Tsunami-Induced Forces on Skewed Bridges

Research on the influence of tsunamis on bridges has been based almost exclusively on the results of field surveys and of two-dimensional analysis. Although these analyses can provide estimates of forces and moments on the structure, they do not account for three-dimensional (3D) phenomena, such as channelization, or geometric effects, such as bridge skew. Using a 3D computational fluid dynamics approach, this work analyzes the temporal and spatial dynamics of a bore-type tsunami loading on a model bridge and shows how the skew angle of the bridge relative to the incoming wave can affect the loading history. The analyses found that, unlike a bridge without skew, (1) the bore impact forces on the skewed deck do not all occur at the same time; (2) the skewed bridge is subjected to a force perpendicular to its abutments, which could lead to unseating; and (3) the skewed bridge is subjected to pitching and spinning moments. These effects combine to lead to increased horizontal reactions in the substructure components nearest the incoming wave. The vertical reactions were relatively insensitive to skew angle.