A Relationship Between Breaking Wave Characteristics and Slamming Forces Acting on Jacket Structures

The goal of this study was to investigate and describe the relationship between breaking wave characteristics and total slamming forces acting on a jacket structure in shallow water, based on the experimental data collected during the WaveSlam experiment. Total slamming forces were filtered from the measurement, using Empirical Mode Decomposition (EMD). From these results impulse slamming forces, peak slamming forces, slamming coefficients, rising time and duration time were calculated. The transformation of the breaking wave parameters along the flume was analysed. Then, breaking points for each wave were identified, based on parameter changes along the flume, combined with visual analysis of video recordings of slamming events. The relationship between slamming forces and geometrical parameters at breaking was investigated. It was found that the breaking wave forces and breaking wave forces' parameters depend most strongly on breaking point location, breaking wave height, wave front steepness and horizontal wave asymmetry.acceptedVersio

Methods for analysing wave slamming loads on truss structures used in offshore wind applications based on experimental data

Offshore wind turbines installed in shallow water regions are subjected to highly varying hydrodynamic loads, also from plunging breaking waves. Many investigations have been made regarding the wave slamming forces acting on both vertical and inclined piles, on flat and sloping bottoms. However, very few studies have been carried out to study the slamming forces on truss structures. In this paper, the wave slamming loads on the truss structure are analysed based on the experimental studies carried out on a 1:8 truss model. The total force and the forces on local members were registered during the experiment. The total and local forces on the structure have been analysed using two different methods. The total slamming loads on the truss structure were analysed using the Empirical Mode Decomposition (EMD) method and for the local forces on the truss structure, the Frequency Response Function (FRF) method was used. The EMD method is based on time series decomposition of the measured force and the FRF method is on the hammer tests performed on the local force members during the experiments. The relative strengths and weaknesses of both the methods have been discussed and conclusions on optimum analysis method for those data set have been proposed. In addition, the slamming forces calculated from the measurements are compared with the values obtained using the existing force models.acceptedVersio