Research On Seismic Response And Reduction-Isolation Control Of Continuous Girder Viaduct Under Near-fault Ground Motion

In recent years near-fault ground motion has begun to attract the attention of bridge engineering because it has its own features comparing to far-field earthquake such as large pulse and long period component. Previous experience and seismic codes did not consider much enough about near-fault earthquake. Along with much severe damage of bridges of in the near fault zone during earthquakes, it has become very essential to pay special attention to near-fault groud motion.The piers of viaduct are very high thus the flexibility is large. It is easy to inspire large displacement and long period vibration modes under the excitation of near-fault ground motion so the damage is worse. On the basis of the predecessors, this paper made a summary of the existing literature study and description of near-fault ground motion and do the ground motion analysis using a four-span continuous girder bridge as the research object. The main contents are as follows:It was summarized that the research achievements of the near-fault ground motion literatures and the characteristics of the near-fault ground motion acceleration timehistory was concluded and several typical ground motion records of acceleration timehistory of the Chi-Chi earthquake and the commonly used El-Centro record and one synthetic seismic wave were chosen as ground motion input distinguishing the difference of near-fault earthquake and others. And a finite element model was built using the mdias/civil program to compare the difference of the dynamic responses of viaduct structure under the excitation of near-fault ground motion and others.Pounding elements were applied in the expansion joints of the model. The influence for viaduct dynamic response considering collision under near-fault excitation. Through comparing the dynamic responses under different pier heights, some special dynamic response features were found about some high pier bridge of continuous beam which was different from short pier one.Lastly, several commonly used effective ways of seismic isolation were selected. By simulation of the finite element calculation, the different effects of seismic isolation mode were studied and suggestions were provided for the seismic design of viaduct.