Research On Seismic Performance Of Steel Frame With Abnormal Joints Of Upper And Lower Columns And Left And Right Beams Simultaneously

In order to study the seismic performance of the steel frame with specialshaped joints with variable cross-sections of upper and lower columns and left and right beams,the article is based on the test of the special-shaped steel frame with variable cross-sections of only left and right beams or upper and lower columns.Analyze the model to evaluate the performance of its failure process,bearing capacity and stiffness degradation;derive the calculation formula of the bearing capacity of double trapezoidal joint domains in the special-shaped nodes with the variable cross-section of upper and lower columns and left and right beams at the same time.The seismic performance of the steel frame system with variable cross-section special-shaped joints of columns,left-right beams and upper and lower columns with different cross-section special-shaped joints simultaneously.The main research contents and conclusions are:(1)First,use ABAQUS software for numerical simulation,and verify the feasibility of the modeling method by comparing with the test results of variablesection column special-shaped nodes.By controlling the variables such as axial compression ratio,column stiffness ratio of upper and lower variable crosssections,and beam stiffness ratio of left and right variable cross-section beams,a finite element model of 27 special-shaped nodes was established to explore the seismic performance of such special-shaped nodes.The results show that: when the axial compression ratio increases from 0.2 to 0.6,the bearing capacity of steel frame special-shaped joint members decreases by 46.7%,and the degree of stiffness degradation increases;the principles of changing the column stiffness ratio and beam line stiffness ratio are similar,all by increasing The overall rigidity of the frame and the increase of the restraint of the members to the core area of the node make the bearing capacity larger.The change of linear stiffness ratio has little effect on the rate of stiffness degradation.(2)Secondly,the calculation formula for the bearing capacity of nodal domains with special-shaped joints with variable cross sections of upper and lower columns and left and right beams is derived,and its rationality is verified according to the experimental data.The calculation results show that the bearing capacity of the double trapezoidal joint domain is related to the parameters of the upper and lower columns,the web thickness of the joint domain,and the strength of the steel.(3)Finally,the static elastoplastic analysis model of the 12-story 4-span steel frame is established to change the arrangement of columns with variable crosssection special-shaped nodes and beam-columns with variable cross-section special-shaped nodes.The analysis of the development of plastic hinges shows that the development path of plastic hinges starts from the bottom layer of the steel frame and the floor where the special-shaped nodes are arranged.It develops along the adjacent layer and adjacent span,and then to the bottom of the bottom column until the structure is pushed.cover.The number of plastic hinges at the beam end is far greater than that at the column end,which meets the requirements of “strong column and weak beam” in seismic design.