Modified Goda Equations to Predict Pressure Distribution and Horizontal Forces for Design of Elevated Coastal Structures

A hydraulic physical model study was conducted to quantify horizontal forces and pressure distributions on an elevated structure under nonbreaking, impulsive breaking, and broken wave conditions. Regular wave trials with varying wave heights and periods were used to estimate phase-averaged horizontal pressure distributions at the time of the maximum horizontal force for a range of air-gap conditions, defined as the distance between the still-water level and the base of the elevated structure. Measured pressures for all wave conditions were compared to the Goda equations, originally developed for wave pressures on a vertical caisson breakwater and modified for elevated structures. For breaking waves, the pressure distribution predicted by both the modified Goda equations and equations in ASCE 7-16 were compared to measured pressures. The modified Goda equations showed good agreement with measured pressures and the total horizontal force per unit width and were generally conservative for all wave conditions over a range of structural elevations, including cases in which the structure was elevated above the still-water level. The ASCE 7-16 equations for breaking wave–induced pressures and forces were conservative by factors of 3–20. Results suggest that the modified Goda equations may be used to improve design guidance for at-grade and elevated coastal structures under wave loads with constant storm surge.