| Steel structure buildings have the advantages of ligh weight,high strength,good seismic peiformance and environmental protection.However,the traditional seismic design of steel structures based on no collapse under strong earthquake at the cost of damage to the main structure,resulting in severe plasticity after the strong earthquake,which is difficult to repair.Therefore,the research and development of seismic steel structure systems that can quickly restore functions after earthquakes has become a hot spot in the field of earthquake engineering.The idea of controllable damage based on replaceable components is an effective way to solve the above problems.However,existing solution have common problems such as insufficient joint shearing capacity and significant joint-floor interaction.For this reason,this paper proposed a damage-controlled steel frame joint with energy-dissipation and centering units based on buckling-restraining mechanism,which includes the cantilever beam and the middle beam.They are connected together by the suspension unit at the upper flange of the beam,the centering unit at the beam web and the energy-dissipation unit at the lower flange of the beam.In the earthquake phase,with the suspension unit as the center of rotation,the seismic energy is dissipated through plastic deformation of the energy-dissipation unit under tension and compression.In the post-earthquake repair phase,the energy-dissipation unit is released from the restraint of the main structure,and the centering unit is used to provide elastic restoring force to realize the restoration of the joint.This paper focuses on the mechanical model,seismic performance,post-earthquake restoration capacity of the new type of joints,and the seismic performance and post-earthquake restoration capacity of the structural system.The main research contents and conclusions are as follows:(1)In the second chapter,the construction and work principle of the new type of joint are proposed.According to its working mechanism and mechanical model,the formulas of the new type of joint,such as the elastic lateral stiffness,splicing section bending moment-angle relationship,the relationship between the interlayer lateral displacement and the deformation of the unit,the centering criterion of joint and steel frame.Based on the damage control,the design method of the new type of joint is proposed,which provides a theoretical basis for the analysis of the mechanical characteristics of the connection under earthquake and the ability of post-earthquake restoration.(2)Based on the above theory,in the third chapter,four new types of beam-column joint pseudo-static tests were carried out,considering the presence/absence of centering unit,the presence/absence of floor slab settings and different suspension connection structures(highstrength bolt connection/weld connection),and two of the joints that have been loaded for the first time are replaced by energy-dissipation units and performed a second time load to examine its functional recovery after the earthquake.The test result shows that the new type of joint can achieve small earthquake elasticity through reasonable design,and the energy-dissipation unit for medium and large earthquakes intensively dissipates the seismic energy,and the main structure and the centering unit maintain elasticity at 4% inter-storey drift angle;the centering unit can provide elastic restoring force during post-earthquake repair,which significantly reduces the residual deformation of the joint after the earthquake,and the new type of joint has good structural and functional recoverability.(3)In the fourth chapter,ABAQUS software is used to carry out the finite element parameter analysis of the mechanical properties of the new joints.Firstly,the position of the splicing section of a beam span is used as a parameter variable to consider the influence of the position of the splicing section on the seismic performance of the joint.Secondly,taking the beam height,the interstory drift at yield,the centering bending moment as the variable parameters,considering the impact of different parameter conditions on the performance goals of the joint.The analysis results show that: The new type of joint is arranged at the zero point of the bending moment of the traditional steel frame beam under the action of vertical load,and the vertical load has the least influence on the seismic performance of the joint.Under different parameter changes,the new joint can achieve performance goals such as "small earthquake elasticity,medium and large earthquake energy consumption,damage transfer,function repairable" and so on.The finite element values of the relevant mechanical parameters are in good agreement with the theoretical values,which proves the theory the universality of calculation formulas.(4)In the fifth chapter,the Open Sees software is used to carry out the structural modal analysis,Pushover analysis and dynamic elastic-plastic time history analysis on the damagecontrolled steel frame of 4th and 8th floors,and compared with the traditional steel frame and the pure energy-dissipating steel frame(only energy-dissipation unit).On this basis,the total centering bending moment of the frame structure is used as a parameter variable,and the feasibility of restoring at the frame level is verified by pseudo-static loading.The analysis results show that: The seismic performance of the new-type steel frame is similar to that of the pure energy-dissipating steel frame.At the same time,compared with the traditional steel frame,the former realizes the distributed energy consumption of each floor,the deformation between the floors is more uniform,the probability of the weak floor of the structure is reduced,and the damage of the column base is reduced;according to the comparison between the new structures with different centering bending moments,The feasibility of the framework level reset and the effectiveness of the theoretical guidelines are verified. |
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