The objective of the ShortCresT JIP Joint Industry Project was to take into account short-crestedness in the design of offshore structures against extreme waves based on a good description of their spectral characteristics, statistics, kinematics, breaking and loading and to deliver a concrete (empirical) design methodology. The second order wave crest distribution showed to be a good basis for the estimation of a design wave crest. However, depending on sea state steepness and directional spreading, crests may exceed the second order distribution in some severe seas by around 10 %. On the other hand, the very highest crests may be limited by breaking and even fall below the second order model. This paper addresses experimental results from the MARIN where directional wave measurements were carried out in two dimensions. Conclusions with respect to evolution of wave spectra in the basin, directional analysis and calibration, sampling variability, local variability of measured crest heights and measured crest height distributions due to different types of spreading are evaluated. Furthermore, the influence of the type of instrumentation and the effect of the spectral high frequency tail on the crest distributions are assessed.

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