TRACC Studies on Flooded Bridges Can Help Communities

Led by Argonne National Laboratory engineer Tanju Sofu, TRACC analysts and FWHA’s Turner-Fairbank Highway Research Center (TFHRC) are currently evaluating the hydrodynamics of submerged bridge decks using computational fluid dynamics (CFD) simulations. These studies are aimed to advance the understanding of forces at work when bridges are flooded by rising water and affected by severe weather patterns similar to what occurred during Hurricane Katrina.

The models of flooded bridge deck behavior are constructed using state-of-the-art commercial CFD software packages, Fluent and Star-CD. Traditionally, hydraulic studies of this sort are done only in one- or two-dimensions relying on empirical approximations. CFD-based techniques offer an opportunity to extend these studies to three dimensions and to assess the broader modeling capabilities of these software packages (such as multi-phase flow, turbulence, and moving-boundary) to capture the important phenomena affecting the bridge hydraulics more mechanistically.

Currently, the CFD simulations focus on a range of hydraulic research including

1. Assessment of lift and drag forces on flooded bridge decks,
2. Analysis of sediment transport and its influence on scouring,
3. Evaluation of countermeasures to avoid or reduce damage,
4. Environmental issues, such as fish passage through culverts.

Evaluation of bridge stability after flooding events, including structural response of the bridge itself and the erosion of the riverbed surrounding bridge support structures, is critical for highway safety. In the past, such evaluations have relied heavily on scaled experiments to provide measurements for flow field and structural response. Efforts to date have focused on the assessment of a spectrum of modeling options for prediction of hydrodynamic loads and pressure scour. Good agreement between the code predictions and experimental data was obtained.  The scalability of these simulations to the TRACC supercomputer, particularly for the simulation of full-scale bridge deck interactions, was evaluated.

Six-girder bridge deck model (top) and calculated flow field under the free surface (bottom).

Using simulation tools and data, TRACC and TFHRC propose further studies to:

1. Apply their findings to real life bridges by working with the Illinois Department of Transportation and others,
2. Use their field data to validate the large scale models, and
3. Assess the structural integrity of real bridges.

This effort will help to identify scour-critical bridges and to propose cost-effective countermeasures to improve bridge structural integrity.

This research is supported by U.S. Department of Transportation.

November 2008