The Elasticity And Plasticity Analysis Of Space Steel Frame With Semi-rigid Connections

Steel structure has a series of advantages, such as light own weight, high strength, good ductility and earthquake resistant capability, green environmental protection, high construction speed, etc., and is loved by architects and structure engineers of home and abroad. Framework system of steel structure is not only being used for multistory and high residence buildings, but for single story and multistory industry structure. With the gradual improvement of Chinese economy and technology level, steel structure will widely be used and will become one of main structure systems in our country's construction industry. At present, design of steel frame existes two disadvantages. The first aspect is lying in construction analysis, linear and elastic analysis for steel frame merely considers the influence of flexural deformation, shearing deformation and axial deformation, without consideration of the influence of geometrically non-linearity, material non-linearity, initial imperfection and so on. The second is lying in the checking of structure design. Rods generally is in the state of elastic-plastic stage when they attach to the state of ultimate bearing capacity, the internal forces of elastic-plastic stage can not accordance with the internal forces of elastic stage, so the degree of reliability of structure design is not coincidence with reality. Based on the present research, this paper mainly researchs several hot questions of geometrically non-linearity and material non-linearity. There are several study aspects of this paper, as follows:1. Geometrically non-linearity analysis of three-dimensional column-beam. This paper has estabished virtual work equation of three-dimensional based on finite deformation theory of 3D continuous body of nonlinear continuum mechanics and up-dated langrange formulation and has deduced real column and beam elemental lateral displacement and angular displacement in consideration of the influence of axis force and shear deformation, then has established geometrically non-linearity increment stiffness equation of 3D column-beam including multiple coupling items by combinating traditional column-beam theory and finite element. Elasticity tangent stiffness matrix including the wagner effect of the coupling items of bowing effect, axis deformation and bending, axis deformation and shear. This equation fully reflects contribution of the coupling items of axis deformation and shear deformation to elemental stiffness matrix. This method can gain a more accurate results by a way of single element, and open a simple and effective way of the geometrically non-linearity analysis of large complex structures.2. Material non-linearity analysis of three-dimensional column-beam. Based on known simple zone method, the theory of non-linearity of 3D continuous body and elastic-plastic theory, this paper has established material non-linearity increment stiffness equation of 3D column-beam under local coordinate system. The increment stiffness equation of this method may be used in the analysis of double large displacement; At the same time, in consideration of elemental cross-section elastic-plastic influence factor and axis elastic-plastic influence factor, the model reflect the plastic spread along the section and the axis, so calculation work muchly reduced relative to plastic zone model, but increased no much compare to plastic hinge model. This model may appropriate to reality and has more accurate result which can meet with the demand of structure advanced analysis.3. Non-linearity analysis of space steel frame with semi-rigid connections. It is more difficult to research the performance of semi-rigid connections. Based on the research method of the performance of semi-rigid connections and connection model, the paper has established non-linearity stiffness equation of space rod element of semi-rigid connection and has discussed solution methods of nonlinear stiffness equation and methods which were used in the program of ANSYS. At last, two models, such as plate double span two-storey and space single span three-storey steel frame, were established in the examples. The paper has detailed analysizes the proformance difference of space steel frames between semi-rigid and rigid and has gained the analysis of space steel frame with semi-rigid connections based on the advanced analysis. The result can accord with actual stress status and can accurately calculate the horizontal deformation and can be refered by designers and researchers.