Seismic Performance And Seismic Vulnerability Analysis Of Elliptic Concrete-filled Steel Tubular Bridge Piers

Concrete filled steel tube structure has the advantadges of large stiffness,high bearing capacity,good seismic performance,among which has a sleek elliptical concrete filled steel tube(ECFST)caused the attention of experts and scholars,ECFST can be divided into standard elliptical concrete filled steel tube(SECFST)and round-ended elliptical concrete-filled steel tube(RECFST)according to the cross section form,ECFST not only has good circumferential collar restraint of circular concrete filled steel tube(CCFST),but also has the advantage of flexible arrangement of long and short axis stiffness of rectangular concrete filled steel tube(RCFST),and its arc section can avoid stress concentration at the sharp corner and reduce its flow resistance coefficient in the flow,so ECFST is especially suitable for bridge pier column.However,the research on concrete filled steel tube(CFST)bridge members at home and abroad mainly focuses on the circular and rectangular(square)CFST,and the research on ECFST mainly focuses on the static properties,but there is still a lack of research on its mechanical properties under the action of ground motion.In view of the good application prospect of ECFST pier,it is necessary to study the seismic performance of ECFST bridge pier.The main work of this paper is as follows:(1)The elliptic section segmentation method was proposed and realized by Matlab programming,the elliptic section definition of Open Sees was completed and the ECFST fiber model was established,based on the ECFST fiber model,the statics test verification of ECFST under axial compression and pure bending conditions was carried out respectively,the correctness and reliability of ECFST fiber model are proved by dynamic test of ECFST pseudo-static test.(2)Carried out ECFST tubular pier seismic performance parameter analysis based on the elliptic section segmentation method,the effects of different parameters on the seismic performance of ECFST piers were combed,including steel strength,concrete strength,axial compression ratio,diameter to thickness ratio,axial ratio and loading direction,considering difference of seismic performance of ECFST,CCFST and square concrete-filled steel tube(SCFST)piers under the condition of the same sectional area and steel quantity.The formula of ultimate bearing capacity of ECFST in long and short axes is fitted,and the correctness and reliability of the formula are verified by pseudostatic test data and parameter analysis data of elliptic concrete-filled steel tube column.(3)The correctness of the bridge seismic analysis model based on the finite element software Open Sees was verified by simulating the pseudo-dynamic test of bridge substructure and the shaking table test of railway gravity pier bridge,on this basis,the section design of ECFST bridge pier column is completed based on ECFST formula of ultimate bearing capacity formula,the dynamic time history analysis of the ECFST piercontinuous steel structure bridge was carried out,the seismic performance of CCFST and SCFST piers-continuous steel structure bridges under the same conditions is compared.(4)The IDA analysis method is introduced for ECFST pier-continuous steel structure bridge seismic vulnerability analysis,The seismic response of ECFST piers in longitudinal and transverse directions is mainly analyzed,bridge pier damage index is determined based on the deformation and failure criterion,the seismic vulnerability of ECFST piers is compared with that of CCFST and SCFST piers.