Finite Element Analysis On Tapered Portal Frame Structure

The light-weight steel portal frame structure is a kind of structure system with a new idea, which developed abroad from the 1960's and has been widely applied from then on. It has been introduced to China in the recent years and has popularized quickly. Due to its light weight and high strength, its reasonable mechanism and high efficiency in construction, it has achieved a great success on the construction market and has a great vitality. The light-weight steel portal frames are often composed of tapered members, which, with its thin-walled webs, permit local buckling happening before global buckling. Therefore, it can utilize the material strength fully. In order to design the light gauge steel structure safely and economically, it is necessary that the static calculation and stability analysis of the frame structure are further researched.Adopting tapered beam element, the bearing and distortion of light weigh steel portal frame structure in its plane is studied using linear elastic finite-element method (FEM) in this paper. Besides, the nonlinear finite-element theory is applied to the stability analysis of light weight steel portal frame structure. In order to obtain elastic stiffness matrices and geometry stiffness matrices, whose precision don't depend on the amount of the subdivided elements, the elastic stiffness matrices and geometry stiffness matrices, which can be used to elastic analysis and geometry nonlinear analysis of taper frame structure, are deduced using axial and lateral displacement function obtained by integrating geometry property of taper member, and a proper and effective model is established. The elastic linear FEM analysis program and nonlinear geometry FEM program of portal frame are programmed using the established model. After the light weight steel portal frame structure been calculated and analyzed adopting uniform beam element and tapered beam element, The discrepancy and astringency of different solutions of tapered portal frame analyzed by the two beam element are compared.Besides, based on the established model, some factors having influences on the stable ultimate bearing capacity of tapered portal frame are compared and analyzed.Assume restriction condition isn't change, the influences of some factors, such as ratio of length to slenderness, taper, and the form of load(roof uniform loading, unsymmetrical loading, on stable ultimate bearing capacity are discussed, this can offer credible reference to engineering design.