Supporting data for “<b>Dynamic soil-structure interaction analysis for offshore wind turbines</b>"

<p dir="ltr">Offshore wind energy is pivotal for the global renewable energy transition, driving the deployment of increasingly large offshore wind turbines (OWTs) in seismically active regions. This necessitates a robust understanding of their seismic performance, particularly the complex dynamic soil-structure interaction (DSSI) phenomena under realistic marine conditions. This doctoral research addresses the critical need for advanced modeling to capture the nonlinear, multi-physical interactions between OWT foundations and the seabed, essential for reliable design and safety in earthquake-prone offshore environments.</p><p dir="ltr">Traditional linear soil models and simplified damping assumptions often inadequately represent seabed soil behavior during strong seismic events. To overcome these limitations, this research implemented a sophisticated soil constitutive model explicitly accounting for nonlinearities including hysteresis, strain-dependent stiffness degradation, and pore pressure generation leading to liquefaction. Crucially, the model simulates both fully saturated and partially saturated seabed conditions, capturing the significant influence of variable saturation on soil stiffness, damping, and liquefaction susceptibility. A comprehensive finite element model (FEM) framework integrates this advanced soil model with detailed structural representations of the OWT and its monopile foundation. This integrated DSSI model underwent rigorous verification and validation against laboratory triaxial tests and centrifuge experiments simulating dynamic soil-structure loading. These validations confirmed the model’s capability to accurately reproduce soil nonlinearities, pore pressure evolution, and foundation seismic response.</p><p dir="ltr">Key findings demonstrate the critical importance of several factors often overlooked in conventional OWT seismic analysis. Neglecting higher vibration modes leads to significant underestimation of seismic demands and dynamic amplification effects in the structure. Furthermore, common damping assumptions introduce substantial uncertainty; this research proposes methodologies for better quantification and incorporation of this uncertainty to improve response prediction reliability. The study also reveals that vertical ground motions significantly alter the dynamic response of OWT foundations on fully saturated seabed, necessitating their explicit consideration. Additionally, variations in pore fluid distribution (partial saturation) profoundly influence seabed stiffness, seismic response, and liquefaction potential, highlighting the necessity of incorporating realistic saturation profiles in DSSI analyses.</p><p dir="ltr">This research provides fundamental insights into the complex interplay between nonlinear soil behavior, seismic loading characteristics, and OWT structural dynamics. The developed, validated FEM framework enables a more accurate assessment of seismic risks, foundation stability, and serviceability. It advances offshore geotechnical engineering by integrating state-of-the-art soil mechanics, structural dynamics, and numerical modeling within a unified seismic DSSI framework. The outcomes contribute directly to enhanced design guidelines and risk mitigation strategies for offshore wind farm development in seismically active areas. In conclusion, this thesis establishes that incorporating nonlinear soil behavior, realistic seabed saturation effects, vertical ground motions, higher structural modes, and quantified damping uncertainties is indispensable for the seismic design and safety evaluation of offshore wind turbines. The validated model serves as a robust tool for engineers and researchers to predict OWT performance under complex environmental and seismic loading, supporting the sustainable expansion of offshore wind energy infrastructure globally.</p>