IMPORTANCE OF CABLE VIBRATION IN DYNAMICS OF CABLE-STAYED BRIDGES

The present study deals with the dynamic behavior of cable-stayed bridges when the vibration characteristics of the stay cables are taken into consideration. Such complex vibrations are strongly coupled with the bridge deck and tower motions and were either overlooked or treated independently in previous dynamic analyses. By discretizing each stay cable into small elements, there results new and numerous very complex pure cable vibration modes, as well as new deck-tower bridge modes. It would be impossible to predict such motions by using, analytically, the linearized natural frequency expressions for the individual inclined cables. The multiple-element cable system also provides coupled deck-cable motions involving lateral bending and torsional motions of the deck as well as vertical and swinging cable motions; such motions cannot be predicted using a one-element cable discretization system. The effect of these modes on the participation factors of any earthquake-response calculation is significant.