Irregular wave loads on a gravity based foundation in shallow water

In order to achieve a safe but cost-effective foundation design of offshore structures, it is important to include effects of run-up and wave breaking in the estimation of wave loads on structures in relatively shallow water. This study presents results from a method applied to estimate wave loads on a gravity based foundation (GBF) coming from irregular waves which are potentially subjected to wave breaking. The objective of the study is to analyse the loads on gravity based foundations for wind turbines on the Thornton Bank, Belgium, due to irregular breaking waves. This study focuses on uncertainties in estimation of maximum loads based on the same wave condition, i.e. (Hs, Tp, Wave Spectrum). To this end three different synthetic irregular wave time series elaborated from the same wave condition are used to simulate the wave load on the GBF. The simulations result in time-series of wave loads and wave elevations on the GBF. The loads obtained from the model indicate a small difference (below 10% in peak values) between the wave-induced inline force for the three simulations, and differences up to 15–20% on the peak values of the obtained wave induced overturning moments. From the simulation results it is also possible to investigate flow patterns and run-up around the structure.