Analysis On Seismic Performance Of High-pier Long-span Continuous Rigid Frame Bridge Under Long-period Ground Motion

Compared with general seismic waves, long-period seismic waves have greater impact on high-pier and long-span continuous rigid frame bridge and other long-period structure on dynamic responses. This kind of problem has been becoming more and more serious as there are many cases that long-span bridges, high-rise buildings and other flexible structures are damaged under the effect of long-period seismic waves.There are many factors that influence the response of this kind of bridge, such as soil-pile effect, height of pier and travelling wave effect. It is of importance to do research on the response of high-pier and long-span rigid bridge under long-period ground motion. Conclusions have obtained through completed research on effect of pile and soil, pier height and traveling wave effect influence on the responses of displacement and internal force of the bridge by the softwave ANSYS:(1) The differences of long-period ground motion and general seismic waves can be found by analysis of their acceleration history and acceleration response spectrum. It can be summarized from the study that long-period waves are characterized by long duration and low peak acceleration, which is rich in low frequency components according to Fourier spectrum. Besides, the spectrum value of long-period waves is bigger than that of general waves in the long-period component in acceleration response spectrum. Besides, the fitting formula of the selection of long period seismic waves with a certain range of application is obtained through statistical analysis of datas.(2) It has been found that the response of displacement of high pier and long-span rigid bridge increase sharply by four times in the top of pier and the response of force increase greatly with the vertical moment of the bridge increasing by four times under the long-period ground motion compared with general ground motion.(3) The displacement of bridge will increase under the excitation of long-period waves when considering the effect of pile-soil interaction, at the same time, the in-plane bending and transverse shear will decrease.(4) The response of displacement increases as the height of the pier become higher with the shearing decreasing at the same time.(5) The response of displacement of bridge decreases while the force is complex to analysis by applying excitation on different piles with different waves at the same time when considering travelling wave effect. Some responses of parts of the bridge increase while some decrease because of superposition or neutralization.(6) The effectiveness of the equipment of lock-up is analyzed to decrease the response in this paper. The results show that equipment lock-up is effective way to decrease the longitudinal displacement sharply as well as the in-plane bending and lateral shear, with the lateral displacement being decreased slightly.