Column Curves Of Spatial Stability For Open Cross-Section Thin-Walled Columns

Based on "warping theory", this paper primarily includes several parts of research below for open cross-section thin-walled components:(1)Basal hypotheses, fundamental concepts, essential tools, and practical calculation formulas of "warping theory" are briefly introduced, and its applications on complicated conditions such as varied-section beams are concretely illustrated by example. "warping theory" entirely contains traditional theories, therefore it has capacious development foreground, and feels no regret to be a new generation engineering practical calculation theory.(2) Making use of the moment vector and radius vector of rotation, the lateral buckling of thin-walled members are analyzed. In addition, considering the instantaneous rotation center as simplified point of the moment vector, the unification calculation formula of critical loadings is educed, besides it is explained that critical loadings indicate the characteristic of members stiffness. At the same time, a lot of rotation center triangles are plotted which denote internal forces characteristic. By axial force, the additional moment vector and double moment of members' section can be synthesized to a new moment vector which traverses the rotation center, and the triangle formed by three critical moment vectors which are orthogonalized each other provides correlative information about the stability of members. From the equilibrium equation of the internal and external double moments, a general simplified calculation formula of critical loadings about lateral buckling for thin-walled members is derived. (3) According to three orthogonal buckling modes, the method how to disassemble initial deformation into three independent deformations is discussed here. Furthermore, in terms of the equilibrium of the internal and external double moments, rotation magnification factors of three orthogonal deformations are deduced, and the consistent of additional combined deformation about the rotation and deflection is simultaneously interpreted.(4) Founding on external fiber yielded criteria, the calculation method of spatial stability column curves is put forward for Bi-plate-type section and three-plate-type section, where initial deflection is taken into account. A new instability mode: shearing instability is pointed out in steel structure, which is an especial phenomenon in Bi-plate-type section. At last, the order of section deformation with the increase of slenderness ratio is visualizedwhen members lose stability in space.As the research about spatial stability column curves of thin-walled columns in this paper is still on its theoretic stage, the values of relevant initial defect factors haven't been adequately accumulated, and the verification of much experimental date is still deficient. Thus few examples are only enumerated to narrate its origin, in order that a new way of spatial stability column curves of thin-walled columns would be inaugurated in theory, and for the purpose of remedying column curves' gaps of current code and providing the code revise reference. As for the analysis about residual stress and elasticity-plasticity, would be left behind to further research.