During tsunami inundation, coastal structures are subject to hydrostatic and hydrodynamic forces from the run-up and rundown and to impact forces from floating debris that is picked up by the flow. A new chapter in the upcoming revised U.S. design load standard covers these loads. To illustrate the application of this methodology for impact loading, it is applied to the determination of shipping-container impact loads for locations in Hilo, Hawaii. The steps include identification of the tsunami design zone, computation of the shipping-container impact hazard region, and computation of the design flow velocity and depth within that region. The flow velocity is used to determine the design impact force for the structure, and the depth is used to define up to what height impact must be considered. The standard provides a new, relatively simple energy grade line method that can be used to obtain estimates of these quantities. Because the method has not been widely validated within the archival literature, the results of the method are compared with results from a two-dimensional tsunami-inundation simulation. A simple extension that can improve the results of the energy grade line is proposed. This paper is meant to provide a reference for those applying these provisions in practice and to indicate areas for improvement.

Office of Oceanic and Atmospheric Research (OAR)