Impacts of Increase in Span Length on Flutter Analysis Method of Cable-Supported Bridges

With reference to the changes of flutter behavior of cable-supported bridges due to increase in span length of a cable-stayed bridge over 1 000 m, and a suspension bridge up to 2 000～3 000 m, this paper investigates the impacts of natural vibration of the stay cables or suspension cables on the flutter behavior and the inapplicability of existing analysis methods, and proposes modifications to the corresponding analysis methods. It is considered in the investigation that the natural vibration of both the cables should be taken into account, and moreover, when characteristic equations are solved, the full-mode method must be employed in order to include the impacts of the natural vibration of the cables; the models of multi-link elements or the generalized DOF element can reveal the natural vibration modes of the cables perfectly; and appropriate treatments must be introduced into the solving process of the characteristic equations used with full-mode method in order to make the obtained characteristic solution include the flutter modes.