Analysis Of Space Stability Of Open Cross-Section Thin-Walled Beam-Columns

Open cross．section thin—walled beam-columns are widely used in practice．Duringits application the key problem to deal with is its stability．Up to date the computation ofthin．walled beam．column'S stability is treated by V．S．Vlasov'S theory。The theory is based on two fundamental independent theories,one relate to the real member as"plane bending theory"and the other on the"constrained twist theory"。The first is known asthe equilibrium system of longitudinal force,the later is the equilibrium system of horizontal force．Because the classical theory of thin-walled beam-columns separate the deformation and internal force of the thin．walled beam—columns and did not take into account internal link and harmony between the plane deformations and warping deformations of the thin．walled beam—columns．In its application the classical theory still have some problems that are difficult to resolve．Consequently,in the standard codethe thin．．walled beam．．column lateral buckling influence can only be handled through some estimated procedures or met,hods。 The thin．．walled beam．．columns calculations have been explored successfully bywarping theory．This document will use warping theory as tools and utilizing themoment vector and radius vector of rotation to analyze the space stability of thebeam．columns．In order to establish the relation between the warping theory and theclassical theory,also for the verification of warping theory,this document will study thespace stability of 3一plate thin—walled beam—columns．Mainly the following related workshave been carried out:(1)Verify the warping theory． Based on the introduction of the first order analysis of thin—-walled beam--columnsand theory of the rotation of a cross section around a fixed axis,a program has beencompiled which compare the warping theory result with that of the traditional theory．Itwas proved that the warping theory is consistent with the classical theory in theundeformable—edge hypothesis．The warping theory has assembled the planedeformation and constrained twist deformation into general warping deformation。(2)Analyze the lateral buckling of thin—walled beam—columns． The lateral buckling of thin·-walled beam··columns are analyzed with the momentvector and radius vector of rotation．The space deformation of the lateral buckling isthen described with the theory of the rotation of a cross section around a fixed axis。 Disassembling the buckling mode of the space stability into 3 buckling modes in the tangent plane,makes the equilibrium of the internal and external force clearly．A general simplified formula about lateral buckling of thin．．walled beam．．columns is then derived．(3)Discuss the general method of the second order analysis of the thin-walled beam．columns． A discussion has been put forward on how to disassemble the known initial deformation into 3 independent deformations．Thus deducing each deformation magnification factor,illustrates the consistent of the factor in the combined deformation．In order to remedy the gaps in the current standard code,based on the warping theory．this paper has discussed the general method of the second order analysis,taking into account initial deformation． The analysis the paper has considered is still on its investigation stage．It hopes t0put forward a common method on the second order analysis of the thin-walled beam—columns,to remedy the gap of the current theory,thus providing the codereference for revision．As for its p．roper application to standard code use i．e．for therevision of column curve,beam-column related formula adj ustment and SO on,thatwould be left to future research．...