Theoretical Study On Web-Flange Distortional Buckling Performance Of Perforated Cold-Formed Steel Channel-Section Beams

With the support of national policies,the development of production and processing technology in the steel industry and the rise of prefabricated buildings,coldformed thin-walled steel(CFS)has been widely used in China's engineering due to its excellent mechanical properties and convenient fabrication and construction.Furthermore,perforated cold-formed thin-walled steel(PCFS)beams have also been greatly developed in engineering applications as the main load-bearing components.The existence of holes will inevitably affect the buckling performance of steel beams.The distortional buckling analysis focused on flanges and lips in the past,the web-flange distortional buckling analysis was limited.This paper studies the distortional buckling behavior of PCFS channel-section beams theoretically and numerically:Firstly,this paper introduces the existing design theories of CFS members,including effective width method,direct strength method and reduced strength method,and briefly describes the application of these design theories in European codes,North American codes,Australian codes and Chinese codes.In addition,three common theoretical models of distortional buckling of CFS members are summarized.Then summarizes several numerical methods for buckling of CFS beams,and the validity of the finite element model is verified by comparing the finite strip and the finite element distortional buckling results of solid web CFS beams.Therefore,the finite element software ANSYS is furtherly used to calculate the distortional buckling critical stress of PCFS channel-section beams,and verifies the correctness of the theoretical solution of the distortional buckling critical load of the members in this paper.This paper derives an explicit formulation of PCFS channel-section beams webflange distortional buckling critical load.It is known that the compressed flange-lip system can be isolated to calculate the critical stress of lip-flange distortional buckling.In fact,near the ultimate failure stage,the web-flange corner would move laterally which indicates the bending of the web should be considered.The theoretical model in this paper is based on the classical energy method,the energy terms of web and flangelip are derived and then solved by Rayleigh-Ritz method.Finally,the theoretical model calculation solution is compared with the finite element solution and it is found in good agreement,which provides a certain theoretical basis for practical application in engineering.Finally,the accuracy of the theoretical formula is verified by comparing the finite element results with the theoretical results.This paper provides a theoretical basis for the practical engineering application of cold-formed thin-walled members.