bridges are designed to withstand flood and debris loads; however, the most frequent causes of bridge failures are attributed to hydraulic events, including floods, debris, and drifts. Floodwater exerts significant hydrodynamic forces on the bridge that may result in bridge failure. The purpose of this study is to investigate the hydrodynamic forces acting on inundated bridges via small-scale model laboratory experiments. Physical models of bridges have been tested to estimate the force and moment coefficients for realistic flow conditions. In these experiments, lift and drag forces and overturning moments on bridge superstructures are measured and compared with existing design guidelines. The effects of flood velocity, bridge submergence, bridge deck types, and depth of the superstructure on the force and moment coefficients have been also investigated. The result of this study indicates that drag, lift force, and moment coefficients: 1) significantly vary with flood velocity and depth, 2) abruptly change, if the depth below the bridge is smaller than three times bridge height, and 3) differ based on the deck width and beam types. |