| In recent years,with the continuous industrialization of housing,concrete-filled steel tubular structure has been widely used.As a key part of the beam column joint,the connection form is more complex and the construction fault tolerance is small,which limits the development of the structure form to a certain extent.In order to popularize the application of concrete-filled steel tubular structure,it is necessary to study a joint form with convenient assembly and large construction fault tolerance.In this paper,the connection between concrete-filled steel tubular column and H-shaped steel beam is carried out by means of the bottom flange bolted and top flange welded,and the seismic test and finite element analysis of the bottom flange bolted and top flange welded joint are carried out to provide sufficient reference for the structural design of this type of joint.In this paper,a new type of the bottom flange bolted and top flange welded joint between concrete-filled steel tubular columns and steel beam with the through diaphragm and the outer rib ring plate is proposed.The core area of the joint only sets a through diaphragm at the joint of the lower flange,which is more conducive to the pouring and vibration of concrete,and the outer rib ring plate on the column side can increase the stiffness of the joint.In order to study its seismic performance,three bottom flange bolted and top flange joints and a full-bolted joint were design for test under low-frequency cyclic loading.In order to evaluate the seismic performance of the bottom-bolted and top-welded joint,the influences of the thickness of the plate and the size of the beam section on the failure characteristics,hysteretic curve,skeleton curve,energy consumption,stiffness degradation and bearing capacity degradation of the joint are analyzed.The results show that the failure mode of three bottom flange bolted and top flange joints is basically the same,mainly due to the beam end buckling and ductile fracture,the load displacement hysteretic curve of the joint is full,the energy dissipation capacity,stiffness degradation capacity and bearing capacity degradation capacity are good,showing the seismic performance close to the full bolt joint.With the increase of beam section size,the ultimate flexural capacity,stiffness and energy dissipation capacity of the joint are significantly improved,while the seismic performance of the joint is not significantly improved with the increase of the thickness of the plate.Through the observation and analysis of the results of strain gauge and non-contact strain tester(DSCM),it is found that the main strain and shear strain mainly develop in a 45 ° oblique direction,the strain of the lower side of the connecting plate,the inner diaphragm near the column side,the middle of the horizontal row and the bottom flange near the beam are larger,and the strain value of the core area of bottom flange bolted and top flange welded joint is smaller than that of the full-bolt joint.In this paper,the finite element analysis software ABAQUS is used to simulate the four nodes,and compared with the test results,it is found that the test results are in good agreement with the simulation results.On this basis,the parametric analysis of the joint is carried out,and the influence of the axial compression ratio,the thickness of the steel pipe,the strength of the upper flange of the steel beam and the thickness of the outer ring plate on the seismic performance of the joint is analyzed,the results show that the change of axial compression ratio and thickness of the steel pipe has a significant impact on the seismic performance of the joint,while the strength of the upper flange of the steel beam and the thickness of the outer ring plate have little impact on the seismic performance of the joint. |
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