The evaluation of wave forces on seawalls
This thesis is divided into two parts, Part A deals with the measurement and analysis of wave pressures on real seawalls and Part B deals with the resulting structural response of these seawalls. There have been only thirteen previous investigations to measure full scale wave impact pressures on coastal structures, and of these only five were conducted with sensitive electronic measuring equipment. The infrequent occurrence of impact pressures in a real sea has meant very little impact pressure data has been collected by these previous investigations. This investigation is the first of its kind to be carried out in the U.K. losing modern measuring, and recording equipment, the volume of wave impact data obtained (over 150 impacts recorded) is significantly greater than the combined results of all previous full scale investigations. The magnitude of the wave impacts measured during this investigation were generally lower than those measured by other investigations, the-maximum impact pressure being of the order of seven times the hydrostatic pressure. The pressures measured were found not to fit any current equations. The data has also shown that impact pressures can occur simultaneously over large areas and are not just localised events as previously thought. The most important parameter in the generation of wave impact pressures in a real sea was found to be the percentage of air entrained in the breaking wave. None of the equations currently in use for estimating wave impact pressures consider this parameter, which probably explains why these equations do not fit the measured data. An explicit equation for estimating the maximum impact pressure was not found but a method is given whereby -the impact pressure is related to local wave parameters including a coefficient based on the percentage air entrainment. Finite element modelling of the seawalls has shown that impact pressures can cause a significant dynamic response in the seawalls although short duration impacts (as measured in most model studies) have a negligible effect on response.