Study On Interactive Buckling Of The Channel-Section Cold-Formed Steel Columns Under Axial Compression

Since 1970,cold-formed steel sections are used widely as structural members due to their properties of light weight,high strength and flexible assembly along with the development of society and technology level,which are becoming especially popular in residential structures.This paper investigates the high-strength cold-formed channel-section steel columns and discusses the critical loadings about local-global buckling for channel-section steel columns when subjected to axial compressive loads.Many thin-walled section columns often experience to buckle locally first,followed by a global buckling.Thus,it is important to investigate how the local deformations affect the behavior of global buckling and how the critical loads of global buckling be calculated when the local deformations are considered.In this paper,an analytical solution is presented for the critical load of global buckling of locally buckled channel-section columns when they are subjected to axial compressive loads.The analytical solution is obtained by using classical energy method,in which the bending rigidity of the channel-section columns is calculated by using the configuration of locally buckled cross-section.Tovalidate the present solution,nonlinear finite element analysis is also performed.A good agreement is demonstrated by the comparison between the present analytical solution and the finite element analysis result for columns with various different member sizes.The average deviation is about 3.68% for short columns,for the long columns,which increases as the member height increases,finally tending to 0%.Comparisons are conducted between theory solution and results calculated by specification for design of cold-formed steel structures in China(GB50018-2013)and the direct strength method in American Standard AISI 2004.The results indicate that GB50018-2013 is not appropriate to be applied to the calculation of overall stability in this research directly.The solution of DSM is more practical compared to theory solution.However,it is still too unconservative to predict the critical buckling load.Theory solution compared to the Euler load is more approaching to the nonlinear finite element solution and DSM results when the high-thickness ratio of the component is larger and the slenderness ratio is not too large with the difference between the local buckling load and the Euler critical load is larger.Therefore,the buckling behavior of thin-walled cold-formed channel-section steel columns when subjected to axial compressive loads can be predicted.