Tsunami-Like Wave Loading of Individual Bridge Components

Abstract

Research concerning tsunami forces on bridges has focused primarily on determining total forces either experimentally or numerically, often with the goal of establishing total force demand equations. However, this approach does not provide an understanding of which bridge components contribute to the total force demands as well as the individual component demands. Using a two-dimensional (2D) computational fluid dynamics approach, the influence of individual bridge components on total bridge forces was assessed in detail to show how this approach can provide critical information for designers, and was applied for bridges with varying superelevation and girder spacing as a proof-of-concept example to illustrate the benefits of this approach in understanding tsunami-like wave impacts on structures with complex geometries. The analyses resulted in the following findings. First, the upstream face of the upstream girder along with the traffic barriers carried the majority of the total horizontal impact load, which remained approximately constant while both the superelevation angle and girder spacing varied. Second, the opposing girder faces between pairs of girders experienced horizontal impact loading due to the compressed fluids between them. These loads were comparable in magnitude to the maximum horizontal impact load; however, these opposing girder forces canceled each other out, with this effect diminishing for increasing girder spacing. Despite its lack of influence on the overall demand, such behavior dictates the local design requirements of bridge girders to resist bore-induced forces. Third, the top deck face as well as the upstream and middle bottom deck faces sustained the majority of the vertical impact loading. As the superelevation angle was increased, a decrease in the total vertical load was observed, whereas when the girder spacing was decreased, an increase in the total vertical load occurred. Fourth, the upstream face of the upstream girder, traffic barriers, and top deck face carried the bulk of the total horizontal postimpact load, which varied parabolically with superelevation independent of the girder spacing. Finally, the deck primarily resisted the vertical postimpact load, which decreased linearly with an increase in superelevation angle, decreasing in magnitude for increased girder spacing.