It is noted that the accuracy of the calculated wave pressure on the wall is very good with respect to the uncertainties introduced in the foundation forces and the determination of the design parameters. Evaluation of Goda's formula is therefore only valid when the whole design process is taken into account. Not only his design parameters but the formulae themselves include safety considerations. Goda's wave pressure formulae turned out to be in fact design formulae. An experiment about the failure mechanisms of the caisson confirms the introducing of uncertainties concerning the placing of the caisson on the rubble mound foundation. This is partly due to the close resemblance of the results of the linear wave theory and Goda's formula for the conditions at Europoort Rotterdam and partly caused by the scatter in the measurements. From the comparison of the measured wave forces of the hydraulic model study and the values calculated with the wave pressure formulae of Goda and of the linear wave theory no conclusions can be drawn. His design wave is the highest wave in the design sea state, which is based on the principle that a breakwater should be designed to be safe against the single wave with the largest pressure among storm waves. Goda sets the design parameters on definite values regardless the cost-benefit analysis of the harbour. Thirdly, the width of the structure sets the weight of the structure which defines the safety against failure. Subsequently the wave load follows from the wave pressure formulae. First the crest elevation of the caisson, the design wave and the design water depth, are determined with probabilistic considerations about the economy of the harbour. In order to be able to analyse Goda's method, the design of a caisson breakwater is roughly divided in three phases. His design method is very useful as a first indication for the dimensions of the caisson. The formula of Goda (1985) is a worldwide used design method for vertical breakwaters based on the quasi-static approach. By understanding the dynamic processes involved, the design of the structure can be soundly based. This causes an abrupt collapse of the structure. Unfortunately, damage at a caisson is often progressive. A caisson is built on shore and towed out to the actual offshore site. Especially in deep water lower construction and maintenance costs and considerable savings in construction time can be realised. Some efforts have focused on the empirical prediction of the volume of maximum overtopping events, Owen (1980) and Franco et al. (1994) and Franco and Franco (1999), Allsop et al. These monolithic structures are more economical compared to rubble mound breakwaters. Formulae for rubble mound structures are also available in literature, Franco et al. The growing need for breakwaters in deep water due to the increasing draught of large vessels draws the attention to caisson breakwaters. Design Caisson breakwater: An evaluation of the formula of Goda
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