A new approach to determine the design wave load on bottom-fixed structures in shallow water breaking waves is presented here. The method takes into account the effects that wave breaking has on both the wave height distribution and the wave induced loads on the structure. The loads on offshore wind turbine foundations in irregular seas with a significant amount of wave breaking are modeled in a physical wave tank. The loads are related to wave characteristics as steepness and Ursell number, and a non-linear transfer function between wave height/period and wave load is established.
Characteristic historical load events are now established by combining the transfer function with a record of the wave climate at the site. The latter is taken from a hindcast database, but could also come from site measurements. The long-term distribution of the load is estimated by adopting traditional extreme value analysis techniques to the historical characteristic loads.