Study On Seismic Behavior Of Irregular Joints Of Large-scale Steel Frame

Earthquake happens frequently in recent years;according to statistics,earthquake above magnitude 7 has appeared six times in the past nine months.To a certain degree,we can consider that earth is in the active stage of earthquake.So,people are all concerned about seismism.To direct toward the several eathquake happened in our country,they all caused serious personal injuries or deaths;meanwhile,collapse accidents of bad seismic behavior building are most serious threat to.the security of the lives.Therefore,judging a building by seismic behavior has been important problem of design.Based on the security of building,steel structure takes on superior seismic behavior;so it is being applied extensively in the construction field.In the course of steel structure failure,joints are always regarded as the critical position and are focused on.Based on extending of research and require of concrete technology,the patterns of joints are also improved and many new patterns appear such as RBS joint and other irregular joints.For normal joints,science workers have studied deeply on them in recent years and got plentiful achievements.But,for irregular joints,both the research of experiment and the study of theory are little.so,it is imperative to accelerate the study on them combined with practice.This paper combines practical engineering datas to design patterns of irregular joints by 1:4 proportion,and makes study on seismic behavior of this joint by cyclic test.In the course of experiment,based on the structural capacity of energy dissipation,the experiment refers to hystertic behavior?ductility?energy dissipation?and stiffness degradation of the specimens.Furthermore,this paper analyses seismic behavior of the specimens under the controlled parameters of diffierent axial load level and diffierent size ratio of the beam.Finally,this paper analyses partial stability of joint core by the means of theory combined with experiment and hunts after instability phenomenon and rule of irregular joints.We get failure pattern of this joint through the analysis of experiment and theory.Although the phenomenon of split of irregular joints and that of normal joints are resemble,distribution and trend of development of the crack are different.we know that this joint still possesses superior hystertic behavior and capacity of energy dissipation,and ductility of this joints is in accord with character of steel structure;and under the different controlled parameters,study bearing capacity of this joints and variation trend of hysteretic curves and envelope curves of this joints under cyclic load.we sum up the rule of strength degradation and stiffness degradation of joints;Moreover,set the limited vaule of the ratio of height and thcikness to make sure unstability of joint core.On the basis of what we did,this paper reaches appropriate conclusions to provide the basic material and reference data for the design of irregular joints.of course,considering the limit of experimental condition,this paper has some deficiency and puts forward some problems needed to research deeply.