Fatigue Analysis Of Prestressed Concrete Wind Turbine Tower Based On GH-Bladed Software

With the rapid development of wind power technology,the wind turbine’s power capacity and blade size are increasing,the height of tower is also increasing.The shipping height of steel tower is limited,which leads to the limitation of the tower’s bottom diameter.There is no limit on concrete tower for its use of local materials and it is widely used in highrise structures.The load case of tower has the characteristics of both highrise structure and power equipment,which puts forward high requirement to fatigue life design.(in-line with the objective of growing energy production from renewable sources,wind turbine dimensions increace inorder to take better advantage of the available wind potential.Taller towers introduce higher wind velocities,while longer blades provide larger incident area.As a result,the wind load acting on wind turbine towers increases significantly)The assessment of fatigue load and the method of fatigue design are two important aspects of wind turbine tower’s fatigue analysis.Generally,the fatigue case is determined by the current specification GL2010 and IEC61400.Fatigue load is calculated according to the load case and wind simulation.The assessment of wind turbine’s fatigue life is mostly based on Miner rule and S-N curves of different materials.In order to obtain the fatigue response accurately,GH-Bladed software is utilized to conduct fatigue analysis based on fatigue response simulation.The method avoids the simulation difficulty of wind field and the coupling effects among wind,blades and tower,thus simplifies the calculation process and provides credible results.Modal analysis is carried out on the whole tower and discussions are made on how the prestressing cable force influences the structural inner force when horizontal load at the top tower,prestressing and sectional area of the steel varies respectively.Stress analysis is proceeded on the refined tower model under dead and limited conditions respectively.In order to conduct fatigue analysis,the GH-Bladed software is utilized to get the time-history internal force in tower’s cross section at different heights in different fatigue load cases.Then the internal force is transformed into external force.Subsequently,series of stress analysis are performed on a refined finite element model under unit external load at each height.Finally,the time-history stress response of the fine finite element model is obtained by linear superposition method,which combines the transformed external force obtained from the GH-Bladed analysis with the stress response from the unit load analysis.On this basis,the fatigue life analysis of wind tower is completed by simplified rainflow counting method and Miner rule,which declares the feasibility of the proposed method.