超长斜拉索的参数振动

研究了斜拉桥中拉索的参数振动,利用三维有限元模型计算了苏通大桥的全桥动力特性和单根拉索的动力特性,得出了可能发生参数振动的拉索;分析参数振动时,取单根索模型(索端受随时间变化的位移激励);计算了在同一激励下不同拉索的响应;对与主梁成一定频率匹配关系的斜拉索进行分析;讨论了各种因素(阻尼、激励幅值、激励频率)对参数振动的影响;指出在一定条件下,拉索可能由于桥面振动的激发而发生参数振动,对桥梁的安全性带来不利影响.在大跨桥梁中,由于拉索和主梁的低频特性,非常有可能发生参数振动.这意味着在大跨斜拉桥设计中出现一个新的研究趋势.

Parametric Oscillation of Super Long Stay Cables

Parametric oscillation in the stay cables of a cable-stayed bridge is examined.The global modes and the modes of the cables are obtained by using a three-dimensional finite element model.Through calculation,the cables in which parametric oscillation may occur are found out.The paramet-ric oscillation of a single stay cable is calculated by using a model in which the cable is subjected to time-varying displacement at one support.The responses of different cables subjected to the same exci-tation are analyzed.For the cables,the frequencies of which are multiple of the frequency of the gird-er,the influences of various factors(damper,amplitude and frequency of the excitation) to the para-metric oscillation are discussed.It is pointed out that the cable possibly produces parametric oscillation owing to the vibration of the beam.It can do harm to the security and endurance of the bridge.In large span stayed bridges,parametric oscillation will be very probable due to the presence of many low frequencies in the girder and in the stay cables.This implies new trends in the design of very large stayed bridges.