Storm Wave Forces on Selected Prototype Coastal Bridges on the Island of Oahu

Abstract

Hydrodynamic study of storm wave loads on four selected coastal bridges (prototype scale) around the Island of Oahu is presented here. These include NewMakaha Stream bridge, New South Punaluu Stream bridge, Maili Stream (Maipalaoa) bridge and Kahaluu Stream bridge on the Island of Oahu. Maximum water level at the location of the selected bridges is determined under extreme conditions of a Category 5 Hurricane making landfall on the island. The maximum wave height and wave period are estimated theoretically based on the highest water level. Several different scenarios are considered for each of the selected bridges. The wave loads on the bridges are calculated by use of several theoretical methods. One is based on Euler’s equations coupled with the Volume of Fluid method, for which OpenFOAM, an open access computational fluid dynamics (CFD) package is used to perform the computations, and another one is based on the Green-Naghdi (Level I) nonlinear shallow water wave equations, and is applied to the cases in which the bridge is fully submerged. Existing theoretical and empirical relations, including the Long-Wave Approximation for a fully submerged bridge, developed based on the linear potential theory, and the empirical relations for an elevated bridge deck are also used. Re- sults are compared with each other. The condition that results in the maximum wave forces for each of the bridges is summarized at the end of the report.