A Modified Numerical Substructure Method And Its Application In Seismic Analysis Of Offshore Wind Turbine System

When studying the nonlinear calculation problems of large complex structures based on the numerical substructure method,it is usually decomposed into the linear elastic analysis of the overall main structure with a moderate scale,and the nonlinear analysis of the local component isolation substructure with a small number and scale.The main sub-structure meets the boundary coordination conditions and is coupled by nonlinear correction forces.However,this method still has some shortcomings,which can not be applied accurately and efficiently in practical engineering problems.First of all,in the past research,the nonlinear correction force was obtained through the static analysis of the isolator structure model,that is,only the static correction was considered.In this paper,the static analysis problem of the substructure is extended to the dynamic analysis problem,the mass redistribution of the refined substructure is considered,and the inertial force correction term is added to the nonlinear correction force,so that the expanded numerical substructure method can be more accurate The dynamic response problem in the simulated substructure.Secondly,the use of non-iterative numerical substructure methods requires high convergence and very small calculation steps,resulting in time-consuming calculations and low calculation efficiency.This paper proposes a response prediction method for the boundary of the isolator structure.The predicted displacement,velocity,and acceleration are used to calculate the nonlinear correction force.This method can significantly increase the calculation step size of the non-iterative algorithm and improve the calculation efficiency while ensuring accuracy.Finally,when analyzing and simulating the situation where the local area of the structure is subjected to external forces and severely damaged,which ultimately leads to the failure of the overall structure,the distribution of external forces and the dynamic response of the local isolator substructure must be considered.This paper deduces the calculation formula of nonlinear correction force when there is external force distribution in the substructure.The numerical substructure method considering the distributed external force in the substructure can refine the failure mechanism of the local area that is severely damaged by external force.Based on the improved numerical substructure method of the above three points,this paper systematically verifies the calculation accuracy and efficiency of the method by performing dynamic analysis on beam-column and planar continuum components,and comparing it with an accurate solution model with different precision grids..As the verification and application of the expanded numerical substructure method,this paper uses this method to study the seismic dynamic response of offshore wind turbine systems.The fluid-solid coupling of the offshore wind turbine system's upper structure and wind,and the effect of nonlinear soil on the dynamic response of the lower support structure under seismic loads are considered.The calculation results show that applying the numerical substructure method to the dynamic response analysis of large offshore wind turbine systems under earthquake action can effectively improve the calculation efficiency.