Computational fluid dynamic analysis of hydrodynamic forces on inundated bridge decks and the effect of scaling.

摘要

The proper estimation of the hydraulic forces experienced by an inundated bridge deck is important for design and evaluation of its vulnerability. During a flood or hurricane, highway bridges over the sea or other waterways may become partially or completely submerged. Flood flows add significant hydrodynamic loading on bridges, possibly resulting in the shearing or overturning of the bridge deck and failure of the bridge superstructures.;The objective of the study was to calculate the hydrodynamic forces on inundated bridge decks via computational fluid dynamic (CFD) simulations. The reduced scale experiments establish the foundations of validated computational practices to address the research needs of the transportation community. Three bridge deck types were used: a typical six-girder highway bridge deck, a three-girder deck, and a streamlined deck designed to better withstand the hydraulic forces. The results of the study show that critical values of the drag coefficient occur when the bridge is well inundated, but the critical values of the lift and moment coefficients occur near the transition from partially to fully inundated for all three bridge types. The critical lift coefficient was in fact negative for all three bridges, which corresponds to a downward pull force. Results showed that the streamlined deck significantly reduces the drag, lift, and moment coefficient in comparison to the other bridge deck types.;The CFD results matched the experimental data in terms of the relationship between the inundation ratio and force measured at the bridge. The next part of the study was conducted to transfer the recent supercomputer models of bridge inundation flows from laboratory scales to field scales. In this study the effect of scaling on turbulent flow and hydrodynamic forces was analyzed based on the Froude similarity method. The results of the present research will provide a tool for designing new bridges and retrofitting old ones so that they are able to withstand the forces and moments that may result from partial or complete inundation.