| Steel constructions have many advantages such as lightweight great intensity quality, well anti-seismic behavior, high industrialization degree, quick construction velocity, accordance with environmental protection request, matching to constant development concept, and high-technical content etc. Along with positive policy adopting steel structure and increasing total steel production in our country, steel structures get speedy development, especially in residence buildings, office blocks, and hotels etc. Steel structures have got more and more extensive application. In fact, most of beam-to-column connections will be neither pinned nor fully rigid ones. They belong to semi-rigid ones. Therefore, In order to study the nonlinearity performance of steel frames with semi-rigid connections, several key problems on it are studied.Firstly, current research and existing problems of steel framed structures are introduced in this dissertation, and the theory of the extended end plate joints and semi-rigid steel frames are widely analyzed and researched at home and abroad. In the analysis of the extended end plate connections, the formulas calculating its ultimate moment and initial stiffness are firstly researched, and a four-parameter power model is proposed to describe its moment-rotation relation, which are compared with the results by finite element method. Then a program named QMR which is used to calculate its ultimate moment and initial stiffness by the computer is established. Through the program and the model above the main influencing factors are discussed accordingly.Based on the theory of beam-to-column, stiffness matrix of member of steel frame has been established, which include the axial force and shear displacement effects. The second elastic stiffness matrix of semi-rigid structures is derived by revising its rotation-displacement equations. According to the superposition principle under small deformation, the moment expressions at two ends of element with semi-rigid connections are inferred under any load. The second elastic and elastic-plastic analysis of this kind of structures are made in these ways. According to this model, two corresponding programs of this kind of structures are worked out by MATLAB. And the effects of semi-rigid behaviors are analyzed in these programs, which include the node displacement, internal-force unit, second-order effect and ultimate bearing capacity. Finally the correctness of the results was validated with ANSYS. From the result we could acknowledge that the existence of the semi-rigid connection have large influence on the X-displacement, moment transfer and so on. |
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