Control On Seismic Response Mitigation For Longitudinal Freely Supported Bridge Based On TMD Damper

Abstract:Longitudinal freely supported bridge allow the oscillation of the girder in longitudinal direction, this oscillation can dissipate the vibration energy. Because of non-restraint in longitudinal direction, the excessive longitudinal displacement caused by external loads can affect normal use of this bridge. Therefore, appropriate control measures should be taken to reduce vibration response. Tuned mass damper(TMD),as a vibration control method of clear principle, simple form and convenient installment,has been largely applied in architectural structure and got a good effect of application.Yet the application of TMD to the earthquake mitigation control of self-anchored suspension bridge is a new attempt. Based on the engineering background of self-anchored suspension bridge named Foshan Pingsheng Bridge, the damping effect under seismic force is explored using TMD damper. The main work can be described as below:(1) Consult the major recent development of vibration control of bridges at home and abroad and the related results. On the basis of systematic summarizing the working principle of TMD and parameter optimization method,design method of TMD is proposed.(2)The finite element model of Pingsheng Bridge is established with the ANSYS software, the results of dynamic analysis show that participation rate of the first-order mode (longitudinal motion of the girder) as controlled mode is very large. Seismic response on the original floating structure of Pingsheng Bridge under the longitudinal seismic waves is analysed in this thesis, using time history analysis method, and the result make clear that the longitudinal displacements in girder are large. So the peak displacement should be controlled.(3)A contrast analysis of seismic response with and without TMD was made under different position of TMD and different vibration excitations (such as Pingsheng wave, Takochi-oki wave, E1-Centro wave, Wenchuan wave, Taft wave)and different mass ratio and different damping ratio. The damping effect related to seismic spectral characteristics generally increases with the increase in the mass ratio. When mass ratio is certain,a most superior damping ratio exsits, which can make sure the structure achieves the best damping effect.