| In traditional steel structure design,beam-column connections are usually assumed to be ideal hinged or rigid joints,but they are often inconsistent with this in practice.Extended end-plate connection has attracted much attention of researchers because of its good energy dissipation capacity,simple structure,convenient construction and installation and so on.The connection form is a typical semi-rigid connection,and its rotation characteristics have a significant impact on the overall response of the frame.And China’s"Steel structure Design Standard GB50017-2017"clearly points out that when using semi-rigid connections,the moment-rotation curve of joints should be used to calculate the internal force and response of the structure.Similar requirements have been put forward in the codes of various countries,but many research results and codes have not yet given a set of moment-rotation curves or corresponding calculation methods which are satisfactory and convenient for engineers to use.Therefore,how to quickly and accurately obtain the mechanical properties of semi-rigid connections and promote the application of semi-rigid connections in practical engineering is the focus of the current research.In this paper,the extension end plate node is studied,and the specific work is as follows:（1）The mechanical properties of a group of in-plane central column and side column extended end-plate joints in the strong axial direction are experimentally studied.In the case of antisymmetric loading,the flexural bearing capacity of the middle column joint is basically the same as that of the side column joint,but the rotational stiffness is quite different,and the initial rotational stiffness is reduced by 15%.Then the finite element analysis of the joint is carried out with ABAQUS software,and the results are compared with the experimental results to verify the validity and accuracy of the finite element model.（2）Based on the secondary development of extended end-plate connections based on Abaqus,referring to the corresponding specifications and from the point of view of practical engineering,9216 extended end-plate joints with different connection structures are created.It is found that the moment-rotation curve of joints is related to the length of beams and columns and the type of joints.The constitutive relation of single joint proposed by researchers based on given beam-column section and end-plate connection is questioned.Then,an improved finite element model is proposed,which can effectively solve the influence of column length on the rotation characteristics of joints and improve the computational efficiency.（3）This paper proposes that Mep-θep curve and Mγ-θs curve should be comprehensively considered,both of which are not affected by beam-column length and joint type,and can represent the inherent physical properties of each component of the joint,so as to avoid errors in engineering use.Finally,this paper compiles the Mini Program,and collates the mechanical properties of all the nodes for designers to query.（4）Several existing steel frame modeling methods considering node semi-rigidity are compared and analyzed.finally,it is determined that the improved beam element including joint domain shear deformation has outstanding advantages in ease of use and accuracy.This method does not need to change the line-bar element model which intersects at the central point in the traditional structural design,and can introduce the rotation characteristics of connection(Mep-θep)and shear（Mγ-θs）in the node database to realize the complete calculation of semi-rigid frame structure.In this paper,a semi-rigid steel frame structure analysis program is compiled by using the improved beam element,and a five-story three-span plane steel frame is analyzed,which explains the application of node library in structural calculation and its influence on the overall response of the frame. |
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