The Research Of Reinforced Beam-to-column Connections With Vertical Stiffener Under Initial Loads

In recent years,many steel are under construction or have been in service for many years.And due to natural disasters,use function changes,aging and other reasons,many steel structures need to be reinforced.At present,there are few studies reinforcement of the panel zone retrofitting in steel frames under load.This paper combines the engineering design practice and the theoretical study of beam-column joint reinforcement.This paper adopted the reinforcement method of increasing the beam-column section and welding vertical stiffener at the beam-column joint.And then the performance of the panel zone reinforced using vertical stiffener was investigated with finite element method.The main research contents and results are as follows:(1)The comparative analysis of the joint domain design method of beam-column joints of beam-column cross-sections in the steel structure design standards of China,the United States,Europe,and Japan.Area,yield bearing capacity and ultimate bearing capacity analysis and calculation differences.These four types of steel structure design standards allow plastic deformation of the node domain to take into account the bearing performance and energy dissipation capacity of the beam-column node domain.Based on the previous research on the external rib ring plate joints,the formula for the bearing capacity of the external rib ring plate joints was derived to make it suitable for the calculation method of the external rib ring plate used in this paper.(2)The ABAQUS finite element software was used to verify the finite element analysis method for strengthening beam-column joints based on existing joint tests to ensure the reliability of the finite element analysis method for strengthening beam-column joints under load.A detailed finite element model of load-reinforcement of outer rib ring plates for box-column-H-beam bolted joints is established,and the entire process of reinforcing beam-column nodes with external rib ring plate loads is simulated.Reinforced monotonic performance and cycling performance.The results show that the H-beams in the steel frame beam-column joints are strengthened with the increased section method to increase the initial stiffness of the joint domain.The vertical rib method is used to strengthen the joint domains,and the post-yield stiffness of the beam-column joints is increased and improved.The ultimate bearing capacity of the joint zone has a significant strengthening effect on the weak beam-column jointzone.(3)Steel frame beam-column joints using external rib ring plates to strengthen the finite element model for the initial column axial compression ratio of 0,0.2,0.4,0.6,0.8,0.9 and different external rib ring plate layout methods to reinforce steel Parametric analysis of frame beam-column joints is performed to analyze the effects of different axial compression ratios and different external rib ring plate layouts on the performance of external rib ring plate reinforcement beam-column joints under load.Parametric analysis results show that: when the column axial pressure ratio is 0 ~0.3,the bearing capacity of the node may not be processed;when the column axial pressure ratio is 0.3~ 0.6,the node bearing capacity may be reduced to a certain extent;the column shaft is not recommended Reinforcement of steel frame beam-column joints reinforced by external rib ring plates with a pressure ratio greater than 0.6.There is no significant difference in the initial stiffness and yield load of the joint zone with the outer rib ring plates arranged on one side and the outer rib ring plates arranged on both sides.The limit bearing capacity of the joint domain is greatly affected by the arrangement of the outer rib ring plates on one side,and the limit corner decreases.trend.The beam-column joints strengthened by external rib-free ring plate loads have poorer hysteretic performance than the beam-column joints strengthened by external rib-ring plate loads,and their ductility and energy dissipation capacity are average.The research results in this paper can bring some reference value to the theoretical analysis and design method research of the existing steel frame beam-column joints under load reinforcement and seismic performance after reinforcement.