Research On The Seismic Performance Of Rectangular Steel Tube Concrete Beam Wind Turbine Towers

The main trends in the development of the wind power industry are high power,long blades and high towers.Wind turbine towers have reached heights of 100 to 150 metres,with the aim of catering for wind power to access wind resources in low wind speed areas.Traditional steel towers have problems such as flexibility,low frequency and material fatigue as the height increases.Based on this,this paper proposes a rectangular steel tube concrete beam wind turbine tower,establishes a finite element model of the tower.Firstly,Static analysis of the tower barrel in compression bending was carried out.The relevant parameters affecting the structural performance of the tower were selected for variable parameter analysis.Then,Three different seismic waves are loaded on the tower.The dynamic response pattern of the tower under seismic action is analysed.Finally,the structural dynamic response of the tower is analysed under the effect of wind-vibration coupling.The effect of seismic wave input angle on the dynamic response and collapse characteristics of the tower structure is analysed.The main conclusions are as follows:(1)The typical compression-bending members of the tower barrel are analysed to obtain the force mechanism of the tower barrel and to identify the main factors affecting the force performance of the tower barrel.The analysis results show that the typical specimen under compression-bending load can be divided into elastic,elasto-plastic and plastic stages.During the loading process,the concrete neutral axis will not produce a large deflection,the tensile zone is larger than the compressive zone,and a certain stress concentration will be generated at the corners.(2)The effects of section steel content,material strength,load eccentricity and shear-to-span ratio on the force performance of the tower were investigated.The results show that the ultimate load capacity of the tower increased by 50.7% from 0.09 to 0.15 steel content in the section.The strength grade of the steel has been increased from Q355 to Q460 and the ultimate load capacity of the tower has been increased by 19.6%.Concrete strength grades greater than C50 are of little significance in increasing the load carrying capacity of the tower.The load eccentricity increases from 0 to 0.4 and the ultimate load capacity of the tower is reduced by 8.7%.The axial pressure ratio increases from 0.1 to 0.4 and the ultimate load capacity of the tower is reduced by 14.7%.The shear-to-span ratio has a significant effect on the initial stiffness of the tower.When the shearto-span ratio is greater than 4.5,the tower is dominated by bending deformation.(3)The tower is excited with different seismic waves(near-field impulse seismic,far-field harmonic-like seismic,normal seismic).The results show that the dynamic response of rectangular steel tube concrete beam wind turbine towers is most pronounced under far-field harmonic-like earthquakes,followed by near-field impulsive earthquakes,and the weakest structural dynamic response of towers under normal earthquakes.The dynamic response of nearfield impulse earthquakes is mainly in the pre-earthquake phase,with the tower structure responding rapidly and strongly.The response to far-field class harmonics and earthquakes is mainly at a later stage and has a clear tendency to amplify.Ordinary earthquakes have no distinctive features.In terms of the displacement of the top of the tower,the maximum horizontal displacement angle limit of 1/100 is not exceeded when the tower is excited by the three seismic waves and the structure is safe.(4)The structural dynamic response of the tower was analysed under the coupling effect of wind and different types of earthquakes.The results show that the stresses and displacements of the tower under the coupled effect of wind and earthquake change significantly compared to those under the earthquake alone.By analyzing the coupling conditions of wind load and different ground motion,it is found that the maximum displacement of tower barrel is achieved under the coupling effect of wind load and far-field earthquake.The influence of ground motion input Angle on dynamic response of tower barrel structure is analyzed.The results show that the most unfavourable working condition from the displacement point of view is the input seismic wave in the 0° direction(i.e.the seismic input direction is the same as the wind load).The displacement of the tower barrel is minimum in the direction of 67.5°.The most unfavourable condition from a stress point of view is the input of seismic waves in the 90° direction(i.e.the direction of seismic input is perpendicular to the wind load).The stress in the tower barrel is minimal in the45° direction.(5)Seismic collapse characteristics of the tower were analysed by increasing the seismic wave PGA step by step.The damage modes of the tower under different seismic effects are compared.The results show that The tower structure is most sensitive to far-field harmonic-like and seismic waves,with damage occurring at the 80 m height position of the tower.The tower is sensitive to near-field pulsed earthquakes,with damage occurring at the 40 m height position of the tower.The tower is the least sensitive to normal earthquakes,with damage occurring at the80 m height position.