Study On Hysteretic Behavior Of Prefabricated Assembly Steel Tube Confined Concrete-energy Dissipation Joint

With the development of the modernization of the construction industry,the prefabricated assembly concrete structure,as one of the forms,has also become a research hotspot,especially the connection mode of prefabricated frame beam-column joints..Therefore,a new type of prefabricated assembly steel tube confined concrete-energy dissipation joint was proposed in this paper.The joint core area was prefabricated with steel tube confined steel fiber reinforced concrete.The precast lower column and the precast core area were connected by grouting,the precast upper column and the precast core area were connected by reinforced sleeve grouting,and the precast beam and the precast core area were connected by local cast-in-place connection section at the beam end.The seismic design concept of "strong node,weak component" is realized.The design concept of "strong joint,weak structure" is realized.The main works are as follows:The hysteretic experiments of four prefabricated assembly steel tube confined concrete-energy dissipation joints and one cast-in-situ frame joint were carried out,which experimental paraters included the thickness of the main core-wrapped steel pipes,the axial compression ratio of the joints and the steel fiber content.The influence of various parameters on the failure mode,shear deformation,ductility and energy dissipation capacity of the joint core were discussed.The results shows that the bearing capacity,ductility and energy dissipation capacity of prefabricated assembly frame joints are better than those of cast-in-place frame joints.Under the premise of beam end plastic hinge failure,the bearing capacity,ductility,energy dissipation capacity and plastic hinge rotational capacity increase slightly with the increase of the steel fiber volume ratio,the degradation of stiffness and strength of the specimen P-Δ curve is slow as well.Within the range of test axial pressure ratio,the higher the axial compression ratio is,the higher the horizontal bearing capacity is and the corresponding energy consumption capacity increase slightly,however,the ductility,the stiffness and strength decrease.When the thickness of the steel pipe changed from 8mm to 4mm,the failure mode of the specimen changed from the beam failure to core area shear failure.The finite element software ABAQUS was used to simulate the joint performance.On the basis of steel tube,beam-column steel bar,steel fiber reinforced concrete,ordinary concrete and steel tube confined concrete under compression and tensile constitutive model as well as contact setting of each prefabricated part,the finite element model of prefabricated assembly steel tube confined concrete-energy dissipation joints and one cast-in-situ frame joint were established.The skeleton curves calculated by finite element method are in good agreement with the experimental results.Combined with the finite element analysis and experimental results,the force transfer process mechanism of prefabricated assembly steel tube confined concrete-energy dissipation joints were analyzed.The parameter analysis of the influence on the flexural capacity of the beam end and the shear bearing capacity of the core area are carried by ABAQUS software.The results of parameter analysis show that the volume ratio of steel fiber and the ratio of reinforcement in the connection zone have a significant effect on the flexural capacity of the beam end.The shear capacity of the new joints is significantly influenced by the steel fiber volume ratio in the core area,the thickness of the outer steel tube in the core area and the strength of the concrete in the core area.On the basis of parameter analysis,the simplified formulas of beam end bending capacity and core shear capacity of prefabricated assembly steel tube confined concrete-energy dissipation joints are obtained by regression.