Finite Element Model Updating And Safety Assessment Of Jacket-Type Offshore Wind Turbine Support Structures

Offshore wind power is an important development direction in the field of clean energy.The harsh marine environments degenerate seriously the performance of offshore wind turbine support structure,which leads to frequent accidents.Structural health monitoring and condition assessment of offshore wind turbine is of great significance to ensure the safe operation of wind turbine,and has become the research focus and hot spot in this engineering field.The establishment of a finite element analysis model reflecting the real state of the structure is the basis for evaluating the performance and state of the structure,and provides an important theoretical analysis support for structural damage identification,safety assessment and operation management.In order to improve the utilization rate of offshore wind turbine,ensure the structural safety and reduce the maintenance cost,this paper takes the jacket-type wind turbine support structure as the object to carry out the research on the model updating of offshore wind turbine support structure and the safety assessment method based on the structural reanalysis of the finite element model.The main contents and conclusions of this paper are as follows:(1)Based on the current design method of offshore wind turbine support structure,the boundary conditions of the calculation model and the calculation method of the main environmental loads are analyzed.Firstly,based on the actual engineering geological data,the elastic-plastic analysis of P-Y curve method is used to determine the foundation reaction of soil at different depths.The mutual restraint between pile foundation and soil is established,and the restraint behavior characteristics of soil to pile foundation are analyzed.Secondly,the calculation methods of the main design loads: wind,wave and seismic loads are analyzed.Finally,for the temperature load ignored in the current design of the structure,the refined finite element calculation is carried out.The temperature load of offshore wind turbine support structure has strong time-varying,and the overall temperature and local temperature difference change significantly.The reasonable determination of boundary conditions and calculation of various loads lay a foundation for the finite element modeling and load effect calculation of the structure.(2)The refined finite element analysis model of the jacket offshore wind turbine support structure offshore under construction is established.Combined with the damage deterioration characteristics of the structure,reasonable and different degrees of damage(parameters to be updated)are constructed to simulate the performance degradation of the structure.Based on the static displacement and natural frequency of the structure,the radial basis function response surface method is used to update the damage parameters.The corrected value is in good agreement with the target value,and the maximum error is less than 5%.The correction error of each parameter is related to its sensitivity to feature information.Based on the response surface method,the finite element calculation model reflecting the current behavior of the structure can be obtained,which provides an accurate structural analysis model for the safety assessment of the structure.(3)Based on combined load effect and fuzzy analytic hierarchy process,a safety assessment method for offshore wind turbine support structure is proposed.Firstly,the basic idea and calculation process of the method are described,and five load cases and five safety evaluation indexes of the jacket support structure are determined.Then,the structural response under single load and combined load is calculated.The wind load is the main control load,and the bending of duct members into the plastic limit is the primary cause of structural failure.Finally,the corrosion damage degree of offshore wind turbine support structure under different service periods is simulated.Based on the structural load response analysis of finite element model,the fuzzy analytic hierarchy process is used to evaluate the safety of the support structure,which can well reflect the impact of damage deterioration on the structural safety.This method can effectively evaluate the safety status of structures in complex marine environment,and provide important information support for operation and maintenance management and ensuring the safe operation of structures.