Analysis For In-plane Overall Stability And Spatial Performance Of Light Steel Structure With Portal Frames

Steels are high strength light weight materials , and thus, the ultimate load-carrying capacity of the light weight steel with portal frame structures is often smaller than the material bearing capacity of its components ,that is, stability of the light weight steel with portal frame structures is even more important. In-plane overall stability checking computations with portal frames mainly adopt individual component length calculation ,which analyze the stability of individual components (such as column) to replace the overall stability of portal frames. In the stability analysis of individual components, also consider other components to its constraints. This analysis method simplified the portal frame geometry size , the stress conditions, in-plane deformation compatibility of components, the special deformation compatibility of whole portal frame structures etc factors in actual project, it is clear that the above-mentioned methods is not close to true as the overall stability analysis with portal frames. In this paper, the finite element analysis soft ware ANSYS is adopt for build special overall model with portal frame, and respectively analyze in-plane and out-of-plane overall stability, accordingly get factors that affect on in-plane and out-of-plane overall stability of portal frames, and put forward some reasonable arrangements with secondary components of frame systems after static force analysis.First introduces the instability type of portal frames and educe the curt formula under each instability conditions with traditional computing methods. Subsequently, the finite element soft ware ANSYS is introduced to analyze two buckling analysis type which is used to analyze the stability of portal frame, and compared with both types of calculation principles and calculations results, consequently make certain the analysis type fit for this paper is the nonlinear arc-length bulking methods.Then, the nonlinear arc-length bulking methods is adopted to make parameters analyze to the factors affect on portal frames in-plane stability, such as horizontal load portal frame height-span ratios Inclined beam gradient bend in portal frame and axial forces in beams height-thickness ratios of the columns and beams webs and edges, and conclude primary and secondary factors affect portal frames in-plane instability.Finally, using the nonlinear arc-length bulking methods to make static forceanalysis to the secondary components of portal frame structures, such as longitudinal bars inter-column bracing and roof horizontal bracing purline and tie rod. One side analyze these secondary components effect on the out-of-plane overall stability of portal frame structures, on the other hand, the force performance of these secondary components is analyzed synthetically considering these two calculating results, bring forward some reasonable arrangements with these secondary components ,which will ground the portal frames well in its design and farther research.