Seismic Performance Of Prefabricated Steel Tube-Confined Concrete Pier

Prefabricated piers have been widely used in the substructure of bridges in China due to their high construction efficiency,high engineering quality,green environmental protection,and economic applicability.Their seismic performance has also become a research hotspot in the field of bridge engineering at home and abroad.The steel tube confined concrete structure stands out in the steel tube concrete structure system with its advantages of simple connection,easy buckling failure of steel tube,good seismic and good economic performance.This thesis combines the current popular prefabricated assembly technology with the structural concept of steel-concrete composite,and proposes a structural system of prefabricated steel tube-confined concrete pier.It is expected to have the advantages of prefabricated assembly pier and steel tube confined concrete pier,including short construction period,good engineering quality,high bearing capacity and good seismic performance.The seismic performance of prefabricated steel tube-confined concrete pier was studied.The specific research contents and results are as follows:(1)The academic literature at home and abroad was investigated.The seismic performance of assembled piers based on grouting sleeve connection,the seismic performance of concretefilled steel tube piers and the research status of steel tube confined concrete structures were summarized and analyzed.The research object,research content and research method of this paper were proposed.(2)The structural characteristics of assembled steel tube confined concrete pier(PSTC)were studied,and two structural systems of cast-in-place reinforced concrete pier(CIP)and prefabricated reinforced concrete pier(PC)were designed.Quasi-static tests were carried out on three types of circular and square piers to analyze the differences in seismic performance of piers of different structural types.The results of quasi-static tests showed that compared with CIP and PC pier specimens,the flexural capacity,energy dissipation capacity,displacement ductility and initial stiffness of PSTC pier specimens were significantly improved,and the stiffness distribution of pier body is more uniform.(3)The ABAQUS finite element models of circular prefabricated steel tube-confined concrete pier(C-PSTC)and square prefabricated steel tube-confined concrete pier(S-PSTC)were established.The relevant parameter analysis of C-PSTC and S-PSTC bridge pier specimens was carried out.The results of parameter analysis showed that for C-PSTC bridge pier,the strength of steel tube,axial compression ratio,slenderness ratio and material ratio coefficient have significant influence on its peak displacement.The thickness of the steel tube,the strength of the steel tube,the axial compression ratio and the material ratio coefficient have a significant effect on the peak load.The thickness,strength and slenderness ratio of the steel tube have a significant effect on its initial tangent stiffness.The thickness,axial compression ratio and slenderness ratio of the steel tube have a significant effect on the tangent stiffness of the descending section of the skeleton curve.For S-PSTC piers,the axial compression ratio and slenderness ratio have a significant effect on the peak displacement;the thickness of steel tube,axial compression ratio and slenderness ratio have significant influence on the peak load.The thickness and slenderness ratio of steel tube have a significant effect on its initial tangent stiffness.The thickness,axial compression ratio and slenderness ratio of the steel tube have a significant effect on the tangent stiffness of the descending section of the skeleton curve.(4)On the basis of quasi-static test and finite element parameter analysis,considering the influence of various parameters on the seismic performance of prefabricated steel tube-confined concrete pier,the restoring force model calculation method of prefabricated steel tube-confined concrete pier was proposed.The quasi-static test results verified the validity of the calculation method of the restoring force model.(5)Based on the actual project,the size design of real bridge piers of cast-in-place piers,assembled reinforced concrete piers and assembled steel tube confined concrete piers was carried out,and the corresponding finite element models of real bridge piers were established by finite element method.The seismic performance of three types of real bridge piers was compared and analyzed.It was found that under low cyclic loading,the steel tube confined core reinforced concrete of the assembled steel tube confined concrete pier improved the flexural bearing capacity,initial stiffness and energy dissipation capacity of the pier,reduced the plastic damage of the pier,and had excellent seismic performance.The validity of the calculation method of the restoring force model was verified by the finite element analysis results of the prefabricated steel tube-confined concrete pier.