A Simplified Method for Estimating the Initial Stiffness of Monopile-Soil Interaction Under Lateral Loads in Offshore Wind Turbine Systems

The interface mechanical behavior of a monopile is an important component of the overall offshore wind turbine structure design.Understanding the soil-structure interaction,particularly the initial soil-structure stiffness,has a significant impact on the study of natural frequency and dynamic response of the monopile.In this paper,a simplified method for estimating the interface mechanical behavior of monopiles under initial lateral loads is proposed.Depending on the principle of minimum potential energy and virtual work theory,the functions of soil reaction components at the interface of monopiles are derived;MATLAB programming has been used to simplify the functions of the initial stiffness by fitting a large number of examples;then the functions are validated against the field test data and FDM results.This method can modify the modulus of the subgrade reaction in the p-y curve method for the monopile-supported offshore wind turbine system.

Interface Mechanical Behavior of Flexible Piles Under Lateral Loads in OWT Systems

This paper investigates the interface mechanical behavior of flexible piles with L_p/D>10 under lateral load and an overturning moment in monotonic loading conditions.To modify the beam-on-Winkler-foundation model of piles in offshore wind farms,the energy-based variational method is used.The soil is treated as a multi-layered elastic continuum with the assumption of three-dimensional displacements,the pile modeled as an Euler-Bernoulli beam.A series of cases using MATLAB programming was conducted to investigate the simplified equations of initial stiffness.The results indicated that the interaction between soil layers and the applied force position should be taken into account in calculating the horizontal soil resistance.Additionally,the distributed moment had a limiting effect on the lateral capacity of a flexible pile.Moreover,to account for the more realistic conditions of OWT systems,field data from the Donghai Bridge offshore wind farm were used.

基于CRITIC-EDAS的方法在离岸风机系统结构健康监测和维护中的应用

Performing structural health monitoring(SHM)and maintaining an offshore wind turbine system(OWTS)involve periodic observations,analysis,and repairs of the malfunctioning part(s)of the system.In this study,criteria importance through inter criteria correlation-evaluation based on distance from average solution methodology is employed to analyze SHM and maintenance technologies for OWTS.Their various applications are highlighted,and the technologies are prioritized using six indicators,namely,compatibility,potential cost reduction,needed investment,technology maturity,ease of application and potential reliability,and availability and maintainability of the considered technology.The study also aimed to improve the reliability of OWTS and minimize its maintenance cost.The results indicate that the technology’s ease of application,with a weight of 0.2018,is the most important criterion.Furthermore,mathematical models as an SHM,along with maintenance technology,is ranked as the best alternative with an appraisal score of 0.7706 and is considered more advantageous than other alternatives.This study provides a new research direction toward improving OWTS reliability.The findings will also aid the decision making of practitioners and researchers in the field of marine and offshore industry in relation to the optimal operations of OWTS.