Global slamming forces on jacket structures for offshore wind applications

Abstract

This study investigates the global slamming forces due to plunging breaking waves on a jacket structure, based on the statistical analysis of the experimental data from the WaveSlam project. Hammer tests and wave tests were conducted in the project, and the data are used to reconstruct the time series of the global slamming force by employing a method based on linear regression. The used wave test data were acquired under one wave condition. A total of 3910 force time series are reconstructed and analyzed statistically to reveal the characteristics of the slamming force. For each force time series, six parameters are introduced to describe it, including the peak force, duration, impulse and rising time, etc. The variability and correlation of these parameters are investigated. The distribution of these parameters is modeled with various probability distributions. The results show the high variability of the slamming force and the importance of statistical analyses. Based on these statistical analyses, the slamming coefficient is estimated from the peak force. For a curling factor of 0.4, the mean slamming coefficient is about 1.29. When considering one standard deviation around the mean, the slamming coefficient varies from 0.70 to 6.78 for a curling factor ranging from 0.1 to 0.5. A representative time series of wave slamming force is obtained by averaging the individual force time series. Accordingly, a 3-parameter triangular force model and a 5-parameter exponential force model are proposed to describe the development of the slamming force in time.