Numerical Considerations in Assessing Earthquake Response of Offshore Monopiles

Liquefaction poses a significant challenge in designing structures on loose silt and sand, particularly in regions with moderate to high seismic risk. Effective designs on liquefiable soils necessitate the use of advanced numerical tools and clear performance standards. This paper explores solutions utilizing the SANISAND-MSu model within the open-source finite element platform OpenSEEs, specifically focusing on large-diameter monopiles used in offshore wind turbines. The study examines the impact of pore water pressure and liquefaction on monopile displacement behavior by analyzing various modeling scenarios, including cases with and without superstructure and static wind load. Additionally, the earthquake response of a pure soil domain is investigated to illustrate the influence of the embedded monopile on soil liquefaction and monopile performance. The findings underscore the benefits of using the SANISAND-MSu model to enhance 3D finite element simulations in dynamic analyses of offshore monopiles. To accurately assess monopile responses during seismic events, it is essential to account for both the monopile (including its embedded section and superstructure load) and wind load simultaneously, fostering a more conservative design strategy.