| In recent years,breakthroughs have been made in the installed capacity of the wind turbine and the height of the tower.The load transferred from the superstructure to the foundation increases sharply,and the concrete near the lower flange of the foundation ring has been subjected to complex coupling effects of various loads such as tension and compression,bending and shear,and torsion,Stress concentration phenomenon appears here.For the above reasons,the concrete near the lower flange of the foundation ring of some wind turbines collapsed and formed cavities,and the wind turbine tower with a heavily damaged foundation has a serious accident such as swaying or even collapsing.Aiming at the wind turbine foundation with the foundation ring,this paper proposes a reinforcement method of arranging vertical anchor rods on the outside of the foundation ring,the tension and pressure of the vertical anchor rods is used to form a resisting bending moment,which can effectively reduce the stress concentration of the concrete near the lower flange of the foundation ring.At the same time,it has the advantages of low cost and convenient construction,and has high engineering application and promotion value in actual projects.This paper takes the 2MW wind turbine foundation of a wind farm in Hunan as the research object,establishes a three-dimensional reinforced finite element model,analyzes the force of each reinforced component under fatigue load conditions,normal operating conditions and ultimate load conditions,and study the contact state of the contact surface between components under various working conditions,select the appropriate bolt diameter and the diameter of the hole in the concrete to ensure that the reinforcement system does not cause material damage and contact damage under fatigue loads and normal operating conditions.According to the results of numerical simulations,the stress conditions of the concrete,foundation ring and steel cage before and after reinforcement are compared,and the maximum tensile and compressive stress of the concrete near the lower flange of the foundation ring,the vertical offset of the foundation ring,and the contact stress between the bottom of the foundation ring and the concrete under various working conditions are the indicators that reflect the reinforcement effect.The relationship between the number of anchor rods and the reinforcement effect is studied,and the bending moment resistance generated by different numbers of anchor rods is calculated.The vertical offset obtained from numerical simulation and experimental monitoring is compared to verify the correctness and rationality of the model of the wind turbine foundation.The results show that when the HRB600 vertical anchor rods with a diameter of 28mm and the diameter of the hole in the concrete is 300mm,the reinforcement system will not cause material damage and contact damage under fatigue loads and normal operating conditions,Vertical anchor reinforcement method has high feasibility.When 28-32 anchor rods are used,the resistive bending moment provided by the vertical anchors reaches about 25%of the overturning moment transmitted from the upper part to the foundation.The stress distribution of the concrete near the foundation ring is significantly improved,and the tension and compression stress is reduced by more than 30%.The vertical offset and the contact stress between the lower part of the foundation ring and the concrete are reduced by about 25%,and a good reinforcement effect has been achieved.Numerical simulation and experimental monitoring of the vertical offset are in good agreement,The vertical displacement deviation of the foundation ring calculated by the finite element method is 0.73mm,and the vertical displacement deviation obtained from the monitoring test is 0.77mm,the monitored value is 6%larger than the simulated value,it shows that the finite element model can simulate the actual operating state of a healthy wind turbine foundation accurately. |
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