Research On Seismic Behavior Of Assembly Joints Of Square CFST Column And H-shaped Steel Beam

Concrete filled steel tube(CFST)structure has a high bearing capacity,good plasticity and ductility,convenient construction,fireproof performance is good,and good economic effect in the domestic and foreign high-level and high-rise building structure is more and more widely used,and along with our country to the building industrialization's vigorous promotion,makes the prefabricated building obtained the very good development prospect.Therefore,based on the existing CFST column-beam joints and precast column assembly joints,this paper proposes an assembly joint of square CFST column and H-shaped steel beam,which can realize the connection between CFST column and H-shaped steel beam while vertical assembly of CFST is carried out.This new type of joint can realize the precast of each component in the factory,avoid the pouring of concrete and welding between steel components on the construction site,ensure the construction quality of components,improve the construction environment,and conform to the development direction of green building.In this paper,the seismic behavior of the assembly joints of square CFST column and H-shaped steel beam is experimentally studied,and the influence of end plate thickness,bolt diameter and different axial compression ratio on the energy dissipation performance of the joint is analyzed by finite element parameterization.The following conclusions were obtained:(1)Through the low-cycle repeated test of the assembly joints of square CFST column and H-shaped steel beam,the effects of failure mode,energy dissipation capacity,stiffness degradation,strength degradation and displacement ductility of the joint are analyzed.The test results show that the joint has good plasticity,ductility,energy dissipation capacity and seismic performance,which indicates that the joint is feasible in practical application.After the test loading,the components were disassembled,and it was found that the external convex deformation of the CFST column wall at the bolt position was significantly improved compared with the local yield failure caused by the excessive convex deformation of the bolt-end plate joints.At the same time,from the installation process of the specimen,it can be seen that the construction of such joints is convenient and easy to operate,showing good assembly performance.(2)The numerical model of the assembly joints of square CFST column and H-shaped steel beam is established,and the reasonable reliability of the numerical model is verified by comparing with the experimental research.The results show that the thickness of the end plate and the strength of the bolts play an important role in the bearing capacity and energy dissipation performance of the joints,while the stiffness of the square CFST column is large,and the variation of axial compression ratio(0.3~0.5)has little effect on the bearing capacity and energy dissipation performance of the joints as a whole.According to the influence of endplate thickness and bolt diameter on the model,if the endplate thickness and bolt diameter are increased within a certain range,the hysteretic curve of the model will be more full,and the energy dissipation performance and seismic resistance will be stronger,and the bearingcapacity and stiffness of the model will be significantly improved.(3)The stress mechanism of the assembly joints of square CFST column and H-shaped steel beam is studied.In this paper,the force transfer mechanism of each component of the joint is clarified by analyzing the stress condition of the joint domain,and a formula for calculating the flexural capacity of the joint is established.