Modal Analysis of Linear Stochastic Structural System

摘要

In this thesis, the variable rules of modal parameters including modal frequency, mode and modal damping ratio are studied by means of Monte-Carlo stochastic finite element method. The concepts, relative mean value deviation factor and variation factor, are introduced. And, from different points of view, they are used for analyzing the modal parameters variability quantitatively in stochastic structure vibration system. The results of numerical experimentations show that, with the creasing of structural parameters variation, the modal parameters variation become large, the mean value of low-order modal frequency is monotonic decreasing, the mean value of high-order model frequency is monotonic increasing, and the mean value of modal damping ratio is monotonic increasing for the small damping scale-model. The variation of structure parameters has more effect on the mean value of mode than of modal frequency and modal damping ratio. Also, the correlation of modal frequencies and stochastic physical parameters are studied in random structural system. The results indicate that cross-correlation coefficients are changed with the increasing of variability of physical parameters. Nevertheless, it has no effect on the evaluation of correlativity between modal frequencies and stochastic physical parameters when the variation coefficients of physical parameters are 1% to 30%.