超长斜拉索张力振动法测量研究

STUDY ON MEASUREMENT OF SUPER LONG STAYED CABLE TENSION USING VIBRATION METHOD

研究超长斜拉索张力的振动测试方法。索力振动测试过程中用人工激励也很难获得超长斜拉索的低阶振型,此时采用高阶频率多阶差平均的办法求取基频往往误差较大;从考虑了抗弯刚度和垂度影响的斜拉索横向自由振动方程出发,通过对拉索进行单模态振动分析得到其自由振动频率变化规律,将计算结果与实测数据比较,进而确定频谱分析得到的拉索高阶振动频率对应的模态阶数,由此对索力计算公式进行了修正,从而拓展了振动法测量斜拉索张力的适用范围;最后结合具体工程实例进行了讨论分析。

Measurement of super long stayed cable tension using vibration method is investigated.It is not easy to excite a super long stayed cable artificially in to lower order mode vibrations during measurement of cable tension with vibration method.In such a case,the error for the fundamental frequency estimated with average of frequency difference between higher order mode vibrations is generally large.The governing equations for planar non-linear free transverse vibration of an inclined cable are established taking the effects of flexural rigidity and sag of a cable into account.Natural frequencies and their characteristics are obtained by means of single mode vibration analysis of the stayed cable.Compared with the theoretical calculation results,the mode order number of the corresponding natural frequencies obtained by spectral analysis can be determined.Then,the formula to estimate the cable tension forces is amended.Finally,as an example,the tension measurement process of a typical super long stayed cable with the above method and some problems that should be paid attention to are also illustrated.