Research On Distortion Buckling Performance And Design Method Of Cold-formed Thin-walled Steel Members With Web Openings

In recent years,cold-formed thin-walled steel has been widely used in building and water conservancy field because of its green,high strength,convenient construction and other advantages.The wall column and floor beam of cold-formed thin-walled steel buildings often need to open holes on the web of members in order to make pipes,wires and other auxiliary facilities pass through.Because of the open section of the member,the wide thickness ratio of the plate and the hole in the web,the member is prone to distortional buckling and related buckling.However,the calculation of distortional buckling capacity of members with openings has not been specified in the China's standard "Technical Standard for Coldformed Steel Structures"(GB50018-202x).In view of this,the distortional buckling behavior of cold-formed thin-walled steel members with web openings is studied by finite element analysis and experiment.Firstly,the general finite element software ABAQUS is used to analyze the effects of different opening sizes,types and spacing on the elastic distortional buckling performance of cold-formed thin-walled lipped channel steel members under axial compression and bending.The results show that the web opening will not only weaken the restraint effect of the connected plate,but also change the distortional buckling half wavelength of the member,and the form of web opening is different The distortional buckling stability coefficient k decreases with different degrees.Based on the results of parametric analysis,the relevant reduction formulas of distortional buckling stability coefficient k of cold-formed thin-walled lipped channel members with different opening types are given.The validity of the effective width method to calculate the distortional buckling strength of members with web openings is verified by using the finite element method.Secondly,the distortional buckling of 66 high-strength cold-formed thin-walled lipped channel steel columns with web openings(circular and rectangular holes)and without holes were tested.The ultimate bearing capacity and load axial displacement curve of the specimens were measured.The test results show that the bearing capacity and buckling mode of the specimens are affected by different section forms,different hole types and opening sizes.The results show that it is feasible to analyze the distortional buckling mode and bearing capacity of cold-formed thin-walled lipped channel steel with web openings by finite element simulation.The results of the finite element analysis show that the buckling mode of the member will be changed with the opening,and the influence of the rectangular hole on the bearing capacity of the member is more obvious than that of the circular hole.Finally,based on the finite element analysis,experimental research and theoretical analysis,the proposed design method of distortional buckling capacity of cold-formed thin-walled steel members with web openings is proposed.The existing test data and finite element calculation results are compared with the results of the proposed formula and the calculation results of North American code.The results show that the proposed method is applicable and feasible.