Study On Seismic Performance Of New Type H-shaped Steel Beam-to-column End Plate And Expanded-flange Two-way Connection Joint

The steel structure is a structural system with good development potential that integrates the advantages of energy saving,high strength and convenience.Since the damage caused by two severe earthquakes in the last century brought huge impact on the traditional steel structure system,a large number of scholars have carried out research on how to improve the overall reliability of the steel structure system.In order to avoid brittle failure of the joints,many scholars have proposed a new joint concept to improve the ductility and energy consumption of the joints.The principle is form the plastic hinges in the beam away from the joint domain.At present,a lot of research work has been carried out on the connection of the strong-axis connection,and the research on the weak-axis connection is relatively little.In this paper,a finite element simulation study is carried out on the two-way connection mode of the strong and weak axis of the beam-column in a local box joints.The joints are bolted with end plates and the beam ends are enlarged flanges to strengthen the performance of the joint domain,so that the plastic hinge is transferred to the weakened section of the beam.On the weak axis,the skin plate is welded with the column web stiffener and the inner side of the column flange to form a local box-shaped node domain.By using ABAQUS finite element software,monotonic loading and low-cycle cyclic loading were carried out on the BASE specimen of the new beam-column bidirectional connection node.Based on the BASE specimen,the end plate thickness,axial compression ratio,weakened section length,the shape of the reinforced ribs and the thickness of the skin plate in the weak axis direction are analyzed with five variable parameters,and the failure state,hysteresis performance,mechanical properties,ductility and energy dissipation capacity of each specimen are studied.The main conclusions are as follows:（1）The new two-way connection node can improve the stiffness of the node area,effectively move the plastic hinge outward,protect the node area from brittle failure,and conform to the principles of"strong column and weak beam"and"strong node and weak member".（2）After the BASE specimen is loaded with monotonic displacement,the bearing capacity in the strong axis direction is 1.17%larger than that in the weak axis direction,the beam flange does not buckle,and finally fails to form a plastic hinge;after low-cycle cyclic displacement loading,the stress and strain are concentrated at the weakened part of the beam flange,The beam flange and web have obvious buckling deformation,forming a plastic hinge.（3）According to the analysis of 5 variable parameters,it is concluded that the thickness of the end plate has an effect on the failure mode of the node.If the thickness of the end plate is too small,the node area is prone to damage first,which violates the seismic principle of"strong column and weak beam";the end plate thickness is too large,Will increase the cost,the recommended value range of the end plate is0.7d≤₀（8）≤d（d is the diameter of the high-strength bolt）;the axial compression ratio has little effect on the force of the node,but if the axial compression ratio is too large,it will cause the buckling failure of the column node domain,It is recommended to take the axial compression ratio≤0.7;the length of the weakened section of the beam flange also has little influence on the force of the joint,but the weakened length will cause the stress concentration area to be closer to the beam end,which may affect the stability of the joint area,so it is recommended to weaken The length of the zone is 0.5?_（7）≤7(（7）≤0.9?₍（7）(?_{（7） is the beam height};ribs of different shapes have different effects on the mechanical properties of the joints.Trapezoidal ribs and long-side triangular ribs can effectively reduce the weld stress and prevent the occurrence of joint domains.Damage,but the effect of trapezoidal ribs on the joints is stronger than that of triangular ribs;the thickness of the skin plate has an influence on the force performance in the direction of the weak axis.The thicker the skin plate,the smaller the stress and strain value of the skin plate.,Comprehensive analysis suggests that the thickness of the skin board is25mm.