Dynamic Response And Vibration Control Of Offshore Towe Under Environmental Load

Wind energy,as clean and renewable energy,is drawing more and more attention.Compared with onshore wind power,offshore wind power has the characteristics of stable wind speed and direction,low turbulence intensity and small surface friction.Offshore wind turbine tower is the carrier of offshore wind energy development.To ensure the safety and stability of the structure under different load conditions is an important part of our research.Offshore wind turbine tower is a tall and flexible structure,and it is prone to vibrate and deform under the effect of wind,wave and earthquake,which can lead to fatigue,damage and even collapse.Studying the dynamic response and collapse rules under the environmental load and controlling the vibration response of the structure through dampers help reduce the fatigue damage and extend the service life of the structure.Depending on real projects,this paper studies the dynamic response and collapse mechanism of 3.6MW offshore wind turbine tower through finite element software and controls its vibration response through vibration dampers.The work of this thesis is divided into the following aspects:(1)According to the structural characteristics and environment of offshore wind power tower,the harmonic superposition method based on trigonometric series superposition is used to simulate the random wind speed schedule,and the Kaimal spectrum changing along the height is employed to simulate the fluctuating wind load.The wave load is generated by the spectral analysis method,and the wave load is generated by the Morrison equation based on the JONSWAP spectrum.The simulation accuracy is verified by comparing the simulated spectrum with the target spectrum.(2)The model of the wind power turbine is established first through ABAQUS,and wind-wave load is applied to the structure through the finite element software.The dynamic response of the tower tube and blade under different wind speed is analyzed,and the fragility analysis of offshore wind tower under wind-wave load is carried out.The collapse critical wind speed and the collapse probability of offshore wind power tower under different wind speed are obtained.(3)The seismic fragility analysis of 3.6MW offshore wind power tower is conducted.The 20 far-field seismic waves recommended by FEMA are selected.The collapse criteria of structures are determined by Pushover analysis,and the ISDR value of structures are obtained by dynamic increment analysis.Then,the collapse probability of 20 different PGA under seismic oscillation excitation is obtained,and the fragility curve of the structure under the effect of earthquake is matched.From the perspective of response spectrum of seismic oscillation acceleration velocity,index used for evaluating the intensity of seismic oscillation is put forward to judge whether the structure is damaged under a certain seismic oscillation.(4)According to the vibration damping principle of tuned mass damper(TMD)and multi tuned mass damper(MTMD),this paper simulates the device through ABAQUS and evaluates its vibration damping effect by tower tip displacement,acceleration velocity,displacement envelope diagram and the displacement value of the tip of blade and simulate the parameters such as mass ratio,frequency and collision gap.The optimal vibration damping effect of the structure is obtained,and the paper provides the basis for guiding practical engineering.