Study On The Mechanical Properties Of Beam-column Joints With U-shaped Dampers Under The Failure Of The Center Column

Steel frame structure is a common structural system,and its beam column joint is a very important force transfer area.After the failure of the steel frame column,the load above the original failure column is transmitted to other components connected with it through the joint,so the deformation and bearing capacity of the beam column joint play an important role in the resistance to progressive collapse of the structure.A repairable beam column joint with U-shaped damper has strong deformation and energy dissipation capacity,and shows good seismic performance.Under the load,the failure of the joint mainly occurs on the U-shaped damper,and the purpose of repairing the joint can be achieved by replacing the U-shaped damper.However,the mechanical performance of the joint under the column failure condition of steel frame structure has not been studied.Therefore,this paper studies the mechanical properties of beam column joints with U-shaped dampers under the failure of the central column.Firstly,the finite element model of the beam column structure is established,and the validity of the model is verified by comparing the finite element simulation with the experiment.Secondly,the mechanical properties of DU50-20-10-20 node and BASE node are compared and analyzed in detail.Finally,according to the U-section diameter d of the U-shaped damper,the joints are divided into three groups.At the same time,the progressive collapse resistance performance of each group of models under different U-section height h,U-section thickness t₁ at the web and U-section thickness t₂ at the lower flange is analyzed.The joint with 40 mm U-section diameter is mainly analyzed The development of bending moment at beam end and axial force in beam is studied,and the stress process of the joint and the proportion and transformation process of bending mechanism and catenary mechanism are studied,so as to explain the influence of various parameters of the joint on the progressive collapse resistance of the structure.It is found that the beam column joint with U-shaped damper has strong deformation capacity and high bearing capacity,and the displacement of the joint in the limit state is greatly improved,which effectively delays the cracking of the joint.Although the bending mechanism in the early stage is weakened,the catenary mechanism in the later stage is fully developed,and the structure mainly relies on the bending mechanism to provide vertical resistance instead of the catenary mechanism.The diameter d and thickness t₂ of the U-shaped section of the U-shaped damper have great influence on the deformation capacity and resistance development of the joint,while the height h and thickness t₁ of the U-shaped section have little influence on it.Finally,combined with the study of its seismic performance,reasonable suggestions for the parameter range of the U-shaped damper are put forward,which can provide reference for the follow-up research and application.