Evaluation of the performance of the nonlinear hysteretic damping model REDWIN for offshore foundations

1. Home
2. Publications
3. Online Library
4. Evaluation of the performance of the nonlinear hysteretic damping model REDWIN for offshore foundations

The shift towards renewable energy, including offshore wind turbines (OWTs), is crucial for addressing climate change and fossil fuel limitations. Designing OWTs exposed to dynamic forces such as wind and waves requires structural integrated load analysis. This paper focuses on the REDWIN model, developed for integrated structural and geotechnical assessments of OWTs, offering an advanced approach to modeling foundation-soil interaction. This contribution evaluates REDWIN's performance in predicting monopile foundation behavior under various loading conditions. The predictions are compared with a 3D finite element model adopting the hardening soil small-strain constitutive law. Furthermore, the implementation in the commercial aero-elastic software Bladed is evaluated by comparing the natural frequency and damping ratios with those commonly adopted in industry practice. A damage equivalent load analysis for several operational load cases is conducted in Bladed using the REDWIN macro element. The obtained results are benchmarked to industry approaches using pile-springs-dashpot models with linearized and nonlinear springs. Findings indicate REDWIN accurately predicts monopile behavior during loading under combined horizontal and bending moment loads. However, discrepancies occur during unloading, particularly in estimating residual displacements, suggesting a potential need for improvement. The aero-elastic analyses indicate REDWIN out-performs the standard approaches. Recommendations are provided on selecting the load level for Fatigue Limit State to achieve comparable results between REDWIN and pile spring with modal damping.

5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)

9 - Monopile design to cyclic loads: quasi-static, dynamic and seismic loads