The Seismic Performance Analysis Of Knee Braced Steel Frame With Semi-rigid Connections

The braced steel frame is a common seismic structure system,which is widely used in modern architecture for the advantages of low weight,high strength,good ductility and high construction speed.People always treat beam-column connections as fully rigid or pinned ones in traditional steel frame designs.But in the practical engineering,beam-column connections are semi-rigid in between.As a new kind of energy dissipating support members,knee braces not only inherit the advantages of high stiffness of the concentrical braces,but also overcome the disadvantages of the energy dissipation capacity of the eccentrically braced frames by sacrificing main components.The knee braced steel frame is characterized by the fact that one end of the brace is connected to beam,and the other end is connected to column.And one end of the diagonal side brace is connected to the knee brace and the other end is connected to beam-column connection.The knee braces are designed as the power-sapping components in the knee braced steel frames.In elastic range,the knee braces provide the lateral stiffness for the whole structures and then meet the lateral displacement of steel frame structures.When the knee braces are under rare earthquake,the knee braces enter the inelastic range,dissipate energy by plastic deformation and yield before the main components to protect the structure from serious failure.The knee braced semi-rigid steel frames combine the advantages of semi-rigid connections and the knee braces,exhibiting excellent seismic behavior.To further understand the cooperation capacity of the two.The main work of this paper are as follows.1、According to the pseudo-dynamic testing in a reference,this paper uses SAP2000 to establish the same semi-rigid steel frames model and makes elastic dynamic analysis.Then the numerical simulation results are compared with the test results in the reference to prove the accuracy of the finite element model established in this paper.2、On the basis of the establishment of the accurate model,this study adds the support members to semi-rigid steel frames,establishes the finite element model of the knee braced semi-rigid steel frames and then make Pushover analysis under rare earthquake to analyze the failure process and failure mode of the knee braced semi-rigid steel frames.This paper also explores the effect of the different initial rotational stiffness on the seismic behavior and the energy-dissipating capacity of the different semi-rigid steel frames,which prove the good seismic behavior of the knee braced semi-rigid steel frames.3、 Based on the previous studies,this paper makes analysis of the elastic dynamic analysis under frequent earthquake and elastoplastic time-history analysis under rare earthquake to the knee braced semi-rigid steel frames in different arrangement forms and then make comparison from the perspectives,such as base share force,top displacement,interlaminar shear force,interstory displacement,and interstory displacement angle.Then,this paper concludes the optimal arrangement form of the knee braces.