Study Of Structure And Design Of Steel-concrete Composite Connection In Precast Piers

The conventional wet connections,which connect the elements inside the concrete column,are commonly used in precast concrete pier-pile cap joints.However,construction procedures,elements quality and application area are limited.Furthermore,the rehabilitation and replacement of concrete piers after the disaster cannot be realized.Based on the existing concrete-steel composite connection and reinforcement-base plate connection,if the embedded steel plate at the bottom of the column was adopted to connect the concrete column and pile cap,mechanical pier-pile cap connection could be achieved.Therefore,a novel demountable precast pier and plie cap connection is proposed.The connection performance,load transfer mechanism and design method of the connections are key scientific issues.Therefore,this study takes the precast concrete pier as the research object,and focuses on the pseudo-static behavior tests,connections transfer mechanism,capacity evaluation and design of steel-concrete composite connection.The study mainly includes the following contents.(1)A novel steel-concrete composite connection for bridge pier-pile cap joint is proposed and the pseudo-static bending tests are designed.Based on the comparison and analysis of various connections,a novel steel-concrete composite connection for bridge pier-pile cap joint is proposed.In order to further realize the rapid assembly and replaceable function of precast concrete piers,the novel bolted connection between reinforcing bars and steel plate is proposed,which forming the global dismountable column-pile cap connection and local dismountable steel plate-rebar connection.To investigate the performance of pier-cap joint connection,four half-scaled precast pier model specimens with axial compression ratios of 0.06 and0.17 and two types of steel plate-rebar connection are designed.The design,measured program,loading program,material testing,fabrication and assembling process of test specimens are introduced.Furthermore,the application range and durability measures of the proposed connection are investigated.(2)The connection behaviors of precast piers with the proposed connection under pseudo-static loading are conducted.Based on the pseudo-static tests,the experimental phenomenon and failure modes of the specimens with different axial compression ratios and steel plate-rebar connections are investigated,and the hysteretic lateral force-displacement curves,strength and stiffness degradation,dissipating energy capacity and residual displacement are discussed.In order to further study the concrete-steel composite connection behavior,the stress of steel plates and column longitudinal reinforcing bars are analyzed.Furthermore,the deformation parameters e.g.the notched perfobond connectors-concrete slip,horizontal displacement of jacket,vertical displacements of base steel plate and bolts,are given.Finally,the reliability of steel-concrete composite connection under design combined loads is evaluated.(3)The numerical simulation analysis of load transfer mechanism for composite connection in the precast concrete piers is carried out.Based on the analysis,the hysteretic lateral force-displacement curves,stiffness and damaged process are compared with that obtained from model tests,which verifies that finite element analysis can be used to accurately simulate the experiments.Furthermore,the stress of base plate and notched prefobond connector,shear force and slip between connectors and concrete,fracture mechanism of longitudinal rebars are discussed,and characteristics of the connection and load path in the proposed connection are revealed.Based on 63 FE models of precast piers,the capacity is compared with cast-in-place concrete pier,and the parametric analysis of the influencing factors(e.g.thickness of base plate and connector,strength,the dimension of the hole on base plate,the height of jacket,axial compression ratio)on ultimate bending capacity are further discussed.Then,the optimized design is suggested.(4)The design method of steel-concrete composite connection in precast concrete piers is proposed.Firstly,based on the numerical and theoretical analysis,the calculation formula of bending resistance of base steel plate,shear resistance of connectors and bending resistance of pre-stressed anchors are proposed,and further,the local design of steel-concrete composite connection in precast concrete piers is conducted.Secondly,the moment-rotation angle curves in the reinforced concrete section and the composite connection respectively employing Ramberg and Osgood Model and the component method are established,which forms the global design of steel-concrete composite connection in precast concrete piers.Finally,based on the local,general and global design under ultimate load,the design method and calculation framework of the connections are proposed,and the design case of a real bridge is given.