Flood vulnerability of inland bridges with foundation scour

Abstract

Extreme floods can cause water level to rise above bridge superstructures. Following worldwide statistics on hydraulic bridge failure, it becomes essential to generate a comprehensive knowledge base to predict probable bridge failure scenarios under future floods and to identify appropriate countermeasures for flood risk mitigation. With this objective, the study here develops a numerical framework for systematic evaluation of forces on vulnerable bridge components during floods and to understand the global response of inland river-crossing bridges under flood hazards. Computational fluid dynamics (CFD) simulations are performed to calculate hydrodynamic forces on superstructure of a representative bridge for different inundation levels and flood velocities resulting from varied intensity flood events. Hydrodynamic forces on piers and scour depths around foundations are estimated for flood cases considered here. Knowing the forces and scour depths, finite element bridge models with and without scour are developed and analyzed to apprehend its global response and progressive failure under various combinations of water height and velocity. Further, regression relations are proposed to project component-level responses based on which damage state of the bridge under future intense flood events and fragility characteristics could be predicted. Thus, results enable identifying key factors to reduce flood vulnerability of inland bridges.