The Study On Seismic Response Of Cable Stayed Bridge And MTMD Wind Response Control Of The Bridge Tower

Large span cable-stayed bridge is one of the most competitive modern bridge types. With the increasing of bridge span, the height of the bridge tower and deck flexibility as well as structure complexity, anti-seismic research for cable-stayed bridge and wind resistance research for the bridge tower have become one of the most important subjects in the field of bridge engineering. The tower becomes more slender with the increasing of the bridge span. The conventional method of wind resistance which uses the tower's rigidity to reduce the deformation under wind load can't meet the requirement of wind resistance. So the structural control technique begins to be adopted for suppressing wind induced vibration responses of the bridge tower of large span cable-stayed bridge. Tuning vibration absorption technology , which is a passive control technology, has attract broad attention in the field of structural vibration control due to its many advantages, such as explicit mechanism, easy realization and good reliability, etc.In this paper, a new foreign cable-stayed bridge is taken for study and a 3-D finite element analysis model with ANSYS is established, the rule of the seismic response of the cable-stayed bridge is studied based on considering geometric nonlinearity. Then the time history of 15-dimensional wind load of the bridge tower is simulated via M.Shinozuka's method. The dynamic time history analysis of the transversal bridge responses of cable-stayed bridge excited by transversal wind is carried out. Furthermore, MTMD vibration absorption control is studied in terms of different MTMD parameters. Some available conclusions have been drawn from above study. The research results are shown as follows:When 1-D seismic input is implemented to the cable-stayed bridge, owing to the anti-symmetry of longitudinal or lateral earthquake motion, more anti-symmetric modes will participate in the seismic response, and the bridge towers always bend toward the same direction. Longitudinal seismic wave arouses most response in vertical plane, and lateral seismic wave arouses most response out vertical plane.The vibration-absorptive ability of MTMD depends on the MTMD parameters and primary structure dynamic parameters as well as wind load characteristics. When MTMD total mass is constant, the MTMD vibration-absorptive effect increases very limitedly as the numbers of TMD increase. However, when the number reaches to a certain value, the effect towards to stability. The effect doesn't increase to large amplitude, but it will increase the structural controlled stability. When the mass of the signal TMD is constant, the effect will increase with the increasing of the total mass ratio of the MTMD. The more mass ratio, the more vibration-absorptive effect. When the mass ratio reaches to a certain value, with the increasing of the mass ratio, the vibration-absorptive effect will increase slightly. The center frequency ratio plays an important role on the vibration-absorptive effect. When the center frequency ratio equals to one, there will be a best vibration-absorptive effect. When the number of TMD and the total mass ratio are invariant, the vibration-absorptive effect is nonlinear and it will increase with the frequency band width. After reaches to a peak value, the vibration-absorptive effect will decrease with the increasing of the frequency band width.