Flutter Research & Analysis On Long-span Bridges

Flutter is a kind of self-excited vibration induced by wind act on structures. The main feature of flutter is that exists a critical status-critical wind velocity and critical frequency. When the wind velocity of coming flow is below the critical wind velocity, the vibration response of a structure will be decrease with the damping, to the opposite, the response would be amplified till the structure damaged. With the construction and planning of cross-sea traffics , the long -span bridges have a much luminous application foreground. Moreover, its spans will be longer gradually. With the increasing spans, modern long-span and super long-span bridge structures are lighter and more flexible. They have weaker stiffness and lower fundamental frequency, thus, they are prone to be damaged under the action of wind. So, wind resistant stability is the controlling factor that determining the safety of long-span bridge structures. Among the four primary wind-induced vibrations, Flutter takes more attentions of researchers for its catastrophic destroy effects in short time. Flutter would be the key problem in long-span bridges design process due to the flexibility itself.This paper mainly discusses and analyzes the two-dimension and three-dimension flutter theory for long-span bridges. To two- dimension flutter equation, a new method called Secant method is obtained, and give a program, from the comparative analysis of two cases ,we can conclude that it can get better results. To multi-mode flutter theory , with the parametric study of a suspension bridge whose span is 1138m,this paper get some valuable conclusion and regularities.