Finite Element Analysis Of Stability On Steel Portal Frame With Tapered Members

In recent years, the light gauge steel structure of low-rise buildings are widely used because of their light weight, beauty, convenience-manufacture, easy erection, reliability and high efficiency. The portal frames, as a main form of low-rise industrial buildings, are generally composed of the tapered columns and beams with thin-walled webs that may undergo local buckling before global buckling of the frame occurs. In order to design the light gauge steel structure safely and economically, it is necessary that the static calculation and stability analysis of frame structures are further researched.Aimed to tapered beam units, the finite element method (FEM) is introduced in this paper. In order to obtain elastic stiffness matrices and geometry stiffness matrices that do not depend on subdivision of the element for convergence, the displacement functions are expressed in terms of the geometry properties of the section and this consideration leads to the formulation of exact stiffness matrices for linear elastic analysis given in this paper. The accuracy of the stiffness matrices is verified by many examples.In this paper, an FEM program is developed for the portal frames with the tapered columns and beams. The tapered beam element is used in the FEM. With the FEM, the linear static and in-plane stability analysis of the frames are carried out conveniently. By use of the FEM program, the paper contrasts the differences of static calculation and stability analysis results of tapered portal frame structure analyzed by uniform section beam elements and tapered section beam elements respectively.