长周期地面运动和SSI效应对风机动力响应的影响

针对建设在软土地基上的大功率风机结构,需要同时考虑长周期地面运动和土-结构相互作用(SSI)的影响。为了全面研究长周期地面运动和SSI效应对风机塔筒结构动力响应的影响,首先基于某1.25 MW变桨距风机结构建立了包含叶片、机舱、塔筒和基础的结构整体有限元模型,并进行了模态分析。其次在世界地震记录数据库中选择了1条普通波(EI-Cento波)和2条长周期波(HKD054波和CDAO波),并对两种波的时频特性进行对比分析,同时建立了考虑与不考虑SSI效应的对比模型。最后利用ANSYS软件并采用时程分析法对考虑与不考虑SSI效应的风机结构在两类地震波作用下的地震响应进行对比分析,并对叶片与塔筒的碰撞问题、门洞区域的应力集中、机舱内主轴在剪力作用下的破坏以及基础的失效问题进行了进一步的研究。结果表明:长周期地震作用下的风机结构位移、加速度、应力和内力响应值均大于普通波作用下的结果,在此基础上某些响应甚至会被SSI效应进一步放大。因此在风机结构的抗震设计中需要考虑长周期地震作用和SSI响应的影响,特别是在软土地基区域。另外,塔筒与门框连接区域、机舱内主轴和基础等薄弱区域需要适当加强。

Effects of long-period ground motion and SSI effect on dynamic response of wind turbine

For large-scale wind turbine structures built on soft soil foundation,effects of both long period ground motion and soil-structure interaction(SSI)should be considered.Here,in order to fully study effects of long period ground motion and SSI on dynamic response of wind turbine tower structures,firstly,based on a certain 1.25 MW variable pitch wind turbine structure,an integral finite element(FE)model for the wind turbine structure consisting of blades,nacelle,tower and foundation was established to conduct modal analysis.Secondly,two long-period waves(HKD054 wave and CDAO wave)and an ordinary wave(EI-Cento wave)were selected in the worldwide earthquake record database,and time-frequency characteristics of the two kinds of seismic waves were analyzed contrastively.Moreover,two FE dynamic models for the wind turbine structure considering SSI effect and not considering SSI effect were established,respectively.Finally,the software ANSYS and the time history analysis method were used to analyze seismic responses of the wind turbine structure considering SSI effect and not considering SSI under action of the two kinds of seismic waves.In addition,collision between blade and tower,stress concentration in door hole area,failure of main shaft in nacelle under action of shear force and failure of foundation were further studied.Results showed that under action of long-period seismic waves,the wind turbine structure responses of displacement,acceleration,stress and internal force are larger than those under action of ordinary seismic wave,some responses even are amplified by SSI effect,so long-period ground motion and SSI effect should be considered in the seismic design of wind turbine structures,especially,in soft soil foundation regions;the connecting area between tower and door frame,and the weak areas of main shaft in nacelle and foundation need to be appropriately enhanced.