Wave-Induced Uplift on Elevated Bridge Decks: A 2D CFD Sensitivity Study of the AASHTO and Modified-Goda Design Equations

Abstract

A 2D incompressible OpenFOAM sensitivity study of the AASHTO 2008 Guide Specifications for Bridges Vulnerable to Coastal Storms and the modified-Goda uplift formulation is reported on elevated coastal bridge decks across B/L in [0.09, 0.53], T in {2, 3, 4} s, and a* in [-0.5, +2.0]. Two CFD-internal, magnitude-independent results are presented. The soffit pressure distribution at peak |F_x|, normalised by its own leading-edge pressure p₆,CFD, is more uniform than the modified-Goda triangular profile at every B/L tested, including cases where the integrated force matches Doyle's prediction within +/- 20 percent. The impulsive amplification ratio F_peak/F_qs varies from 2.0 times to 4.2 times over the T x B cross-product and peaks at the dwell-time-matched corner B/L approximately 0.25 to 0.35, identifying impulsive amplification as the design-relevant unknown for bearing- and connection-capacity sizing. CFD-to-equation ratio observations (geometry-axis sign change of CFD/AASHTO; period dependence of CFD/Doyle outside the slender calibration band) are reported as exploratory: two PRJ-2131 matched-condition anchors span the CFD residual from 2.64 times over-prediction (slamming-spike artifact) to severe under-prediction (incident wave lost to shoaling-induced breaking before reaching the deck), so the spread is dominated by distinct CFD error mechanisms rather than by loading-model configuration sensitivity.