Seismic performance of a 10 MW OWT on different foundation systems from dynamic centrifuge testing

As the offshore wind industry expands into the Asia-Pacific (APAC) countries, seismic considerations become important in the design of the foundations, especially when earthquake-induced liquefaction may occur. This paper presents centrifuge modelling of two foundations for offshore wind turbines (OWTs) installed in liquefiable soil, specifically a monopile, and an outrigger system, which aims to represent the behaviour of a jacket foundation. The performance of the two foundations in supporting identical OWTs subjected to a combination of operational and earthquake loading is discussed. The key findings suggest that the monopile experiences earthquake-induced rotation exceeding the allowable threshold recommended by DNV-ST-0126 and DNV-RP-0585. Although the outrigger exhibits less earthquake-induced rotation than the monopile, this advantage comes at the cost of larger settlements. Overall, the outrigger foundation provided a reasonably consistent solution for supporting OWTs in areas prone to liquefaction induced by earthquakes.