| Steel structure buildings are characterized by light weight,high strength,excellent seismic behavior,high production efficiency,high degree of industrialization,and short construction period.As an important constituent part of steel structures,the beam–column connection joint plays a significant role in transmitting the internal force in the structure,and its performance will have a direct bearing on the safety and reliability of the overall structure.Based on the design concept of prefabricated connection joint,a new-type prefabricated square steel tubular column to H-shaped steel beam column high-strength bolted joint with external diaphragms was proposed,and its seismic behaviors were deeply explored and analyzed through the experimental study,finite element numerical analysis,and theoretical analysis methods.The study results can provide a theoretical reference for engineering application.(1)Four prefabricated square steel tubular column to H-shaped steel beam column high-strength bolted joint specimens with external diaphragms were designed and fabricated.The cross-shaped joint specimens of the steel frames were selected to conduct the low-cycle reciprocal load test,and their hysteretic behavior and energy-dissipating capacity were investigating by changing their structural parameters.The experimental study showed that the hysteretic curves of the joint specimens exhibited a “Z shape” with a large area of hysteresis loop,thereby reflecting their strong plastic deformability and good absorption of seismic energy.The four joint specimens experienced significant stiffness degradation phenomenon.Moreover,their equivalent energy dissipation coefficients ranged from 1.84 to 2.93,equivalent viscous damping coefficients ranged from 0.18 to 0.24,ductility factors ranged from 5.24 to 13.31,and story drift angles ranged from 0.09 rad to 0.12 rad.Therefore,the joints demonstrated strong energydissipating performance and excellent seismic behavior.(2)The nonlinear finite element numerical analysis was implemented,and the analysis results were compared with the test results from the stress nephograms,hysteretic curve,skeleton curve,stiffness degradation curve,and energy-dissipating capacity of the specimens.According to the comparison results,the finite element numerical calculation results fitted well with the test results,thereby verifying the effectiveness of the finite element numerical analysis method when used to investigate the seismic behavior of the joint.(3)The influence laws of the specimens’ parameter changes on their failure mode,yield bearing capacity,ultimate bearing capacity,and initial rotational stiffness were investigated.The study results manifested that the external diaphragm should match with the thickness of the beam flange in the joint design,and the beam flange and high-strength bolt should reach the design ultimate bearing capacity simultaneously.When the thickness of external diaphragm was approximate to that of beam flange,their collaborative deformation could be realized,thereby forming favorable ductility and energy dissipation mechanism.Moreover,the seismic behavior of the joint would be optimal,and the width of the external diaphragm should satisfy the design requirements of the joint bearing capacity.The small width of the external diaphragm went against the energy dissipation of the joint.With the increase in the width of the external diaphragm,the joint’s seismic capacity would be strengthened.The joint bearing capacity and seismic behavior would be influenced slightly by the length change in the external diaphragm.Furthermore,as the circular arc radius increased,the joint bearing capacity presented an initially increasing and then declining trend.(4)The mechanical properties of the beam–column high-strength bolted joint with external diaphragms were analyzed,and the calculation formula for the joint shear bearing capacity was derived through the superposition method.The failure modes of the joint specimens were analyzed,and the calculation formula of their ultimate flexural bearing capacity was probed and derived.The two aforementioned formulates were verified comparatively through the test and finite element analysis.Study findings showed that the values calculated by the two formulas coincided with the test and finite element numerical calculation results very well,thereby proving the accuracy of the theoretical formulas.(5)The calculation of initial rotational stiffness was derived for the joint specimens,and the joint bending moment-angle curve calculation method was proposed.The threeparameter power function was established to fit the joint bending moment-angle skeleton curve model and the hysteretic curve model through the experimental fitting method.The accuracies of the derived theoretical formula of initial rotational stiffness,bending moment-angle curve calculation method,restoring force model were verified by comparing the test results with the finite element numerical calculation results. |
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