Runup is known to cause damage to deck plates in the vicinity of the columns of semi-submersibles. Previous studies have related the extent of the runup to the kinetic energy of the wave crest particle motion. However, these studies have been limited in the wave heights which were used. In this study, wave runup on vertical cylinders is investigated with the use of video cameras. The waves are generated in a narrow wave flume and are representative of storm waves in the North Sea. Wave period and wave height are used as the independent variables and the extent of the runup is compared to the kinetic energy calculated from high order wave theory. It is shown that even high order wave theory is insufficient to calculate the extent of the runup, and that the measured values exceed the calculated values by about one third over a wide range of conditions.
This paper describes an extension of the experiments reported by Bruce & Easson (1997), which dealt with the enhancement of waves due to structure blockage, such: as might occur on the large columns of a semi-submersible or tension-leg platform. In that paper, the authors observed significant runup on the columns of a test model in large waves. The purpose of this study was to investigate whether the extent of runup could be easily predicted from the wave parameters. The parameters for these experiments and those of Bruce & Easson were drawn from a particular range of short, steep waves which may have been responsible for deck damage on semi-submersibles. The spatial scale for these experiments is about 100:1. 2. Estimates of runup Runup height is a function of the scattering parameter ka where k is the wavenumber and a is the cylinder radius.
