Research On Seismic Vulnerability Of Railway Gravity Pier Bridge Based On Main Shock And Aftershock Sequence

Gravity pier bridges are a unique structure of high-speed railways in China,occupying a large proportion of railway bridges in our country,and most of them are located in frequent earthquake areas and high-intensity earthquake areas.Past seismic data indicates that an earthquake is likely to be accompanied by aftershocks in most cases.When the main shock causes irreversible damage or destruction to the structure,the secondary damage caused by the aftershock to the damaged structure cannot be ignored.At present,the research on this type of bridge in our country is limited to the analysis of internal force and displacement,and there is no systematic research from the perspective of failure probability.Therefore,the main research contents of this article are as follows based on an engineering example:(1)Extensive collection of domestic and foreign related data on bridge seismic damage under the main-aftershocks was made as the research background.The current research status of gravity bridge piers,main-aftershocks and seismic vulnerability at home and abroad were expounded.The research content,research significance and detailed technical route of this article were introduced.(2)The theory of bridge seismic vulnerability analysis was described;the commonly used main-aftershock sequences selection and construction methods were introduced according to the current research on main-aftershocks and 11 as-recorded main-aftershock sequences from the PEER website for input were selected;Through comparison,the strength index used in this paper and the damage index of the gravity piers were determined,and the calculation formulas of each damage limit value and important parameters inside were listed;The failure type of gravity pier and the corresponding judgment method were determined from the perspective of pier reinforcement ratio and shear span ratio.(3)Taking a four-span continuous beam bridge of a high-speed railway as the research object,a 3D model was established through CSI Bridge finite element software,and the simulation of different components and the constitutive model of material used were introduced,and the natural vibration characteristics were analyzed.(4)The structure of the friction pendulum bearing and the calculation of related parameters were introduced;based on the IDA method,the vulnerability curves of the bearings,gravity piers and piles under the main shocks and main-aftershocks were established respectively.Based on the first-order limit method,the vulnerability curves of the bridge system considering the main-aftershocks were established and the impact of the aftershocks on the vulnerability of the bridge system was analyzed.(5)In order to reduce the vulnerability of the bearings,the influence of the dampers on the seismic response of the bridge was further considered.The composition of the viscous damper and its simulation in the finite element software were introduced;the seismic response of the bearings and piers before and after the damper was analyzed,as well as the vulnerability curves of each component and the system.