Seismic Pounding Response Of Elevated Bridges Considering Traveling Wave Effect

Caused by an earthquake at home and abroad in recent years in the form of bridge destruction is the displacement by the earthquake, which is caused the unseating of bridge girder, the bridge structure clash, bridge abutment subside and rotate, the combination of piers and columns pull off, or damage by shear, the failure of bent cap, the destruction of pile foundation and so on. But the unseating of bridge girder was the most severe damage of the bridge during the major earthquakes, which is a direct result of the traffic gridlock. Bridges as an important part of the transportation line, it was expected to be able to play a huge role in the earthquake relief and post-disaster reconstruction, bridge seismic analysis has been paid more and more attention now. Based on the characteristics of multi-segment and multi-span continuous highway bridges, the characteristics of seismic response considering pounding effects was studied. The main contents of this dissertation are described as follows:(1) Based on the comprehensive reviewing of related literatures, the state of the theory and the analytical method on seismic response for continuous bridges under non-uniform excitation, the theoretical studies on pounding effects between adjacent bridge decks were summarized. The simulation method of traveling waves effects were briefly introduced, the analysis method of pounding effects between adjacent bridge decks was introduced and evaluated.(2) An analytical model of pounding has been employed based on the characteristics of Chinese highway bridges. The impact element based on the Kelvin model was selected in this paper. The ranges of impact element’s parameters were discussed, and a suggestion value of impact spring stiffness was given. Then how to achieve traveling wave effect in ANSYS was described.(3) Using the analytical model of two span continuous girder elevated bridges, the affect of pounding under uniform earthquake excitation was studied. The effects of pounding when earthquake occurred cannot be ignored The effects of three parameters such as different waves, initial gap at expansion joints and natural periods were investigated.(4) Some parameters considering traveling wave input caused seismic pounding response were studied. Different apparent velocity comparing uniform excitation and traveling wave input was using. Then the effects of the parameters such as the period ratio of adjacent bridge decks, initial gap at expansion joints were discussed by the time-history analysis method under traveling wave input. The effect of uniform excitation and traveling wave input considering pounding or not were discussed, either.(5) The provision of other countries’specification was introduced. For example, adding a simple limit device through in the bridge, the effect of falling-off prevention was analysis. The existing bridge by adding a limit device could reduce the unseating of bridge girder caused by pounding was point out.(6) This thesis provides some reference for the future study of reducing or avoiding pounding and how to reduce the unseating of bridge girder when uniform excitation and traveling wave input for elevated bridges.