Nonlinear Analysis Of Portal Frames With Hot-Rolled H-Section Steel Members

The portal frame is a kind of the common structural styles of single-storey industrial buildings, residential buildings and storages, and it is the most familiar lightweight steel structure. At present, the portal frame is designed by tapered welded steel members, which can be suitable for the variety of the bending moment diagram. Whereas, tapered welded steel members needs many operations of welds and installations, and which has brought into descending of the structure bearing capacity because of welding residual stress. The portal frame is designed of hot-rolled H-section steel members which may be yielded in the paper, in order to avoid influence of the welds and reduce the cost of welds and installations in the proportion of the Cost of engineering project.Firstly, second-order elastic-plastic tangent stiffness matrix of space beam-column element was derived through equilibrium equations which were deduced by the principles of functional stationary potential energy. And then second-order elastic-plastic analysis of hot-rolled H-section steel beams, single steel portal frames and three-dimension portal frame structures were carried through finite element analysis software ANSYS, and they were all considered out with the effect factors of geometry nonlinear,material nonlinear,geometric initial imperfection and steel material hardening. Finally, the normal processes of advanced analyze design is introduced, and it is adopted in steel structure advanced analyze design.With tracking complete process balance path for load-displacement using Newton-Raphson method, it is analyzed and tracked elastic-plastic characteristic of portal frame structures with nonlinearity, substantiated buckling position of structure members and formation orders of plastic hinge. The ANSYS analytical results are accordant with reference data preferably. It could be considered that Hot-rolled H-section steel portal frames structures are broken mainly because of structure instability, but not many plastic hinge formation in the whole structures.