无源环境振动的有限元分析方法及在北京光源工程应用

Finite element method for analyzing environmental vibration without apparent sources and its application in Beijing High-Energy Photon Source

无源环境微振动是指工程场地中没有明显振源时存在的微小振动,其可能导致高精密科学装置无法正常工作,如何准确分析无源条件下结构的环境微振动是此类工程亟需攻克的难题。系统介绍了一种无源环境条件下微振动的有限元分析方法。首先采用实测与理论方法得到地表任意点的振动时程,再利用传递矩阵法计算土层瑞利波弥散曲线及各频率振动沿深度衰减因子,再结合地表振动时程可计算出任意深度处的振动时程。将上述方法计算得到的每个节点的振动时程施加到有限元模型边界的相应节点上,使有限元模型的边界振动场与实际环境微振动场趋于一致。最终将该方法应用于国家“十三五”重大科技基础设施北京高能同步辐射光源工程(HEPS)地基基础的环境微振动分析,结果表明该方法能很好地反映无源振动的特性,为类似高精密科学装置的无源环境微振动分析提供了重要参考。

The environmental vibration without apparent sources refers to the vibration with very small amplitude in the field where there are no apparent excitation sources.It may significantly affect the normal operation of high-precision scientific apparatuses,and therefore appropriate methods are needed to analyze such environmental vibration precisely.A dynamic finite element method is introduced to analyze the environmental vibration without apparent sources in this study.Firstly,the time histories of vibration at the soil surface are obtained through the field measurements.Then,the transfer-matrix method is utilized to calculate the dispersion curve of the Rayleigh waves and the vibration attenuation factors with depth for each frequency.With the measured time histories on the ground and the attenuation factors,the time histories at different depths can be calculated.The calculated time history at each node is applied to the corresponding node on the finite element model boundary,which ensures the similarity of vibration conditions in the model and the reality.Finally,the proposed method is adopted to analyze the environmental vibration of the raft foundation of High-Energy Photon Source(HEPS).The results indicate that the proposed method can successfully capture the characteristics of vibration without apparent sources and provide useful reference for similar projects.