Research On Elastic-plastic Seismic Response Of Large-span High-speed Railway Bridge-Soil-Pile System Subjected To The Near-fault Ground Motions

According to the current code for high speed railway bridge seismic design,the pile foundation usually has been designed as a capability protection component,which in general mean that the damage occur at the the bridge pier subjected to the earthquake anction.However,seismic damage data show that the failure of the pile foundation of the structure result in the damage of the bridge.In this study,taking a large span continuous girder bridge,which is three span bridge,the span length is 72m,120m and 72m,respectively,named Dongchagou bridge in Baolan passenger dedicated line for a case study.The dynamic response analysis of the high-speed train bridge-soil-pile foundation system is conducted subjected to the near fault earthquake and train loading.The article main research contents is are as follows:(1)Based on the improved Penzien model to simulate the pile-soil interaction(PSI).The XTRACT software is used to calculate the bending moment and curvature of the pier and pile foundation.The two nonlinear global bridge model are established using the ANSYS software,one model consider the piles and soil interaction,another model is a fixed-base bridge.(2)Based the above model,the time history analysis of the bridge are conducted subjected to the pulse typed near fault,non-pulse typed near fault and far fault ground motion.Moreover,the dynamic response of the two nonlinear models under earthquake action is compared.It is concluded that the vibration frequency of the bridge structure is decrease and the period is prolonged when considering the PSI,which avoid the predominant period of the earthquake for this case study.As a result,the internal force of the bridge decreases,and the structural displacement increase.(3)According to the high-speed train bridge-soil-pile foundation system model subject three type of earthquakes,the nonlinear time history analysis method is used to study the influence of the peak ground acceleration and the peak ground velocity ratio(Ap/Vp)and damping ratio.The results show that the dynamic response of the bridge is dependent on the ApAVp ratio,and the dynamic response of the bridge is decrease with the increase of the damping ratio.(4)Considering the effect of vertical ground motion,the effect of the ratio of peak acceleration to peak velocity of vertical ground motion(Av/Vv)and the ratio of vertical and horizontal ground acceleration(V/H)on the seismic response of bridges is analyzed.