Research On Mechanical Behavior Of End-plate Semi-rigid Connection Of Hybrid Steel Frame

In recent years,the application of high-strength steel in building structures has become more and more extensive.However,due to its large yield ratio and poor plastic deformation ability,the application of high-strength steel is limited in seismic fortification areas.The seismic design principle of “strong column and weak beam” and the application of semi-rigid joints are effective means to improve the ductility of high-strength steel frame structures.However,at present,the study of the mechanical behavior of semi-rigid joints of hybrid steel frame whose column is made of high-strength steel and beam is made of ordinary strength steel is still rarely carried out whether at home or abroad,and there is no special calculation method for such joints.Therefore,this paper studies the mechanical behavior of end-plate semi-rigid connection of hybrid steel frame by finite element method.The main contents are as follows:(1)Establish finite element models of end-plate semi-rigid connection of hybrid steel frame by finite element software Abaqus,and then compare the calculation results with similar test results to verify the accuracy of the models.(2)Initially,three finite element models are established.The first one uses Q345 steel,the second one uses Q690 steel for column,and the third one uses Q690 steel for column and end-plate.Monotonic loading curve,stress development process,initial rotational stiffness,flexural capacity,ductility,failure modes and hysteretic performance are analyzed.The effects of high-strength column and high-strength end-plate on the mechanical behavior of the joint are studied.(3)Parameter analysis of the joint is carried out.The considered parameters include: thickness of column web,transverse stiffener of column web,thickness of column flange,strength of end-plate,thickness of end-plate,diameter of bolts,axial compression ratio of column and friction coefficient.The effects of these parameters on initial rotational stiffness,flexural capacity,ductility coefficient and failure mode of the joint are studied.(4)Find out three parameters that have a major influence on flexural capacity and ductility coefficient of the joint,which are strength of end-plate,thickness of end-plate and diameter of bolts.By orthogonal test analysis method,the combinations of parameters are obtained which separately make the joint get maximum flexural capacity,maximum ductility coefficient and optimal comprehensive mechanical behavior.(5)Refer to the results of parameter analysis and orthogonal test analysis,the accuracy of the EC3 component method and the “Technical specification for steel structures with end-plate semi-rigid connection” for calculating the flexural capacity of the joint is tested.Based on the EC3 component method,a correction formula for calculating the initial rotational stiffness of the joint is proposed by multiple nonlinear regression analysis and considering the influence of the axial force in the column.(6)The time-varying laws of steel material property and friction coefficient under atmospheric corrosion are substituted into the finite element models,and the joint models for different atmospheric corrosion ages are established,from which the degradation law of the mechanical behavior of the joint under atmospheric corrosion is obtained.