浮置板轨道的模态分析

Modal Analysis on the Floating Slab Track

为了研究低频振动对地铁线路附近精密仪器的影响，设计一种新型参数的浮置板轨道。应用MIDAS／GTS软件，对浮置板轨道进行三维的模态分析，得到6种不同分析工况下轨道的固有频率、振型和振型参与质量，并进一步研究浮置板轨道的传导比。结果表明：①设计的浮置板轨道基本频率为5．7～8．2Hz，弹簧刚度不变、支承间距增大，或者支承间距不变、减小弹簧刚度，均可以降低浮置板轨道的基本频率；②浮置板轨道的振型以道床板振动为主，同一支承间距下，弹簧刚度不同，浮置板轨道振型相似；同种弹簧刚度下，支承间距不同，振型在低阶部分差别较大，在高阶部分相似；③浮置板轨道的基本频率越低，浮置板轨道的传导比峰值就越小。

A kind of floating slab track is designed to study the impact of the low-frequency vibration from trains on precision instruments near the underground railway alignments. In this paper, three-dimensional modal analysis on the floating slab track is simulated by Software MIDAS/GTS. Vibration eigenfrequencies, mode shapes of vibration and modal participation masses are obtained in six cases. The transmission ratio of the floating slab track is further studied. The analysis results indicate as follows： ① The basic frequency of the floating slab track lies in the range of 5.7-8.2 Hz. When the stiffness of steel springs is invariable and the spacing of steel spring is lengthened, or when the spacing of steel springs is constant and the stiffness of steel spring is re- duced, the basic frequency of the floating slab track will fall down. ② Slab vibration takes the dominant position in all mode shapes of vibration. Mode shapes of vibration are similar under the condition of the same spacing of steel springs with varied stiffness. Mode shapes of vibration are found different in the low range of eigenfrequencies but similar in the high range of eigenfrequencies when the spacing of steel springs is variable and the stiffness of steel springs remains the same. ③ The smaller the basic frequency of the floating slab track, the smaller the peak value of the transmission ratio of the floating slab track.