Study On Seismic Behavior Of Assembly Concrete Double-column Pier With Semi-grouting Sleeve Connection

With the change of development concept,assembled bridge technology has become the focus of accelerating the construction of ecological civilization,promoting the development of new industrialization and building a green city.Assembled integrated concrete structure has the advantages of prefabrication standardization,construction efficiency,modularization and less wet operation.Based on this idea,in the field of bridge engineering,the construction of the assembled bridge structure will inevitably become the mainstream construction technology in the future.The connection point of prefabricated component is the weak point of assembled concrete pier structure in theory and the core point.At present,due to the technical and theoretical limitations in our country.Full-grouting sleeve is often used to connect the steel bar at the joint in the assembled building structure,so this paper is of great significance to the study of the assembled pier based on the semi-grouting sleeve connections.Based on the construction of Hun River Bridge in Central Avenue of Shenyang,this paper designs the model of cast-in-place pier and assembly pier with semi-grouting sleeves.Through the quasi static analysis test,the yield and failure process of assembly pier is studied,and the aseismic performance of two kinds of pier is compared.Using ABAQUS finite element analysis software,two kinds of pier models and semi-grouting sleeve components are modeled and analyzed.The force transfer mechanism and failure form of semi-grouting sleeve members under axial load are studied.The results are compared with the experimental results to verify the accuracy of the model and strengthen the integrity of the experiment.The results are as follows:(1)The compression damage of the cast-in-place pier is concentrated in the plastic hinge area at both ends of the pier and bottom.The fabricated bridge pier is larger than the grouting sleeve at the bottom of the pier column,so the compressive damage of the pier is concentrated at the length of the sleeve up from the bottom of the pier column at the distance of 19cm?60cm,then plastic hinge forms.The failure form of the assembly pier designed in this paper is bending failure,which meets the design requirements of "strong shear and weak bending" of the structure,and the grouting sleeve member can effectively transfer the stress between steel bars without tensile failure;(2)Because of the large stiffness of the sleeve at the bottom of the assembly pier column,the rebars yield of the pier occurs at the top of the pier column,and the yield displacement of 10.01 mm is greater than that of the cast-in-place pier with 8.99 mm.The yield strength of 293.29kN is higher than that of cast-in-place piers 263.81kN,and the bearing capacity is 384.43kN slightly higher than that of cast-in-place piers with 383.79kN.The initial stiffness of assembled pier is large.The reduction of sleeve stiffness in late loading period and the serious damage of slurry layer make the stiffness degradation of pier slightly larger than that of cast-in-place pier,and the cumulative energy consumption is slightly lower,and the ductility is poor.But the gap is small compared with the cast-in-place pier.Ductility 7.22 is smaller than cast-in-place pier 9.27;The energy consumption at the end of loading is lower than that of cast-in-place structure.(3)When the semi-grouting sleeve is subjected to axial loading,the grouting material forms an oblique compression band of 45° to the contact area of the steel bar.The formation of the pressure belt is the main way to realize the stress transmission between the " Steel bar-Grouting-Sleeve ".When the stress value of the steel bar at the two ends of the grouting sleeve reaches the ultimate tensile strength,the deformation of the sleeve is located at the connection between the grouting section and the threaded section,and the maximum stress value of 489.6 MPa does not reach 625 MPa of tensile strength of steel sleeve.Therefore,the grouting sleeve component designed in this paper can meet the construction quality requirements.The deformation of the sleeve will accumulate large plastic deformation during processing,so it is necessary to prevent the sleeve from breaking due to insufficient bearing capacity or insufficient plastic properties.