During the design process of the new sea lock in IJmuiden the design wave conditions were described by a bimodal wave spectrum. With a spectral calculation method it was observed that a small low frequency component leaded to a large influence in the force spectrum. This observation served as the starting point for this thesis, where different design methods were validated for the non-breaking wave load of bimodal wave spectra on a vertical wall. The design methods under consideration were the formulae of Sainflou, Goda, the linear wave theory and the spectral calculation method. These methods were validated by the phase-resolved numerical model SWASH. First, the characteristic wave force for different shapes of spectra was addressed. In addition, the probability distribution of wave force was compared with the Rayleigh distribution. It turned out that the large influence of a low frequency component in a bimodal wave spectrum may cause underestimations of the traditional design formulae. The spectral calculation method performed accurate for all considered wave conditions.