Research On Interactive Buckling Of Cold-formed Thin-walled Steel Columns Based On The Theory Of ECBL

Due to its excellent mechanical properties,cold-formed thin-walled steel members have become an important part of construction steel structures such as storage shelves,low-rise residential buildings and light steel buildings.The failure mode and ultimate load calculation of each model has always been the focus of structural engineering research.Cold-formed thin-walled steel column members are affected by initial defects,cross-sectional shape and wall thickness.Local buckling,distortional buckling,overall buckling and interactive buckling between them occur during compression.For a long time,scholars at home and abroad have conducted extensive and in-depth studies on the effect of three basic buckling failure modes of cold-formed thin-walled steel column members,namely local buckling,distortional buckling and overall buckling,on carrying capacity,and forming design theories of effective width method and direct strength method.There are relatively few studies on the interactive buckling of cold-formed thin-walled steels,but only the relevant effects of local buckling and global buckling are considered in the direct strength method.The results of the existing experiments show that under the effect of pressure,local-distortional interactive buckling,distortional-buckling interactive buckling and local-distortional-overall buckling occurring,and the effect of interactive buckling on bearing capacity of cold-formed thin-walled steel members are more significant,need to pay attention to design.In steel construction,holes are usually formed in the webs of the pillars to facilitate the passage of auxiliary facilities such as wires and pipes.The appearance of the hole will affect the mechanical properties of the members.The elastic buckling stress,the length of the buckling half wave,the buckling mode and the ultimate bearing capacity of the column are different from those of the unopened one.In view of the above problems,this paper introduces a theory of analyzing the related buckling of cold-formed thin-walled steel column members,the critical bifurcation load erosion theory(ECBL theory),which considers the specimens in section buckling(local buckling or distortion buckling)and overall buckling(bendin g buckling,torsional buckling,or flexural-torsional buckling)ultimate bearing capacity under failure mode interactions,by evaluating,quantifying erosion factors(?)and deficiencies(?)of members,making the Ayrton-Perry equation represent the buckling curve suitable for cold-formed thin-walled steel components.Based on the existing theoretical and experimental data,the finite element software ANSYS was used to simulate and analyze the buckling failure modes and partial load influencing factors of the cold-formed and thin-walled cold-rolled steel channel members.The main content of this article includes:(1)The application and basic characteristics of cold-formed thin-walled steel members are summarized.The status quo at home and abroad of various buckling failure modes and calculation methods of the ultimate load corresponding to each failure mode of cold-formed thin-walled steel column members are introduced.Based on the existing experimental results,the validity of the finite element model constructed in this paper is verified.(2)Finite element software ANSYS was used to simulate and analyze the influence of initial defects,hole opening ratio,ratio of web to flange width,and length on the mechanical properties of cold-formed thin-walled channel steel column members.And received partial conclusions finally.(3)Based on the ECBL theory,using numerical simulation and experimental analysis methods,we propose a more fitting and practical distortion-overall interactive buckling curve and local-distortion-globally related buckling curve.