Study On In-out-plant Vibration Of Cable In Multi-tower Cable-stayed Bridge And Finite Element Analysis

Cable-stayed bridge, as one of the widely used bridges, has graceful design and big span capability. As the most important part of cable-stayed bridge, cable has characteristics of quality small, damping low and soft, it will generate a severe vibration under the circumstances of wind load、vehicle load and earthquake. Thus, this makes it to become the major factor of cable-stayed bridge security, and then, detailed analysis and precise research of cable vibration characteristics has became a crucial part of cable-stayed bridge design. For multi-tower cable-stayed bridge, a insufficient rigidity and multiple cables structure, the low rigidity make it easy to vibrate, thus it makes resonance of the cables possible. Therefore, how to improve the rigidity of multi-tower cable-stayed bridge has become one of the hot topics today.In order to study how the rigidity effect the vibration of cables in multi-tower cable-stayed bridge, at first, this article establish numerical models of different rigidities in primary beam、bridge tower and different number of bridge tower, and discuss the effects of rigidity in dynamic characteristics of bridge. Then based on the former experiences, we set up a cable-bridge coupling vibration model of in-out-plane and bridge deck, and obtain equations of cable-bridge coupling vibration model of in-out-plane and bridge deck, according to multiple-scale method, figure out the characteristics of it. Finally, by calculating the half-side tower cables natural frequencies of in plant and out plant, matching them with the different model frequencies that we build in the above chapter, we find out the cables which may occur resonance, as well as its vibration characteristics of in-out-plane. The result shows that, the rigidity of main girders in multi-tower cable-stayed bridge has a certain effect on in-out-plane resonance possibility and a great effect on amplitude of in-plane, the effect of rigidity of tower can be neglected, however, the rigidity of whole bridge may has a critical impact on resonance possibility.