Dynamic responses of monopile offshore wind turbines in cold sea regions: Ice and aerodynamic loads with soil-structure interaction

Abstract

Offshore wind turbines (OWTs) constructed in ice-covered sea areas are subjected to a multitude of challenges in complex marine environments. These challenges encompass not only strong winds and weak foundations but also the formidable task of withstanding the impact of floating ice. To address these issues comprehensively, this study introduces a dynamic analysis framework for OWTs that incorporates soil-structure interaction (SSI), stochastic ice loads, and aerodynamic loads. This framework takes into account the intricate interplay between these factors, providing a holistic approach to the analysis of OWTs in icy marine environments. The research holds significance in elucidating the dynamic response laws of OWTs situated in icy waters under diverse factors. This understanding is vital for ensuring the structural safety and reliability of OWTs and fostering sustainable development in this field. In the present study, stochastic ice loads are generated using a real ice load spectrum model, while the aerodynamic loads are determined through the Blade Element Momentum (BEM) methodology. A comprehensive numerical model of the NREL 5-MW OWT, which includes the blades, tower, monopile, and soil system, is constructed based on the ABAQUS platform. The dynamic responses of the 5-MW OWT are systematically investigated under ice loads alone, as well as under combinations of ice and aerodynamic loads. The results of the study demonstrate that considering SSI and greater water depth amplifies the dynamic responses of OWTs subjected to stochastic ice loads. Specifically, significant acceleration is observed at the tower-base, posing potential safety risks to operators on the OWT operating platform. Moreover, when ice and aerodynamic loads act in conjunction, the bending moment experienced by OWTs is lower compared to the cumulative effect of individual ice and aerodynamic load contributions. This finding highlights the possibility of overestimating structural responses when employing a summation analysis approach. Additionally, this study advances the comprehension of ice-induced vibration phenomena and establishes a theoretical foundation for the anti-ice design of OWTs in cold marine environments.