On Cable Force Identification Of Cable Structure With Multiple Intermediate Supports

Vibration-based cable force estimation has been widely used in engineering dueto its convenience, rapidity and repeatablity. In the practical engineering, cable willbe divided into several segments by the shock absorber, damping frame, supportingframe installed on it and then forms cable-multiple supports system which makes thecorresponding relationship between the cable force and frequency more complex, andthe traditional single spa n cable force and frequency relations are no longer applicable.In this article, according to the different forms of supports, this kind of cable will bedivided into cable-double damper system and cable-intermediate elastic supportssystem, and then their cable force identification will be studied respectively.(1) Cable force Identification of Cable-double damper system: Based onengineering practice, Cable-double damper system composed of Kelvin model andstandard linearity solid model is constructed, and it’s dimensionless complexfrequency equation and complex frequency asymptotic expression are deduced. Basedon the accurate and approximate solution of complex frequency, parameter analysisabout modal damping and frequency ratio of cable system is perf ormed. Meanwhile,iteration relation of cable force and frequency is attained according to frequency ratio,which can be used in frequency method.(2) Dynamic stiffness matrix method based cable force estimation ofCable-intermediate elastic supports system: The relationship between frequency andcable force is established on the basis of dynamic stiffness matrix method. Byintroducing the dimensionless parameter, the influence of intermediate elasticsupports to cable force estimation is analyzed. And a te nsion solving method withobtained frequency is presented according to the essence of frequency algorithm ofdynamic stiffness matrix method.(3) Mode shape based cable force estimation of cables under complex boundarycondition: Find out two zero-amplitude points of mode shape between adjacentsupports by modal test, and regard the cable between the two zero-amplitude points asequivalent model under pinned-pinned end condition. Then see the equivalent cableforce calculated based on the relationship between cable force and frequency ofequivalent model as of the original cable. The error analysis shows that as long asestablishing the equivalent model reasonably, the influence of the end condition of the original can be neglected.