Performance Analysis Of Steel Connection And Theoretical Study On Rotational Stiffness Based On Plate And Shell Theory

For many years,the semi-rigid connections in steel frames have been assumed as rigid or hinged connections,which makes the internal force analysis of the frame inaccurate,and leads to the reduction of structural reliability,steel waste and other problems.Therefore,it is necessary to find an accurate method for calculating the rotational stiffness of connections.In engineering,in order to obtain the connection’s construction parameters of a rotational stiffness,it’s necessary to calculate the rotational stiffness of connections with different connection parameters.To improve the calculation efficiency,the sensitivity of the connection parameters to the rotational stiffness of the connection should be analyzed first.Therefore,it is necessary to find an efficient sensitivity analysis method of the steel connection parameters.In addition,since the steel frame connections are generally spatial connections,how to consider the spatial effect of connections is also a problem that needs to be deeply studied in the analysis of steel frames.Based on the above problems,this paper mainly uses experimental research,finite element analysis,connection parameters sensitivity analysis and theoretical analysis to study the beamcolumn connections.The main works are as follows:(1)The low cycle reciprocating loading tests of three typical beam column main axis connections(end plate connection,web angle steel connection and tree connection)are carried out.Then,based on the test results,the finite element models of side column and middle column connections of three typical connections are established to study the stress mechanism of the connections.The results show that the connection failure mode,lateral resistance,rotation performance,seismic performance and mechanical mechanism of the connections with different structures are quite different.(2)Taking the end plate connection as an example,the connection parameter sensitivity analysis method is obtained: 1)Python is used to write a program that can automatically establish finite element modeling and analysis of connections;2)The finite element analysis results are processed by second derivative method to obtain the initial rotational stiffness of the joint;3)The partial correlation coefficient between the construction parameters and the rotational stiffness of connection was calculated by SPSS.Based on the above work,the sensitivity of the connection parameter sensitivity can be obtained.(3)Based on the sensitivity analysis of 1117 groups of end plate connections,the sensitivity coefficients of different connection parameters to the initial rotational stiffness of the connections were obtained.The results show that the sensitivity coefficient of the thickness of the end plate to the rotational stiffness was the largest,and the sensitivity coefficient of the horizontal spacing between bolts to the rotational stiffness was the smallest.(4)Six T-stub connections with different constructions were tested to study the differences in the lateral resistance,bending resistance,failure mode and energy dissipation capacity of the connections considering the spatial construction.Then the finite element models were established to analyze the stress mechanism of the connections,which shows that the stiffness of the connection components changed greatly after considering the spatial structure,so that the connection performance was also significantly different.(5)For end plate connection,T-shaped connection and top and seat angle steel connection,they were divided into plates with out of plane deformation,bolts with tensile deformation and column web shear regions with shear deformation.For the out-of-plane deformation plate with complex stress deformation,this paper used the plate and shell theory to establish the partial differential equations of the plate boundary conditions,and uses the difference method to solve the partial differential equations to obtain the out-of-plane deformation stiffness of the plate.After analyzed the stiffness of each component,each component was connected in series or in parallel to form a connection spring model.Finally,the initial rotational stiffness of the connection was obtained by using the internal force balance and deformation coordination conditions of the model.(6)Based on the calculation method of initial rotational stiffness of connection in this paper,the calculation software of connections was developed.By inputting the construction parameters of end-plate connection,T-stub connection or top and seat angle connection,the initial rotational stiffness can be calculated efficiently and conveniently.